'use strict';

module.exports.create = function (deps, conf, greenlockMiddleware) {
  var PromiseA = require('bluebird');
  var express = require('express');
  var app = express();
  var adminApp = require('./admin').create(deps, conf);
  var domainMatches = require('../domain-utils').match;
  var separatePort = require('../domain-utils').separatePort;

  var adminDomains = [
    /\blocalhost\.admin\./
  , /\blocalhost\.alpha\./
  , /\badmin\.localhost\./
  , /\balpha\.localhost\./
  ];

  function parseHeaders(conn, opts) {
    // There should already be a `firstChunk` on the opts, but because we might sometimes
    // need more than that to get all the headers it's easier to always read the data off
    // the connection and put it back later if we need to.
    opts.firstChunk = Buffer.alloc(0);

    // First we make sure we have all of the headers.
    return new PromiseA(function (resolve, reject) {
      if (opts.firstChunk.includes('\r\n\r\n')) {
        resolve(opts.firstChunk.toString());
        return;
      }

      var errored = false;
      function handleErr(err) {
        errored = true;
        reject(err);
      }
      conn.once('error', handleErr);

      function handleChunk(chunk) {
        if (!errored) {
          opts.firstChunk = Buffer.concat([opts.firstChunk, chunk]);
          if (opts.firstChunk.includes('\r\n\r\n')) {
            resolve(opts.firstChunk.toString());
            conn.removeListener('error', handleErr);
          } else {
            conn.once('data', handleChunk);
          }
        }
      }
      conn.once('data', handleChunk);
    }).then(function (firstStr) {
      var headerSection = firstStr.split('\r\n\r\n')[0];
      var lines = headerSection.split('\r\n');
      var result = {};

      lines.slice(1).forEach(function (line) {
        var match = /(.*)\s*:\s*(.*)/.exec(line);
        if (match) {
          result[match[1].toLowerCase()] = match[2];
        } else {
          console.error('HTTP header line does not match pattern', line);
        }
      });

      var match = /^([a-zA-Z]+)\s+(\S+)\s+HTTP/.exec(lines[0]);
      if (!match) {
        throw new Error('first line of "HTTP" does not match pattern: '+lines[0]);
      }
      result.method = match[1].toUpperCase();
      result.url = match[2];

      return result;
    });
  }

  function moduleMatchesHost(req, mod) {
    var host = separatePort((req.headers || req).host).host;

    return mod.domains.some(function (pattern) {
      return domainMatches(pattern, host);
    });
  }

  function verifyHost(fullHost) {
    var host = separatePort(fullHost).host;

    if (host === 'localhost') {
      return fullHost.replace(host, 'localhost.daplie.me');
    }

    // Test for IPv4 and IPv6 addresses. These patterns will match some invalid addresses,
    // but since those still won't be valid domains that won't really be a problem.
    if (/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/.test(host) || /^\[[0-9a-fA-F:]+\]$/.test(host)) {
      if (!conf.http.primaryDomain) {
        (conf.http.modules || []).some(function (mod) {
          return mod.domains.some(function (domain) {
            if (domain[0] !== '*') {
              conf.http.primaryDomain = domain;
              return true;
            }
          });
        });
      }
      return fullHost.replace(host, conf.http.primaryDomain || host);
    }

    return fullHost;
  }

  // We handle both HTTPS and HTTP traffic on the same ports, and we want to redirect
  // any unencrypted requests to the same port they came from unless it came in on
  // the default HTTP port, in which case there wont be a port specified in the host.
  var redirecters = {};
  function redirectHttps(req, res, next) {
    if (conf.http.allowInsecure) {
      next();
      return;
    }

    var port = separatePort(req.headers.host).port;
    if (!redirecters[port]) {
      redirecters[port] = require('redirect-https')({
        port: port
      , trustProxy: conf.http.trustProxy
      });
    }

    // localhost and IP addresses cannot have real SSL certs (and don't contain any useful
    // info for redirection either), so we direct some hosts to either localhost.daplie.me
    // or the "primary domain" ie the first manually specified domain.
    req.headers.host = verifyHost(req.headers.host);

    redirecters[port](req, res, next);
  }

  function handleAdmin(req, res, next) {
    var admin = adminDomains.some(function (re) {
      return re.test(req.headers.host);
    });

    if (admin) {
      adminApp(req, res);
    } else {
      next();
    }
  }

  function respond404(req, res) {
    res.writeHead(404);
    res.end('Not Found');
  }

  function createRedirectRoute(mod) {
    // Escape any characters that (can) have special meaning in regular expression
    // but that aren't the special characters we have interest in.
    var from = mod.from.replace(/[-\/\\^$+?.()|[\]{}]/g, '\\$&');
    // Then modify the characters we are interested in so they do what we want in
    // the regular expression after being compiled.
    from = from.replace(/\*/g, '(.*)');
    var fromRe = new RegExp('^' + from + '/?$');

