#!/usr/bin/env node

// If you can't quite trust node to find it on its own
var localModules = '/usr/local/lib/node_modules/';
var http = require('http');
var net = require('net');
var url = require('url');
var path = require('path');
var fs = require('fs');
var events = require('events');
var child_process = require('child_process');
var daemon = require(path.join(localModules, "daemon"));
var pty = require(path.join(localModules, "pty.js"));
var WebSocketServer = require(path.join(localModules, "websocket")).server;

/* Configuration variables */
// These first two files are NOT in the chroot.
var ctlsocket = "/var/local/rlgwebd/ctl";
var logfile = "/var/local/rlgwebd/log";
var httpPort = 8080;
var chrootDir = "/var/dgl/";
var dropToUID = 501;
var dropToGID = 501;
var serveStaticRoot = "/var/www/"; // inside the chroot
var playtimeout = 3600000; // Idle time before games are autosaved, in ms

/* Data on the games available. */
var games = {
  "rogue3": {
    "name": "Rogue V3",
    "uname": "rogue3",
    "suffix": ".r3sav",
    "path": "/bin/rogue3",
    "clear": new Buffer([27, 91, 72, 27, 91, 50, 74]) // CSI H CSI 2J
  },
  "rogue4": {
    "name": "Rogue V4",
    "uname": "rogue4",
    "suffix": ".r4sav",
    "path": "/bin/rogue4",
    "clear": new Buffer([27, 91, 72, 27, 91, 50, 74]) // CSI H CSI 2J
  },
  "rogue5": {
    "name": "Rogue V5",
    "uname": "rogue5",
    "suffix": ".r5sav",
    "path": "/bin/rogue5",
    "clear": new Buffer([27, 91, 72, 27, 91, 50, 74]) // CSI H CSI 2J
  },
  "srogue": {
    "name": "Super-Rogue",
    "uname": "srogue",
    "suffix": ".srsav",
    "path": "/bin/srogue",
    "clear": new Buffer([27, 91, 72, 27, 91, 74]) // CSI H CSI J
  }
};

/* Global state */
var logins = {};
var sessions = {};
var clients = {};
var allowlogin = true;
var nextsession = 0;
var gamemux = new events.EventEmitter();

