CableGUI/docs/design.md

# CableGUI — Design v4.1

Cable-management **framework + solver** for m's setup. Inventor shift 1
design, revised through v2 (rescope to multi-project framework), v3
(global cable_types + guardrails), v4 (solver-as-core), and now
**v4.1 — six locked answers from m's v4 review**.

> **What changed in v4.1** (tight pass on v4)
> 1. **CableGUI is a schematic, not a physical-routing tool.** Cables are
>    straight lines between endpoints; the solver and the renderer do not
>    care about paths, trunks, frame edges, or cable-tray polylines.
>    "Maximum bundling" reduces to the v3 rule: **≥2 cables between the
>    same endpoint pair → bundle them.** All path-routing language has
>    been stripped from §5b.1, §5b.2, §7, §8, §9.
> 2. **Solver fires on the Solve button (v0).** Live-solve stays in §8
>    slices 9+ as an opt-in toggle.
> 3. **Unmet-requirement quick-fix**: when the solver returns
>    `unsatisfied[]`, the device inspector renders a red badge per unmet
>    requirement with a single button — **"+ Add <type> port to
>    <device> and re-solve"** — that POSTs a new port to the
>    device AND immediately re-runs `POST /api/projects/:pid/solve` in
>    the same UI action. See §5b.4 + §7 inspector-states.
> 4. **Setup templates fold INTO v4.1.** New tables `setup_templates`,
>    `setup_template_devices`, `setup_template_requirements` in
>    migration 004 + 3 built-in templates ('Living Room', 'Home Office',
>    'Server Rack'). New endpoints `GET /api/setup-templates` and
>    `POST /api/projects/:pid/apply-template`. UI: a "Templates" panel
>    in the New Project flow + an "Apply template" action on an empty
>    project. See new §2.4 + slice 6 fold-in below.
> 5. **Catalog distribution: SQL seed** in migration 002 (no change).
> 6. **Promote to manual: explicit button** on the cable inspector
>    (no change).

Sources: the live `Cable-Management.excalidraw` on mxdrw.msbls.de (used as
the *visual-grammar reference*, not a bootstrap import target),
`mai-memory` (`cablegui`, `m`), and the live mDock services for deploy
conventions (§10). v4 driven by m's product-vision clarification:

> "we provide a cable manager — I say what devices we have, the app tells
> me how to bundle cables and how the most efficient connection looks like"

CableGUI shifts from a manual draw-and-click editor to a **solver** that
takes a list of devices + the connections m needs and emits the cable
plan + bundle recommendations. The manual editor stays (it's the only way
to inspect + tweak the plan) but is no longer the primary surface.

> **What changed in v4** (new mental model on top of v3 mechanics)
> - **Hybrid device-type catalog** (§2.1, §3.1). A built-in `device_types`
>   table seeds common devices (NAS, PC, Mac, TV, Soundbar, Switch, fritz,
>   ChromeCast, SteamLink, IOx-3/6/8, Notebook, …) with default port
>   profiles (`device_type_ports` rows: cable_type + count + label).
>   Adding a device → pick a type → ports auto-seed. m can override per
>   instance (this PC has 3 USB, not 2). Catalog is extendable per project.
> - **`connection_requirements` table** (§2.2). m declares "NAS must
>   connect to Switch via RJ45" once. Many per device. The solver consumes
>   these.
> - **`POST /api/projects/:pid/solve` endpoint** (§3.2). Reads devices +
>   their ports + connection_requirements + frame positions, emits a diff
>   of `cables` + `bundles`. Two modes: `?preview=1` returns the diff
>   without applying; default applies.
> - **Solver objective: maximum bundling** (§5b.1). Schematic only: when
>   two or more cables share the same endpoint pair, group them into one
>   bundle. No path or trunk geometry — CableGUI is a wiring schematic,
>   not a routing tool. v4.1 strips all path/trunk language from the v4
>   draft.
> - **UI: device-type dropdown** on device-create, **Connection
>   Requirements** left panel, **Solve** button next to Export. Inspector
>   shows type + ports + unmet requirements (selected device) or the
>   driving requirement + bundle (selected cable).
> - **Slices reshape** (§8). Catalog seeding lands early (slice 1.5); the
>   solver MVP and connection-requirements UI move ahead of the
>   bundle-rendering polish.
>
> **What carried over from v3 (unchanged in v4)**
> - CableGUI is a framework: top-level `projects`, each backed by one
>   `.excalidraw` drawing. `UNIQUE(projects.name)`.
> - `cable_types` is global. Migration 001 seeds Power/USB/HDMI/DP/RJ45.
> - `devices` UNIQUE(project_id, name); `frame_id` nullable; FrameRef
>   tri-state on PATCH.
> - IO diamonds = wall-outlet terminators (type=Power by convention).
> - `projects.drawing_name` auto-defaults to `<name>.excalidraw`.
> - `DELETE /api/projects/:pid?confirm=<name>` guardrail.
> - No cable inventory metadata; visual + connectivity structure only.
> - DB at `./data/cablegui.db` (gitignored). Bind `0.0.0.0:7777` LAN, no auth.
> - Deploy on mDock under `/home/m/stacks/cablegui/`, raw docker-compose.
>
> **What's superseded in v4**
> - The "manual draw-a-cable port-to-port" flow from v3 §7 is *kept* as a
>   tweak path on the solver output, but is no longer the *primary* device-
>   connecting flow. The solve button is the headline action.
> - The v3 §8 slice order changes — catalog + types-driven devices + solver
>   come earlier; the manual-draw-cable slice slides later. See new §8.

---

## 0. The seed drawing — visual grammar reference

`Cable-Management.excalidraw` on mxdrw.msbls.de is **not** ingested at
runtime. It is the visual-grammar reference we lock the export onto so that
when m rebuilds LOFT and OFFICE inside CableGUI, the exported `.excalidraw`
looks like the seed.

Concrete numbers from the live file (180 elements):

| Kind | Count | Excalidraw shape | What it represents |
|---|---|---|---|
| Frames | 2 | `frame` (`name`) | Sub-areas inside a project (`desk`, `rack`, …) |
| Devices | 27 | `rectangle` with bound text | Hardware items |
| Ports | 74 | `ellipse` ~12×9 | Connectors on a device edge, colour = cable type |
| Cables | 31 | `arrow` | Typed connections between ports/devices/outlets |
| IO markers | 6 | `diamond` text=`IO` | **Wall outlet / power-entry terminators** (type=Power) |
| Legend | 5 | `text` | Colour key in the top-left of the frame |
| Lines | 5 | `line` | **Decorative** (separator under the legend). Ignored. |

**Legend → cable type → colour**, picked up directly from the seed:

| Type | Colour | Hex |
|---|---|---|
| Power | red | `#e03131` |
| USB | green | `#2f9e44` |
| HDMI | blue | `#1971c2` |
| DP | purple | `#9c36b5` |
| RJ45 | yellow | `#ffd500` |

Three observations about the seed's visual grammar — these constrain the
**exporter** (§4):

1. **Ports sit on a device edge as small ellipses (~12×9)**, coloured by
   cable type. They are not children of the device in the Excalidraw sense
   (no `containerId`/`boundElements` link) — purely positional. When we
   export from CableGUI we mimic that: port ellipse at `(device.x +
   port.x_offset, device.y + port.y_offset)`, stroke colour = type colour.
2. **Cable arrows bind to elements**. In the seed: 44 endpoints to ellipses
   (ports), 12 to whole rectangles (device-level, no specific port), 3 to
   diamonds (wall outlets). Our exporter sets `startBinding.elementId` /
   `endBinding.elementId` to whichever Excalidraw element ID we wrote for
   the port / device / IO marker.
3. **IO diamonds = wall outlets.** They are terminals: a cable goes from a
   device-port → an IO marker, meaning "this cable plugs into a wall socket
   outside the diagram". They are always type=Power in m's setup but the
   schema doesn't enforce that (a future "network jack in the wall"
   wouldn't fit, and we can lift the constraint then).

---

## 1. Frontend stack — vanilla JS + SVG

**Locked**: vanilla ES modules (TS-typed via JSDoc, no build step) + SVG
diagram surface, served from a single Go binary via `embed.FS`.

Why this fits m: matches the no-build-step preference; same single-binary
aesthetic as `m`, `mai`, `youpcms`, `mExDraw`. Type-checking is opt-in via
`make typecheck` (`tsc --noEmit`), not gating runtime. SVG is one DOM node
per port/device/cable → trivial hit-testing, CSS-driven colouring by
`data-type=hdmi`, drag via pointer events + `getScreenCTM()`.

Escape hatch only if state for half-drawn cables + multi-select gets
painful: switch to Preact-via-CDN-ESM (still no build step). Not v0.

