const path = require('path');
const fs = require('fs');
const os = require('os');
const express = require('express');
const ServiceManager = require('./service-manager');
const Patcher = require('./patcher');
const UpdateClient = require('./update-client');

const debugLogPath = path.join(os.homedir(), 'Downloads', 'vyla-node-debug.log');
function debugLog(msg) {
  try { fs.appendFileSync(debugLogPath, `[NODE] ${msg}\n`, 'utf8'); } catch (e) { }
}

debugLog("--- Node.js Process Started ---");

let serviceManager;
let expressApp;
let expressServer;
let playerExpressApp;
let playerExpressServer;

const APPDATA_DIR = process.env.APPDATA_PATH || path.join(os.homedir(), 'AppData', 'Roaming', 'vyla-home', 'vyla-home-files');
fs.mkdirSync(APPDATA_DIR, { recursive: true });
debugLog(`AppData Dir: ${APPDATA_DIR}`);

const envConfig = JSON.parse(fs.readFileSync(path.join(__dirname, 'config/env.json'), 'utf8'));
const replacementsConfig = JSON.parse(fs.readFileSync(path.join(__dirname, 'config/replacements.json'), 'utf8'));

const updateClient = new UpdateClient(APPDATA_DIR);

function sendToTauri(event, data) {
  debugLog(`Emitting to Tauri: [${event}] -> ${JSON.stringify(data)}`);
  process.stdout.write(JSON.stringify({ event, data }) + '\n');
}

process.on('unhandledRejection', (reason) => {
  const message = reason && reason.message ? reason.message : String(reason);
  debugLog(`UNHANDLED REJECTION: ${message}`);
  sendToTauri('error', { message });
});

process.on('uncaughtException', (err) => {
  debugLog(`UNCAUGHT EXCEPTION: ${err.message}`);
  sendToTauri('error', { message: err.message });
});

async function start() {
  debugLog("Inside start() function");
  sendToTauri('status', { message: 'Initializing patcher...' });
  const patcher = new Patcher(APPDATA_DIR);
  serviceManager = new ServiceManager(APPDATA_DIR, envConfig);

  const installBuild = async (release) => {
    const tempZipPath = path.join(APPDATA_DIR, 'download-temp.zip');
    let attempts = 0;
    let downloadSuccess = false;

    while (attempts < 3 && !downloadSuccess) {
      attempts++;
      try {
        debugLog(`Attempting to download update (Attempt ${attempts})...`);
        sendToTauri('status', { message: `Downloading update (Attempt ${attempts}/3)...` });

        await updateClient.downloadUpdate(release, tempZipPath, (downloaded, total) => {
          const percent = total > 0 ? Math.round((downloaded / total) * 100) : 0;
          sendToTauri('download-progress', { downloaded, total, percent });
        });

        debugLog('Download complete. Verifying checksum...');
        sendToTauri('status', { message: 'Verifying payload checksum...' });
        if (!patcher.verifyChecksum(tempZipPath, release.sha256)) {
          throw new Error('SHA-256 checksum verification failed.');
        }

        debugLog('Checksum verified. Extracting...');
        sendToTauri('status', { message: 'Extracting update files...' });
        patcher.purgeOldCode();
        patcher.extractZipPayload(tempZipPath);

        if (!patcher.verifyExtraction()) {
          throw new Error('Extraction verification failed: critical startup files missing.');
        }

        debugLog('Extraction complete. Applying patches...');
        sendToTauri('status', { message: 'Applying patches & configuring...' });
        patcher.applyPatches(replacementsConfig);
        patcher.bridgeCredentials(serviceManager.credentialManager);
        patcher.saveCurrentVersion(release.version, release.sha256);

        if (fs.existsSync(tempZipPath)) {
          fs.unlinkSync(tempZipPath);
        }
        downloadSuccess = true;
        debugLog('Update installed successfully!');
      } catch (err) {
        debugLog(`Download/Install error on attempt ${attempts}: ${err.message}`);
        if (fs.existsSync(tempZipPath)) {
          try { fs.unlinkSync(tempZipPath); } catch (e) { }
        }
        if (attempts >= 3) {
          throw new Error(`Failed to download and verify build after 3 attempts: ${err.message}`);
        }
        await new Promise(r => setTimeout(r, 2000));
      }
    }
  };

