webglmapview/js/wsclient.js

//////////////////////////////////////////////////////////////////
// WebSockClient for PennMUSH
// There is no license. Just make a neato game with it.
//////////////////////////////////////////////////////////////////

var WSClient = (function (window, document, undefined) {

  //////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////

  // MU* protocol carried over the WebSocket API.
  function Connection(url) {
    var that = this;
    
    this.url = url;
    this.socket = null;
    this.isOpen = false;
    
    Connection.reconnect(that);
  }
  
  Connection.CHANNEL_TEXT = 't';
  Connection.CHANNEL_JSON = 'j';
  Connection.CHANNEL_HTML = 'h';
  Connection.CHANNEL_PUEBLO = 'p';
  Connection.CHANNEL_PROMPT = '>';

  Connection.reconnect = function (that) {
    that.reconnect();
  };
  
  Connection.onopen = function (that, evt) {
    that.isOpen = true;
    that.onOpen && that.onOpen(evt);
  };

  Connection.onerror = function (that, evt) {
    that.onError && that.onError(evt);
  };

  Connection.onclose = function (that, evt) {
    that.onClose && that.onClose(evt);
  };

  Connection.onmessage = function (that, evt) {
    that.onMessage && that.onMessage(evt.data[0], evt.data.substring(1));
  };

  Connection.prototype.reconnect = function () {
    var that = this;
    
    // quit the old connection, if we have one
    if (this.socket) {
      var old = this.socket;
      this.sendText('QUIT');
      setTimeout(old.close, 1000);
    }

    this.socket = new window.WebSocket(this.url);
    this.isOpen = false;

    this.socket.onopen = function (evt) {
      Connection.onopen(that, evt);
    };

    this.socket.onerror = function (evt) {
      Connection.onerror(that, evt);
    };

    this.socket.onclose = function (evt) {
      Connection.onclose(that, evt);
    };

    this.socket.onmessage = function (evt) {
      Connection.onmessage(that, evt);
    };
  };
  
  Connection.prototype.isConnected = function() {
    return (this.socket && this.isOpen && (this.socket.readyState === 1));
  };

  Connection.prototype.close = function () {
    this.socket && this.socket.close();
  };

  Connection.prototype.sendText = function (data) {
    this.isConnected() && this.socket.send(Connection.CHANNEL_TEXT + data + '\r\n');
  };

  Connection.prototype.sendObject = function (data) {
    this.isConnected() && this.socket.send(Connection.CHANNEL_JSON + window.JSON.stringify(data));
  };

  Connection.prototype.onOpen = null;
  Connection.prototype.onError = null;
  Connection.prototype.onClose = null;

  Connection.prototype.onMessage = function (channel, data) {
    switch (channel) {
    case Connection.CHANNEL_TEXT:
      this.onText && this.onText(data);
      break;

    case Connection.CHANNEL_JSON:
      this.onObject && this.onObject(window.JSON.parse(data));
      break;

    case Connection.CHANNEL_HTML:
      if (this.onHTML) {
        var div = document.createElement('div');
        div.innerHTML = data;

        var fragment = document.createDocumentFragment();
        for (var child = div.firstChild; child; child = child.nextSibling) {
          fragment.appendChild(child);
        }

        this.onHTML(fragment);
      }
      break;

    case Connection.CHANNEL_PUEBLO:
      if (this.onPueblo) {
        var tag, attrs;

        var idx = data.indexOf(' ');
        if (idx !== -1) {
          tag = data.substring(0, idx);
          attrs = data.substring(idx + 1);
        } else {
          tag = data;
          attrs = '';
        }

        this.onPueblo(tag.toUpperCase(), attrs);
      }
      break;
    
    case Connection.CHANNEL_PROMPT:
      this.onPrompt && this.onPrompt(data);
      break;

    default:
      window.console && window.console.log('unhandled message', channel, data);
      return false;
    }

    return true;
  };

