const fs = require('fs');
const path = require('path');
const crypto = require('crypto');
const AdmZip = require('adm-zip');
const CryptoUtils = require('./crypto-utils');

class Patcher {
  constructor(appDataPath) {
    this.appDataPath = appDataPath;
  }

  getCurrentVersion() {
    const versionFile = path.join(this.appDataPath, 'version.json');
    if (fs.existsSync(versionFile)) {
      try {
        return JSON.parse(fs.readFileSync(versionFile, 'utf8')).version || '0.0.0';
      } catch (e) {
        return '0.0.0';
      }
    }
    return '0.0.0';
  }

  getCurrentSha() {
    const versionFile = path.join(this.appDataPath, 'version.json');
    if (fs.existsSync(versionFile)) {
      try {
        return JSON.parse(fs.readFileSync(versionFile, 'utf8')).sha256 || null;
      } catch (e) {
        return null;
      }
    }
    return null;
  }

  bridgeCredentials(credentialManager) {
    const encryptedPath = path.join(this.appDataPath, 'encrypted-credentials.json');
    if (!fs.existsSync(encryptedPath)) {
      return false;
    }

    const buildKey = CryptoUtils.deriveKey('vyla-home-build-key', 'vyla-home-payload-salt-v1');
    const encryptedData = fs.readFileSync(encryptedPath, 'utf8');
    const credentials = CryptoUtils.decryptObject(encryptedData, buildKey);

    for (const [service, keys] of Object.entries(credentials)) {
      credentialManager.setServiceCredentials(service, keys);
    }

    fs.unlinkSync(encryptedPath);
    return true;
  }

  saveCurrentVersion(version, sha256 = null) {
    const versionFile = path.join(this.appDataPath, 'version.json');
    fs.mkdirSync(this.appDataPath, { recursive: true });
    fs.writeFileSync(versionFile, JSON.stringify({ version, sha256 }, null, 2), 'utf8');
  }

  purgeOldCode() {
    const dirs = ['frontend', 'player', 'stream-api', 'auth-proxy', 'config'];
    for (const dir of dirs) {
      const fullPath = path.join(this.appDataPath, dir);
      if (fs.existsSync(fullPath)) {
        try {
          fs.rmSync(fullPath, { recursive: true, force: true });
        } catch (e) { }
      }
    }
  }

  extractZipPayload(zipPath) {
    const zip = new AdmZip(zipPath);
    const entries = zip.getEntries();

    if (!entries || entries.length === 0) {
      throw new Error('Archive is empty, invalid, or truncated.');
    }

    const targetDir = path.resolve(this.appDataPath);
    for (const entry of entries) {
      const entryPath = path.normalize(entry.entryName);
      const resolvedPath = path.resolve(targetDir, entryPath);
      if (!resolvedPath.startsWith(targetDir)) {
        throw new Error(`Directory traversal attempt detected in archive: ${entry.entryName}`);
      }
    }

    zip.extractAllTo(this.appDataPath, true);
  }

  async extractToStaging(zipPath, onFile) {
    const stagingDir = path.join(this.appDataPath, '.staging');
    fs.rmSync(stagingDir, { recursive: true, force: true });
    fs.mkdirSync(stagingDir, { recursive: true });
    const zip = new AdmZip(zipPath);
    const entries = zip.getEntries().filter((e) => !e.isDirectory);
    if (entries.length === 0) {
      throw new Error('Downloaded archive is empty, invalid, or truncated.');
    }

    const resolvedStaging = path.resolve(stagingDir);
    for (const entry of entries) {
      const entryPath = path.normalize(entry.entryName);
      const resolvedPath = path.resolve(resolvedStaging, entryPath);
      if (!resolvedPath.startsWith(resolvedStaging)) {
        throw new Error(`Directory traversal attempt detected: ${entry.entryName}`);
      }
    }

    for (let i = 0; i < entries.length; i++) {
      const entry = entries[i];
      zip.extractEntryTo(entry, stagingDir, true, true);
      if (onFile) onFile(entry.entryName, i + 1, entries.length);
      if (i % 20 === 0) await new Promise((resolve) => setImmediate(resolve));
    }
    return stagingDir;
  }

  commitStaging(stagingDir) {
    this.purgeOldCode();
    for (const name of fs.readdirSync(stagingDir)) {
      const dest = path.join(this.appDataPath, name);
      fs.rmSync(dest, { recursive: true, force: true });
      fs.renameSync(path.join(stagingDir, name), dest);
    }
    fs.rmSync(stagingDir, { recursive: true, force: true });
  }

  verifyChecksum(zipPath, expectedSha256) {
    if (!expectedSha256) return false;
    const hash = crypto.createHash('sha256');
    const data = fs.readFileSync(zipPath);
    hash.update(data);
    const calculated = hash.digest('hex');
    return calculated === String(expectedSha256).trim().toLowerCase();
  }

  verifyExtraction(root = this.appDataPath) {
    const requiredFiles = [
      'frontend/server.js',
      'player/server.js'
    ];

    for (const file of requiredFiles) {
      const fullPath = path.join(root, file);
      if (!fs.existsSync(fullPath)) {
        return false;
      }
      const stat = fs.statSync(fullPath);
      if (stat.size === 0) {
        return false;
      }
      try {
        const sampleSize = Math.min(stat.size, 4096);
        const fd = fs.openSync(fullPath, 'r');
        const buffer = Buffer.alloc(sampleSize);
        fs.readSync(fd, buffer, 0, sampleSize, 0);
        fs.closeSync(fd);
        if (buffer.every(byte => byte === 0)) {
          return false;
        }
      } catch (e) {
        return false;
      }
    }
    return true;
  }

  processDirectory(dir, replacementList = []) {
    const files = fs.readdirSync(dir);
    for (const file of files) {
      const fullPath = path.join(dir, file);
      const stat = fs.statSync(fullPath);

      if (stat.isDirectory()) {
        if (file === 'node_modules' || file === '.git') continue;
        this.processDirectory(fullPath, replacementList);
      } else if (stat.isFile()) {
        let content = fs.readFileSync(fullPath, 'utf8');
        let modified = false;

        for (const rep of replacementList) {
          if (content.includes(rep.find)) {
            content = content.split(rep.find).join(rep.replace);
            modified = true;
          }
        }

        if (modified) {
          fs.writeFileSync(fullPath, content, 'utf8');
        }
      }
    }
  }

  applyPatches(replacements) {
    const targetDirs = ['frontend', 'player'];
    for (const dirName of targetDirs) {
      const dirPath = path.join(this.appDataPath, dirName);
      if (!fs.existsSync(dirPath)) continue;
      const replacementList = replacements[dirName] || [];
      this.processDirectory(dirPath, replacementList);
    }
  }
}

module.exports = Patcher;