  try {
    const isFirstRun = !patcher.verifyExtraction();
    const localVersion = patcher.getCurrentVersion();
    const localSha = patcher.getCurrentSha();
    debugLog(`Is First Run: ${isFirstRun}, Local Version: ${localVersion}`);

    sendToTauri('status', { message: 'Checking for updates...' });
    let release = null;
    try {
      debugLog("Fetching updates from updateClient...");
      release = await updateClient.checkForUpdates();
      debugLog(`Update check finished. Found: ${release ? release.version : 'None'}`);
    } catch (e) {
      debugLog(`Update check failed (offline?): ${e.message}`);
    }

    if (release) {
      const hasUpdate = release.version !== localVersion || (release.sha256 && release.sha256 !== localSha);
      if (isFirstRun || hasUpdate) {
        debugLog("Update required or first run. Installing remote build...");
        await installBuild(release);
      } else {
        debugLog("Already on the latest version.");
      }
    } else if (isFirstRun) {
      debugLog("No remote release found, but it's the first run. Looking for local update-payload.zip...");
      const localZip = path.join(__dirname, 'update-payload.zip');
      if (fs.existsSync(localZip)) {
        sendToTauri('status', { message: 'Extracting initial local payload...' });
        patcher.purgeOldCode();
        patcher.extractZipPayload(localZip);
        patcher.applyPatches(replacementsConfig);
        patcher.bridgeCredentials(serviceManager.credentialManager);
        patcher.saveCurrentVersion("1.0.0");
        debugLog("Local payload extracted successfully.");
      } else {
        debugLog("No local payload found!");
      }
    }

    if (!patcher.verifyExtraction()) {
      throw new Error('No application files found. Check your internet connection and try again.');
    }

    sendToTauri('status', { message: 'Loading credentials...' });
    serviceManager.credentialManager.loadCredentials();

    sendToTauri('status', { message: 'Starting backend services...' });
    await serviceManager.startServices([
      { name: 'auth-proxy', relativeDir: 'auth-proxy' },
      { name: 'stream-api', relativeDir: 'stream-api' },
    ]);
    debugLog("Backend services spawn requested.");

    const playerDir = path.join(APPDATA_DIR, 'player');
    playerExpressApp = express();
    playerExpressApp.use(express.static(playerDir, { maxAge: '1d', etag: true }));
    playerExpressApp.get('*', (req, res) => { res.sendFile(path.join(playerDir, 'index.html')); });
    playerExpressServer = playerExpressApp.listen(3001, '0.0.0.0');
    debugLog("Player Express running on 3001");

    sendToTauri('status', { message: 'Waiting for ports 3000, 3001, 7860...' });
    await serviceManager.waitForPorts([3000, 3001, 7860]);
    debugLog("Ports 3000, 3001, 7860 are ready.");

    const frontendDir = path.join(APPDATA_DIR, 'frontend');
    expressApp = express();
    expressApp.use(express.static(frontendDir, { maxAge: '1d', etag: true }));
    expressApp.get('*', (req, res) => { res.sendFile(path.join(frontendDir, 'index.html')); });

    const FRONTEND_PORT = 4890;
    expressServer = expressApp.listen(FRONTEND_PORT, '0.0.0.0', () => {
      debugLog("Frontend Express running on 4890. Sending READY to Tauri.");
      sendToTauri('ready', { url: `http://localhost:${FRONTEND_PORT}` });
    });

  } catch (error) {
    debugLog(`Fatal Start Error: ${error.message}`);
    sendToTauri('error', { message: error.message });
  }
}

process.on('exit', () => {
  if (serviceManager) {
    for (const name of Object.keys(serviceManager.processes)) {
      const proc = serviceManager.processes[name];
      if (proc && proc.child) {
        try { proc.child.kill('SIGKILL'); } catch (e) { }
      }
    }
  }
});

process.on('SIGINT', async () => {
  if (expressServer) expressServer.close();
  if (playerExpressServer) playerExpressServer.close();
  if (serviceManager) await serviceManager.stopAll();
  process.exit(0);
});

start();