  Connection.prototype.onText = null;
  Connection.prototype.onObject = null;
  Connection.prototype.onHTML = null;
  Connection.prototype.onPueblo = null;
  Connection.prototype.onPrompt = null;

  //////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////

  // MU* terminal emulator.
  function Terminal(root) {
    this.root = root;
    
    this.clear();
  }

  Terminal.PARSE_PLAIN = 0;
  Terminal.PARSE_CR = 1;
  Terminal.PARSE_ESC1 = 2;
  Terminal.PARSE_ESC2 = 3;

  Terminal.ANSI_NORMAL = 0;
  Terminal.ANSI_BRIGHT = 1;
  Terminal.ANSI_UNDERLINE = 4;
  Terminal.ANSI_BLINK = 5;
  Terminal.ANSI_INVERSE = 7;
  Terminal.ANSI_XTERM_FG = 38;
  Terminal.ANSI_XTERM_BG = 48;

  Terminal.DEFAULT_FG = 37;
  Terminal.DEFAULT_BG = 30;
  
  Terminal.UNCLOSED_TAGS = ['area', 'base', 'br', 'col', 'command', 'embed', 'hr', 'img',
          'input', 'keygen', 'link', 'menuitem', 'meta', 'param', 'source', 'track', 'wbr'];


  /////////////////////////////////////////////////////
  // ansi parsing routines
  
  Terminal.encodeState = function (state) {
    if (!state) {
      return '';
    }

    var classes = [];

    if (state[Terminal.ANSI_INVERSE]) {
      var value = state.fg;
      state.fg = state.bg;
      state.bg = value;
      
      value = state.fg256;
      state.fg256 = state.bg256;
      state.bg256 = value;
    }
    
    var fg = state.fg;
    var bg = state.bg;
    
    if (state[Terminal.ANSI_UNDERLINE]) {
      classes[classes.length] = 'ansi-' + Terminal.ANSI_UNDERLINE;
    }

    // make sure to avoid conflict with XTERM256 color's usage of blink (code 5)
    if (state.fg256) {
      classes[classes.length] = 'ansi-38-5-' + state.fg;
    } else {  
      if (state[Terminal.ANSI_BRIGHT]) {
        if (state[Terminal.ANSI_INVERSE]) {
          if (fg !== Terminal.DEFAULT_FG) {
            classes[classes.length] = 'ansi-' + fg;
          }
        } else {
          classes[classes.length] = 'ansi-1-' + fg;
        }
      } else if (fg !== Terminal.DEFAULT_FG) {
        classes[classes.length] = 'ansi-' + fg;
      }
    }
    
    if (state.bg256) {
      classes[classes.length] = 'ansi-48-5-' + state.bg;
    } else {
      if (state[Terminal.ANSI_BRIGHT]) {
        if (state[Terminal.ANSI_INVERSE]) {
          classes[classes.length] = 'ansi-1-' + (bg + 10);
        } else {
          if (bg !== Terminal.DEFAULT_BG) {
            classes[classes.length] = 'ansi-' + (bg + 10);
          }
        }
      } else if (bg !== Terminal.DEFAULT_BG) {
        classes[classes.length] = 'ansi-' + (bg + 10);
      }
    }

    if (state[Terminal.ANSI_BLINK] && !(state.fg256 || state.bg256)) {
      classes[classes.length] = 'ansi-' + Terminal.ANSI_BLINK;
    }
    
    return classes.join(' ');
  };

  Terminal.prototype.getANSI = function () {
    if (!this.ansiState) {
      this.ansiState = {
        fg: Terminal.DEFAULT_FG,
        bg: Terminal.DEFAULT_BG,
        fg256: false,
        bg256: false
      };
    }

    return this.ansiState;
  };