/* Constructor.  A TermSession handles a pty and the game running on it.
 *   game: (String) Name of the game to launch.
 *   lkey: (String, key) The user's id, a key into logins.
 *   dims: (Array [Number, Number]) Height and width of the pty.
 *   handlers: (Object) Key-value pairs, event names and functions to
 *           install to handle them.
 *  Events:
 *   "open": Emitted on startup.  Parameters: success (Boolean)
 *   "data": Data generated by child. Parameters: buf (Buffer)
 *   "exit": Child terminated. Parameters: none
 */
function TermSession(game, lkey, dims, handlers) {
  var ss = this;
  /* Subclass EventEmitter to do the hard work. */
  events.EventEmitter.call(this);
  for (var evname in handlers)
    this.on(evname, handlers[evname]);
  /* Don't launch anything that's not a real game. */
  if (game in games) {
    this.game = games[game];
  }
  else {
    this.emit('open', false);
    return;
  }
  if (lkey in logins) {
    this.key = lkey;
    this.pname = logins[lkey].name;
  }
  else {
    this.emit('open', false);
    return;
  }
  /* Grab a spot in the sessions table. */
  this.sessid = nextsession++;
  sessions[this.sessid] = this;
  /* Set up the sizes. */
  this.w = Math.floor(Number(dims[1]));
  if (!(this.w > 0 && this.w < 256))
    this.w = 80;
  this.h = Math.floor(Number(dims[0]));
  if (!(this.h > 0 && this.h < 256))
    this.h = 24;
  /* Environment. */
  var childenv = {};
  for (var key in process.env) {
    childenv[key] = process.env[key];
  }
  var args = ["-n", this.pname];
  var spawnopts = {"env": childenv, "cwd": "/", "rows": this.h, "cols": this.w,
                   "name": "xterm-256color"};
  this.term = pty.spawn(this.game.path, args, spawnopts);
  tslog("%s playing %s (index %d, pid %d)", this.pname, this.game.uname, 
            this.sessid, this.term.pid);
  this.emit('open', true, this.sessid);
  gamemux.emit('begin', this.sessid, this.pname, this.game.uname);
  /* Set up the lockfile and ttyrec */
  var ts = timestamp();
  var progressdir = "/dgldir/inprogress-" + this.game.uname;
  this.lock = path.join(progressdir, this.pname + ":node:" + ts + ".ttyrec");
  var lmsg = this.term.pid.toString() + '\n' + this.h + '\n' + this.w + '\n'; 
  fs.writeFile(this.lock, lmsg, "utf8"); 
  var ttyrec = path.join("/dgldir/ttyrec", this.pname, this.game.uname, 
               ts + ".ttyrec");
  this.record = fs.createWriteStream(ttyrec, { mode: 0664 });
  /* Holds the output since the last screen clear, so watchers can begin
   * with a complete screen. */
  this.framebuf = new Buffer(1024);
  this.frameoff = 0;
  logins[lkey].sessions.push(this.sessid);
  /* END setup */
  function ttyrec_chunk(datastr) {
    var ts = new Date();
    var buf = new Buffer(datastr);
    var chunk = new Buffer(buf.length + 12);
    /* TTYREC headers */
    chunk.writeUInt32LE(Math.floor(ts.getTime() / 1000), 0);
    chunk.writeUInt32LE(1000 * (ts.getTime() % 1000), 4);
    chunk.writeUInt32LE(buf.length, 8);
    buf.copy(chunk, 12);
    ss.record.write(chunk);
    ss.framepush(buf);
    ss.emit('data', buf);
  }
  this.term.on("data", ttyrec_chunk);
  this.framepush = function(chunk) {
    /* If this chunk resets the screen, discard what preceded it. */
    if (bufncmp(chunk, this.game.clear, this.game.clear.length)) {
      this.framebuf = new Buffer(1024);
      this.frameoff = 0;
    }
    /* Make sure there's space. */
    while (this.framebuf.length < chunk.length + this.frameoff) {
      var nbuf = new Buffer(this.framebuf.length * 2);
      this.framebuf.copy(nbuf, 0, 0, this.frameoff);
      this.framebuf = nbuf;
      if (this.framebuf.length > 65536) {
        tslog("Warning: Game %d frame buffer at %d bytes", this.sessid, 
                this.framebuf.length);
      }
    }
    chunk.copy(this.framebuf, this.frameoff);
    this.frameoff += chunk.length;
  };
  this.write = function(data) {
    this.term.write(data);
  };
  // Teardown.
  this.term.on("exit", function () {
    fs.unlink(ss.lock);
    ss.record.end();
    ss.emit('exit');
    var id = ss.sessid;
    delete sessions[id];
    tslog("Game %s ended.", id);
    gamemux.emit('end', id);
  });
  this.close = function () {
    if (this.sessid in sessions)
      this.term.kill('SIGHUP');
  };
}
TermSession.prototype = new events.EventEmitter();

function Watcher(session) {
  var ss = this; // that
  this.session = session;
  this.alive = true;
  /* State for messaging. */
  this.nsend = 0;
  this.sendQ = [];
  /* Get a place in the table. */
  this.id = randkey(2);
  while (this.id in clients) {
    this.id = randkey(2);
  }
  clients[this.id] = this;
  /* Recreate the current screen state from the session's buffer. */
  this.sendQ.push({"t": "d", "n": this.nsend++, 
        "d": session.framebuf.toString("hex", 0, session.frameoff)});
  function dataH(buf) {
    var reply = {};
    reply.t = "d";
    reply.n = ss.nsend++;
    reply.d = buf.toString("hex");
    ss.sendQ.push(reply);
  }
  function exitH() {
    ss.alive = false;
    ss.sendQ.push({"t": "q"});
  }
  session.on('data', dataH);
  session.on('exit', exitH);
  this.read = function() {
    /* Returns an array of all outstanding messages, empty if none. */
    var temp = this.sendQ;
    this.sendQ = [];
    /* Clean up if finished. */
    if (!this.alive) {
      delete clients[this.id];
    }
    return temp;
  };
  this.quit = function() {
    this.session.removeListener('data', dataH);
    this.session.removeListener('exit', exitH);
    delete clients[this.id];
  };
}

function Player(gamename, lkey, dims, callback) {
  var ss = this;
  this.alive = false;
  /* State for messaging. */
  this.nsend = 0;
  this.nrecv = 0;
  this.sendQ = [];
  this.recvQ = []
  this.Qtimeout = null;
  /* Get a place in the table. */
  this.id = randkey(2);
  while (this.id in clients) {
    this.id = randkey(2);
  }
  clients[this.id] = this;

