import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { isValidObjectId } from "mongoose";
import { connectDb } from "@/lib/server/db";
import { Branch } from "@/lib/server/models/Branch";
import { User } from "@/lib/server/models/User";
import { authorize } from "@/lib/server/auth";
import { branchLimitError } from "@/lib/server/subscription";
import { getStockLevels } from "@/lib/server/stock";

export const runtime = "nodejs";

const updateSchema = z
  .object({
    branchName: z.string().trim().min(1).max(120).optional(),
    locationCity: z.string().trim().min(1).max(120).optional(),
    isActive: z.boolean().optional(),
  })
  .refine((v) => Object.keys(v).length > 0, { message: "No fields to update" });

/**
 * PATCH /api/branches/:id — owner renames a branch, or deactivates /
 * reactivates it. This is how an owner "removes" a branch: nothing is
 * deleted, so its sales, purchases and stock history stay in every report.
 *
 * A branch can only be deactivated once it is empty, so nothing is left
 * stranded in it:
 *   - no stock on hand (transfer it out or count it to zero first), and
 *   - no active staff (move or deactivate them first).
 * Reactivating counts against the plan's branch limit again.
 */
export async function PATCH(req: NextRequest, { params }: { params: { id: string } }) {
  await connectDb();
  const gate = authorize(req, ["SUPER_ADMIN"]);
  if (!gate.ok) return gate.response;
  const auth = gate.auth;

  if (!isValidObjectId(params.id)) return NextResponse.json({ error: "Branch not found" }, { status: 404 });

  const json = await req.json().catch(() => null);
  const parsed = updateSchema.safeParse(json);
  if (!parsed.success) {
    return NextResponse.json({ error: parsed.error.issues[0]?.message ?? "Invalid request" }, { status: 400 });
  }
  const { isActive, ...details } = parsed.data;

  const branch = await Branch.findOne({ _id: params.id, businessId: auth.businessId });
  if (!branch) return NextResponse.json({ error: "Branch not found" }, { status: 404 });
  const wasActive = branch.isActive !== false;

  if (isActive === false && wasActive) {
    const stock = (await getStockLevels(auth.businessId, branch._id)).filter((l) => l.quantity !== 0);
    if (stock.length > 0) {
      const list = stock.map((l) => `${l.quantity} x ${l.productLabel}`).join(", ");
      return NextResponse.json(
        { error: `Move or count out this branch's stock first (${list}).`, stock },
        { status: 409 }
      );
    }
    const staff = await User.countDocuments({ businessId: auth.businessId, branchId: branch._id, isActive: true });
    if (staff > 0) {
      return NextResponse.json(
        { error: `${staff} active staff member(s) still work at this branch. Move or deactivate them first.` },
        { status: 409 }
      );
    }
  }
  if (isActive === true && !wasActive) {
    const limitError = await branchLimitError(auth.businessId);
    if (limitError) return NextResponse.json({ error: limitError }, { status: 403 });
  }

  Object.assign(branch, details);
  if (isActive !== undefined) branch.isActive = isActive;
  await branch.save();
  return NextResponse.json({ branch });
}