import type { Database } from 'bun:sqlite';
import { mkdirSync, appendFileSync } from 'fs';
import { join } from 'path';
import { migrations, type Migration } from './migrations';

const MIGRATIONS_LOG_LEVEL = (process.env.MIGRATIONS_LOG_LEVEL || '').toLowerCase();
const MIGRATIONS_QUIET = process.env.NODE_ENV === 'test' || MIGRATIONS_LOG_LEVEL === 'silent';

function nowIso(): string {
  return new Date().toISOString().replace('T', ' ').replace('Z', '');
}

function logEvent(level: 'info' | 'error', event: string, data: any = {}) {
  // En modo test o nivel 'silent', no registrar eventos para evitar ruido
  if (MIGRATIONS_QUIET) return;
  try {
    mkdirSync('data', { recursive: true });
  } catch {}
  try {
    const line = JSON.stringify({ ts: nowIso(), level, event, ...data });
    appendFileSync(join('data', 'migrations.log'), line + '\n');
  } catch {}
}

function ensureMigrationsTable(db: Database) {
  db.exec(`
    CREATE TABLE IF NOT EXISTS schema_migrations (
      version INTEGER PRIMARY KEY,
      name TEXT NOT NULL,
      checksum TEXT NOT NULL,
      applied_at TEXT NOT NULL
    );
  `);
}

function getAppliedVersions(db: Database): Map<number, { name: string; checksum: string; applied_at: string }> {
  const rows = db.query(`SELECT version, name, checksum, applied_at FROM schema_migrations ORDER BY version`).all() as any[];
  const map = new Map<number, { name: string; checksum: string; applied_at: string }>();
  for (const r of rows) {
    map.set(Number(r.version), { name: String(r.name), checksum: String(r.checksum), applied_at: String(r.applied_at) });
  }
  return map;
}

function tableExists(db: Database, table: string): boolean {
  const row = db.query(`SELECT name FROM sqlite_master WHERE type='table' AND name=?`).get(table) as any;
  return !!row;
}

function detectExistingSchema(db: Database): boolean {
  // Consideramos esquema "existente" si ya hay tablas clave
  const coreTables = ['users', 'tasks', 'response_queue'];
  return coreTables.every(t => tableExists(db, t));
}

function insertMigrationRow(db: Database, mig: Migration) {
  db.prepare(
    `INSERT INTO schema_migrations (version, name, checksum, applied_at) VALUES (?, ?, ?, ?)`
  ).run(mig.version, mig.name, mig.checksum, nowIso());
}

function backupDatabaseIfNeeded(db: Database): string | null {
  if (process.env.NODE_ENV === 'test') return null;
  try {
    mkdirSync('data', { recursive: true });
  } catch {}
  const stamp = new Date().toISOString().replace(/[-:T.Z]/g, '').slice(0, 14);
  const backupPath = join('data', `tasks.db.bak-${stamp}.sqlite`);
  try {
    // VACUUM INTO hace copia consistente del estado actual
    db.exec(`VACUUM INTO '${backupPath.replace(/'/g, "''")}'`);
    if (!MIGRATIONS_QUIET) console.log(`ℹ️ Backup de base de datos creado en: ${backupPath}`);
    return backupPath;
  } catch (e) {
    if (!MIGRATIONS_QUIET) console.warn('⚠️ No se pudo crear el backup con VACUUM INTO (continuando de todos modos):', e);
    return null;
  }
}

export const Migrator = {
  ensureMigrationsTable,
  getAppliedVersions,

  migrateToLatest(db: Database, options?: { withBackup?: boolean; allowBaseline?: boolean }) {
    const withBackup = options?.withBackup !== false;
    const allowBaseline = options?.allowBaseline === true;

    ensureMigrationsTable(db);
    const applied = getAppliedVersions(db);
    const pending = migrations.filter(m => !applied.has(m.version)).sort((a, b) => a.version - b.version);

    // Validación de checksum (estricta por defecto, configurable)
    const strict = (process.env.MIGRATOR_CHECKSUM_STRICT ?? 'true').toLowerCase() !== 'false';
    for (const [version, info] of applied) {
      const codeMig = migrations.find(m => m.version === version);
      if (codeMig && codeMig.checksum !== info.checksum) {
        const msg = `❌ Checksum mismatch en migración v${version}: aplicado=${info.checksum}, código=${codeMig.checksum}`;
        console.error(msg);
        try { logEvent('error', 'checksum_mismatch', { version, applied_checksum: info.checksum, code_checksum: codeMig.checksum }); } catch {}
        if (strict) throw new Error(msg);
      }
    }

    // Resumen inicial
    const jmRow = db.query(`PRAGMA journal_mode`).get() as any;
    const journalMode = jmRow ? (jmRow.journal_mode || jmRow.value || jmRow.mode || 'unknown') : 'unknown';
    const currentVersion = applied.size ? Math.max(...Array.from(applied.keys())) : 0;
    if (!MIGRATIONS_QUIET) console.log(`ℹ️ Migrador — journal_mode=${journalMode}, versión_actual=${currentVersion}, pendientes=${pending.length}`);
    try { logEvent('info', 'startup_summary', { journal_mode: journalMode, current_version: currentVersion, pending: pending.length }); } catch {}

    if (applied.size === 0 && allowBaseline && detectExistingSchema(db)) {
      // Baseline a v1 si ya existe el esquema pero no hay registro
      const v1 = migrations.find(m => m.version === 1)!;
      db.transaction(() => {
        insertMigrationRow(db, v1);
      })();
      if (!MIGRATIONS_QUIET) console.log('ℹ️ Baseline aplicado: schema_migrations marcada en v1 (sin ejecutar up)');
      try { logEvent('info', 'baseline_applied', { version: 1 }); } catch {}
      // Recalcular pendientes
      pending.splice(0, pending.length, ...migrations.filter(m => m.version > 1));
    }

    if (pending.length === 0) {
      if (!MIGRATIONS_QUIET) console.log('ℹ️ No hay migraciones pendientes');
      try { logEvent('info', 'no_pending', {}); } catch {}
      return;
    }

    if (withBackup) {
      const backupPath = backupDatabaseIfNeeded(db);
      try { logEvent('info', 'backup', { path: backupPath }); } catch {}
    }

    for (const mig of pending) {
      if (!MIGRATIONS_QUIET) console.log(`➡️ Aplicando migración v${mig.version} - ${mig.name}`);
      try {
        try { logEvent('info', 'apply_start', { version: mig.version, name: mig.name, checksum: mig.checksum }); } catch {}
        const t0 = Date.now();
        db.transaction(() => {
          // Ejecutar up
          const res = mig.up(db);
          if (res instanceof Promise) {
            throw new Error('Las migraciones up no deben ser asíncronas en este migrador');
          }
          // Registrar
          insertMigrationRow(db, mig);
        })();
        const ms = Date.now() - t0;
        if (!MIGRATIONS_QUIET) console.log(`✅ Migración v${mig.version} aplicada (${ms} ms)`);
        try { logEvent('info', 'apply_success', { version: mig.version, name: mig.name, checksum: mig.checksum, duration_ms: ms }); } catch {}
      } catch (e) {
        console.error(`❌ Error aplicando migración v${mig.version}:`, e);
        try { logEvent('error', 'apply_error', { version: mig.version, name: mig.name, checksum: mig.checksum, error: String(e) }); } catch {}
        throw e;
      }
    }
  }
};