/* shterm.js: browser-side JavaScript to handle I/O for termemu.js when it 
 * is running a shell via the webtty.js server.
 */

var isalive = false; // Whether the session is currently active.
var nsend = 0; // The number of the next packet to send.
var nrecv = 0; // The next packet expected.
var msgQ = []; // Queue for out-of-order messages.

// A state machine that keeps track of polling the server.
var ajaxstate = {
  state: 0,
  timerID: null,
  clear: function () {
    if (this.timerID != null) {
      window.clearTimeout(this.timerID);
      this.timerID = null;
    }
  },
  set: function (ms) {
    this.clear();
    this.timerID = window.setTimeout(getData, ms);
  },
  gotdata: function () {
    this.set(100);
    this.state = 0;
  },
  gotnothing: function () {
    if (this.state == 0) {
      this.set(100);
      this.state = 1;
    }
    else if (this.state == 1) {
      this.set(300);
      this.state = 2;
    }
    else if (this.state == 2) {
      this.set(1000);
      this.state = 3;
    }
    else {
      this.set(5000);
      this.state = 3;
    }
  },
  posted: function () {
    this.set(100);
    this.state = 0;
  }
};

function writeData(hexstr) {
  var codenum;
  var codes = [];
  var nc;
  var u8wait = 0; /* Stores bits from previous bytes of multibyte sequences. */
  var expect = 0; /* The number of 10------ bytes expected. */
  /* UTF-8 translation. */
  for (var i = 0; i < hexstr.length; i += 2) {
    nc = Number("0x" + hexstr.substr(i, 2));
    if (nc < 0x7F) {
      /* 0------- */
      codes.push(nc);
      /* Any incomplete sequence will be discarded. */
      u8wait = 0;
      expect = 0;
    }
    else if (nc < 0xC0) {
      /* 10------ : part of a multibyte sequence */
      if (expect > 0) {
        u8wait <<= 6;
        u8wait += (nc & 0x3F);
        expect--;
        if (expect == 0) {
          codes.push(u8wait);
          u8wait = 0;
        }
      }
      else {
        /* Assume an initial byte was missed. */
        u8wait = 0;
      }
    }
    /* These will all discard any incomplete sequence. */
    else if (nc < 0xE0) {
      /* 110----- : introduces 2-byte sequence */
      u8wait = (nc & 0x1F);
      expect = 1;
    }
    else if (nc < 0xF0) {
      /* 1110---- : introduces 3-byte sequence */
      u8wait = (nc & 0x0F);
      expect = 2;
    }
    else if (nc < 0xF8) {
      /* 11110--- : introduces 4-byte sequence */
      u8wait = (nc & 0x07);
      expect = 3;
    }
    else if (nc < 0xFC) {
      /* 111110-- : introduces 5-byte sequence */
      u8wait = (nc & 0x03);
      expect = 4;
    }
    else if (nc < 0xFE) {
      /* 1111110- : introduces 6-byte sequence */
      u8wait = (nc & 0x01);
      expect = 5;
    }
    else {
      /* 1111111- : should never appear */
      u8wait = 0;
      expect = 0;
    }
    /* Supporting all 31 bits is probably overkill... */
  }
  termemu.write(codes);
  return;
}

function processMsg(response) {
  if (response.t != "d" || typeof(response.d) != "string")
    return;
  if (response.n === nrecv) {
    writeData(response.d);
    nrecv++;
    var next;
    /* msgQ must be shifted every time nrecv is incremented, but the process
     * stops whenever an empty space, corresponding to an unarrived message,
     * is encountered.
     */
    while ((next = msgQ.shift()) !== undefined) {
      writeData(next.d);
      nrecv++;
    }
  }
  else if (response.n > nrecv) {
    /* The current message comes after one still missing.  Queue this one
     * for later use.
     */
    debug(1, "Got packet " + response.n + ", expected " + nrecv);
    msgQ[response.n - nrecv - 1] = response;
  }
  else {
    /* This message's number was encountered previously. */
    debug(1, "Discarding packet " + response.n + ", expected " + nrecv);
  }
}