---

## 2. SQLite schema

`./data/cablegui.db` (project-local, gitignored). WAL mode, FKs on.
Driver: **`modernc.org/sqlite`** (cgo-free — clean cross-compile, simple
Dockerfile).

```sql
-- 001_init.sql
PRAGMA journal_mode = WAL;
PRAGMA foreign_keys = ON;

-- A project IS a drawing. LOFT and OFFICE are separate projects.
-- One project ↔ one .excalidraw file in mExDraw.
CREATE TABLE projects (
    id              INTEGER PRIMARY KEY,
    name            TEXT NOT NULL UNIQUE,        -- "LOFT", "OFFICE"
    drawing_name    TEXT NOT NULL,               -- mExDraw drawing name, e.g. "LOFT.excalidraw"
    description     TEXT NOT NULL DEFAULT '',
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now'))
);

-- Cable types: GLOBAL legend, one set shared across all projects.
-- Migration 001 seeds the 5 defaults (Power/USB/HDMI/DP/RJ45) once.
-- Renaming or recolouring a type from anywhere in the UI propagates to
-- every project's legend and to every cable already typed as it.
CREATE TABLE cable_types (
    id              INTEGER PRIMARY KEY,
    name            TEXT NOT NULL UNIQUE,        -- "Power", "USB", "HDMI", "DP", "RJ45"
    color           TEXT NOT NULL,               -- "#e03131"
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now'))
);

-- v4 — device-type catalog. Seeded built-in types live globally (so
-- multiple projects share the "NAS" definition without duplication).
-- Per-project custom types are also allowed (project_id non-null for those).
-- Renaming a built-in type doesn't propagate retroactively to existing
-- devices that already had their ports seeded — they own their port set
-- from the moment they were created.
CREATE TABLE device_types (
    id              INTEGER PRIMARY KEY,
    project_id      INTEGER REFERENCES projects(id) ON DELETE CASCADE,
                                                  -- NULL = built-in (shared), non-null = project-custom
    name            TEXT NOT NULL,                -- "NAS", "PC", "TV", "Switch", "IOx-8", "Custom-Foo"
    kind            TEXT NOT NULL DEFAULT 'generic',
                                                  -- coarse category for UI grouping: 'storage', 'compute',
                                                  -- 'display', 'audio', 'network', 'hub', 'accessory',
                                                  -- 'generic'
    icon            TEXT,                         -- emoji or short symbol (🖥, 📺, 🔊, 📡) — UI hint
    description     TEXT NOT NULL DEFAULT '',
    built_in        INTEGER NOT NULL DEFAULT 0,   -- 1 for migration-seeded rows, 0 for user-created
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now')),
    UNIQUE (project_id, name)                     -- two projects can both have a custom "Foo";
                                                  -- built-ins (project_id NULL) get UNIQUE on name globally
);
CREATE INDEX device_types_project_idx ON device_types(project_id);

-- v4 — port profile per device type. "NAS has 1 Power + 1 RJ45" is two
-- rows; "PC has 1 Power + 1 RJ45 + 1 HDMI + 2 USB" is four rows.
-- When a device is created with type_id=X, the seeder inserts `count`
-- rows into the `ports` table for each device_type_ports entry,
-- numbering label as "<label_prefix> N" if count > 1.
CREATE TABLE device_type_ports (
    id              INTEGER PRIMARY KEY,
    device_type_id  INTEGER NOT NULL REFERENCES device_types(id) ON DELETE CASCADE,
    cable_type_id   INTEGER NOT NULL REFERENCES cable_types(id)  ON DELETE RESTRICT,
    label_prefix    TEXT NOT NULL DEFAULT '',     -- "HDMI", "USB", "Power" — UI label root
    count           INTEGER NOT NULL DEFAULT 1 CHECK (count >= 1),
    -- Position hint: the seeder lays ports along the device edge using
    -- these biases (0..1 along the edge fraction). NULL = even spread.
    edge            TEXT NOT NULL DEFAULT 'bottom' CHECK (edge IN ('top','bottom','left','right')),
    sort_order      INTEGER NOT NULL DEFAULT 0
);
CREATE INDEX device_type_ports_type_idx ON device_type_ports(device_type_id);

-- A frame is a named container *inside* a project: 'desk', 'rack', 'media'.
CREATE TABLE frames (
    id              INTEGER PRIMARY KEY,
    project_id      INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    name            TEXT NOT NULL,
    x               REAL NOT NULL DEFAULT 0,
    y               REAL NOT NULL DEFAULT 0,
    width           REAL NOT NULL DEFAULT 1200,
    height          REAL NOT NULL DEFAULT 800,
    excalidraw_id   TEXT,                        -- stable across exports
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now')),
    UNIQUE (project_id, name),
    UNIQUE (project_id, excalidraw_id)
);
CREATE INDEX frames_project_idx ON frames(project_id);

-- Devices live in a frame (and transitively in a project).
-- Stored project_id is denormalised for cheap project-scoped queries; FK
-- to frame_id is the structural truth. Both are kept consistent in code.
--
-- v4 — type_id (nullable) lets a device inherit its port profile from
-- a `device_types` row. Once ports are seeded the device "owns" them;
-- changing/clearing type_id later does not retroactively re-seed (m's
-- per-instance overrides survive). Custom freeform devices (no template)
-- keep type_id NULL — that's the v3 "just a rectangle" device.
CREATE TABLE devices (
    id              INTEGER PRIMARY KEY,
    project_id      INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    frame_id        INTEGER REFERENCES frames(id) ON DELETE SET NULL,
    type_id         INTEGER REFERENCES device_types(id) ON DELETE SET NULL,
                                                  -- v4: nullable; SET NULL on type delete so we don't
                                                  -- cascade-delete a device the user still wants
    name            TEXT NOT NULL,
    color           TEXT NOT NULL DEFAULT '#1e1e1e',
    x               REAL NOT NULL,
    y               REAL NOT NULL,
    width           REAL NOT NULL,
    height          REAL NOT NULL,
    excalidraw_id   TEXT,
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now')),
    UNIQUE (project_id, name),                   -- no two devices in one project share a name
    UNIQUE (project_id, excalidraw_id)
);
CREATE INDEX devices_project_idx ON devices(project_id);
CREATE INDEX devices_frame_idx   ON devices(frame_id);
CREATE INDEX devices_type_idx    ON devices(type_id);

-- Ports belong to a device. x_offset/y_offset are relative to the device's
-- top-left so ports follow when the device moves. project_id denormalised.
CREATE TABLE ports (
    id              INTEGER PRIMARY KEY,
    project_id      INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    device_id       INTEGER NOT NULL REFERENCES devices(id) ON DELETE CASCADE,
    type_id         INTEGER NOT NULL REFERENCES cable_types(id) ON DELETE RESTRICT,
    label           TEXT,                        -- optional ("HDMI 1", "USB-C rear")
    x_offset        REAL NOT NULL,
    y_offset        REAL NOT NULL,
    excalidraw_id   TEXT,
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now')),
    UNIQUE (project_id, excalidraw_id)
);
CREATE INDEX ports_project_idx ON ports(project_id);
CREATE INDEX ports_device_idx  ON ports(device_id);
CREATE INDEX ports_type_idx    ON ports(type_id);

-- IO markers = wall outlets / power-entry terminators.
-- One end of a Power cable. They are NOT bridges and they do NOT pair.
CREATE TABLE io_markers (
    id              INTEGER PRIMARY KEY,
    project_id      INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    frame_id        INTEGER REFERENCES frames(id) ON DELETE SET NULL,
    label           TEXT NOT NULL DEFAULT 'IO',  -- "Wall A", "UPS rear", …
    x               REAL NOT NULL,
    y               REAL NOT NULL,
    excalidraw_id   TEXT,
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now')),
    UNIQUE (project_id, excalidraw_id)
);
CREATE INDEX io_markers_project_idx ON io_markers(project_id);
CREATE INDEX io_markers_frame_idx   ON io_markers(frame_id);

-- A cable. Each endpoint is exactly one of (port, device, io-marker).
-- All foreign-key targets must be in the same project_id as the cable —
-- enforced in code (the CHECK below only enforces the one-non-null rule).
CREATE TABLE cables (
    id              INTEGER PRIMARY KEY,
    project_id      INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    type_id         INTEGER NOT NULL REFERENCES cable_types(id) ON DELETE RESTRICT,
    label           TEXT,
    from_port_id    INTEGER REFERENCES ports(id)      ON DELETE SET NULL,
    from_device_id  INTEGER REFERENCES devices(id)    ON DELETE SET NULL,
    from_io_id      INTEGER REFERENCES io_markers(id) ON DELETE SET NULL,
    to_port_id      INTEGER REFERENCES ports(id)      ON DELETE SET NULL,
    to_device_id    INTEGER REFERENCES devices(id)    ON DELETE SET NULL,
    to_io_id        INTEGER REFERENCES io_markers(id) ON DELETE SET NULL,
    excalidraw_id   TEXT,
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now')),
    CHECK (
        (from_port_id IS NOT NULL) + (from_device_id IS NOT NULL) + (from_io_id IS NOT NULL) = 1
    ),
    CHECK (
        (to_port_id IS NOT NULL) + (to_device_id IS NOT NULL) + (to_io_id IS NOT NULL) = 1
    ),
    UNIQUE (project_id, excalidraw_id)
);
CREATE INDEX cables_project_idx     ON cables(project_id);
CREATE INDEX cables_from_port_idx   ON cables(from_port_id);
CREATE INDEX cables_to_port_idx     ON cables(to_port_id);
CREATE INDEX cables_from_device_idx ON cables(from_device_id);
CREATE INDEX cables_to_device_idx   ON cables(to_device_id);
CREATE INDEX cables_type_idx        ON cables(type_id);

-- Bundles: named groups of cables that physically run together, within
-- a single project (a bundle does not span LOFT ↔ OFFICE).
CREATE TABLE bundles (
    id              INTEGER PRIMARY KEY,
    project_id      INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    name            TEXT NOT NULL,
    auto            INTEGER NOT NULL DEFAULT 0,
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now')),
    UNIQUE (project_id, name)
);
CREATE INDEX bundles_project_idx ON bundles(project_id);

CREATE TABLE bundle_cables (
    bundle_id       INTEGER NOT NULL REFERENCES bundles(id) ON DELETE CASCADE,
    cable_id        INTEGER NOT NULL REFERENCES cables(id)  ON DELETE CASCADE,
    PRIMARY KEY (bundle_id, cable_id)
);
CREATE INDEX bundle_cables_cable_idx ON bundle_cables(cable_id);

-- v4 — connection_requirements: the input m gives the solver.
-- "NAS must connect to Switch via RJ45" is one row. Many per device.
--
-- preferred_cable_type_id is the cable type m intends — the solver
-- needs it to match port colours. NULL means "solver picks" (the solver
-- will pick the unique cable_type that is compatible with both ends'
-- available port types; if ambiguous it surfaces an error for m).
--
-- must_connect = 1 (default) means the solver MUST satisfy this; an
-- unsatisfiable must_connect surfaces as a hard error in the solve
-- result. must_connect = 0 = "nice to have, drop if you run out of
-- ports". Used for templates that over-spec.
--
-- The (from_device_id, to_device_id) pair is normalised on insert so
-- (A,B) and (B,A) are the same requirement — UNIQUE on the unordered
-- pair + cable type prevents duplicates.
CREATE TABLE connection_requirements (
    id                       INTEGER PRIMARY KEY,
    project_id               INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    from_device_id           INTEGER NOT NULL REFERENCES devices(id) ON DELETE CASCADE,
    to_device_id             INTEGER NOT NULL REFERENCES devices(id) ON DELETE CASCADE,
    preferred_cable_type_id  INTEGER REFERENCES cable_types(id) ON DELETE SET NULL,
    must_connect             INTEGER NOT NULL DEFAULT 1 CHECK (must_connect IN (0, 1)),
    notes                    TEXT NOT NULL DEFAULT '',
    -- Order-normalised pair: lo = MIN(from, to), hi = MAX(from, to). Set
    -- in code on insert; the UNIQUE then prevents (A,B,Power) AND
    -- (B,A,Power) from coexisting. Stored alongside the m-facing
    -- from/to so the UI doesn't have to denormalise.
    pair_lo                  INTEGER NOT NULL,
    pair_hi                  INTEGER NOT NULL,
    CHECK (from_device_id != to_device_id),
    UNIQUE (project_id, pair_lo, pair_hi, preferred_cable_type_id),
    created_at               TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at               TEXT NOT NULL DEFAULT (datetime('now'))
);
CREATE INDEX conn_reqs_project_idx ON connection_requirements(project_id);
CREATE INDEX conn_reqs_pair_idx    ON connection_requirements(project_id, pair_lo, pair_hi);
CREATE INDEX conn_reqs_from_idx    ON connection_requirements(from_device_id);
CREATE INDEX conn_reqs_to_idx      ON connection_requirements(to_device_id);
```

