const http = require( 'http' );
const fs = require( 'fs' );
const path = require( 'path' );
const crypto = require( 'crypto' );
const puppeteer = require( 'puppeteer' );
const express = require( 'express' );

const PORT = 6860;
const CACHE_DIR = path.join( __dirname, 'cache' );

const host = "https://networkheaven.net";
const app = express();

if( !fs.existsSync( CACHE_DIR ) ) fs.mkdirSync( CACHE_DIR );

function hash( str ) {
  return crypto.createHash( 'sha1' ).update( str ).digest( 'hex' );
}

let browser = null;
let cache = async ( req, res ) => {
  const { url } = req;
  console.log( `incoming req from ${req.headers['user-agent']} for ${url}` );

  const urlObj = new URL( req.url, host );
  const target = urlObj.href;

  const key = hash( target );
  const file = path.join( CACHE_DIR, key + '.html' );

  if( fs.existsSync( file ) ) {
    const html = fs.readFileSync( file );
    res.writeHead( 200, { 'content-type': 'text/html' } );
    return res.end( html );
  }

  try {
    const page = await browser.newPage();

    const r = await page.goto( target, {
      waitUntil: 'networkidle2',
      timeout: 30000
    } );

    const html = await page.content();
    console.log( "caching page: " + target );
    fs.writeFileSync( file, html );

    await page.close();
    const headers = r.headers();

    res.writeHead( 200, {
      'content-type': headers['content-type'],
      'date': headers['date'],
      'etag': headers['etag'],
    } );
    res.end( html );

  } catch( e ) {
    res.writeHead( 500, { 'content-type': 'text/plain' } );
    res.end( 'render failed: ' + e.message );
  }
}

app.get( "/", cache );
app.get( /\/$/, cache );
app.get( /#$/, cache );
app.get( /^\/[^.]*$/, cache );
app.use( async ( req, res ) => {
  let url = new URL( req.url, host );
  const r = await fetch( url.href );

  if( r.ok ) {
    const html = await r.text();
    const headers = [];
    for( const [k, v] of r.headers.entries() )
      headers[k] = v;

    res.writeHead( 200, {
      'content-type': headers['content-type'],
      'date': headers['date'],
      'etag': headers['etag'],
    } );
    res.end( html );
  }
} );

(async () => {
  browser = await puppeteer.launch( { headless: 'new' } );
  app.listen( PORT, async () => {

    console.log( "listening on http://localhost:" + PORT );
  } );
})();