  Terminal.prototype.applyANSI = function (ansi) {
    switch (ansi.charCodeAt(ansi.length - 1)) {
    case 109: // m (SGR)
      var codes = ansi.substring(0, ansi.length - 1).split(';');

      var value, state;
      for (var ii = 0; (value = codes[ii]) !== undefined; ++ii) {
        if (value.length === 0) {
          // Empty is treated as the equivalent of 0.
          value = Terminal.ANSI_NORMAL;
        } else {
          value = parseInt(value);
        }
        
        state = this.getANSI();
        
        // check for xterm256 fg/bg first, fallback to standard codes otherwise
        if (state[Terminal.ANSI_XTERM_FG] && state[Terminal.ANSI_BLINK]) {
          if (value >= 0 && value <= 255) {
            state.fg = value;
            state.fg256 = true;
            state[Terminal.ANSI_XTERM_FG] = false;
            state[Terminal.ANSI_BLINK] = false;
          } else {
            // invalid xterm256, let's reset the ansi state due to bad codes
            this.ansiState = null;
          }
        } else if (state[Terminal.ANSI_XTERM_BG] && state[Terminal.ANSI_BLINK]) {
          if (value >= 0 && value <= 255) {
            state.bg = value;
            state.bg256 = true;
            state[Terminal.ANSI_XTERM_BG] = false;
            state[Terminal.ANSI_BLINK] = false;
          } else {
            // invalid xterm256, let's reset the ansi state due to bad codes
            this.ansiState = null;
          }
        } else {
          // detect regular ansi codes
          switch (value) {
          case Terminal.ANSI_NORMAL: // reset
            this.ansiState = null;
            break;

          case Terminal.ANSI_BRIGHT:
          case Terminal.ANSI_UNDERLINE:
          case Terminal.ANSI_BLINK:
          case Terminal.ANSI_INVERSE:
          case Terminal.ANSI_XTERM_FG:
          case Terminal.ANSI_XTERM_BG:
            state[value] = true;
            break;

          default:
            if (30 <= value && value <= 37) {
              state.fg = value;
            } else if (40 <= value && value <= 47) {
              state.bg = value - 10;
            }
           break;
          }
        }

        this.ansiDirty = true;
      }
      break;
    }
  };

  Terminal.prototype.write = function (value, start, end) {
    if (start === end) {
      return;
    }

    if (this.ansiDirty) {
      var next = Terminal.encodeState(this.ansiState);

      if (this.ansiClass !== next) {
        this.ansiClass = next;
        this.span = null;
      }

      this.ansiDirty = false;
    }

    if (this.ansiClass && !this.span) {
      this.span = document.createElement('span');
      this.span.className = this.ansiClass;
      this.stack[this.stack.length - 1].appendChild(this.span);
    }

    var text = document.createTextNode(value.substring(start, end));
    this.lineBuf[this.lineBuf.length] = text;

    this.appendHTML(text);
  };

  Terminal.prototype.endLine = function () {
    var that = this;
    this.onLine && this.onLine(that, this.lineBuf);

    this.write('\n', 0, 1);
    this.lineBuf.length = 0;
  };

  Terminal.prototype.abortParse = function (value, start, end) {
    switch (this.state) {
    case Terminal.PARSE_PLAIN:
      this.write(value, start, end);
      break;

    case Terminal.PARSE_ESC1:
      this.write('\u001B', 0, 1);
      break;

    case Terminal.PARSE_ESC2:
      this.write('\u001B[', 0, 2);
      this.write(this.parseBuf, 0, this.parseBuf.length);
      this.parseBuf = '';
      break;
    }
  };

  /////////////////////////////////////////////////////
  // message appending routines
  
  // appends a text string to the terminal, parsing ansi escape codes into html/css
  Terminal.prototype.appendText = function (data) {
    var start = 0;

    // Scan for sequence start characters.
    // TODO: Could scan with RegExp; not convinced sufficiently simpler/faster.
    for (var ii = 0, ilen = data.length; ii < ilen; ++ii) {
      var ch = data.charCodeAt(ii);