### 2.1 Migration sequence

- **001_init.sql** (v3) — projects, frames, devices (no type_id), ports,
  cable_types (5 seeded), io_markers, cables, bundles, bundle_cables.
- **002_device_catalog.sql** (v4) — `device_types` +
  `device_type_ports`. Seeds the built-in catalog (§2.2). Adds
  `devices.type_id` (`ALTER TABLE devices ADD COLUMN type_id INTEGER
  REFERENCES device_types(id) ON DELETE SET NULL`) and the matching
  index.
- **003_connection_requirements.sql** (v4) — `connection_requirements`.
  Also adds `cables.auto` (`ALTER TABLE cables ADD COLUMN auto INTEGER
  NOT NULL DEFAULT 0`) so the solver can distinguish its rows from
  m's hand-drawn ones (§5b.3).
- **004_setup_templates.sql** (v4.1 NEW) — `setup_templates` +
  `setup_template_devices` + `setup_template_requirements`. Seeds 3
  built-in templates ('Living Room', 'Home Office', 'Server Rack').

Slices 1 and 2 already shipped 001. Slice 4 lands 002; slice 5 lands
003; slice 6 lands 004 alongside the solver MVP + templates UI.

### 2.2 Built-in catalog seed (002 INSERTs)

The 14 built-in types m's setup uses today, with their default port
profiles. Stored as `(project_id NULL, built_in 1)`. v4.1 added the
three peripheral types (Screen, Keyboard, Mouse) to support the Home
Office setup template:

| `device_types.name` | `kind` | Default ports (cable_type × count) |
|---|---|---|
| NAS | storage | Power × 1; RJ45 × 1 |
| PC | compute | Power × 1; RJ45 × 1; HDMI × 1; USB × 2 |
| Mac | compute | Power × 1; HDMI × 1; USB × 2 |
| Notebook | compute | Power × 1; USB × 2 |
| TV | display | Power × 1; HDMI × 2 |
| Soundbar | audio | Power × 1; HDMI × 1 |
| Switch | network | Power × 1; RJ45 × 5 |
| fritz | network | Power × 1; RJ45 × 4 |
| ChromeCast | display | Power × 1; HDMI × 1 |
| SteamLink | compute | Power × 1; HDMI × 1; USB × 2 |
| IOx-3 | hub | Power In × 1 (top/back); Power Out × 3 (bottom/front) |
| IOx-6 | hub | Power In × 1 (top/back); Power Out × 6 (bottom/front) |
| IOx-8 | hub | Power In × 1 (top/back); Power Out × 8 (bottom/front) |
| **Screen** | display | Power × 1; HDMI × 1 |
| **Keyboard** | accessory | USB × 1 |
| **Mouse** | accessory | USB × 1 |
| **Multi-plug 3** | hub | Power In × 1 (top/back); Power Out × 3 (bottom/front) |
| **Multi-plug 4** | hub | Power In × 1 (top/back); Power Out × 4 (bottom/front) |
| **Multi-plug 5** | hub | Power In × 1 (top/back); Power Out × 5 (bottom/front) |
| **Multi-plug 6** | hub | Power In × 1 (top/back); Power Out × 6 (bottom/front) |
| **Wifi-plug** | accessory | Power In × 1 (top/back); Power Out × 1 (bottom/front) — pass-through outlet |

v5 (migration 005) added the Multi-plug 3–6 strips and the Wifi-plug
pass-through outlet. v6 (migration 006) re-shaped the IOx-* and
Multi-plug-* profiles to the "1 in on top / N out on bottom" layout —
the IOx-* devices are physical power strips, not USB hubs (m's
hardware), and the Multi-plug-* outputs are now visually distinct from
the input. Convention: `top = back`, `bottom = front`. Existing device
instances keep their already-seeded ports per §2.3 — to pick up the
new layout, delete + re-create the instance.

m can also add **project-custom types** at any time (UI: "+ New device
type" inside the device-create modal) with `project_id = current`.

### 2.3 Why ports are still instance-owned

When m picks a type to create a device, the seeder calls `count` × INSERT
into `ports`. From that moment on, ports are instance-level rows owned by
that device. Deleting a port from this PC doesn't touch other PCs;
changing a type's port profile (in slice 4.5) doesn't retroactively
re-seed already-created devices — it only affects subsequent device
creations.

Trade-off acknowledged: m may want a "re-seed from type" action later
(slice 5+) to wipe + reset a device's ports. Out of v0 scope; not
blocked by the schema.

### 2.4 Setup templates (v4.1 NEW)

A setup template is a named recipe of "device-types to add + connection
requirements between them" that bootstraps a project from blank to
solver-ready in one click. m's three archetypes:

| Template name | Devices | Default requirements |
|---|---|---|
| **Living Room** | TV, Soundbar, ChromeCast | TV ↔ Soundbar (HDMI, must); TV ↔ ChromeCast (HDMI, must) |
| **Home Office** | PC, Screen, Keyboard, Mouse | PC ↔ Screen (HDMI, must); PC ↔ Keyboard (USB, must); PC ↔ Mouse (USB, must) |
| **Server Rack** | NAS, Switch, fritz | NAS ↔ Switch (RJ45, must); Switch ↔ fritz (RJ45, must); fritz ↔ NAS (Power, nice) |

> "Screen", "Keyboard", "Mouse" are added to the v4 built-in catalog
> alongside the existing 11 (Screen: Power × 1 + HDMI × 1; Keyboard: USB × 1;
> Mouse: USB × 1). Migration 002 grows to seed 14 built-ins.

Schema (`004_setup_templates.sql`):

```sql
-- A named recipe: a list of device types + requirements between them.
CREATE TABLE setup_templates (
    id              INTEGER PRIMARY KEY,
    name            TEXT NOT NULL UNIQUE,
    description     TEXT NOT NULL DEFAULT '',
    built_in        INTEGER NOT NULL DEFAULT 0,
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now'))
);

-- The devices a template stamps into a project. suggested_name is
-- pre-filled into the apply-template form; m can override.
CREATE TABLE setup_template_devices (
    id              INTEGER PRIMARY KEY,
    template_id     INTEGER NOT NULL REFERENCES setup_templates(id) ON DELETE CASCADE,
    device_type_id  INTEGER NOT NULL REFERENCES device_types(id)    ON DELETE RESTRICT,
    suggested_name  TEXT,                        -- "TV", "Bedroom TV", "Mac (work)"
    sort_order      INTEGER NOT NULL DEFAULT 0
);
CREATE INDEX setup_template_devices_template_idx ON setup_template_devices(template_id);

-- Requirements between devices in the template, addressed by
-- `setup_template_devices.id` (not the runtime device id — they're
-- resolved at apply time).
CREATE TABLE setup_template_requirements (
    id                       INTEGER PRIMARY KEY,
    template_id              INTEGER NOT NULL REFERENCES setup_templates(id) ON DELETE CASCADE,
    from_template_device_id  INTEGER NOT NULL REFERENCES setup_template_devices(id) ON DELETE CASCADE,
    to_template_device_id    INTEGER NOT NULL REFERENCES setup_template_devices(id) ON DELETE CASCADE,
    preferred_cable_type_id  INTEGER REFERENCES cable_types(id) ON DELETE SET NULL,
    must_connect             INTEGER NOT NULL DEFAULT 1 CHECK (must_connect IN (0, 1)),
    CHECK (from_template_device_id != to_template_device_id)
);
CREATE INDEX setup_template_reqs_template_idx ON setup_template_requirements(template_id);
```

API:

```
GET  /api/setup-templates                          → [SetupTemplate {id, name, description, built_in,
                                                                     devices: [{id, device_type_id,
                                                                                device_type: {…},
                                                                                suggested_name, sort_order}],
                                                                     requirements: [{id, from_template_device_id,
                                                                                     to_template_device_id,
                                                                                     preferred_cable_type_id,
                                                                                     must_connect}]}, …]
                                                     Read-only; built-ins are not editable via API in v4.1.

POST /api/projects/:pid/apply-template             ← {
                                                       template_id: <int>,
                                                       name_overrides: { <template_device_id>: "<name>", … },
                                                       skip_devices: [<template_device_id>, …]    # optional
                                                     }
                                                     → {
                                                       devices_added: [Device, …],
                                                       requirements_added: [ConnectionRequirement, …],
                                                       skipped_devices: [{template_device_id, reason}, …]
                                                     }
                                                     Idempotency:
                                                     - A name collision with an existing device in the
                                                       project skips that template device (reason = "name
                                                       already in use"). Caller can pass `name_overrides`
                                                       to resolve.
                                                     - Requirements whose endpoints both resolve fire;
                                                       any whose endpoint was skipped are themselves
                                                       skipped (logged in `requirements_skipped[]` — same
                                                       shape).
                                                     The whole call runs in a single transaction.
```

The seed migration creates the 3 built-ins + their template_devices and
template_requirements rows referencing the 14 built-in `device_types` and
the 5 built-in `cable_types`. No project_id anywhere — templates are
global.