  this.read = function() {
    var temp = this.sendQ;
    this.sendQ = [];
    /* Clean up if finished. */
    if (!this.alive) {
      clearTimeout(this.Qtimeout);
      delete clients[this.id];
    }
    return temp;
  };
  this.write = function (data, n) {
    if (!this.alive || typeof (n) != "number") {
      return;
    }
    var oindex = n - this.nrecv;
    if (oindex === 0) {
      this.session.write(data);
      this.nrecv++;
      var next;
      while ((next = this.recvQ.shift()) !== undefined) {
        this.session.write(next);
        this.nrecv++;
      }
      if (this.recvQ.length == 0 && this.Qtimeout) {
        clearTimeout(this.Qtimeout);
        this.Qtimeout = null;
      }
    }
    else if (oindex > 0 && oindex <= 1024) {
      tslog("Client %s: Stashing message %d at %d", this.id,  n, oindex - 1);
      this.recvQ[oindex - 1] = data;
      if (!this.Qtimeout) {
        var nextn = this.nrecv + this.recvQ.length + 1;
        this.Qtimeout = setTimeout(this.flushQ, 30000, this, nextn);
      }
    }
    /* Otherwise, discard it */
    return;
  };
  this.flushQ = function (client, n) {
    /* Callback for when an unreceived message times out.
     * n is the first empty space that will not be given up on. */
    if (!client.alive || client.nrecv >= n)
      return;
    client.nrecv++;
    var next;
    /* Clear the queue up to n */
    while (client.nrecv < n) {
      next = client.recvQ.shift();
      if (next !== undefined)
        client.session.write(next);
      client.nrecv++;
    }
    /* Clear out anything that's ready. */
    while ((next = client.recvQ.shift()) !== undefined) {
      client.session.write(next);
      client.nrecv++;
    }
    /* Now set another timeout if necessary. */
    if (client.recvQ.length != 0) {
      var nextn = client.nrecv + client.recvQ.length + 1;
      client.Qtimeout = setTimeout(client.flushQ, 30000, client, nextn);
    }
    tslog("Flushing queue for player %s", player.id);
  };
  this.reset = function () {
    /* To be called when the game is taken over. */
    if (this.Qtimeout) {
      clearTimeout(this.Qtimeout);
      this.Qtimeout = null;
    }
    for (var i = 0; i < this.recvQ.length; i++) {
      if (this.recvQ[i] !== undefined) {
        this.session.write(this.recvQ[i]);
      }
    }
    this.recvQ = [];
    this.nrecv = 0;
    this.nsend = 0;
    this.sendQ = [{"t": "d", "n": this.nsend++, 
        "d": this.session.framebuf.toString("hex", 0, this.session.frameoff)}];
  };
  this.quit = function() {
    if (this.alive)
      this.session.close();
  };
  function openH(success, id) {
    if (success) {
      ss.alive = true;
      ss.session = sessions[id];
      ss.h = sessions[id].h;
      ss.w = sessions[id].w;
    }
    callback(ss, success);
  }
  function dataH(chunk) {
    var reply = {};
    reply.t = "d";
    reply.n = ss.nsend++;
    reply.d = chunk.toString("hex");
    ss.sendQ.push(reply);
  }
  function exitH() {
    ss.alive = false;
    ss.sendQ.push({"t": "q"});
  }
  var handlers = {'open': openH, 'data': dataH, 'exit': exitH};
  this.session = new TermSession(gamename, lkey, dims, handlers);
}

// Also known as WebSocketAndTermSessionClosureGlueFactory
function wsWatcher(conn, session) {
  var ss = this; // is this even needed?
  var dataH = function(buf) {
    conn.sendUTF(JSON.stringify({"t": "d", "d": buf.toString("hex")}));
  };
  var exitH = function() {
    if (conn.connected)
      conn.close();
  }
  session.on('data', dataH);
  session.on('exit', exitH);
  conn.on('close', function(code, desc) {
    session.removeListener('data', dataH);
    session.removeListener('exit', exitH);
    if (session.sessid in sessions)
      tslog("A WebSocket watcher has left game %d", session.sessid);
  });
  conn.sendUTF(JSON.stringify({
            "t": "w", "w": session.w, "h": session.h, 
            "p": session.pname, "g": session.game.uname
  }));
  conn.sendUTF(JSON.stringify({"t": "d",
        "d": session.framebuf.toString("hex", 0, session.frameoff)}));
}