      // Resynchronize at special characters.
      switch (ch) {
      case 10: // newline
        if (this.state !== Terminal.PARSE_CR) {
          this.abortParse(data, start, ii);
          this.endLine();
        }

        start = ii + 1;
        this.state = Terminal.PARSE_PLAIN;
        continue;

      case 13: // carriage return
        this.abortParse(data, start, ii);
        this.endLine();
        start = ii + 1;
        this.state = Terminal.PARSE_CR;
        continue;

      case 27: // escape
        this.abortParse(data, start, ii);
        start = ii + 1;
        this.state = Terminal.PARSE_ESC1;
        continue;
      }

      // Parse other characters.
      switch (this.state) {
      case Terminal.PARSE_CR:
        this.state = Terminal.PARSE_PLAIN;
        break;

      case Terminal.PARSE_ESC1:
        if (ch === 91) {
          // Start of escape sequence (\e[).
          start = ii + 1;
          this.state = Terminal.PARSE_ESC2;
        } else {
          // Not an escape sequence.
          this.abortParse(data, start, ii);
          start = ii;
          this.state = Terminal.PARSE_PLAIN;
        }
        break;

      case Terminal.PARSE_ESC2:
        if (64 <= ch && ch <= 126) {
          // End of escape sequence.
          this.parseBuf += data.substring(start, (start = ii + 1));
          this.applyANSI(this.parseBuf);
          this.parseBuf = '';
          this.state = Terminal.PARSE_PLAIN;
        }
        break;
      }
    }

    // Handle tail.
    switch (this.state) {
    case Terminal.PARSE_PLAIN:
      this.write(data, start, data.length);
      break;

    case Terminal.PARSE_ESC2:
      this.parseBuf += data.substring(start);
      break;
    }
  };

  // append an HTML fragment to the terminal
  Terminal.prototype.appendHTML = function (fragment) {
    (this.span || this.stack[this.stack.length - 1]).appendChild(fragment);

    // TODO: May want to animate this, to make it less abrupt.
    this.root.scrollTop = this.root.scrollHeight;
  };
  
  // append a log message to the terminal
  Terminal.prototype.appendMessage = function (classid, message) {
    var div = document.createElement('div');
    div.className = classid;
    
    // create a text node to safely append the string without rendering code
    var text = document.createTextNode(message);
    div.appendChild(text);
    
    this.appendHTML(div);
  };
  
  // push a new html element onto the stack
  Terminal.prototype.pushElement = function (element) {
    this.span = null;
    this.stack[this.stack.length - 1].appendChild(element);
    this.stack[this.stack.length] = element;
  };

  // remove 1 level from the stack, check consistency 
  Terminal.prototype.popElement = function () {
    this.span = null;

    if (this.stack.length > 1) {
      --this.stack.length;
    } else {
      window.console && window.console.warn('element stack underflow');
    }
  };

  // append a pueblo tag to the terminal stack (or pop if an end tag)
  Terminal.prototype.appendPueblo = function (tag, attrs) {
    var html = '<' + tag + (attrs ? ' ' : '') + attrs + '>';

    var start;
    if (tag[0] !== '/') {
      start = true;
    } else {
      start = false;
      tag = tag.substring(1);
    }

    var selfClosing = false;
    if ((tag.substring(-1) === '/') || (attrs.substring(-1) === '/')) {
      selfClosing = true;
    }
    
    if (Terminal.UNCLOSED_TAGS.indexOf(tag.toLowerCase()) > -1) {
      selfClosing = true;
    }

    if ((tag === 'XCH_PAGE') || 
        ((tag === 'IMG') && (attrs.search(/xch_graph=(("[^"]*")|('[^']*')|([^\s]*))/i) !== -1))) {
      //console.log("unhandled pueblo", html);
      return;
    }

