import { app, BrowserWindow, dialog, ipcMain, session } from 'electron';
import path from 'path';
import fs from 'fs';
import https from 'https';

const AUTH_HOST = 'https://account.rokojori.com';
const PORT = 3000;

// ── Persistence helpers ────────────────────────────────────────────────────────

function tokenFile(): string {
  return path.join( app.getPath( 'userData' ), 'tokens.json' );
}

function emailFile(): string {
  return path.join( app.getPath( 'userData' ), 'last-email.txt' );
}

interface Tokens {
  accessToken: string;
  refreshToken: string;
}

function loadTokens(): Tokens | null {
  try {
    const raw = fs.readFileSync( tokenFile(), 'utf-8' );
    return JSON.parse( raw ) as Tokens;
  } catch {
    return null;
  }
}

function saveTokens( tokens: Tokens ): void {
  fs.writeFileSync( tokenFile(), JSON.stringify( tokens ), 'utf-8' );
}

function clearTokens(): void {
  try { fs.unlinkSync( tokenFile() ); } catch { /* already gone */ }
}

function loadLastEmail(): string {
  try { return fs.readFileSync( emailFile(), 'utf-8' ).trim(); } catch { return ''; }
}

function saveLastEmail( email: string ): void {
  fs.writeFileSync( emailFile(), email, 'utf-8' );
}

function clearCredentials(): void {
  try { fs.unlinkSync( emailFile() ); } catch { /* already gone */ }
}

function localRecentsFile(): string {
  return path.join( app.getPath( 'userData' ), 'local-recents.json' );
}

function loadLocalRecents(): string[] {
  try {
    const raw = fs.readFileSync( localRecentsFile(), 'utf-8' );
    return JSON.parse( raw ) as string[];
  } catch {
    return [];
  }
}

function saveLocalRecents( recents: string[] ): void {
  fs.writeFileSync( localRecentsFile(), JSON.stringify( recents ), 'utf-8' );
}

function addLocalRecent( folderPath: string ): void {
  const recents = loadLocalRecents().filter( r => r !== folderPath );
  recents.unshift( folderPath );
  saveLocalRecents( recents.slice( 0, 10 ) );
}

function removeLocalRecent( folderPath: string ): string[] {
  const recents = loadLocalRecents().filter( r => r !== folderPath );
  saveLocalRecents( recents );
  return recents;
}

// ── Clock offset ───────────────────────────────────────────────────────────────
// Electron holds the access token directly, so expiry comparisons must use
// server-authoritative time, not the local clock (which can be significantly wrong).
// We read the Date header from the first auth-server response and cache the offset.

let _serverClockOffsetMs: number | null = null;

function updateClockOffset( dateHeader: string | undefined ): void {
  if ( _serverClockOffsetMs !== null || !dateHeader ) return;
  const serverMs = new Date( dateHeader ).getTime();
  if ( isNaN( serverMs ) ) return;
  _serverClockOffsetMs = serverMs - Date.now();
}

function serverNow(): number {
  return Date.now() + ( _serverClockOffsetMs ?? 0 );
}

// ── Network ────────────────────────────────────────────────────────────────────

function postJson( url: string, body: unknown, extraHeaders?: Record<string, string> ): Promise<unknown> {
  return new Promise( ( resolve, reject ) => {
    const data = JSON.stringify( body );
    const parsed = new URL( url );
    const req = https.request(
      {
        hostname: parsed.hostname,
        path: parsed.pathname,
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Content-Length': Buffer.byteLength( data ),
          ...( extraHeaders ?? {} ),
        },
      },
      ( res ) => {
        updateClockOffset( res.headers.date );
        let raw = '';
        res.on( 'data', ( chunk: string ) => { raw += chunk; } );
        res.on( 'end', () => {
          try { resolve( JSON.parse( raw ) ); }
          catch { reject( new Error( `Non-JSON response: ${raw}` ) ); }
        } );
      }
    );
    req.on( 'error', reject );
    req.write( data );
    req.end();
  } );
}

// ── Electron token updater ─────────────────────────────────────────────────────
// Checks the access token's expiry (decoded from the JWT payload) against
// server-corrected time every 5 minutes. Refreshes proactively when within
// 15 minutes of expiry — matching the server-side PROACTIVE_REFRESH_MARGIN_SEC.
// On refresh failure: network errors are silently retried next tick;
// auth failures (revoked / expired refresh token) close the main window and
// show the login screen.