function wsPlay(wsReq, game, lkey, dims) {
  var conn;
  var session;
  /* Listeners on the WebSocket */
  function messageH(message) {
    var parsedMsg = getMsgWS(message);
    if (parsedMsg.t == 'q') {
      session.close();
    }
    else if (parsedMsg.t == 'd') {
      var hexstr = parsedMsg.d.replace(/[^0-9a-f]/gi, "");
      if (hexstr.length % 2 != 0) {
        hexstr = hexstr.slice(0, -1);
      }
      var keybuf = new Buffer(hexstr, "hex");
      session.write(keybuf);
    }
  }
  function closeH() {
    session.close();
  }
  /* These listen on the TermSession. */
  function openH(success, id) {
    if (success) {
      var reply = {"t": "s", "id": id, "w": sessions[id].w, "h": 
                   sessions[id].h, "p": sessions[id].pname, "g": game};
      conn = wsReq.accept(null, wsReq.origin);
      conn.sendUTF(JSON.stringify(reply));
      conn.on('message', messageH);
      conn.on('close', closeH);
    }
    else {
      wsReq.reject(500, errorcodes[5]);
      tslog("Unable to allocate TTY for %s", game);
    }
  }
  function dataH(chunk) {
    var msg = {};
    msg.t = "d";
    msg.d = chunk.toString("hex");
    conn.sendUTF(JSON.stringify(msg));
  }
  function exitH() {
    if (conn.connected)
      conn.sendUTF(JSON.stringify({"t": "q"}));
    conn.close();
    session.removeListener('open', openH);
    session.removeListener('data', dataH);
    session.removeListener('exit', exitH);
  }
  var handlers = {'open': openH, 'data': dataH, 'exit': exitH};
  session = new TermSession(game, lkey, dims, handlers);
}

function wsStart(wsReq) {
  var playmatch = wsReq.resourceURL.pathname.match(/^\/play\/([^\/]*)$/);
  if (!playmatch[1] || !(playmatch[1] in games)) {
    wsReq.reject(404, errorcodes[2]);
    return;
  }
  var gname = playmatch[1];
  if (!allowlogin) {
    wsReq.reject(404, errorcodes[6]);
    return;
  }
  if (!("key" in wsReq.resourceURL.query)) {
    wsReq.reject(404, "No key given.");
    return;
  }
  var lkey = wsReq.resourceURL.query["key"];
  if (!(lkey in logins)) {
    wsReq.reject(404, errorcodes[1]);
    return;
  }
  var pname = logins[lkey].name;
  var dims = [wsReq.resourceURL.query.h, wsReq.resourceURL.query.w];
  function progcallback(err, fname) {
    if (fname) {
      wsReq.reject(404, errorcodes[4]);
      tslog("%s is already playing %s", pname, gname);
    }
    else
      wsPlay(wsReq, gname, lkey, dims);
  };
  checkprogress(pname, games[gname], progcallback, []);
}

/* Some functions which check whether a player is currently playing or 
 * has a saved game.  Maybe someday they will provide information on 
 * the game. */
function checkprogress(user, game, callback, args) {
  var progressdir = "/dgldir/inprogress-" + game.uname;
  fs.readdir(progressdir, function(err, files) {
    if (err) {
      args.unshift(err, null);
      callback.apply(null, args);
      return;
    }
    var fre = RegExp("^" + user + ":");
    for (var i = 0; i < files.length; i++) {
      if (files[i].match(fre)) {
        args.unshift(null, files[i]);
        callback.apply(null, args);
        return;
      }
    }
    args.unshift(null, false);
    callback.apply(null, args);
  });
}

function checksaved(user, game, callback, args) {
  var savedirc = game.uname + "save";
  var basename = String(dropToUID) + "-" + user + game.suffix;
  var savefile = path.join("/var/games/roguelike", savedirc, basename);
  fs.exists(savefile, function (exist) {
    args.unshift(exist);
    callback.apply(null, args);
  });
}

function playerstatus(user, callback) {
  var sdata = {};
  function finishp() {
    for (var gname in games) {
      if (!(gname in sdata))
        return;
    }
    callback(sdata);
  }
  function regsaved(exists, game) {
    if (exists)
      sdata[game.uname] = "s";
    else
      sdata[game.uname] = "0";
    finishp();
  }
  function regactive(err, filename, game) {
    if (!err && filename) {
      if (filename.match(/^[^:]*:node:/))
        sdata[game.uname] = "p";
      else
        sdata[game.uname] = "d";
      finishp();
    }
    else
      checksaved(user, game, regsaved, [game]);
  }
  for (var gname in games) {
    checkprogress(user, games[gname], regactive, [games[gname]]);
  }
}