    return function (req, res, next) {
      if (!moduleMatchesHost(req, mod)) {
        next();
        return;
      }

      var match = fromRe.exec(req.url);
      if (!match) {
        next();
        return;
      }

      var to = mod.to;
      match.slice(1).forEach(function (globMatch, index) {
        to = to.replace(':'+(index+1), globMatch);
      });
      res.writeHead(mod.status || 301, { 'Location': to });
      res.end();
    };
  }

  function createStaticRoute(mod) {
    var getStaticApp, staticApp;
    if (/:hostname/.test(mod.root)) {
      staticApp = {};
      getStaticApp = function (hostname) {
        if (!staticApp[hostname]) {
          staticApp[hostname] = express.static(mod.root.replace(':hostname', hostname));
        }
        return staticApp[hostname];
      };
    }
    else {
      staticApp = express.static(mod.root);
      getStaticApp = function () {
        return staticApp;
      };
    }

    return function (req, res, next) {
      if (moduleMatchesHost(req, mod)) {
        getStaticApp(separatePort(req.headers.host).host)(req, res, next);
      } else {
        next();
      }
    };
  }

  app.use(greenlockMiddleware);
  app.use(redirectHttps);
  app.use(handleAdmin);

  (conf.http.modules || []).forEach(function (mod) {
    if (mod.name === 'redirect') {
      app.use(createRedirectRoute(mod));
    }
    else if (mod.name === 'static') {
      app.use(createStaticRoute(mod));
    }
    else {
      console.warn('unknown HTTP module', mod);
    }
  });

  app.use(respond404);

  var server = require('http').createServer(app);

  function handleHttp(conn, opts) {
    server.emit('connection', conn);

    // We need to put back whatever data we read off to determine the connection was HTTP
    // and to parse the headers. Must be done after data handlers added but before any new
    // data comes in.
    process.nextTick(function () {
      conn.unshift(opts.firstChunk);
    });

    // Convenience return for all the check* functions.
    return true;
  }

  function checkACME(conn, opts, headers) {
    if (headers.url.indexOf('/.well-known/acme-challenge/') !== 0) {
      return false;
    }

    return handleHttp(conn, opts);
  }

  function checkRedirect(conn, opts, headers) {
    if (conf.http.allowInsecure || conn.encrypted) {
      return false;
    }
    if (conf.http.trustProxy && 'https' === headers['x-forwarded-proto']) {
      return false;
    }

    return handleHttp(conn, opts);
  }

  function checkAdmin(conn, opts, headers) {
    var admin = adminDomains.some(function (re) {
      return re.test(headers.host);
    });

    if (admin) {
      return handleHttp(conn, opts);
    }
    return false;
  }

  function checkProxy(mod, conn, opts, headers) {
    if (!moduleMatchesHost(headers, mod)) {
      return false;
    }

    var connected = false;
    var newConnOpts = separatePort(mod.address);
    newConnOpts.servername = separatePort(headers.host).host;
    newConnOpts.data = opts.firstChunk;

    newConnOpts.remoteFamily  = opts.family  || conn.remoteFamily;
    newConnOpts.remoteAddress = opts.address || conn.remoteAddress;
    newConnOpts.remotePort    = opts.port    || conn.remotePort;

    var newConn = deps.net.createConnection(newConnOpts, function () {
      connected = true;
      newConn.write(opts.firstChunk);
      newConn.pipe(conn);
      conn.pipe(newConn);
    });

    // Not sure how to effectively report this to the user or client, but we need to listen
    // for the event to prevent it from crashing us.
    newConn.on('error', function (err) {
      if (connected) {
        console.error('HTTP proxy remote error', err);
        conn.end();
      } else {
        require('../proxy-err-resp').sendBadGateway(conn, err, conf.debug);
      }
    });
    conn.on('error', function (err) {
      console.error('HTTP proxy client error', err);
      newConn.end();
    });

    return true;
  }

  function handleConnection(conn) {
    var opts = conn.__opts;
    parseHeaders(conn, opts)
      .then(function (headers) {
        if (checkACME(conn, opts, headers))     { return; }
        if (checkRedirect(conn, opts, headers)) { return; }
        if (checkAdmin(conn, opts, headers))    { return; }

        var handled = (conf.http.modules || []).some(function (mod) {
          if (mod.name === 'proxy') {
            return checkProxy(mod, conn, opts, headers);
          }
        });
        if (handled) {
          return;
        }

        server.emit('connection', conn);
        process.nextTick(function () {
          conn.unshift(opts.firstChunk);
        });
      })
      ;
  }

  return {
    emit: function (type, value) {
      if (type === 'connection') {
        handleConnection(value);
      }
    }
  };
};