const REFRESH_MARGIN_MS  = 15 * 60 * 1000;
const UPDATER_INTERVAL_MS =  5 * 60 * 1000;

function decodeJwtPayload( token: string ): Record<string, unknown> | null {
  try {
    const parts = token.split( '.' );
    if ( parts.length !== 3 ) return null;
    const json = Buffer.from(
      parts[ 1 ].replace( /-/g, '+' ).replace( /_/g, '/' ),
      'base64'
    ).toString( 'utf-8' );
    return JSON.parse( json ) as Record<string, unknown>;
  } catch { return null; }
}

function tokenExpMs( token: string ): number | null {
  const payload = decodeJwtPayload( token );
  if ( !payload || typeof payload.exp !== 'number' ) return null;
  return payload.exp * 1000;
}

async function refreshCurrentTokens(): Promise<void> {
  const tokens = currentTokens;
  if ( !tokens ) return;
  try {
    const result = await postJson(
      `${ AUTH_HOST }/api/auth/refresh`,
      { refreshToken: tokens.refreshToken }
    ) as Record<string, unknown>;
    if ( result.accessToken && result.refreshToken ) {
      currentTokens = {
        accessToken:  result.accessToken  as string,
        refreshToken: result.refreshToken as string,
      };
      saveTokens( currentTokens );
    } else {
      clearTokens();
      currentTokens = null;
      mainWindow?.close();
      createLoginWindow();
    }
  } catch {
    // network error — keep current tokens and retry next tick
  }
}

async function checkAndRefreshIfDue(): Promise<void> {
  const tokens = currentTokens;
  if ( !tokens ) return;
  const expMs = tokenExpMs( tokens.accessToken );
  if ( expMs === null ) return;
  if ( expMs - serverNow() < REFRESH_MARGIN_MS ) {
    await refreshCurrentTokens();
  }
}

function startElectronTokenUpdater(): void {
  setInterval( () => void checkAndRefreshIfDue(), UPDATER_INTERVAL_MS );
  setInterval( () => writeHeartbeat(), HEARTBEAT_WRITE_INTERVAL_MS );
}

// ── Session heartbeat ───────────────────────────────────────────────────────────
// A running instance writes its current access token + timestamp every 10 s.
// A newly-starting instance reads this file on launch: if ≤ 30 s old it calls
// POST /api/auth/new-session (requireAuth-guarded) to mint its own independent
// token pair, avoiding the login screen when at least one other instance is live.
// This replaces the plaintext last-password.txt auto-login that was here before.

const HEARTBEAT_WRITE_INTERVAL_MS = 10_000;
const HEARTBEAT_MAX_AGE_MS        = 30_000;

interface Heartbeat { accessToken: string; timestamp: number; }

function heartbeatFile(): string {
  return path.join( app.getPath( 'userData' ), 'session-heartbeat.json' );
}

function writeHeartbeat(): void {
  const tokens = currentTokens;
  if ( !tokens ) return;
  const hb: Heartbeat = { accessToken: tokens.accessToken, timestamp: Date.now() };
  try { fs.writeFileSync( heartbeatFile(), JSON.stringify( hb ), 'utf-8' ); } catch { /* ignore */ }
}

function loadHeartbeat(): Heartbeat | null {
  try {
    const raw = fs.readFileSync( heartbeatFile(), 'utf-8' );
    return JSON.parse( raw ) as Heartbeat;
  } catch { return null; }
}

async function tryHeartbeatLogin(): Promise<boolean> {
  const hb = loadHeartbeat();
  if ( !hb ) return false;
  if ( Date.now() - hb.timestamp > HEARTBEAT_MAX_AGE_MS ) return false;
  try {
    const result = await postJson(
      `${ AUTH_HOST }/api/auth/new-session`,
      {},
      { Authorization: `Bearer ${ hb.accessToken }` }
    ) as Record<string, unknown>;
    if ( result.accessToken && result.refreshToken ) {
      currentTokens = {
        accessToken:  result.accessToken  as string,
        refreshToken: result.refreshToken as string,
      };
      saveTokens( currentTokens );
      return true;
    }
  } catch { /* network error — fall through to login screen */ }
  return false;
}

// ── Header injection ───────────────────────────────────────────────────────────

function registerHeaderInjector( getToken: () => string | null ): void {
  session.defaultSession.webRequest.onBeforeSendHeaders(
    { urls: [ `http://localhost:${PORT}/*` ] },
    ( details, callback ) => {
      const token = getToken();
      const headers = { ...details.requestHeaders };
      if ( token ) headers[ 'Authorization' ] = `Bearer ${token}`;
      callback( { requestHeaders: headers } );
    }
  );
}

// ── Windows ────────────────────────────────────────────────────────────────────

let mainWindow: BrowserWindow | null = null;
let loginWindow: BrowserWindow | null = null;
let currentTokens: Tokens | null = null;

function createLoginWindow(): void {
  loginWindow = new BrowserWindow( {
    width: 420,
    height: 520,
    resizable: false,
    webPreferences: {
      nodeIntegration: false,
      contextIsolation: true,
      preload: path.join( __dirname, 'preload.js' ),
    },
    title: 'Roject — Sign in',
  } );

  loginWindow.loadFile( path.join( __dirname, 'login.html' ) );
  loginWindow.on( 'closed', () => { loginWindow = null; } );
}

async function createMainWindow(): Promise<void> {
  await session.defaultSession.clearStorageData( { storages: [ 'cookies' ] } );

  mainWindow = new BrowserWindow( {
    width: 1400,
    height: 900,
    webPreferences: {
      nodeIntegration: false,
      contextIsolation: true,
      preload: path.join( __dirname, 'preload.js' ),
    },
    title: 'Roject',
  } );