**FK shape — why `project_id` on every project-scoped row, not just transitively:**

The structural truth is `cable → port → device → frame → project`. But
project-scoped queries ("give me all cables in OFFICE") would otherwise need
three joins. Denormalising `project_id` onto every project-scoped row is a
small, load-bearing pragma: `cables WHERE project_id=?` is a one-column
index hit. The cost: code must keep `project_id` consistent with `frame_id`
/ `device_id` on insert+update. That's enforced at the Go layer
(`internal/db/store.go` setter functions), not by SQL — `CHECK` constraints
in SQLite can't reference another table.

`cable_types` is the **one global table** — it has no `project_id`.
Cables reference it cross-project. Renaming or recolouring a type updates
the legend everywhere immediately and re-renders every cable of that type
on the next paint.

`ON DELETE CASCADE` from `projects` cleanly wipes a project's whole subgraph
in one statement, which is what we want when m says "delete OFFICE". The
cascade does **not** touch `cable_types` (no FK to projects).

---

## 3. Go HTTP API

Single binary `cmd/cablegui`, `net/http`, no router framework. Listens on
`0.0.0.0:7777` by default (overridable via `CABLEGUI_ADDR`). Static frontend
from `embed.FS` at `/`, JSON API under `/api/`.

```
GET    /                                            → index.html (embedded)
GET    /assets/*                                    → JS/CSS/SVG (embedded)
GET    /api/healthz                                 → 200 ok

# Projects — top-level
GET    /api/projects                                → [Project, …]
POST   /api/projects                                ← {name, drawing_name?, description?}
                                                     If drawing_name is omitted, server defaults to
                                                     "<name>.excalidraw". No cable-type seeding —
                                                     cable_types is global (see /api/cable-types).
GET    /api/projects/:pid                           → full snapshot
                                                      {project, frames, devices, ports, cables,
                                                       io_markers, bundles}
                                                      Plus the global cable_types (clients can also
                                                      fetch them via /api/cable-types). Editor's
                                                      one-shot loader.
PATCH  /api/projects/:pid                           ← partial {name, drawing_name, description}
DELETE /api/projects/:pid?confirm=<name>            Confirmation guardrail — the query param must
                                                     equal the project's current name. 400 if missing
                                                     or mismatched. Cascades through all child rows
                                                     (frames, devices, ports, cables, io_markers,
                                                     bundles, bundle_cables). Does NOT touch
                                                     cable_types.

# Cable types — GLOBAL, NOT under a project
GET    /api/cable-types                             → [CableType, …]
POST   /api/cable-types                             ← {name, color}            # name must be unique globally
PATCH  /api/cable-types/:id                         ← {name?, color?}          # affects every project's legend + every cable using this type
DELETE /api/cable-types/:id                                                    # blocked if any cable still references it (ON DELETE RESTRICT)

# Inside a project — everything below scoped under :pid
GET    /api/projects/:pid/frames
POST   /api/projects/:pid/frames                    ← {name, x, y, width, height}
PATCH  /api/projects/:pid/frames/:id
DELETE /api/projects/:pid/frames/:id

GET    /api/projects/:pid/devices
POST   /api/projects/:pid/devices                   ← {name, type_id?, frame_id?, x, y, width, height, color?}
                                                     v4: type_id (optional) seeds ports from the catalog;
                                                     without it, a freeform device (no ports) is created.
PATCH  /api/projects/:pid/devices/:id               (e.g. {x, y} on drag). type_id can be set or cleared;
                                                     clearing does NOT delete existing ports (instance-owned).
DELETE /api/projects/:pid/devices/:id

GET    /api/projects/:pid/devices/:id/ports
POST   /api/projects/:pid/devices/:id/ports         ← {type_id, x_offset, y_offset, label?}
PATCH  /api/projects/:pid/ports/:id
DELETE /api/projects/:pid/ports/:id

GET    /api/projects/:pid/cables
POST   /api/projects/:pid/cables                    ← {type_id, from_{port|device|io}_id,
                                                      to_{port|device|io}_id, label?}
PATCH  /api/projects/:pid/cables/:id
DELETE /api/projects/:pid/cables/:id

GET    /api/projects/:pid/io-markers
POST   /api/projects/:pid/io-markers                ← {frame_id?, label, x, y}
PATCH  /api/projects/:pid/io-markers/:id
DELETE /api/projects/:pid/io-markers/:id

GET    /api/projects/:pid/bundles                   → [{Bundle, cable_ids: [int]}, …]
POST   /api/projects/:pid/bundles                   ← {name, cable_ids: [int]}
GET    /api/projects/:pid/bundles/suggestions       → [{name, cable_ids}, …]    (see §5)
PATCH  /api/projects/:pid/bundles/:id
DELETE /api/projects/:pid/bundles/:id

# v4 — Device-type catalog (mostly global, project-scoped writes for custom rows)
GET    /api/device-types                            → built-in catalog (project_id NULL) — read-only listing
GET    /api/projects/:pid/device-types              → built-ins + this project's custom types, merged
POST   /api/projects/:pid/device-types              ← {name, kind?, icon?, description?, ports: [{cable_type_id, count, label_prefix?, edge?}]}
                                                     Creates a project-custom row (built_in=0); inserts
                                                     device_type_ports rows in the same transaction.
PATCH  /api/projects/:pid/device-types/:id          ← partial. Only project-custom types are PATCHable;
                                                     mutating a built-in row → 403 (UI hides edit affordance).
                                                     Editing ports replaces the device_type_ports rows;
                                                     existing devices' ports are NOT retroactively reseeded.
DELETE /api/projects/:pid/device-types/:id          Only project-custom; built-ins → 403.
                                                     ON DELETE SET NULL on devices.type_id so devices
                                                     keep their already-seeded ports.

# v4 — Connection requirements (the solver's input)
GET    /api/projects/:pid/connection-requirements   → [ConnectionRequirement, …]
POST   /api/projects/:pid/connection-requirements   ← {from_device_id, to_device_id,
                                                       preferred_cable_type_id?, must_connect?, notes?}
                                                     Server normalises (from, to) into (pair_lo, pair_hi)
                                                     before insert; duplicate (project, pair_lo, pair_hi,
                                                     preferred_cable_type_id) → 409 conflict.
PATCH  /api/projects/:pid/connection-requirements/:id
DELETE /api/projects/:pid/connection-requirements/:id

# v4 — Solver
POST   /api/projects/:pid/solve                     ← {} (or {?preview=1} to compute without applying)
                                                     → {
                                                       cables_added:    [Cable, …],
                                                       cables_kept:     [int, …],   # ids preserved by the diff
                                                       cables_removed:  [int, …],   # ids deleted (auto cables only)
                                                       bundles_added:   [{Bundle, cable_ids: [int]}, …],
                                                       bundles_removed: [int, …],
                                                       unsatisfied:     [{requirement_id, reason}, …],
                                                       warnings:        [string, …],
                                                     }
                                                     Default applies in a single transaction. ?preview=1
                                                     returns the same shape without writing. User-created
                                                     cables (auto=0 in the cables table; see §5.1) are
                                                     never touched — the solver only adds/removes its own.

# v4 — Solver quick-fix combo endpoint (powers the inspector's
# "+ Add <type> port to <device> and re-solve" button — §5b.4).
POST   /api/projects/:pid/devices/:id/ports-and-resolve
                                                     ← {type_id: <int>,
                                                       label?: <str>,
                                                       x_offset?: <num>, y_offset?: <num>}
                                                     → {port: Port, solve: <solve response>}
                                                     Single tx: inserts the port + re-runs solve. Used by
                                                     the quick-fix UI so the unmet badge resolves in one
                                                     server round-trip.

# v4.1 — Setup templates
GET    /api/setup-templates                         → [SetupTemplate, …]
                                                     Read-only listing of built-in (and any project-custom,
                                                     post-v4.1) templates with their device/requirement
                                                     shapes (see §2.4).
POST   /api/projects/:pid/apply-template            ← {template_id: <int>,
                                                       name_overrides?: { <template_device_id>: "<name>" },
                                                       skip_devices?: [<template_device_id>, …]}
                                                     → {devices_added: [Device, …],
                                                       requirements_added: [ConnectionRequirement, …],
                                                       skipped_devices: [{template_device_id, reason}, …],
                                                       requirements_skipped: [{template_requirement_id, reason}, …]}
                                                     Idempotent in spirit: name collisions surface in
                                                     skipped_devices; m resolves with name_overrides on
                                                     re-apply. Whole call is one transaction.

# Sync — export only in MVP
POST   /api/projects/:pid/sync/export               → writes the project's drawing to mExDraw
                                                     (overwrites previous version; mExDraw keeps
                                                     git-version-history sidecar)
```

### 3.1 v4 wire-shape additions

- `ConnectionRequirement` (response):
  `{id, project_id, from_device_id, to_device_id, preferred_cable_type_id|null, must_connect: bool, notes, created_at, updated_at}`.
- `DeviceType` (response):
  `{id, project_id|null, name, kind, icon|null, description, built_in: bool, ports: [{cable_type_id, count, label_prefix, edge, sort_order}]}`.
- `cables` gets an `auto: bool` field on the row (slice 5.5 migration adds
  the column with default 0; the solver sets 1 on its own creations). The
  v3 cable rows m hand-drew keep `auto=0`. `POST /api/.../cables`
  continues to default `auto=0`; only the solver writes `auto=1`.

No `POST /api/sync/import` in MVP. Import is post-MVP and only ever serves
a one-shot migration use case (e.g. seeding LOFT from the legacy
Cable-Management drawing if m later changes his mind).

All write endpoints return the updated row. Errors are
`{error: "string", details?: any}`. No auth.

mExDraw HTTP credentials live in `MEXDRAW_BASE_URL` (e.g.
`https://mxdrw.msbls.de`) + `MEXDRAW_TOKEN` (bearer). The exporter calls
`PUT $MEXDRAW_BASE_URL/api/drawings/<drawing_name>.excalidraw` with the
generated scene JSON.

---

## 4. Export — DB → Excalidraw (visual-grammar conformance)

CableGUI generates a `.excalidraw` scene from a project's rows. The seed
drawing's grammar is the contract.

