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

export async function GET(
  req: NextRequest,
  { params }: { params: Promise<{ id: string }> }
) {
  const user = await getCurrentUser(req);
  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 403 });
  const { id } = await params;
  const stmt = await getStatementById(Number(id));
  if (!stmt || stmt.owner_id !== user.id) {
    return NextResponse.json({ error: "Not found" }, { status: 404 });
  }
  return NextResponse.json(stmt);
}

/**
 * Reassign a statement — whose account it is.
 *
 * The statements page has had an owner dropdown since it was built, wired to
 * `useUpdateStatement`, which PATCHed a route that had no PATCH handler. Every
 * change 405'd, and because the hook never checked `res.ok` the failure was
 * silent: the select snapped back on refetch and looked like a UI glitch.
 *
 * Both tables are written because both carry the owner. The effective owner is
 * `COALESCE(t.owner_id, s.owner_id)`, and 2,194 statement rows carry their own
 * copy against 1,803 that inherit — so updating `statements` alone would move
 * less than half the rows and split one account's history between two people.
 * All 2,194 agree with their statement today; a row that disagrees was set
 * deliberately and is left alone rather than swept up.
 */
export async function PATCH(
  req: NextRequest,
  { params }: { params: Promise<{ id: string }> }
) {
  const user = await getCurrentUser(req);
  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 403 });
  const { id } = await params;
  const statementId = Number(id);

  const stmt = await getStatementById(statementId);
  // Only the current owner reassigns. A statement is an account, not a shared
  // expense — there is no split that grants a second person a say in it.
  if (!stmt || stmt.owner_id !== user.id) {
    return NextResponse.json({ error: "Not found" }, { status: 404 });
  }

  const { owner_id } = (await req.json()) as { owner_id?: number };
  if (typeof owner_id !== "number" || !Number.isInteger(owner_id)) {
    return NextResponse.json({ error: "owner_id must be a participant id" }, { status: 400 });
  }
  const known = await queryRaw(`SELECT id FROM participants WHERE id = $1`, [owner_id]);
  if (!known.length) {
    return NextResponse.json({ error: "Unknown participant" }, { status: 400 });
  }
  if (owner_id === stmt.owner_id) {
    return NextResponse.json({ ok: true, statement_id: statementId, rows_moved: 0 });
  }

  const [, rowsMoved] = await prisma.$transaction([
    prisma.$executeRawUnsafe(`UPDATE statements SET owner_id = $1 WHERE id = $2`, owner_id, statementId),
    prisma.$executeRawUnsafe(
      `UPDATE transactions SET owner_id = $1 WHERE statement_id = $2 AND owner_id = $3`,
      owner_id,
      statementId,
      stmt.owner_id
    ),
  ]);

  return NextResponse.json({ ok: true, statement_id: statementId, rows_moved: rowsMoved });
}