    // we have a starting <tag> (not </tag>)
    if (start) {
      var div = document.createElement('div');

      html = html.replace(
        /xch_graph=(("[^"]*")|('[^']*')|([^\s]*))/i,
        ''
      );

      html = html.replace(
        /xch_mode=(("[^"]*")|('[^']*')|([^\s]*))/i,
        ''
      );

      html = html.replace(
        /xch_hint="([^"]*)"/i,
        'title="$1"'
      );

      div.innerHTML = html.replace(
        /xch_cmd="([^"]*)"/i,
        "onClick='this.onCommand(&quot;$1&quot;)'"
      );
      
      div.firstChild.onCommand = this.onCommand;

      div.setAttribute('target', '_blank');
      
      // add this tag to the stack to keep track of nested elements
      this.pushElement(div.firstChild);

      // automatically pop the tag if it is self closing
      if (selfClosing) {
        this.popElement();
      }

    } else {
      // we have an ending </tag> so remove the closed tag from the stack
      // don't bother for self closing tags with an explicit end tag, we already popped them
      if (!selfClosing) {
        this.popElement();
      }
    }
  };
  
  Terminal.prototype.clear = function() {
    this.root.innerHTML = '';

    this.stack = [this.root];

    this.state = Terminal.PARSE_PLAIN;
    this.line = null;
    this.lineBuf = [];
    this.span = null;
    this.parseBuf = '';

    this.ansiClass = '';
    this.ansiState = null;
    this.ansiDirty = false;
  };

  // setup the pueblo xch_cmd callback
  Terminal.prototype.onCommand = null;



  //////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////

  // User input handler (command history, callback events)
  function UserInput(root) {
    var that = this;
    
    this.root = root;
    this.history = [];
    this.ncommand = 0;
    this.save_current = '';
    this.current = -1;

    this.root.onkeydown = function(evt) {
      UserInput.onkeydown(that, evt);
    };
    
    this.root.onkeyup = function(evt) {
      UserInput.onkeyup(that, evt);
    };
  }
  
  // passthrough to the local onKeyDown callback
  UserInput.onkeydown = function(that, evt) {
    that.onKeyDown && that.onKeyDown(evt);
  };

  // passthrough to the local onKeyUp callback
  UserInput.onkeyup = function(that, evt) {
    that.onKeyUp && that.onKeyUp(evt);
  };
  
  // set the default onKeyDown handler
  UserInput.prototype.onKeyDown = function(e) {
    PressKey(this, e);
  };
  
  // set the default onKeyUp handler
  UserInput.prototype.onKeyUp = function(e) {
    ReleaseKey(this, e);
  };
  
  UserInput.prototype.onEnter = null;
  UserInput.prototype.onEscape = null;
  
  // push a command onto the history list and clear the input box
  UserInput.prototype.saveCommand = function() {
    if (this.root.value !== '') {
      this.history[this.ncommand] = this.root.value;
      this.ncommand++;
      this.save_current = '';
      this.current = -1;
      this.root.value = '';
    }
  };
  
  // cycle the history backward
  UserInput.prototype.cycleBackward = function() {
    // save the current entry in case we come back
    if (this.current < 0) {
      this.save_current = this.root.value;
    }
    
    // cycle command history backward
    if (this.current < this.ncommand - 1) {
      this.current++;
      this.root.value = this.history[this.ncommand - this.current - 1];
    }
  };
  
  // cycle the history forward
  UserInput.prototype.cycleForward = function () {
    // cycle command history forward
    if (this.current > 0) {
      this.current--;
      this.root.value = this.history[this.ncommand - this.current - 1];
    } else if (this.current === 0) {
      // recall the current entry if they had typed something already
      this.current = -1;
      this.root.value = this.save_current;
    }
  };
  
  
  
  // move the input cursor to the end of the input elements current text
  UserInput.prototype.moveCursor = function() {
    if (typeof this.root.selectionStart === "number") {
        this.root.selectionStart = this.root.selectionEnd = this.root.value.length;
    } else if (typeof this.root.createTextRange !== "undefined") {
        this.focus();
        var range = this.root.createTextRange();
        range.collapse(false);
        range.select();
    }
  };
  