### 4.1 Element mapping

| DB row | Excalidraw element | Notes |
|---|---|---|
| `projects.drawing_name` | drawing filename in mExDraw | one drawing per project |
| `frames` | `type=frame`, `name=frames.name` | x/y/width/height straight across |
| `devices` | `type=rectangle` + bound `text` with `name` | `strokeColor=color`, `frameId=frames.excalidraw_id` |
| `ports` | `type=ellipse`, ~12×9 | `strokeColor=type.color`, absolute pos = `(device.x + port.x_offset, device.y + port.y_offset)`, no containerId binding (matches seed) |
| `io_markers` | `type=diamond` with bound `text=label` | small (~30×30), `strokeColor` = the Power cable type's colour |
| `cables` | `type=arrow` | `strokeColor=type.color`, `startBinding.elementId` = port/device/io excalidraw_id, same for end |
| `cable_types` legend (global) | one `type=text` row per `cable_types` row, top-left of the project's first frame | `strokeColor=color`, `text=name`. Pulled from the global table, regenerated each export. |
| `bundles` | (rendering open question — see §5) | post-MVP: render as a thick path; v0: ignored on export |

### 4.2 Element IDs are stable across exports

Every CableGUI row carries `excalidraw_id` (TEXT, generated on first export
via `crypto/rand` → 21-char Excalidraw-style ID). On re-export the same row
reuses the same ID. This means:

- m's `.excalidraw` collaborator-cursors, element-comments, and undo
  history survive a re-export.
- If m manually edits a port colour in Excalidraw (someday, once import
  exists), we can match it back to the right DB row by ID.

### 4.3 What is *not* in the export

- The legend's decorative separator lines (the 5 `type=line` elements in
  the seed) — purely visual, m said they're not load-bearing.
- Big "enclosure" rectangles like the seed's `tAs8zMDI` desk-surface. In
  v0 those are imported as plain devices when m draws them, and exported
  as plain rectangles too. No zone/enclosure concept in the schema.

### 4.4 Wall-outlet IO markers

A cable with `to_io_id != NULL` exports to an arrow whose `endBinding`
points to the IO diamond's element ID. The diamond is rendered with a small
`IO` text label (or `m.label` if customised). No pair link.

---

## 5. Bundle detection — project-scoped

A *bundle* is a set of cables that physically run together. Bundles never
cross projects (a LOFT bundle and an OFFICE bundle are separate).

MVP detection rule, on `GET /api/projects/:pid/bundles/suggestions`:

```
Within project :pid, group cables by (from_endpoint, to_endpoint):
    from_endpoint = (kind, id) where kind ∈ {port, device, io} and id = whichever *_id is set
    to_endpoint   = same shape
Treat the endpoint pair as unordered: {A, B} == {B, A}
A candidate suggestion = any group with ≥ 2 cables.
```

i.e. "two or more cables run between the same two endpoints" → almost
certainly a bundle. Types in the group can be mixed (Power + USB + HDMI
from desk → wall).

Suggestions are reviewed in the UI; clicking *Accept* creates a real
`bundles` row (`auto=0`). m can also create bundles manually by
shift-clicking cables.

Rendering bundles in the SVG view is a slice 6+ concern; in the export
they're ignored in v0 (open question §9).

---

## 5b. v4 — Solver

The solver is the headline addition in v4. m's product-vision sentence
maps onto it directly:

> "I say what devices we have, the app tells me how to bundle cables and
> how the most efficient connection looks like"

The solver reads a project's `devices` (with their `ports`) and
`connection_requirements`, and writes a set of solver-owned `cables`
(rows with `auto=1`) + `bundles`. m's hand-drawn cables (`auto=0`) are
left strictly alone — the solver only adds and removes its own.

### 5b.1 Objective: maximum bundling — schematic only

CableGUI is a **schematic**, not a physical-routing tool. Cables are
straight lines between endpoints; the solver has no model of walls,
floors, cable trays, or path geometry. "Maximum bundling" therefore
reduces to a single rule on the schematic:

> When two or more cables share the same endpoint pair (device A ↔
> device B), group them into one bundle.

This is the v3 endpoint-pair rule, applied to the solver's output. m's
"visually cleaner setups" benefit comes from the bundle being a single
labelled set in the inspector + a single mixed-colour glyph in the
render (slice 9+), rather than from any path optimisation. Anything
about trunks, frame-edge corridors, or auto-routing is out of scope —
filed for "post-v0 ambient" in §8.

### 5b.2 Algorithm (v0)

Pure function. No graph search; no LP; no path optimisation. Single
pass with greedy port allocation.

```
solve(project) ⇒ {add, remove, bundles, unsatisfied}:
  let auto_cables_before = SELECT * FROM cables WHERE project=p AND auto=1
  let port_free := {port_id -> bool}  initialised TRUE for every port
                  minus ports already used by manual cables (auto=0)

  for each requirement r in order(must_connect DESC, id ASC):
    let ct = r.preferred_cable_type_id
          ?? auto_pick_cable_type(r.from_device, r.to_device)
          ?? fail("ambiguous")
    let pa = first_free_port(r.from_device, ct, port_free)
    let pb = first_free_port(r.to_device,   ct, port_free)
    if !pa or !pb:
      if r.must_connect: unsatisfied.push({r.id, reason})
      else:              skip
      continue
    port_free[pa] = port_free[pb] = false
    add.push(cable{type=ct, from_port=pa, to_port=pb, auto=1})

  // Bundle by endpoint-pair (v3 rule, applied only to auto cables).
  for each (device_a, device_b) pair with ≥ 2 add-cables:
    bundles_add.push({auto=1, cables: those add-cables})

  // Diff against auto_cables_before to compute remove[] (any prior auto
  // cable whose (from, to, type) doesn't appear in add[]).
  remove = auto_cables_before - add
  return {add, remove, bundles_add, unsatisfied}
```

`first_free_port(device, cable_type, free_map)` picks the lowest-id port
on the device whose `type_id` matches and that is still free, returning
NULL if none. The `lowest-id` tiebreak is deterministic so repeated
solves produce the same plan.

`auto_pick_cable_type(from, to)` (used when `preferred_cable_type_id` is
NULL): find the set of cable types `T = ports(from).types ∩
ports(to).types`. If `|T| == 1`, return it. If `|T| > 1`, fail
("ambiguous; specify preferred_cable_type_id"). The UI surfaces this
as a "specify type" inline edit on the requirement.

### 5b.3 Solver-owned vs. user-owned cables

`cables.auto` distinguishes them.

| Operation | Effect on `auto=0` cables | Effect on `auto=1` cables |
|---|---|---|
| POST /api/.../cables (m draws by hand) | inserts auto=0 | n/a |
| PATCH cables (m moves endpoint, relabels) | applies | applies (and the cable is "promoted" to auto=0 — m owns it now) |
| DELETE cables | applies | applies |
| POST /api/.../solve | left alone (their used ports are reserved before the solver runs) | replaced wholesale (remove[] + add[] in one tx) |

This way a manual cable m doesn't want the solver to second-guess
survives every solve. If m wants the solver to take it over, he deletes
his hand-drawn cable and re-solves; the solver re-creates an equivalent
auto cable.

### 5b.4 When solver fails — quick-fix UX

Three classes of failure surface in the response's `unsatisfied[]`:

1. **No compatible cable type** — `T = ports(from).types ∩
   ports(to).types` is empty (e.g. a Power-only device to an HDMI-only
   device).
2. **Ambiguous cable type** — `|T| > 1`, no preferred set on the
   requirement.
3. **No free port** — the cable type matches but every port on one side
   is already used.

The solver does **not** auto-add ports without m's consent. v4.1 ships
an explicit one-click quick-fix per class of failure, surfaced as a red
badge on the affected device in the inspector (§7) and as a button on
each `unsatisfied[]` entry in the preview-diff modal:

| Failure class | Quick-fix button | What it does |
|---|---|---|
| No compatible cable type | **"+ Add &lt;preferred_type&gt; port to &lt;device&gt; and re-solve"** | POST `/api/projects/:pid/devices/:id/ports` with `type_id=preferred_type` + sensible default offset, then immediately POST `/solve` again. The preferred_type is the requirement's `preferred_cable_type_id`. If the requirement has no preferred type, the button reads "Specify cable type" and opens an inline cable-type picker on the requirement instead. |
| Ambiguous cable type | **"Specify cable type"** | Opens an inline picker on the requirement row with the candidates from `T` pre-listed. On select → PATCH the requirement → re-solve. |
| No free port | **"+ Add &lt;type&gt; port to &lt;device&gt; and re-solve"** | Same as the no-compat case but the `type` is already determined (it's the requirement's preferred or auto-picked type). Adds a port on whichever side ran out (the response's `reason` carries `which_side`). |

All three quick-fixes do their work in a single round-trip request from
the UI perspective: the click fires a POST that either chains the port
insert + the re-solve server-side, or fires both calls back-to-back from
the client (server-side chaining is simpler — see §3.2 for the endpoint
shape).

The quick-fix never adds a port silently; the button text always names
the device + cable type so m sees what's about to mutate.

### 5b.5 Preview vs. apply

`?preview=1` returns the same shape without writing. The UI shows a diff
modal with `add[]`, `remove[]`, `unsatisfied[]`; m clicks Apply to fire
the same endpoint without `preview=1`. Default (no flag) applies
immediately. Live-solve (no Solve button — every requirement edit
triggers a debounced re-solve) is parked at slice 9+ as an opt-in.

---

## 6. Sync — export-only for v0

```
                ┌─────────────────────┐
                │ CableGUI DB (truth)  │
                └──────────┬──────────┘
                           │
              export       ▼
              (push)   ┌────────────────────────┐
                       │ <project>.excalidraw   │
                       │   on mxdrw.msbls.de    │
                       └────────────────────────┘
```

- CableGUI UI → DB: synchronous (every drag/add/remove persists immediately).
- DB → Excalidraw: **manual** button "Export to Excalidraw" in the header,
  per project. Calls `POST /api/projects/:pid/sync/export`.
- Excalidraw → DB: **not implemented** in v0. Anything m draws in
  Excalidraw stays in Excalidraw until he redraws it in CableGUI.

