import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { connectDb } from "@/lib/server/db";
import { Branch } from "@/lib/server/models/Branch";
import { Product } from "@/lib/server/models/Product";
import { StockMovement } from "@/lib/server/models/StockMovement";
import { authorize, MANAGERS } from "@/lib/server/auth";
import { objectId } from "@/lib/server/validation";
import { clientRefId, recordMovement, stockOf } from "@/lib/server/stock";

export const runtime = "nodejs";

const adjustmentSchema = z.object({
  clientUuid: z.string().uuid(),
  branchId: objectId.optional(), // owners must give one; managers default to their own branch
  productId: objectId,
  // COUNT: "we physically counted N", so the ledger is corrected to N.
  // DELTA: "add or remove N", e.g. opening stock, breakage, or a delivery
  //        that was not recorded as a purchase.
  mode: z.enum(["COUNT", "DELTA"]),
  quantity: z.number().int().min(-1_000_000).max(1_000_000),
  note: z.string().trim().max(300).optional(),
});

// POST /api/stock/adjustments — managers (own branch) and owners (any branch).
export async function POST(req: NextRequest) {
  await connectDb();
  const gate = authorize(req, MANAGERS);
  if (!gate.ok) return gate.response;
  const auth = gate.auth;

  const parsed = adjustmentSchema.safeParse(await req.json().catch(() => null));
  if (!parsed.success) {
    return NextResponse.json({ error: parsed.error.issues[0]?.message ?? "Invalid request" }, { status: 400 });
  }
  const data = parsed.data;
  if (data.mode === "COUNT" && data.quantity < 0) {
    return NextResponse.json({ error: "A counted quantity cannot be negative" }, { status: 400 });
  }

  let branchId: string | null;
  if (auth.role === "SUPER_ADMIN") {
    branchId = data.branchId ?? null;
    if (!branchId) return NextResponse.json({ error: "branchId is required" }, { status: 400 });
  } else {
    branchId = auth.branchId;
    if (data.branchId && data.branchId !== auth.branchId) {
      return NextResponse.json({ error: "Cannot adjust stock for another branch" }, { status: 403 });
    }
  }
  if (!branchId) return NextResponse.json({ error: "No branch assignment for this account" }, { status: 403 });

  const [branch, product] = await Promise.all([
    Branch.exists({ _id: branchId, businessId: auth.businessId }),
    Product.exists({ _id: data.productId, businessId: auth.businessId }),
  ]);
  if (!branch) return NextResponse.json({ error: "Branch not found in your business" }, { status: 404 });
  if (!product) return NextResponse.json({ error: "Product not found in your business" }, { status: 404 });

  // A retried submit with the same clientUuid is a no-op.
  const refId = clientRefId(auth.businessId, data.clientUuid);
  const already = await StockMovement.exists({ type: "ADJUSTMENT", refId });
  if (!already) {
    const before = await stockOf(auth.businessId, branchId, data.productId);
    const delta = data.mode === "COUNT" ? data.quantity - before : data.quantity;
    if (delta !== 0) {
      const label = data.mode === "COUNT" ? `Count: ${before} -> ${data.quantity}` : "Adjustment";
      await recordMovement({
        businessId: auth.businessId,
        branchId,
        productId: data.productId,
        type: "ADJUSTMENT",
        quantity: delta,
        refId,
        note: data.note ? `${label}. ${data.note}` : label,
        recordedBy: auth.sub,
      });
    }
  }

  const quantity = await stockOf(auth.businessId, branchId, data.productId);
  return NextResponse.json({ branchId, productId: data.productId, quantity }, { status: 201 });
}