  
  
  // clear the current input text
  UserInput.prototype.clear = function() {
    this.root.value = '';
  };
  
  // get the current text in the input box
  UserInput.prototype.value = function() {
    return this.root.value;
  };
  
  // refocus the input box
  UserInput.prototype.focus = function() {
    this.root.focus();
  };
  
  // user-defined keys for command history
  UserInput.prototype.keyCycleForward = null;
  UserInput.prototype.keyCycleBackward = null;
  
  UserInput.isKeyCycleForward = function(that, key) {
    if (that && that.keyCycleForward) {
      return that.keyCycleForward(key);
    } else {
      // default key is ctrl+n
      return (key.code === 78 && key.ctrl);
    }
  };
  
  UserInput.isKeyCycleBackward = function (that, key) {
    if (that && that.keyCycleBackward) {
      return that.keyCycleBackward(key);
    } else {
      // default key is ctrl+p
      return (key.code === 80 && key.ctrl);
    }
  };
  
  
  

  //////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////
  // some string helper functions for replacing links and user input tokens

  // Example onLine() handler that linkifies URLs in text.
  function LinkHandler(that, lineBuf) {
    // Merge text so we can scan it.
    if (!lineBuf.length) {
      return;
    }

    var line = '';
    for (var ii = 0, ilen = lineBuf.length; ii < ilen; ++ii) {
      line += lineBuf[ii].nodeValue;
    }

    // Scan the merged text for links.
    var links = LinkHandler.scan(line);
    if (!links.length) {
      return;
    }

    // Find the start and end text nodes.
    var nodeIdx = 0, nodeStart = 0, nodeEnd = lineBuf[0].nodeValue.length;
    for (var ii = 0, ilen = links.length; ii < ilen; ++ii) {
      var info = links[ii], startOff, startNode, endOff, endNode;

      while (nodeEnd <= info.start) {
        nodeStart = nodeEnd;
        nodeEnd += lineBuf[++nodeIdx].nodeValue.length;
      }

      startOff = info.start - nodeStart;
      startNode = lineBuf[nodeIdx];

      while (nodeEnd < info.end) {
        nodeStart = nodeEnd;
        nodeEnd += lineBuf[++nodeIdx].nodeValue.length;
      }

      endOff = info.end - nodeStart;
      endNode = lineBuf[nodeIdx];

      // Wrap the link text.
      // TODO: In this version, we won't try to cross text nodes.
      // TODO: Discard any text nodes that are already part of links?
      if (startNode !== endNode) {
        window.console && window.console.warn('link', info);
        continue;
      }

      lineBuf[nodeIdx] = endNode.splitText(endOff);
      nodeStart += endOff;

      var middleNode = startNode.splitText(startOff);
      var anchor = document.createElement('a');
      middleNode.parentNode.replaceChild(anchor, middleNode);

      anchor.target = '_blank';
      if (info.url === '' && info.xch_cmd !== '') {
        anchor.setAttribute('onClick', 'this.onCommand("'+info.xch_cmd+'");');
        anchor.onCommand = that.onCommand;
      } else {
        anchor.href = info.url;
      }
      anchor.appendChild(middleNode);
    }
  }

  // Link scanner function.
  // TODO: Customizers may want to replace this, since regular expressions
  // ultimately limit how clever our heuristics can be.
  LinkHandler.scan = function (line) {
    var links = [], result;

    LinkHandler.regex.lastIndex = 0;
    while ((result = LinkHandler.regex.exec(line))) {
      var info = {};

      info.start = result.index + result[1].length;
      info.xch_cmd = '';
      if (result[2]) {
        result = result[2];
        info.url = result;
      } else if (result[3]) {
        result = result[3];
        info.url = 'mailto:' + result;
      } else if (result[4]) {
        result = result[4];
        info.url = '';
        info.xch_cmd = 'help ' + result;
        info.className = "ansi-1-37";
      }

      info.end = info.start + result.length;

      links[links.length] = info;
    }

    return links;
  };