This keeps the v0 scope tight: no conflict resolution, no element-diff
import, no auto-debounce. mExDraw keeps its own version history (git
sidecar in the mdraw deploy) so a bad export is recoverable from there.

When mxdrw is unreachable: the export button shows a tooltip and disables;
the editor keeps working against the local DB.

Post-MVP, import returns as a one-shot migration tool (separate
`cablegui-migrate` CLI tool, not part of the running server) for seeding
new projects from existing `.excalidraw` files.

---

## 7. UI flows

The editor lives at `/`. Layout:

```
┌────────────────────────────────────────────────────────────────────┐
│ CableGUI   [LOFT ▾ projects-picker]            [Export] [+ Project] │  ← header
├────────┬───────────────────────────────────────────────────────────┤
│        │                                                           │
│ Legend │                                                           │
│        │                                                           │
│ Power  │              Diagram surface (SVG)                        │
│ USB    │                                                           │
│ HDMI   │       ┌─desk─────────────┐  ┌─rack──────────┐             │
│ DP     │       │ [Mac] [Screen] … │  │ [NAS] [fritz] │             │
│ RJ45   │       └──────────────────┘  └───────────────┘             │
│ + Type │                                                           │
│        │                                                           │
│ Tools  │                                                           │
│  + Dev │                                                           │
│  + Frm │                                                           │
│  + IO  │                                                           │
│  draw  │                                                           │
│        │                                                           │
├────────┴───────────────────────────────────────────────────────────┤
│ Inspector (selection-dependent: project / frame / device / port /  │
│            cable / bundle details and actions)                     │
└────────────────────────────────────────────────────────────────────┘
```

### Flow: pick a project

Header has a dropdown "LOFT ▾". Clicking it lists all projects from
`GET /api/projects`; clicking one swaps the diagram (`GET /api/projects/:pid`
loads the full snapshot in one round-trip). The picker also shows a
`+ New Project` action → modal with `name`, `drawing_name` (defaults to
`<name>.excalidraw`), `description` → `POST /api/projects` → switches to
the new project (which has 5 seeded cable types and no frames yet).

The currently active project's id is kept in URL state
(`/?project=LOFT`) so reload returns to the same project.

### v4.1 — Flow: apply a setup template

The New Project modal gains a **"or start from a template"** section
under the description field. Each built-in template ('Living Room',
'Home Office', 'Server Rack') is a clickable card listing its devices +
the requirement edges between them. Selecting one expands an inline
override form:

- A pre-filled name for each template device (m can edit each, e.g.
  rename `TV` to `Bedroom TV`).
- Per-device "skip" checkbox.

On Create, the server does `POST /api/projects` first; on success,
immediately fires `POST /api/projects/:pid/apply-template` with the
collected overrides. The response's `devices_added` + `requirements_added`
are merged into the local snapshot and the project switches to it,
already populated.

For an already-existing empty project, the inspector's project header
shows an **"Apply template"** action that opens the same override form
without the project-create round-trip.

Once the template has stamped its devices + requirements, hit **Solve**
(§7 "Flow: run the solver") to produce the wired diagram.

### Flow: add a frame

1. `+ Frm` in the left toolbar (or `F`).
2. Click + drag on the canvas → rubber-band rectangle becomes a frame.
3. Name prompt centered in the frame; Enter → `POST .../frames`.

### Flow: add a device (v4 — type-aware)

1. `+ Dev` (or `D`) → click on canvas → device placeholder appears.
2. **First field in the inline namer: type dropdown** (replaces the
   v1 plain-name input). Options pulled from
   `GET /api/projects/:pid/device-types` — built-ins listed first
   grouped by `kind`, then project-custom rows, then `Custom (no type)`.
   Typing in the dropdown filters by `name` (m types "n" → NAS jumps
   to top). Below the dropdown: a name input pre-filled with the type
   name + a digit if a same-named device already exists ("PC", "PC-2").
3. Hit Enter → `POST .../devices` with `type_id` + name. The server
   seeds the ports from `device_type_ports` in the same transaction
   and returns the device with its `ports`.
4. Picking `Custom (no type)` keeps the v3 behaviour: rectangle, no
   ports, m adds ports manually via the inspector.
5. The device renders with its ports already visible along the
   configured edge.

### Flow: add a port

Select a device → inspector shows `+ Port` button. Click → cursor becomes
a "ghost port" of the active cable type (legend selection). Snap to device
edge → click commits → `POST .../devices/:id/ports`.

### Flow: draw a cable

Click a port → port highlights. Hover any other endpoint (port / device /
IO marker) → preview cable drawn in the source's type colour. Click commits
→ `POST .../cables`. `Shift`-click to bind to a whole device. Click an IO
diamond to terminate at a wall outlet.

### Flow: add an IO marker (wall outlet)

`+ IO` (or `I`) → click on canvas → small diamond placed → optional label
text edit → `POST .../io-markers`. By design, the only cables that
terminate at an IO marker are Power cables, but the schema doesn't enforce
that — the UI shows a soft warning if m draws a non-Power cable to an IO.

### Flow: pick / edit a cable type

Legend on the left is interactive and **global** (the same legend shows up
in every project). Click a row → that type becomes the active "drawing
type" for the current project's session. Drag the swatch → colour picker →
updates `cable_types.color` via `PATCH /api/cable-types/:id`. `+ Type` at
the bottom → "new cable type" modal — `POST /api/cable-types`. Names are
globally unique.

The modal for editing / adding shows a banner:
*"Cable types are shared across all projects. Renaming or recolouring
affects every project that uses this type."* Deleting a type that's still
in use by any cable returns a 400 with the offending cable count — the
client surfaces it as an inline error in the modal.

### Flow: drag a device

Pointer-drag → live `transform` on the SVG; on `pointerup`,
`PATCH .../devices/:id` persists `x, y`. Ports follow because their
offsets are relative.

### Flow: bundles

In the inspector with nothing else selected, "Bundle suggestions" pulls
`.../bundles/suggestions`. Each suggestion shows the cables highlighted
on the diagram + an Accept button. Manual: shift-click multiple cables →
"Group as bundle" → name it → save.

### v4 — Flow: declare connection requirements

The left sidebar gains a **Requirements** section under the legend:

```
Cable types
  Power, USB, HDMI, DP, RJ45, + Type

Requirements                       ← new in v4
  NAS ↔ Switch       RJ45    must
  PC  ↔ TV           HDMI    must
  Mac ↔ Soundbar     HDMI    nice
  + Requirement
```

Click `+ Requirement` → modal with two device pickers (autocomplete from
the project's current devices), a cable-type picker (defaults to
auto-resolve if the device pair has only one matching type), and a
must/nice toggle. `POST .../connection-requirements`.

Alternative gesture (no tool armed, no selection): **drag from device A
to device B** to seed a requirement modal with the pair pre-filled. The
solver-edge preview drags out from the source device's edge in a thin
dashed line until release.

m can also right-click a requirement row → edit / delete.

### v4 — Flow: run the solver

Header gains a **Solve** button next to **Export**.

1. Click Solve (or `S`) → `POST /api/projects/:pid/solve?preview=1`.
2. A diff modal opens listing `add[]`, `remove[]`, `unsatisfied[]` — the
   canvas behind it dims and previews the new cables in a translucent
   stroke + the to-be-removed cables in a strikethrough red.
3. Buttons:
   - **Apply** → fires `POST .../solve` (no `preview`), applies in one
     transaction, closes the modal, re-renders canvas with the real
     cables in place.
   - **Cancel** → leaves everything as it was.
4. Unsatisfied requirements get their own list at the bottom of the
   modal, each with a quick-action button: "Specify type", "+ Add port
   to device X", or "Drop requirement (set must=0)".

If `unsatisfied[]` is non-empty, the Solve button stays in a
soft-error state (yellow) until either every requirement is satisfiable
or m explicitly accepts the partial plan.

### v4 — Inspector states

| Selection | Inspector shows |
|---|---|
| nothing | empty, with "Bundle suggestions" + "Project requirements" headlines |
| project header | name, drawing_name, description (editable), device count, requirement count, Solve / Export buttons |
| frame | name (editable), x/y/w/h, contained-device count, delete |
| **device** | name + type + icon, ports grid (type / label / connected? / +Port), **unmet requirements list** with red badges. Each badge carries a single quick-fix button — "+ Add &lt;type&gt; port to &lt;device&gt; and re-solve" (no-compat-type / no-free-port cases) or "Specify cable type" (ambiguous case) per §5b.4. delete |
| **port** | type, label, parent device, current cable (if any), delete |
| **cable (auto=1)** | source/target, type, driving requirement (clickable → opens requirement edit), parent bundle (if any), label, "Promote to manual" (sets auto=0) |
| cable (auto=0) | as v3 — type, source/target, label, delete |
| bundle | name, member cables (clickable to focus), the endpoint pair (`Device A ↔ Device B`), auto-detected flag |

### Keyboard

`P` switch project, `F` add frame, `D` add device, `I` add IO marker,
`T` start cable from selected port, `R` add requirement,
**`S` solve project (v4)**, `E` export, `Esc` cancel, `Backspace` delete
selection, `?` show shortcuts.

