import { fileURLToPath } from "node:url";
import { Database } from "bun:sqlite";
import { chmodSync, closeSync, constants, copyFileSync, existsSync, fsyncSync, linkSync, mkdirSync, openSync, readdirSync, renameSync, rmSync, statSync, unlinkSync } from "node:fs";
import { dirname, join, resolve } from "node:path";

export type BackupConfig = { directory: string; replica?: string; retain: number; intervalMs: number; enabled: boolean };
const filenamePattern = /^minabot-\d{4}-\d{2}-\d{2}T[\d-]+Z-[a-f0-9-]+\.sqlite$/;
export function backupConfig(database: string, env = process.env): BackupConfig {
  const retain = Number(env.BACKUP_RETAIN ?? 7);
  const hours = Number(env.BACKUP_INTERVAL_HOURS ?? 24);
  if (!Number.isInteger(retain) || retain < 2 || retain > 365 || !Number.isFinite(hours) || hours < 1 || hours > 168)
    throw new Error("BACKUP_RETAIN must be 2–365 and BACKUP_INTERVAL_HOURS must be 1–168");
  const base = dirname(database);
  const directory = resolve(base, env.BACKUP_DIR ?? "backups");
  const replica = env.BACKUP_REPLICA_DIR ? resolve(base, env.BACKUP_REPLICA_DIR) : undefined;
  if (replica === directory) throw new Error("The backup replica must use a separate directory");
  return { directory, replica, retain, intervalMs: hours * 3600000, enabled: env.BACKUP_ENABLED !== "false" };
}
function durable(path: string) {
  chmodSync(path, 0o600);
  const fd = openSync(path, "r"); try { fsyncSync(fd); } finally { closeSync(fd); }
}
export function verifyBackup(path: string) {
  const db = new Database(path, { readonly: true, strict: true });
  try {
    const integrity = db.query("PRAGMA integrity_check").all() as { integrity_check: string }[];
    if (integrity.length !== 1 || integrity[0]?.integrity_check !== "ok" || db.query("PRAGMA foreign_key_check").all().length)
      throw new Error("Backup integrity check failed");
    db.query("SELECT id FROM users LIMIT 1").all();
    db.query("SELECT id FROM habits LIMIT 1").all();
    db.query("SELECT hash FROM __drizzle_migrations LIMIT 1").all();
  } finally { db.close(); }
}
function snapshots(directory: string) {
  if (!existsSync(directory)) return [];
  return readdirSync(directory).filter(name => filenamePattern.test(name)).sort().reverse();
}
export function latestBackupTime(config: BackupConfig) {
  const latest = snapshots(config.directory)[0];
  if (!latest || (config.replica && !existsSync(join(config.replica, latest)))) return 0;
  return statSync(join(config.directory, latest)).mtimeMs;
}
export function createBackup(database: Database, config: BackupConfig) {
  const name = `minabot-${new Date().toISOString().replace(/[:.]/g, "-")}-${crypto.randomUUID()}.sqlite`;
  mkdirSync(config.directory, { recursive: true, mode: 0o700 });
  const path = join(config.directory, name);
  const staging = `${path}.partial`;
  mkdirSync(staging, { mode: 0o700 });
  const temporary = join(staging, "snapshot.sqlite");
  try {
    // VACUUM INTO includes committed WAL transactions in one consistent snapshot.
    // SQLite creates the output inside a private staging directory.
    database.query("VACUUM INTO ?").run(temporary);
    verifyBackup(temporary); durable(temporary); renameSync(temporary, path);
    if (config.replica) {
      // Require the configured mount to exist; never silently create an absent mount.
      if (!statSync(config.replica).isDirectory()) throw new Error("Backup replica directory unavailable");
      const replica = join(config.replica, name);
      copyFileSync(path, `${replica}.partial`, constants.COPYFILE_EXCL);
      durable(`${replica}.partial`); verifyBackup(`${replica}.partial`); renameSync(`${replica}.partial`, replica);
    }
    for (const directory of [config.directory, ...(config.replica ? [config.replica] : [])])
      for (const old of snapshots(directory).slice(config.retain)) unlinkSync(join(directory, old));
    return path;
  } finally { rmSync(staging, { recursive: true, force: true }); }
}
export function restoreBackup(source: string, destination: string) {
  if (existsSync(destination) || existsSync(`${destination}-wal`) || existsSync(`${destination}-shm`))
    throw new Error("Restore destination must be a new path with no SQLite sidecars");
  verifyBackup(source);
  mkdirSync(dirname(destination), { recursive: true, mode: 0o700 });
  const temporary = `${destination}.${crypto.randomUUID()}.partial`;
  try {
    copyFileSync(source, temporary, constants.COPYFILE_EXCL); chmodSync(temporary, 0o600);
    const restored = new Database(temporary);
    try {
      restored.exec("PRAGMA journal_mode=DELETE; DELETE FROM sessions;");
      if (restored.query("SELECT name FROM sqlite_master WHERE name = 'reminder_settings'").get()) restored.exec("UPDATE reminder_settings SET enabled=0");
    } finally { restored.close(); }
    verifyBackup(temporary); durable(temporary);
    // Link is exclusive: a concurrently-created destination is never overwritten.
    linkSync(temporary, destination);
  } finally { if (existsSync(temporary)) unlinkSync(temporary); }
  return destination;
}
/** Runs all filesystem and SQLite backup work in a separate Bun process. */
export async function runScheduledBackup(database: string, config: BackupConfig): Promise<number> {
  const source = new URL("../../scripts/scheduled-backup.ts", import.meta.url);
  const built = new URL("../scripts/scheduled-backup.ts", import.meta.url);
  const script = fileURLToPath(existsSync(source) ? source : built);
  const child = Bun.spawn([process.execPath, script, resolve(database), JSON.stringify(config)], {
    stdout: "pipe", stderr: "ignore",
  });
  const [output, status] = await Promise.all([new Response(child.stdout).text(), child.exited]);
  if (status !== 0) throw new Error("Scheduled backup process failed");
  const { timestamp, created } = JSON.parse(output) as { timestamp: number; created: boolean };
  if (!Number.isFinite(timestamp) || timestamp <= 0) throw new Error("Scheduled backup returned an invalid timestamp");
  if (created) console.log(JSON.stringify({ event: "backup_completed", timestamp: new Date(timestamp).toISOString() }));
  return timestamp;
}
export function startBackups(database: Database | string, config: BackupConfig, run = runScheduledBackup) {
  const state = { enabled: config.enabled, lastSuccess: 0, failed: false };
  let running: Promise<void> | undefined;
  let stopped = false;
  const tick = (): Promise<void> => {
    if (stopped || !config.enabled) return Promise.resolve();
    if (running) return running;
    running = (async () => {
      try {
        const path = typeof database === 'string' ? database : database.filename;
        if (!path || path === ':memory:') throw new Error('Scheduled backups require a file database');
        state.lastSuccess = await run(path, config); state.failed = false;
      } catch { state.failed = true; console.error(JSON.stringify({ event: "backup_failed", timestamp: new Date().toISOString() })); }
    })().finally(() => { running = undefined; });
    return running;
  };
  // Callers await readiness before accepting traffic, matching the original startup check.
  const ready = tick();
  const timer = config.enabled ? setInterval(() => { void tick(); }, 60000) : undefined;
  timer?.unref();
  return { state, ready, tick, stop: () => { stopped = true; clearInterval(timer); } };
}