  // LinkHandler regex:
  //
  // 1. Links must be preceded by a non-alphanumeric delimiter.
  // 2. Links are matched greedily.
  // 3. URLs must start with a supported scheme.
  // 4. E-mail addresses are also linkified.
  // 5. Twitter users and hash tags are also linkified.
  //
  // TODO: This can be improved (but also customized). One enhancement might be
  // to support internationalized syntax.
  LinkHandler.regex = /(^|[^a-zA-Z0-9]+)(?:((?:http|https):\/\/[-a-zA-Z0-9_.~:\/?#[\]@!$&'()*+,;=%]+)|([-.+a-zA-Z0-9_]+@[-a-zA-Z0-9]+(?:\.[-a-zA-Z0-9]+)+)|(@[a-zA-Z]\w*))/g;

  // set the default line handler for the terminal to use the LinkHandler
  Terminal.prototype.onLine = LinkHandler;

  // detect if more user input is required for a pueblo command
  function ReplaceToken(command) {
    var cmd = command;
    var regex = /\?\?/;
    
    // check for the search token '??'
    if (cmd.search(regex) !== -1) {
      var val = prompt(command);
      
      if (val === null) {
        // user cancelled the prompt, don't send any command
        cmd = '';
      } else {
        // replace the ?? token with the prompt value
        cmd = cmd.replace(regex, val);
      }
    }
    
    return cmd;
  };



  //////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////

  // default handler for key press events
  function PressKey(that, e) {
    var key = { code: (e.keyCode ? e.keyCode : e.which),
                ctrl: e.ctrlKey,
                shift: e.shiftKey,
                alt: e.altKey };

    var prevent = true;
    
    if (UserInput.isKeyCycleBackward(that, key)) {

      // cycle history backward
      that.cycleBackward();

    } else if (UserInput.isKeyCycleForward(that, key)) {

      // cycle history forward
      that.cycleForward();

    } else if (key.code === 13) {
      // enter key
      
      // save the command string and clear the input box
      var cmd = that.root.value;
      that.saveCommand();

      // pass through to the local callback for sending data
      that.onEnter && that.onEnter(cmd);
        
    } else if (key.code === 27) {

      // pass through to the local callback for the escape key
      that.onEscape && that.onEscape();

    } else { 
      // didn't capture anything, pass it through
      prevent = false;

    }
    
    if (prevent) {
      e.preventDefault();
    }

    // make sure input retains focus
    that.focus();
  };



  // default handler for key release events
  function ReleaseKey(that, e) {
    var key = { code: (e.keyCode ? e.keyCode : e.which),
                ctrl: e.ctrlKey,
                shift: e.shiftKey,
                alt: e.altKey };

    if (UserInput.isKeyCycleBackward(that, key) ||
        UserInput.isKeyCycleForward(that, key)) {

      // move the cursor to end of the input text after a history change
      that.moveCursor();
    }
  };



  //////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////

  // Module exports.
  var exports = {};

  // open a websocket connection to url
  exports.connect = function (url) {
    return new Connection(url);
  };

  // create a terminal emulator that appends output to root
  exports.output = function (root) {
    return new Terminal(root);
  };
  
  // create an input handler that saves and recalls command history
  exports.input = function (root) {
    return new UserInput(root);
  };
  
  // default key event callback handlers
  exports.pressKey = PressKey;
  exports.releaseKey = ReleaseKey;
  
  // helper for replacing ?? in string with user input
  exports.parseCommand = ReplaceToken;
  
  // export the LinkHandler just in case it's useful elsewhere
  exports.parseLinks = LinkHandler;
  
  return exports;
})(window, document);