---

## 8. First slices — v4 reshape

Slices 1 + 2 have shipped (see git history). v4 inserts new slices ahead
of the original 3-5 because the solver depends on the catalog + the
requirements model, not on manual cable drawing. The old "manual port +
cable draw" slice is still in scope as a tweak path on the solver
output, but it follows the solver instead of leading.

| # | Slice | Status | What's shipped |
|---|---|---|---|
| 1 | **Bootstrap + project CRUD + global cable_types** | ✅ shipped | See git: branch `mai/picasso/slice-1-bootstrap`. |
| 2 | **Frames + devices + drag** | ✅ shipped | See git: branch `mai/picasso/slice-2-frames-devices`. |
| **3 (was 4)** | **IO markers + cable-type editing** | pending | Unchanged scope. `+ IO` places a wall-outlet diamond. Legend swatch is a colour picker; renaming a type updates the legend on the fly. `+ Type` adds new global types. |
| **4 (NEW)** | **Device-type catalog + type-aware device create** | pending | Migration 002: `device_types` + `device_type_ports`, seeded with the 11 built-ins (§2.2). Migration adds `devices.type_id`. API: `GET /api/device-types`, `GET /api/projects/:pid/device-types`. Frontend: the +Dev inline namer becomes a type dropdown + name input; choosing a built-in type seeds the device's ports on the backend. Picking `Custom (no type)` falls back to v3 freeform. m can create a typed NAS + see its Power + RJ45 ports appear on the canvas. |
| **4.5 (NEW)** | **Manage device-type catalog (per project)** | pending | Modal: `POST/PATCH/DELETE /api/projects/:pid/device-types` for project-custom rows. Edit affordance hidden for built-ins. Lets m add an exotic device type without contributing to the built-in catalog. Validation: a custom type can't share a name with a built-in (already enforced by `UNIQUE(project_id, name)` + a separate code-level check against built-ins). |
| **5 (NEW)** | **Connection requirements UI + CRUD** | pending | Migration 003: `connection_requirements`. API: full CRUD under `/api/projects/:pid/connection-requirements`. Frontend: left-sidebar "Requirements" section, `+ Requirement` modal (autocomplete from project's current devices, cable-type picker, must/nice toggle). Drag from device A to device B gestures the same modal pre-filled. Inspector for a selected device lists its requirements. |
| **6 (v4.1 EXPANDED)** | **Solver MVP + Solve button + setup templates** | pending | `POST /api/projects/:pid/solve` with `?preview=1` support. v0 algorithm (§5b.2): pure-function, greedy port allocation, endpoint-pair bundling. Migration 003 adds `cables.auto`. Header gains a Solve button that opens the preview-diff modal. m clicks Solve → sees the cable plan + unmet requirements (each with its quick-fix button per §5b.4) → applies. **Folded in v4.1: setup templates.** Migration 004 adds `setup_templates` + `setup_template_devices` + `setup_template_requirements` and seeds 3 built-ins ('Living Room', 'Home Office', 'Server Rack'). API: `GET /api/setup-templates`, `POST /api/projects/:pid/apply-template`. UI: a "Templates" section in the New Project modal + an "Apply template" action on empty projects → seeds devices + requirements in one transaction → Solve produces the wired diagram. |
| **7 (was 3, slimmed)** | **Manual port + manual cable draw** | pending | The v3 flow as a tweak path on solver output. `+ Port` on an instance-owned device; click-port → click-port creates a hand-drawn cable (`auto=0`). Used to override the solver's choices or to extend its plan. |
| **8 (was 5)** | **Export to mxdrw.msbls.de** | pending | `POST .../sync/export` writes a `.excalidraw` scene per the visual grammar (§4). Bundles ignored on export in v0. |

Slices 9+ (not promised for the first coder shift):
- Live-solve mode: re-run solver on every device/requirement edit with a debounce + previewed-but-not-applied diff in a toast. Opt-in toggle in project settings.
- Bundle rendering in the SVG (a single thick line with mixed-colour stops between the endpoint pair, plus a small badge with the cable count). Cables in a bundle still render as their individual lines underneath; the bundle is a visual overlay m can toggle.
- "Re-seed from type" action on a device.
- Custom setup templates (m authors them in-UI, not just the built-in three).
- Cable inventory metadata (length/SKU) if m later wants it.
- Dark mode.

Out of scope, period (would change CableGUI's mental model): path
routing, cable-tray polylines, frame-edge corridors, wall-axis bundling,
3D, anything that treats a cable as more than a labelled endpoint pair.

---

## 9. Open questions for m — all closed in v4.1

The six v4 questions are now answered. Locked answers:

1. **Where do paths come from?** → **Nowhere — CableGUI is a schematic.**
   Cables are straight lines between endpoints. The solver does not
   route, the renderer does not route, and "maximum bundling" reduces to
   the endpoint-pair rule (§5b.1). Anything resembling a path, trunk,
   cable tray, or frame-edge corridor is **out of scope, period**
   (§8 "Out of scope, period").
2. **Live solve or button-only?** → **Button-only for v0.** Live-solve
   stays parked at slice 9+ as an opt-in.
3. **No-compatible-port-pair UX.** → **Explicit quick-fix.** The
   unsatisfied-requirement badge in the inspector carries a single
   button — "+ Add &lt;type&gt; port to &lt;device&gt; and re-solve" —
   that POSTs the port AND fires `/solve` in one UI action. The button
   text always names the device + type, so m sees what's about to
   mutate (§5b.4 + §7).
4. **Setup templates.** → **Folded INTO v4.1, in slice 6.** Migration 004
   adds `setup_templates` + child tables + 3 built-ins. `GET
   /api/setup-templates` and `POST /api/projects/:pid/apply-template`
   ship alongside the solver (§2.4 + §3 + slice 6 in §8). Custom
   templates (m authors his own) parked at slice 9+.
5. **Catalog distribution.** → **SQL seed in migration 002.** No
   external file loader.
6. **Promote to manual.** → **Explicit button** on the cable inspector
   (§7 row "cable (auto=1)"). PATCHes that only update labels stay auto.

No open design questions remain. The coder shift is gated on m's
go/no-go for v4.1 — not on any unanswered design question from picasso.

---

## 10. Deployment on mDock (raw docker)

Inspected mDock's live services on 2026-05-15 to lock the conventions
before writing this:

- All m-built services on mDock live under `/home/m/stacks/<project>/`
  with a single `docker-compose.yml`. Older services in `/home/m/<project>/`
  use the same pattern; the canonical-new path is `stacks/`.
- Compose v2 (`docker compose`), images built from Gitea container registry
  (`mgit.msbls.de/m/<project>:latest`), `restart: unless-stopped` on every
  service, `container_name: <project>` explicit.
- Host port mappings: deliberately collision-free across the host. Existing
  high ports in use include 3300 (mgreen), 3077 (paperless-ai), 7878
  (radarr), 8082 (mgeo-tileserver), 8989 (sonarr), 9696 (prowlarr).
  **Port 7777 is free** — taking it for CableGUI.
- Bind-mount volumes: `/home/m/<project>-data:/app/data` is the canonical
  pattern (mgreen). For project-local data we put `data/` *next to* the
  compose file so a `git pull && docker compose up -d` is the whole deploy:
  `/home/m/stacks/cablegui/data:/app/data`.
- Secrets via `env_file: /home/m/secrets/<project>/.env` (msports-garmin
  pattern). CableGUI only needs `MEXDRAW_TOKEN` for export.
- No reverse proxy on mDock. Services expose ports directly on the LAN
  (mDock = `192.168.178.131` / Tailscale `mdock`). Public exposure goes via
  mlake/Dokploy + Caddy when needed — out of scope for CableGUI (LAN-only).
- Auto-deploy via the Gitea Actions self-hosted runner already installed
  on mDock (`/home/m/act-runner/`, label `self-hosted:host`). Push to
  `main` → workflow on mDock → `docker compose up --build -d`.

### Repo layout for CableGUI

```
CableGUI/
├── cmd/cablegui/main.go        # Go binary
├── internal/
│   ├── db/                    # migrations + store
│   ├── importer/              # post-MVP only (not in MVP)
│   ├── exporter/              # DB → .excalidraw
│   └── server/                # net/http handlers
├── web/                       # embedded static frontend
│   ├── index.html
│   ├── main.js                # ES module entry
│   ├── style.css
│   └── lib/...                # SVG helpers, store, components
├── data/                      # CableGUI runtime DB lives here (gitignored)
│   └── .gitkeep
├── docs/design.md             # this file
├── Dockerfile
├── docker-compose.yml
├── .gitea/workflows/deploy.yml
├── .gitignore                 # data/, *.db, *.db-wal, *.db-shm
├── Makefile                   # build, typecheck, test, run
├── go.mod / go.sum
└── README.md
```

### Dockerfile sketch

Multi-stage; the final image is `scratch` because `modernc.org/sqlite` is
pure Go.

```dockerfile
# syntax=docker/dockerfile:1.7
FROM golang:1.23-alpine AS build
WORKDIR /src
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w" \
        -o /out/cablegui ./cmd/cablegui

FROM gcr.io/distroless/static-debian12:nonroot
WORKDIR /app
COPY --from=build /out/cablegui /app/cablegui
ENV CABLEGUI_ADDR=0.0.0.0:7777
ENV CABLEGUI_DB=/app/data/cablegui.db
USER nonroot:nonroot
EXPOSE 7777
ENTRYPOINT ["/app/cablegui"]
```

### docker-compose.yml (on mDock at `/home/m/stacks/cablegui/`)

```yaml
services:
  cablegui:
    image: mgit.msbls.de/m/cablegui:latest
    container_name: cablegui
    restart: unless-stopped
    ports:
      - "7777:7777"
    environment:
      - TZ=Europe/Berlin
      - CABLEGUI_ADDR=0.0.0.0:7777
      - CABLEGUI_DB=/app/data/cablegui.db
      - MEXDRAW_BASE_URL=https://mxdrw.msbls.de
    env_file:
      - /home/m/secrets/cablegui/.env       # contains MEXDRAW_TOKEN
    volumes:
      - /home/m/stacks/cablegui/data:/app/data
```

LAN URL: `http://mdock:7777` (or `http://192.168.178.131:7777`).

### Gitea Actions deploy workflow

`.gitea/workflows/deploy.yml`:

```yaml
name: deploy
on:
  push:
    branches: [main]

jobs:
  deploy:
    runs-on: self-hosted
    steps:
      - uses: actions/checkout@v4
      - name: Build image
        run: docker build -t mgit.msbls.de/m/cablegui:latest .
      - name: Push image
        run: |
          echo "${{ secrets.GITEA_TOKEN }}" | \
            docker login mgit.msbls.de -u mAi --password-stdin
          docker push mgit.msbls.de/m/cablegui:latest
      - name: Up
        run: |
          cd /home/m/stacks/cablegui
          docker compose pull
          docker compose up -d
```

### Local-development run (no Docker)

```
make run          # go run ./cmd/cablegui → :7777 against ./data/cablegui.db
make typecheck    # tsc --noEmit on web/
make test         # go test ./...
```

The repo has `data/` checked-in-empty (with `.gitkeep`); `data/*.db*` is
gitignored.

