/**
 * Backup manager for Holesail Browser.
 * Creates/restores tar.gz backups of the state directory and certificates directory.
 * Uses the system `tar` command via bare-subprocess.
 *
 * Archive layout:
 *   storage/   ← contents of holesail-browser-storage (excluding backups/)
 *   certs/     ← contents of holesail-browser-certs (CA key, cert, domain certs)
 */

const path = require('bare-path');
const fs = require('bare-fs');

let spawn = null;
try {
  const cp = require('child_process');
  if (cp && typeof cp.spawn === 'function') spawn = cp.spawn;
} catch (_) {}

const BACKUP_DIR_NAME = 'backups';
const DEFAULT_RETENTION = 5;

let storageDir = null;
let certsDir = null;

function setStoragePath(dir) {
  storageDir = dir;
}

function setCertsPath(dir) {
  certsDir = dir;
}

function getBackupDir() {
  if (!storageDir) throw new Error('Storage path not set');
  return path.join(storageDir, BACKUP_DIR_NAME);
}

function ensureBackupDir() {
  const dir = getBackupDir();
  if (!fs.existsSync(dir)) {
    fs.mkdirSync(dir, { recursive: true });
  }
  return dir;
}

function runCommand(cmd, args, opts) {
  return new Promise((resolve, reject) => {
    if (!spawn) return reject(new Error('child_process.spawn not available'));
    const proc = spawn(cmd, args, opts || {});
    let stdout = '';
    let stderr = '';
    if (proc.stdout) proc.stdout.on('data', (d) => { stdout += d.toString(); });
    if (proc.stderr) proc.stderr.on('data', (d) => { stderr += d.toString(); });
    proc.on('exit', (code) => {
      if (code === 0) resolve({ stdout, stderr });
      else reject(new Error('Command failed (exit ' + code + '): ' + stderr.trim()));
    });
    proc.on('error', reject);
  });
}

/**
 * Creates a backup of the storage directory and certs directory.
 * Archive layout:
 *   storage/<entries>  ← state.json, etc. (backups/ subdir excluded)
 *   certs/<entries>    ← CA key/cert and domain cert dirs
 * Returns { ok, filename, path, size, createdAt }
 */
async function createBackup() {
  if (!storageDir) return { ok: false, error: 'Storage path not set' };
  if (!spawn) return { ok: false, error: 'child_process.spawn not available — cannot run tar' };

  const backupDir = ensureBackupDir();
  const ts = new Date().toISOString().replace(/[:.]/g, '-').replace('T', '_').slice(0, 19);
  const filename = 'holesail-backup-' + ts + '.tar.gz';
  const outPath = path.join(backupDir, filename);

  // Build tar args: interleave -C <dir> <entry> pairs so each entry is
  // placed under a named prefix inside the archive.
  // tar supports: tar -czf out.tar.gz -C /base/of/a storage/file1 -C /base/of/b certs/file2
  // We achieve the prefix by creating a temp staging area... but that requires
  // write access and cleanup. Instead, use the simpler approach of archiving
  // each directory separately using --transform (GNU tar) or -s (BSD tar).
  // Most reliable cross-platform: stage into a temp dir inside backupDir, then tar it.

  const stagingDir = path.join(backupDir, '.staging-' + ts);
  const stagingStorage = path.join(stagingDir, 'storage');
  const stagingCerts = path.join(stagingDir, 'certs');

  try {
    fs.mkdirSync(stagingStorage, { recursive: true });
  } catch (e) {
    return { ok: false, error: 'Failed to create staging dir: ' + e.message };
  }

  // Copy storage entries (excluding backups/)
  let storageEntries;
  try {
    storageEntries = fs.readdirSync(storageDir).filter(e => e !== BACKUP_DIR_NAME);
  } catch (e) {
    cleanupStaging(stagingDir);
    return { ok: false, error: 'Failed to read storage directory: ' + e.message };
  }

  try {
    for (const entry of storageEntries) {
      await runCommand('cp', ['-R', path.join(storageDir, entry), path.join(stagingStorage, entry)]);
    }
  } catch (e) {
    cleanupStaging(stagingDir);
    return { ok: false, error: 'Failed to copy storage files: ' + e.message };
  }

