#!/usr/bin/env bun
/**
 * Migration rehearsal script — Stage 2.2 DoD.
 *
 * Applies every forward migration against a clean staging DB, then every rollback
 * in reverse order, capturing row counts and a content-hash at each step. Fails
 * the run if forward+rollback don't return the DB to its pre-migration state.
 *
 * Usage:
 *   DATABASE_URL=postgres://... bun run db/migrations/rehearse.ts
 */

import { readdirSync, readFileSync } from "node:fs";
import { join } from "node:path";
import { createHash } from "node:crypto";
import postgres from "postgres";

const MIGRATIONS_DIR = join(import.meta.dir);

interface Migration {
  number: string;
  name: string;
  forward: string;
  rollback: string;
}

const loadMigrations = (): Migration[] => {
  const all = readdirSync(MIGRATIONS_DIR);
  const forwards = all.filter((f) => /^\d{4}_.*\.sql$/.test(f) && !f.endsWith(".down.sql")).sort();
  return forwards.map((forwardName) => {
    const number = forwardName.slice(0, 4);
    const base = forwardName.slice(0, -4);
    const downName = `${base}.down.sql`;
    const rollbackPath = join(MIGRATIONS_DIR, downName);
    if (!all.includes(downName)) {
      throw new Error(`Missing rollback file: ${downName}`);
    }
    return {
      number,
      name: base,
      forward: readFileSync(join(MIGRATIONS_DIR, forwardName), "utf8"),
      rollback: readFileSync(rollbackPath, "utf8"),
    };
  });
};

const tableSnapshot = async (sql: postgres.Sql): Promise<string> => {
  const tables = await sql<{ tablename: string }[]>`
    SELECT tablename FROM pg_tables WHERE schemaname = 'public' ORDER BY tablename
  `;
  const lines: string[] = [];
  for (const { tablename } of tables) {
    const rows = await sql.unsafe(`SELECT COUNT(*)::text AS c FROM "${tablename}"`);
    const count = (rows[0] as { c: string } | undefined)?.c ?? "0";
    lines.push(`${tablename}=${count}`);
  }
  return createHash("sha256").update(lines.join("|")).digest("hex");
};

const main = async (): Promise<void> => {
  const url = process.env.DATABASE_URL;
  if (!url) {
    console.error("DATABASE_URL not set");
    process.exit(2);
  }
  const sql = postgres(url, { max: 1, onnotice: () => {} });
  const migrations = loadMigrations();
  console.log(`[rehearse] ${migrations.length} migration(s) to test`);

  const before = await tableSnapshot(sql);
  console.log(`[rehearse] pre-state hash: ${before}`);

  for (const m of migrations) {
    console.log(`[rehearse] forward: ${m.name}`);
    for (const stmt of m.forward.split("--> statement-breakpoint")) {
      const trimmed = stmt.trim();
      if (trimmed) await sql.unsafe(trimmed);
    }
  }
  const afterForward = await tableSnapshot(sql);
  console.log(`[rehearse] post-forward hash: ${afterForward}`);

  for (const m of [...migrations].reverse()) {
    console.log(`[rehearse] rollback: ${m.name}`);
    for (const stmt of m.rollback.split(";")) {
      const trimmed = stmt.trim();
      if (trimmed) await sql.unsafe(trimmed);
    }
  }
  const afterRollback = await tableSnapshot(sql);
  console.log(`[rehearse] post-rollback hash: ${afterRollback}`);

  await sql.end();

  if (afterRollback !== before) {
    console.error(`[rehearse] FAIL — rollback did not restore pre-state`);
    console.error(`  before:        ${before}`);
    console.error(`  afterRollback: ${afterRollback}`);
    process.exit(1);
  }
  console.log(`[rehearse] PASS — forward + rollback round-trip clean`);
};

main().catch((e) => {
  console.error(e);
  process.exit(1);
});