---

## 11. v5 — Cable routing via clamps

m's bundling primitive: a **clamp** is a physical anchor on the canvas
(think cable tie / clip). A cable routes from its `from` endpoint,
through zero or more clamps **in order**, to its `to` endpoint. Two
cables that share an ordered pair of consecutive clamps are visibly
bundled along that segment — no detection pass, no inference: the
overlap *is* the bundle.

This replaces the abandoned waypoints + segment-detection approach.
v0's straight-line schematic stays as the empty-clamps case
(`cable_clamps` is empty for a fresh solver-emitted cable).

### 11.1 Schema (migration 007)

```sql
CREATE TABLE clamps (
    id              INTEGER PRIMARY KEY,
    project_id      INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    x               REAL NOT NULL,
    y               REAL NOT NULL,
    label           TEXT NOT NULL DEFAULT '',
    frame_id        INTEGER REFERENCES frames(id) ON DELETE SET NULL,
    excalidraw_id   TEXT,
    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at      TEXT NOT NULL DEFAULT (datetime('now')),
    UNIQUE (project_id, excalidraw_id)
);
CREATE INDEX clamps_project_idx ON clamps(project_id);

CREATE TABLE cable_clamps (
    cable_id        INTEGER NOT NULL REFERENCES cables(id) ON DELETE CASCADE,
    clamp_id        INTEGER NOT NULL REFERENCES clamps(id) ON DELETE CASCADE,
    ord             INTEGER NOT NULL,    -- 1..N along from→to
    PRIMARY KEY (cable_id, ord),
    UNIQUE (cable_id, clamp_id)          -- a cable can't visit the same clamp twice
);
CREATE INDEX cable_clamps_clamp_idx ON cable_clamps(clamp_id);
```

`frame_id` on clamps mirrors devices + IO markers — m can put a clamp
inside a frame and the frame-drag carries it.

`UNIQUE (cable_id, clamp_id)` blocks loops. `ord` is a small int, 1-based;
nothing requires it to be contiguous (m can renumber 1, 2, 3 → 1, 3, 5
during edits and the renderer is fine with that), but the UI keeps them
contiguous on every mutation for sanity.

### 11.2 Cable rendering model

Each cable resolves to a polyline `[from-anchor, clamp₁, clamp₂, …, clampₙ, to-anchor]`
where:
- `from-anchor` / `to-anchor` come from the existing `anchorForEndpoint`
  resolver (port / device / IO).
- clamp anchors are `(clamp.x, clamp.y)` directly — clamps don't have a
  width/height to centre.

For N=0 clamps the result is the v0 straight line. For N≥1 we render
a `<polyline>` instead of a `<line>`.

The endpoint-replug handles from §10 (cable-replug) stay on the **first
and last** vertices. Mid-polyline vertices get their own clamp-handle —
small grab points only on the selected cable, which behave like
clamp-detach when dragged onto empty canvas (drop a clamp off the
cable's path).

### 11.3 Bundle visualisation — derived from shared segments

A **segment** is a directed pair `(A, B)` where A and B are consecutive
nodes of a cable's polyline. Two cables share a segment when their
polyline contains the same A→B (or B→A — segment matching is
undirected).

For each segment, compute `cables[]` — the cables that traverse it.
If `len(cables) ≥ 2`, render the segment as a single thick line on top
of the individual ones:

- **Width**: `2 + N` px (N = cable count). Caps at ~12 px.
- **Colour**: a striped pattern, one stripe per distinct cable type in
  the bundle, ordered by cable_type.id. SVG `<linearGradient>` with
  hard stops produces the stripe band cheaply; render it on a sibling
  `<polyline>` over the individual lines.
- **Tooltip**: `<title>` child listing the cables ("Power · USB · HDMI").

At a clamp where ≥ 2 cables meet, the clamp icon (10×10 rounded square)
shows a small count badge (`×N`) when N > 1. At fan-out points
(endpoint with no clamp before it on the polyline) the individual
coloured lines re-emerge, so m sees which port each strand goes to.

Shared-segment computation is O(C·N̄) where C = #cables and N̄ = average
polyline length. For a v0-sized project (≤ ~30 cables, ≤ ~5 clamps per
cable) this is trivial. We rebuild the segment map on every renderCanvas
— no caching layer.

### 11.4 UI gestures

**+ Clamp tool (`C` shortcut, also a sidebar button):**
- Click empty canvas → place a clamp at the cursor (POST `/clamps`).
  Standalone clamp — not on any cable yet.
- Click a cable line → insert this clamp into that cable. The new clamp
  sits at the click position (snapped to the nearest point on the
  cable's polyline) and its `ord` is computed so it falls between the
  two existing vertices it lies between.

**Drag a cable's mid-segment:**
- Pointerdown on a cable line (not on an endpoint handle) and drag.
  Live preview shows a bend at the cursor. Pointerup:
  - If the cursor is within snap-radius (~16 px) of an existing clamp:
    insert that clamp into the cable's polyline at the right `ord`.
  - Otherwise: create a fresh clamp at the release point and insert it.

**Clamp inspector** (selecting a clamp on the canvas):
- Position (x, y editable + label)
- "Cables through this clamp": list with each cable's two endpoints,
  click → select that cable
- "Remove from this cable" (per row) → DELETE the matching cable_clamps
  row; cable's polyline collapses around the gap.
- "Delete clamp" → cascade-removes from every cable_clamps row.

**Right-click on a clamp icon ON a cable** → "Remove from this cable"
inline.

**Frame drag** carries clamps the same way it carries devices + IO
markers (clamp.frame_id mirrors the existing pattern, drag handler
already iterates frame-contained items).

### 11.5 Relationship to the existing `bundles` table

**Recommendation: keep `bundles` and `bundle_cables`, repurpose them.**

- Implicit/auto bundles → derived live from shared clamp segments. No
  DB rows. The §5 `GET /bundles/suggestions` endpoint stays useful as a
  "you might want to route these through the same clamps" hint.
- Explicit named bundles → still in the `bundles` table. m names a
  group ("desk → wall trunk"), the UI offers "route all members through
  these clamps" as a one-click action. Useful for the case where m
  wants a stable label on a logical bundle that isn't yet routed.

Migration 007 leaves `bundles` + `bundle_cables` untouched. A v6 cleanup
can drop them if m decides the explicit-named path isn't worth keeping.

### 11.6 Solver coupling

The v0 solver still emits **straight cables** — no clamp rows. m
hand-routes after Solve. The solver's preview-diff is unaffected
(solver compares endpoint pairs; clamp routing is independent of the
endpoint identity).

Future v5.1: solver-suggested clamps based on shared paths between
endpoint pairs. Out of scope here.

### 11.7 Export to mxdrw

Clamps map to small diamond elements (separate from IO markers — IO
diamonds are red wall-outlets; clamps are grey routing points).
`excalidraw_id` is stable across re-exports per the existing pattern.

Cable arrows become Excalidraw `arrow` elements with mid-points (the
clamp positions) when N≥1 — Excalidraw supports multi-vertex arrows
via the `points` array. Each `startBinding` / `endBinding` resolves to
the from/to anchor's excalidraw_id; mid-vertices are unbound.

Bundle visualisation (thick striped lines on shared segments) is **not
exported** in v0 — Excalidraw doesn't natively support gradient strokes,
and the mxdrw round-trip would lose them. We export each cable as its
own polyline; bundling is a viewer-only concept.

### 11.8 API additions

```
POST   /api/projects/:pid/clamps                   { x, y, label?, frame_id? } → Clamp
PATCH  /api/projects/:pid/clamps/:id               { x?, y?, label?, frame_id? } → Clamp
DELETE /api/projects/:pid/clamps/:id

POST   /api/projects/:pid/cables/:cid/clamps       { clamp_id, ord? } → CableClamp
DELETE /api/projects/:pid/cables/:cid/clamps/:cmid

# Convenience: re-order clamps on a cable in one call
PUT    /api/projects/:pid/cables/:cid/clamps       { clamp_ids: [int, int, …] }
```

Snapshot endpoint grows two arrays:
- `clamps: []Clamp`
- `cable_clamps: []{ cable_id, clamp_id, ord }`

### 11.9 Open questions for m

1. **Clamp icon shape.** Diamond (overlaps visually with IO markers
   when zoomed out), small filled circle (overlaps with port circles),
   or rounded square `▢` 10×10? Recommend rounded square — distinct from
   everything else on the canvas today.
2. **Snap radius when inserting onto a cable.** ~16 px world-units feels
   right at 1× zoom. Should it scale with zoom (visual constant) or stay
   world-constant (gesture stays the same regardless of zoom)? Recommend
   visual constant — divide by current zoom.
3. **Clamp deletion when shared.** If a clamp is used by 4 cables and m
   clicks "Delete clamp", do we (a) refuse with a "still in use" prompt,
   (b) cascade-remove from all 4 cables, or (c) cascade silently? Current
   draft says cascade silently. Worth a confirmation?
4. **Bundle stripe order.** Cable-type id is stable but arbitrary; visual
   order on a thick line affects readability. Order by stripe-count
   (Power first if 3 Power + 1 USB), or by cable-type-id (deterministic
   but unrelated to importance)? Recommend by-count, ties broken by id.
5. **Solver respect for existing routing.** When m re-runs Solve after
   hand-routing, should the solver preserve existing clamp routing on
   user-owned (`auto=0`) cables? Auto cables are wiped + rebuilt, so
   their clamps disappear with them — that's expected. But manual cables
   with clamps should clearly keep them. Confirm.

### 11.10 Slice plan (post-design)

1. Schema migration + tx-aware store helpers (Create/Update/DeleteClamp,
   AttachClampToCable, DetachClampFromCable, ReorderClamps).
2. HTTP endpoints + snapshot extension.
3. Frontend: clamp render + + Clamp tool + canvas placement (no
   cable attach yet).
4. Cable polyline render via clamps, mid-segment drag-to-clamp,
   clamp inspector.
5. Shared-segment bundle visualisation (gradient stripe + count badge).
6. Export pipeline extension — mxdrw arrows with mid-points + clamp
   diamonds. Bundle viz stays viewer-only.

---

DESIGN v5 READY FOR REVIEW