  // Copy certs directory if it exists
  if (certsDir && fs.existsSync(certsDir)) {
    try {
      fs.mkdirSync(stagingCerts, { recursive: true });
      const certEntries = fs.readdirSync(certsDir);
      for (const entry of certEntries) {
        await runCommand('cp', ['-R', path.join(certsDir, entry), path.join(stagingCerts, entry)]);
      }
    } catch (e) {
      // Non-fatal: log but continue — state backup is still valuable without certs
      if (process.stderr) process.stderr.write('[backup-manager] Warning: failed to copy certs: ' + e.message + '\n');
    }
  }

  // Check we have something to archive
  let hasContent = false;
  try {
    hasContent = fs.readdirSync(stagingDir).length > 0;
  } catch (_) {}

  if (!hasContent) {
    cleanupStaging(stagingDir);
    return { ok: false, error: 'Nothing to back up' };
  }

  try {
    // tar -czf <outPath> -C <stagingDir> storage certs (whichever exist)
    const stagingEntries = fs.readdirSync(stagingDir);
    await runCommand('tar', ['-czf', outPath, '-C', stagingDir, ...stagingEntries]);
  } catch (e) {
    cleanupStaging(stagingDir);
    return { ok: false, error: 'tar failed: ' + e.message };
  }

  cleanupStaging(stagingDir);

  // Verify archive integrity before reporting success
  try {
    await runCommand('tar', ['-tzf', outPath]);
  } catch (e) {
    try { fs.unlinkSync(outPath); } catch (_) {}
    return { ok: false, error: 'Backup archive failed integrity check: ' + e.message };
  }

  let size = 0;
  try {
    const stat = fs.statSync(outPath);
    size = stat.size;
  } catch (_) {}

  return { ok: true, filename, path: outPath, size, createdAt: Date.now() };
}

function cleanupStaging(stagingDir) {
  try {
    if (spawn) {
      const proc = spawn('rm', ['-rf', stagingDir]);
      proc.on('error', (err) => {
        if (process.stderr) process.stderr.write('[backup-manager] cleanupStaging error: ' + err.message + '\n');
      });
      proc.on('exit', (code) => {
        if (code !== 0 && process.stderr) {
          process.stderr.write('[backup-manager] cleanupStaging exited with code ' + code + ' for ' + stagingDir + '\n');
        }
      });
    }
  } catch (_) {}
}

/**
 * Lists all backups sorted newest-first.
 * Returns { ok, backups: [{ filename, path, size, createdAt }] }
 */
function listBackups() {
  if (!storageDir) return { ok: false, error: 'Storage path not set' };

  let backupDir;
  try {
    backupDir = getBackupDir();
  } catch (e) {
    return { ok: false, error: e.message };
  }

  if (!fs.existsSync(backupDir)) {
    return { ok: true, backups: [] };
  }

  let files;
  try {
    files = fs.readdirSync(backupDir);
  } catch (e) {
    return { ok: false, error: 'Failed to read backup directory: ' + e.message };
  }

  const backups = [];
  for (const f of files) {
    if (!f.endsWith('.tar.gz')) continue;
    const fullPath = path.join(backupDir, f);
    let stat;
    try {
      stat = fs.statSync(fullPath);
    } catch (_) {
      continue;
    }
    backups.push({
      filename: f,
      path: fullPath,
      size: stat.size,
      createdAt: stat.mtimeMs || stat.mtime
    });
  }

  // Sort newest first
  backups.sort((a, b) => b.createdAt - a.createdAt);
  return { ok: true, backups };
}

/**
 * Restores a backup by filename.
 * The archive has a storage/ prefix and optionally a certs/ prefix.
 * Extracts each prefix to its corresponding real directory.
 * Returns { ok, restoredStorage, restoredCerts }
 */
async function restoreBackup(filename) {
  if (!storageDir) return { ok: false, error: 'Storage path not set' };
  if (!spawn) return { ok: false, error: 'child_process.spawn not available — cannot run tar' };
  if (!filename || typeof filename !== 'string') return { ok: false, error: 'filename is required' };

  // Sanitize: only allow the basename, no path traversal
  const safe = path.basename(filename);
  if (!safe.endsWith('.tar.gz')) return { ok: false, error: 'Invalid backup filename' };

  const backupDir = getBackupDir();
  const backupPath = path.join(backupDir, safe);

  if (!fs.existsSync(backupPath)) {
    return { ok: false, error: 'Backup not found: ' + safe };
  }

  // List top-level entries in the archive to detect layout
  let topEntries = [];
  try {
    const { stdout } = await runCommand('tar', ['-tzf', backupPath]);
    // Get unique top-level directory names
    const seen = new Set();
    for (const line of stdout.split('\n')) {
      const top = line.split('/')[0];
      if (top) seen.add(top);
    }
    topEntries = Array.from(seen);
  } catch (e) {
    return { ok: false, error: 'Failed to inspect archive: ' + e.message };
  }

  const hasStoragePrefix = topEntries.includes('storage');
  const hasCertsPrefix = topEntries.includes('certs');

