import { NextRequest, NextResponse } from "next/server";
import { queryRaw } from "@/lib/db";
import { getCurrentUser } from "@/lib/auth";

// A split may be settled by the transaction's effective owner or by the
// participant the split belongs to.
const SCOPE = `
  AND EXISTS (
    SELECT 1 FROM transactions t
    LEFT JOIN statements s ON s.id = t.statement_id
    WHERE t.id = transaction_splits.transaction_id
      AND (COALESCE(t.owner_id, s.owner_id) = $2 OR transaction_splits.participant_id = $2)
  )`;

export async function POST(req: NextRequest) {
  const user = await getCurrentUser(req);
  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 403 });

  const body = await req.json();
  const { participant_id, split_ids } = body as {
    participant_id?: number;
    split_ids?: number[];
  };

  if (participant_id) {
    const rows = await queryRaw<{ id: number }>(
      `UPDATE transaction_splits SET settled = true, settled_at = NOW()
       WHERE participant_id = $1 AND settled = false ${SCOPE}
       RETURNING id`,
      [participant_id, user.id]
    );
    return NextResponse.json({ settled: rows.length });
  }

  if (split_ids?.length) {
    const rows = await queryRaw<{ id: number }>(
      `UPDATE transaction_splits SET settled = true, settled_at = NOW()
       WHERE id = ANY($1::int[]) AND settled = false ${SCOPE}
       RETURNING id`,
      [split_ids, user.id]
    );
    return NextResponse.json({ settled: rows.length });
  }

  return NextResponse.json({ error: "participant_id or split_ids required" }, { status: 400 });
}