/* A few utility functions */
function timestamp() {
  dd = new Date();
  sd = dd.toISOString();
  sd = sd.slice(0, sd.indexOf("."));
  return sd.replace("T", ".");
}

function randkey(words) {
  if (!words || !(words > 0))
    words = 1;
  function rand32() {
    rnum = Math.floor(Math.random() * 65536 * 65536);
    hexstr = rnum.toString(16);
    while (hexstr.length < 8)
      hexstr = "0" + hexstr;
    return hexstr;
  }
  var key = "";
  for (var i = 0; i < words; i++)
    key += rand32();
  return key;
}

/* Compares two buffers, returns true for equality up to index n */
function bufncmp(buf1, buf2, n) {
  if (!Buffer.isBuffer(buf1) || !Buffer.isBuffer(buf2))
    return false;
  for (var i = 0; i < n; i++) {
    if (i == buf1.length && i == buf2.length)
      return true;
    if (i == buf1.length || i == buf2.length)
      return false;
    if (buf1[i] != buf2[i])
      return false;
  }
  return true;
}

function tslog() {
  arguments[0] = new Date().toISOString() + ": " + String(arguments[0]);
  console.log.apply(console, arguments);
}

/* Returns a list of the cookies in the request, obviously. */
function getCookies(req) {
  cookies = [];
  if ("cookie" in req.headers) {
    cookstrs = req.headers["cookie"].split("; ");
    for (var i = 0; i < cookstrs.length; i++) {
      eqsign = cookstrs[i].indexOf("=");
      if (eqsign > 0) {
        name = cookstrs[i].slice(0, eqsign).toLowerCase();
        val = cookstrs[i].slice(eqsign + 1);
        cookies[name] = val;
      }
      else if (eqsign < 0)
        cookies[cookstrs[i]] = null;
    }
  }
  return cookies;
}

function getMsg(posttext) {
  var jsonobj;
  if (!posttext)
    return {};
  try {
    jsonobj = JSON.parse(posttext);
  }
  catch (e) {
    if (e instanceof SyntaxError)
      return {};
  }
  if (typeof(jsonobj) != "object")
    return {};
  return jsonobj;
}

function getMsgWS(msgObj) {
  if (msgObj.type != "utf8")
    return {};
  return getMsg(msgObj.utf8Data);
}

function reaper() {
  var now = new Date();
  function reapcheck(session) {
    fs.fstat(session.record.fd, function (err, stats) {
      if (!err && now - stats.mtime > playtimeout) {
        tslog("Reaping session %s", session.sessid);
        /* Dissociate it with its login name. */
        var sn = logins[session.key].sessions.indexOf(session.sessid);
        if (sn >= 0) {
          logins[session.key].sessions.splice(sn, 1);
          if (now - logins[session.key].ts > playtimeout)
            logins[session.key].ts = new Date(now - playtimeout);
        }
        /* Shut it down. */
        session.close();
      }
    });
  }
  for (var sessid in sessions) {
    reapcheck(sessions[sessid]);
  }
  /* HELPME this is about as clever as I can code, so I can't tell whether
   * there are any bugs. */
  for (var lkey in logins) {
    if (logins[lkey].sessions.length == 0) {
      /* A login with no current games can be killed for inactivity. */
      if (now - logins[lkey].ts > playtimeout * 4) {
        tslog("Login for %s (key %s) timed out", logins[lkey].name, lkey);
        delete logins[lkey];
      }
    }
    else {
      /* Check for games that have terminated normally, and update
       * the timestamp. */
      var expired = [];
      var targarray = logins[lkey].sessions;
      /* Let's not find out what happens if you modify an array
       * you're iterating through. */
      for (var i = 0; i < targarray.length; i++) {
        if (!(targarray[i] in sessions))
          expired.push(targarray[i]);
      }
      if (expired.length > 0) {
        logins[lkey].ts = new Date(now);
        for (var j = 0; j < expired.length; j++) {
          targarray.splice(targarray.indexOf(expired[j]), 1);
        }
      }
    }
  }
}