  // Legacy backup (no storage/ prefix): extract directly into storageDir
  if (!hasStoragePrefix) {
    try {
      await runCommand('tar', ['-xzf', backupPath, '-C', storageDir]);
    } catch (e) {
      return { ok: false, error: 'tar extract failed: ' + e.message };
    }
    return { ok: true, restoredStorage: true, restoredCerts: false };
  }

  // New-style backup: extract storage/ into storageDir, certs/ into certsDir
  // Use a temp staging dir to extract, then move files into place
  const ts = Date.now().toString();
  const stagingDir = path.join(backupDir, '.restore-' + ts);
  try {
    fs.mkdirSync(stagingDir, { recursive: true });
    await runCommand('tar', ['-xzf', backupPath, '-C', stagingDir]);
  } catch (e) {
    cleanupStaging(stagingDir);
    return { ok: false, error: 'tar extract failed: ' + e.message };
  }

  let restoredStorage = false;
  let restoredCerts = false;

  // Restore storage/
  // Remove existing destination entries before copying to avoid macOS cp -R
  // nesting bug (when dst already exists, cp -R src dst/ creates dst/src/).
  const extractedStorage = path.join(stagingDir, 'storage');
  if (fs.existsSync(extractedStorage)) {
    try {
      const entries = fs.readdirSync(extractedStorage);
      for (const entry of entries) {
        const dest = path.join(storageDir, entry);
        if (fs.existsSync(dest)) {
          await runCommand('rm', ['-rf', dest]);
        }
        await runCommand('cp', ['-R', path.join(extractedStorage, entry), dest]);
      }
      restoredStorage = true;
    } catch (e) {
      cleanupStaging(stagingDir);
      return { ok: false, error: 'Failed to restore storage files: ' + e.message };
    }
  }

  // Restore certs/
  const extractedCerts = path.join(stagingDir, 'certs');
  if (hasCertsPrefix && fs.existsSync(extractedCerts) && certsDir) {
    try {
      if (!fs.existsSync(certsDir)) fs.mkdirSync(certsDir, { recursive: true });
      const entries = fs.readdirSync(extractedCerts);
      for (const entry of entries) {
        const dest = path.join(certsDir, entry);
        if (fs.existsSync(dest)) {
          await runCommand('rm', ['-rf', dest]);
        }
        await runCommand('cp', ['-R', path.join(extractedCerts, entry), dest]);
      }
      restoredCerts = true;
    } catch (e) {
      // Non-fatal: storage was already restored
      if (process.stderr) process.stderr.write('[backup-manager] Warning: failed to restore certs: ' + e.message + '\n');
    }
  }

  cleanupStaging(stagingDir);
  return { ok: true, restoredStorage, restoredCerts };
}

/**
 * Deletes a backup by filename.
 * Returns { ok }
 */
function deleteBackup(filename) {
  if (!storageDir) return { ok: false, error: 'Storage path not set' };
  if (!filename || typeof filename !== 'string') return { ok: false, error: 'filename is required' };

  const safe = path.basename(filename);
  if (!safe.endsWith('.tar.gz')) return { ok: false, error: 'Invalid backup filename' };

  const backupDir = getBackupDir();
  const backupPath = path.join(backupDir, safe);

  if (!fs.existsSync(backupPath)) {
    return { ok: false, error: 'Backup not found: ' + safe };
  }

  try {
    fs.unlinkSync(backupPath);
  } catch (e) {
    return { ok: false, error: 'Failed to delete backup: ' + e.message };
  }

  return { ok: true };
}

/**
 * Prunes old backups, keeping only the `retention` most recent.
 * Called automatically after createBackup.
 */
function pruneOldBackups(retention) {
  const n = typeof retention === 'number' && retention > 0 ? retention : DEFAULT_RETENTION;
  const result = listBackups();
  if (!result.ok) return;
  const toDelete = result.backups.slice(n);
  for (const b of toDelete) {
    try { fs.unlinkSync(b.path); } catch (_) {}
  }
}

module.exports = {
  setStoragePath,
  setCertsPath,
  createBackup,
  listBackups,
  restoreBackup,
  deleteBackup,
  pruneOldBackups,
  DEFAULT_RETENTION
};