import { NextRequest, NextResponse } from "next/server";
import { getPb } from "../../../lib/pb";

const BATCHES = "JEI_payment_batches";
const INVOICES = "JEI_invoices";
const ALLOWED_MIME = new Set(["application/pdf", "image/jpeg", "image/png"]);
const MAX_POP_BYTES = 8 * 1024 * 1024;

export const dynamic = "force-dynamic";

export async function POST(req: NextRequest) {
  const pb = getPb();
  let form: FormData;
  try {
    form = await req.formData();
  } catch (e: any) {
    return NextResponse.json({ error: `Invalid form-data: ${e?.message || e}` }, { status: 400 });
  }

  const batchRef = String(form.get("batch_ref") || "").trim();
  const paymentDate = String(form.get("payment_date") || "").trim();
  const invoiceIdsRaw = String(form.get("invoice_ids") || "");
  const popFile = form.get("pop_file");

  // 1. invoice_ids
  let invoiceIds: string[];
  try {
    const parsed = JSON.parse(invoiceIdsRaw);
    if (!Array.isArray(parsed) || parsed.length === 0 || !parsed.every((x) => typeof x === "string")) {
      throw new Error("invoice_ids must be a non-empty JSON array of strings");
    }
    invoiceIds = parsed;
  } catch (e: any) {
    return NextResponse.json({ error: e?.message || "Invalid invoice_ids" }, { status: 400 });
  }

  // 2. batch_ref
  if (!/^[A-Za-z0-9_-]{1,50}$/.test(batchRef)) {
    return NextResponse.json(
      { error: "batch_ref must match ^[A-Za-z0-9_-]{1,50}$" },
      { status: 400 },
    );
  }

  // 3. payment_date
  if (!/^\d{4}-\d{2}-\d{2}$/.test(paymentDate)) {
    return NextResponse.json(
      { error: "payment_date must be YYYY-MM-DD" },
      { status: 400 },
    );
  }

  // 4. pop_file
  if (!(popFile instanceof File)) {
    return NextResponse.json({ error: "pop_file is required" }, { status: 400 });
  }
  if (!ALLOWED_MIME.has(popFile.type)) {
    return NextResponse.json(
      { error: `pop_file type must be PDF, JPG or PNG (got ${popFile.type})` },
      { status: 400 },
    );
  }
  if (popFile.size > MAX_POP_BYTES) {
    return NextResponse.json(
      { error: `pop_file exceeds 8 MB (got ${popFile.size} bytes)` },
      { status: 400 },
    );
  }

  // 5. batch_ref uniqueness
  try {
    const dupe = await pb.collection(BATCHES).getList(1, 1, {
      filter: `batch_ref="${batchRef.replace(/"/g, '\\"')}"`,
    });
    if (dupe.totalItems > 0) {
      return NextResponse.json(
        { error: `Batch ref "${batchRef}" already exists` },
        { status: 409 },
      );
    }
  } catch (e: any) {
    return NextResponse.json(
      { error: `batch_ref uniqueness check failed: ${e?.message || e}` },
      { status: 500 },
    );
  }

  // 6. Re-validate each invoice is still unpaid
  const conflicts: string[] = [];
  const validIds: string[] = [];
  for (const id of invoiceIds) {
    try {
      const inv = await pb.collection(INVOICES).getOne(id);
      if (inv.payment_batch && inv.payment_batch !== "") {
        conflicts.push(id);
      } else {
        validIds.push(id);
      }
    } catch (e: any) {
      conflicts.push(id); // missing or 404 → treat as conflict
    }
  }
  if (conflicts.length > 0) {
    return NextResponse.json(
      { error: `These invoices are already paid or missing: ${conflicts.join(", ")}` },
      { status: 409 },
    );
  }

  // 7. Create the batch
  let batchId: string;
  try {
    const created = await pb.collection(BATCHES).create({
      batch_ref: batchRef,
      payment_date: paymentDate,
      pop_file: popFile,
    });
    batchId = created.id;
  } catch (e: any) {
    return NextResponse.json(
      { error: `Failed to create batch: ${e?.message || e}` },
      { status: 500 },
    );
  }

  // 8. PATCH each invoice (best-effort, parallel)
  const patchErrors: string[] = [];
  await Promise.all(
    validIds.map(async (id) => {
      try {
        await pb.collection(INVOICES).update(id, { payment_batch: batchId });
      } catch (e: any) {
        patchErrors.push(`${id}: ${e?.message || e}`);
      }
    }),
  );

  return NextResponse.json({
    ok: true,
    batchId,
    batchRef,
    invoiceCount: validIds.length,
    patchErrors: patchErrors.length > 0 ? patchErrors : undefined,
  });
}