function login(req, res, formdata) {
  if (!allowlogin) {
    sendError(res, 6, null, false);
    return;
  }
  if (!("name" in formdata)) {
    sendError(res, 2, "Username not given.", false);
    return;
  }
  else if (!("pw" in formdata)) {
    sendError(res, 2, "Password not given.", false);
    return;
  }
  var username = String(formdata["name"]);
  var password = String(formdata["pw"]);
  function checkit(code, signal) {
    /* Checks the exit status, see sqlickrypt.c for details. */
    if (code != 0) {
      sendError(res, 3);
      if (code == 1)
        tslog("Password check failed for user %s", username);
      else if (code == 2)
        tslog("Attempted login by nonexistent user %s", username);
      else
        tslog("Login failed: sqlickrypt error %d", code);
      return;
    }
    var lkey = randkey(2);
    while (lkey in logins)
      lkey = randkey(2);
    logins[lkey] = {"name": username, "ts": new Date(), "sessions": []};
    res.writeHead(200, {'Content-Type': 'application/json'});
    var reply = {"t": "l", "k": lkey, "u": username};
    res.write(JSON.stringify(reply));
    res.end();
    tslog("%s has logged in (key %s)", username, lkey);
    return;
  }
  /* Launch the sqlickrypt utility to check the password. */
  var pwchecker = child_process.spawn("/bin/sqlickrypt", ["check"]);
  pwchecker.on("exit", checkit);
  pwchecker.stdin.end(username + '\n' + password + '\n', "utf8");
  return;
}

function startgame(req, res, formdata) {
  if (!allowlogin) {
    sendError(res, 6, null);
    return;
  }
  if (!("key" in formdata)) {
    sendError(res, 2, "No key given.");
    return;
  }
  else if (!("game" in formdata)) {
    sendError(res, 2, "No game specified.");
    return;
  }
  var lkey = String(formdata["key"]);
  if (!(lkey in logins)) {
    sendError(res, 1, null);
    return;
  }
  else {
    logins[lkey].ts = new Date();
  }
  var username = logins[lkey].name;
  var gname = formdata["game"];
  // If dims are not given or invalid, the constructor will handle it.
  var dims = [formdata["h"], formdata["w"]];
  if (!(gname in games)) {
    sendError(res, 2, "No such game: " + gname);
    tslog("Request for nonexistant game \"%s\"", gname);
    return;
  }
  // A callback to pass to the game-in-progress checker.
  var launch = function(err, fname) {
    var nodematch = new RegExp("^" + username + ":node:");
    if (fname && (fname.match(nodematch) === null)) {
      /* It's being played in dgamelaunch. */
      sendError(res, 4, "dgamelaunch");
      tslog("%s is already playing %s", username, gname);
      return;
    }
    // Game starting has been approved.
    var respondlaunch = function(nclient, success) {
      if (success) {
        res.writeHead(200, {'Content-Type': 'application/json'});
        var reply = {"t": "s", "id": nclient.id, "w": nclient.w, "h": 
                     nclient.h, "p": username, "g": gname};
        res.write(JSON.stringify(reply));
        res.end();
      }
      else {
        sendError(res, 5, "Failed to open TTY");
        tslog("Unable to allocate TTY for %s", gname);
      }
    };
    if (fname) {
      for (var cid in clients) {
        cli = clients[cid];
        if ((cli instanceof Player) && 
             cli.session.pname == username &&
             cli.session.game.uname == gname) {
          cli.reset();
          respondlaunch(cli, true);
          tslog("Game %d has been taken over.", cli.session.sessid);
          return;
        }
      }
      /* If there's no player, it's a WebSocket game, and shouldn't be 
       * seized. */
      sendError(res, 4, "WebSocket");
    }
    else {
      new Player(gname, lkey, dims, respondlaunch);
    }
  };
  checkprogress(username, games[gname], launch, []);
}

function watch(req, res, formdata) {
  if (!("n" in formdata)) {
    sendError(res, 2, "Game number not given");
    return;
  }
  var gamenumber = Number(formdata["n"]);
  if (!(gamenumber in sessions)) {
    sendError(res, 7);
    return;
  }
  var session = sessions[gamenumber];
  var watch = new Watcher(session);
  var reply = {"t": "w", "id": watch.id, "w": session.w, "h": session.h, 
               "p": session.pname, "g": session.game.uname};
  res.writeHead(200, {'Content-Type': 'application/json'});
  res.write(JSON.stringify(reply));
  res.end();
  tslog("Game %d is being watched (key %s)", gamenumber, watch.id);
}

/* Sets things up for a new user, like dgamelaunch's commands[register] */