  mainWindow.loadURL( `http://localhost:${PORT}/` );

  const localBase = `http://localhost:${PORT}/`;

  mainWindow.webContents.on( 'will-navigate', ( event, url ) => {
    if ( !url.startsWith( localBase ) ) {
      event.preventDefault();
      clearTokens();
      currentTokens = null;
      mainWindow?.close();
      createLoginWindow();
    }
  } );

  mainWindow.on( 'closed', () => { mainWindow = null; } );
}

// ── Server ─────────────────────────────────────────────────────────────────────

function loadEnv(): void {
  const envPath = path.join( __dirname, '..', '..', '.env' );
  try {
    const lines = fs.readFileSync( envPath, 'utf-8' ).split( /\r?\n/ );
    for ( const line of lines ) {
      const trimmed = line.trim();
      if ( !trimmed || trimmed.startsWith( '#' ) ) continue;
      const eq = trimmed.indexOf( '=' );
      if ( eq === -1 ) continue;
      const key = trimmed.slice( 0, eq ).trim();
      const val = trimmed.slice( eq + 1 ).trim().replace( /^["']|["']$/g, '' );
      if ( key && !( key in process.env ) ) process.env[ key ] = val;
    }
  } catch { /* no .env file — rely on inherited env */ }
}

function startExpressServer(): void {
  loadEnv();
  process.env.ROJECT_ROOT = path.join( __dirname, '..', '..' );
  process.env.ROJECT_ELECTRON = 'true';
  const serverPath = path.join( __dirname, '..', 'server', 'server', 'index.js' );
  // eslint-disable-next-line @typescript-eslint/no-require-imports
  const { startServer } = require( serverPath ) as { startServer: ( port: number ) => void };
  startServer( PORT );
}

// ── App lifecycle ──────────────────────────────────────────────────────────────

app.whenReady().then( () => {
  startElectronTokenUpdater();
  registerHeaderInjector( () => currentTokens?.accessToken ?? null );

  ipcMain.handle( 'auth:login', async ( _event, email: string, password: string, remember: boolean ) => {
    try {
      const result = await postJson( `${ AUTH_HOST }/api/auth/login`, { email, password } ) as Record<string, unknown>;
      if ( result.accessToken && result.refreshToken ) {
        currentTokens = { accessToken: result.accessToken as string, refreshToken: result.refreshToken as string };
        saveTokens( currentTokens );
        if ( remember ) saveLastEmail( email );
        else            clearCredentials();
        return { ok: true };
      }
      return { ok: false, error: ( result.error as string ) ?? 'Login failed' };
    } catch ( err ) {
      return { ok: false, error: String( err ) };
    }
  } );

  ipcMain.handle( 'auth:last-email',        () => loadLastEmail() );
  ipcMain.handle( 'auth:clear-credentials', () => { clearCredentials(); } );

  ipcMain.handle( 'local:open-folder', async () => {
    const win = mainWindow ?? BrowserWindow.getFocusedWindow();
    if ( !win ) return null;
    const result = await dialog.showOpenDialog( win, { properties: [ 'openDirectory' ] } );
    if ( result.canceled || result.filePaths.length === 0 ) return null;
    const folderPath = result.filePaths[ 0 ];
    addLocalRecent( folderPath );
    return folderPath;
  } );

  ipcMain.handle( 'local:get-recents', () => loadLocalRecents() );

  ipcMain.handle( 'local:remove-recent', ( _event, folderPath: string ) => {
    return removeLocalRecent( folderPath );
  } );

  ipcMain.on( 'auth:login-success', () => {
    // Create the main window first, close login only after it exists.
    // Closing login before main is ready triggers window-all-closed → app quit.
    createMainWindow().then( () => loginWindow?.close() );
  } );

  startExpressServer();

  setTimeout( async () => {
    currentTokens = loadTokens();
    if ( currentTokens ) {
      try {
        const result = await postJson(
          `${ AUTH_HOST }/api/auth/refresh`,
          { refreshToken: currentTokens.refreshToken }
        ) as Record<string, unknown>;
        if ( result.accessToken && result.refreshToken ) {
          currentTokens = { accessToken: result.accessToken as string, refreshToken: result.refreshToken as string };
          saveTokens( currentTokens );
          createMainWindow();
        } else {
          clearTokens();
          currentTokens = null;
          createLoginWindow();
        }
      } catch {
        clearTokens();
        currentTokens = null;
        createLoginWindow();
      }
    } else {
      // No saved tokens — try to mint a new independent session from a running instance's
      // heartbeat before falling through to the login screen.
      const gotSession = await tryHeartbeatLogin();
      if ( gotSession ) createMainWindow();
      else              createLoginWindow();
    }
  }, 500 );

  app.on( 'activate', () => {
    if ( BrowserWindow.getAllWindows().length === 0 ) {
      if ( currentTokens ) void createMainWindow();
      else createLoginWindow();
    }
  } );
} );

app.on( 'window-all-closed', () => {
  if ( process.platform !== 'darwin' ) app.quit();
} );