package web

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/m/projax/store"
)

// handleLinksAdd processes POST /i/{path}/links/add. Accepts ref_type, ref_id,
// note, event_date (YYYY-MM-DD). Anti-forgery isn't a concern at v1 since the
// trust model is Tailscale-only + cookie auth.
func (s *Server) handleLinksAdd(w http.ResponseWriter, r *http.Request, path string) {
	it, err := s.Items.GetByPath(r.Context(), path)
	if err != nil {
		s.fail(w, r, err)
		return
	}
	if err := r.ParseForm(); err != nil {
		s.fail(w, r, err)
		return
	}
	refType := strings.TrimSpace(r.FormValue("ref_type"))
	refID := strings.TrimSpace(r.FormValue("ref_id"))
	noteVal := strings.TrimSpace(r.FormValue("note"))
	dateStr := strings.TrimSpace(r.FormValue("event_date"))
	banner := ""
	if refType == "" || refID == "" {
		banner = "ref_type and ref_id are required."
	}
	var date *time.Time
	if banner == "" && dateStr != "" {
		t, err := time.Parse("2006-01-02", dateStr)
		if err != nil {
			banner = "event_date must be YYYY-MM-DD."
		} else {
			date = &t
		}
	}
	if banner == "" {
		var notePtr *string
		if noteVal != "" {
			notePtr = &noteVal
		}
		if _, err := s.Store.AddLinkDated(r.Context(), it.ID, refType, refID, "", notePtr, date, nil); err != nil {
			banner = fmt.Sprintf("Could not add link: %v", err)
		}
	}
	// New dated link → bust the timeline cache so the row surfaces on next view.
	s.timeline.InvalidateAll()
	s.renderDocumentsSection(w, r, it, nil, banner)
}

// handleLinksRemove processes POST /i/{path}/links/remove.
func (s *Server) handleLinksRemove(w http.ResponseWriter, r *http.Request, path string) {
	it, err := s.Items.GetByPath(r.Context(), path)
	if err != nil {
		s.fail(w, r, err)
		return
	}
	if err := r.ParseForm(); err != nil {
		s.fail(w, r, err)
		return
	}
	linkID := strings.TrimSpace(r.FormValue("link_id"))
	banner := ""
	if linkID == "" {
		banner = "link_id required"
	} else {
		// Belt-and-braces: ensure the link belongs to this item before
		// deleting, so a crafted form can't snipe an unrelated row.
		owns, err := s.linkBelongsToItem(r.Context(), linkID, it.ID)
		if err != nil {
			s.fail(w, r, err)
			return
		}
		if !owns {
			banner = "Link does not belong to this item."
		} else if err := s.Store.DeleteLink(r.Context(), linkID); err != nil {
			banner = fmt.Sprintf("Could not remove link: %v", err)
		}
	}
	// Bust the dashboard + timeline caches: a removed dated link should
	// disappear from both surfaces on next render.
	s.dashboard.InvalidateAll()
	s.timeline.InvalidateAll()
	// When the delete came from the timeline (HX-Target = timeline-section),
	// re-render the timeline so the row vanishes in place instead of trying to
	// swap a Documents fragment into it.
	if r.Header.Get("HX-Target") == "timeline-section" {
		s.handleTimeline(w, r)
		return
	}
	s.renderDocumentsSection(w, r, it, nil, banner)
}

// renderDocumentsSection re-pulls dated links, computes PERs, and renders the
// Documents fragment for HTMX swaps. Non-HTMX requests fall back to a full
// detail-page redirect.
func (s *Server) renderDocumentsSection(w http.ResponseWriter, r *http.Request, it *store.Item, highlight *time.Time, banner string) {
	if r.Header.Get("HX-Request") != "true" {
		http.Redirect(w, r, "/i/"+it.PrimaryPath()+"#documents-section", http.StatusSeeOther)
		return
	}
	docs, err := s.Items.DatedLinks(r.Context(), it.ID)
	if err != nil {
		s.fail(w, r, err)
		return
	}
	documents := computePERs(it.PrimaryPath(), docs)
	s.render(w, r, "documents_section", map[string]any{
		"Item":          it,
		"Documents":     documents,
		"HighlightDate": highlight,
		"DocBanner":     banner,
	})
}

// linkBelongsToItem returns true when the link's item_id equals the supplied
// item id. Used as an anti-forgery check before delete.
func (s *Server) linkBelongsToItem(ctx context.Context, linkID, itemID string) (bool, error) {
	var owner string
	err := s.Store.Pool.QueryRow(ctx,
		`select item_id from projax.item_links where id = $1`, linkID).Scan(&owner)
	if err != nil {
		if isNoRows(err) {
			return false, nil
		}
		return false, err
	}
	return owner == itemID, nil
}

func isNoRows(err error) bool {
	return err != nil && (errors.Is(err, store.ErrNotFound) || err.Error() == "no rows in result set")
}