"use client";

import { useState } from "react";
import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
import { toast } from "sonner";
import { UserPlus, Trash2, Users } from "lucide-react";
import { api } from "@/lib/api";
import type { CaseAssignment, UserTenant } from "@/lib/types";
import { CASE_ASSIGNMENT_ROLE_LABELS } from "@/lib/types";
import type { CaseAssignmentRole } from "@/lib/types";
import { Skeleton } from "@/components/ui/Skeleton";
import { EmptyState } from "@/components/ui/EmptyState";
import { usePermissions } from "@/lib/hooks/usePermissions";

export function CaseAssignments({ caseId }: { caseId: string }) {
  const queryClient = useQueryClient();
  const { can } = usePermissions();
  const canManage = can("manage_team");

  const tenantId =
    typeof window !== "undefined"
      ? localStorage.getItem("kanzlai_tenant_id")
      : null;

  const [selectedUser, setSelectedUser] = useState("");
  const [assignRole, setAssignRole] = useState<CaseAssignmentRole>("team");

  const { data, isLoading } = useQuery({
    queryKey: ["case-assignments", caseId],
    queryFn: () =>
      api.get<{ assignments: CaseAssignment[]; total: number }>(
        `/cases/${caseId}/assignments`,
      ),
  });

  const { data: members } = useQuery({
    queryKey: ["tenant-members", tenantId],
    queryFn: () =>
      api.get<UserTenant[]>(`/tenants/${tenantId}/members`),
    enabled: !!tenantId && canManage,
  });

  const assignMutation = useMutation({
    mutationFn: (input: { user_id: string; role: string }) =>
      api.post(`/cases/${caseId}/assignments`, input),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ["case-assignments", caseId] });
      setSelectedUser("");
      toast.success("Mitarbeiter zugewiesen");
    },
    onError: (err: { error?: string }) => {
      toast.error(err.error || "Fehler beim Zuweisen");
    },
  });

  const unassignMutation = useMutation({
    mutationFn: (userId: string) =>
      api.delete(`/cases/${caseId}/assignments/${userId}`),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ["case-assignments", caseId] });
      toast.success("Zuweisung entfernt");
    },
    onError: (err: { error?: string }) => {
      toast.error(err.error || "Fehler beim Entfernen");
    },
  });

  const assignments = data?.assignments ?? [];
  const assignedUserIds = new Set(assignments.map((a) => a.user_id));
  const availableMembers = (members ?? []).filter(
    (m) => !assignedUserIds.has(m.user_id),
  );

  const handleAssign = (e: React.FormEvent) => {
    e.preventDefault();
    if (!selectedUser) return;
    assignMutation.mutate({ user_id: selectedUser, role: assignRole });
  };

  if (isLoading) {
    return (
      <div className="space-y-3">
        <Skeleton className="h-10 w-full" />
        <Skeleton className="h-10 w-full" />
      </div>
    );
  }

  return (
    <div className="space-y-4">
      <h3 className="text-sm font-semibold text-neutral-900">
        Zugewiesene Mitarbeiter
      </h3>

      {/* Assign form — only for owners/partners */}
      {canManage && availableMembers.length > 0 && (
        <form onSubmit={handleAssign} className="flex flex-col gap-2 sm:flex-row">
          <select
            value={selectedUser}
            onChange={(e) => setSelectedUser(e.target.value)}
            className="flex-1 rounded-md border border-neutral-200 px-2 py-1.5 text-sm outline-none focus:border-neutral-400 focus:ring-1 focus:ring-neutral-400"
          >
            <option value="">Mitarbeiter auswählen...</option>
            {availableMembers.map((m) => (
              <option key={m.user_id} value={m.user_id}>
                {m.user_id.slice(0, 8)}... ({m.role})
              </option>
            ))}
          </select>
          <select
            value={assignRole}
            onChange={(e) => setAssignRole(e.target.value as CaseAssignmentRole)}
            className="rounded-md border border-neutral-200 px-2 py-1.5 text-sm outline-none focus:border-neutral-400 focus:ring-1 focus:ring-neutral-400"
          >
            {(Object.keys(CASE_ASSIGNMENT_ROLE_LABELS) as CaseAssignmentRole[]).map(
              (r) => (
                <option key={r} value={r}>
                  {CASE_ASSIGNMENT_ROLE_LABELS[r]}
                </option>
              ),
            )}
          </select>
          <button
            type="submit"
            disabled={assignMutation.isPending || !selectedUser}
            className="inline-flex items-center gap-1.5 rounded-md bg-neutral-900 px-3 py-1.5 text-sm font-medium text-white hover:bg-neutral-800 disabled:opacity-50"
          >
            <UserPlus className="h-3.5 w-3.5" />
            Zuweisen
          </button>
        </form>
      )}

      {/* Assignments list */}
      {assignments.length > 0 ? (
        <div className="overflow-hidden rounded-md border border-neutral-200">
          {assignments.map((a, i) => (
            <div
              key={a.id}
              className={`flex items-center justify-between px-4 py-2.5 ${
                i < assignments.length - 1 ? "border-b border-neutral-100" : ""
              }`}
            >
              <div className="flex items-center gap-3">
                <div className="flex h-7 w-7 items-center justify-center rounded-full bg-neutral-100">
                  <Users className="h-3.5 w-3.5 text-neutral-500" />
                </div>
                <div>
                  <p className="text-sm text-neutral-900">
                    {a.user_id.slice(0, 8)}...
                  </p>
                  <p className="text-xs text-neutral-500">
                    {CASE_ASSIGNMENT_ROLE_LABELS[a.role as CaseAssignmentRole] ??
                      a.role}
                  </p>
                </div>
              </div>
              {canManage && (
                <button
                  onClick={() => unassignMutation.mutate(a.user_id)}
                  disabled={unassignMutation.isPending}
                  className="rounded-md p-1 text-neutral-400 hover:bg-red-50 hover:text-red-600 disabled:opacity-50"
                  title="Zuweisung entfernen"
                >
                  <Trash2 className="h-3.5 w-3.5" />
                </button>
              )}
            </div>
          ))}
        </div>
      ) : (
        <EmptyState
          icon={Users}
          title="Keine Zuweisungen"
          description="Noch keine Mitarbeiter zugewiesen."
        />
      )}
    </div>
  );
}