function getData() {
  if (!isalive)
    return;
  var datareq = new XMLHttpRequest();
  datareq.onreadystatechange = function () {
    if (datareq.readyState == 4 && datareq.status == 200) {
      var response = JSON.parse(this.responseText);
      if (!response.t)
        return;
      else if (response.t == "E") {
        if (response.c == 1) {
          isalive = false;
          debug(1, "Server error: " + response.s);
        }
      }
      else if (response.t == "n")
        ajaxstate.gotnothing();
      else if (response.t == "d") {
        processMsg(response);
        ajaxstate.gotdata();
      }
      return;
    }
  };
  datareq.open('GET', '/feed', true);
  datareq.send(null);
  return;
}

function postResponseHandler() {
  if (this.readyState == 4 && this.status == 200) {
    var response = JSON.parse(this.responseText);
    if (!response.t || response.t == "n")
      return;
    else if (response.t == "E") {
      if (response.c == 1) {
        isalive = false;
        debug(1, "Server error: " + response.s);
      }
      return;
    }
    else if (response.t != "d")
      return;
    /* It is a data message */
    if (response.d) {
      processMsg(response);
      //debug(1, "Got packet " + response.n);
    }
    ajaxstate.posted();
    return;
  }
}

function sendback(str) {
  /* For responding to terminal queries. */
  var formdata = {"t": "d", "n": nsend++, "d": str};
  var datareq = new XMLHttpRequest();
  datareq.onreadystatechange = postResponseHandler;
  datareq.open('POST', '/feed', true);
  datareq.send(JSON.stringify(formdata));
  return;
}

function sendkey(ev) {
  var keynum = ev.keyCode;
  var code;
  if (keynum >= 65 && keynum <= 90) {
    /* Letters. */
    if (ev.ctrlKey)
      keynum -= 64;
    else if (!ev.shiftKey)
      keynum += 32;
    code = keynum.toString(16);
    if (code.length < 2)
      code = "0" + code;
  }
  else if (keynum >= 48 && keynum <= 57) {
    /* The number row. */
    if (ev.shiftKey) {
      code = numShifts[keynum - 48].toString(16);
    }
    else {
      code = keynum.toString(16);
    }
  }
  else if (keynum in keyHexCodes) {
    if (ev.shiftKey)
      code = keyHexCodes[keynum][1];
    else
      code = keyHexCodes[keynum][0];
  }
  else if (keynum >= 16 && keynum <= 20) {
    return;
  }
  else {
    debug(1, "Ignoring keycode " + keynum);
    return;
  }
  if (isalive)
    ev.preventDefault();
  var formdata = {"t": "d", "n": nsend++, "d": code};
  var datareq = new XMLHttpRequest();
  datareq.onreadystatechange = postResponseHandler;
  datareq.open('POST', '/feed', true);
  datareq.send(JSON.stringify(formdata));
  //dkey(code);
  return;
}

var charshifts = { '-': "5f", '=': "2b", '[': "7b", ']': "7d", '\\': "7c",
  ';': "3a", '\'': "22", ',': "3c", '.': "3e", '/': "3f", '`': "7e"
}

function vkey(c) {
  var keystr;
  if (c.match(/^[a-z]$/)) {
    if (termemu.ctrlp()) {
      var n = c.charCodeAt(0) - 96;
      keystr = n.toString(16);
      if (keystr.length < 2)
        keystr = "0" + keystr;
    }
    else if (termemu.shiftp())
      keystr = c.toUpperCase().charCodeAt(0).toString(16);
    else
      keystr = c.charCodeAt(0).toString(16);
  }
  else if (c.match(/^[0-9]$/)) {
    if (termemu.shiftp())
      keystr = numShifts[c.charCodeAt(0) - 48].toString(16);
    else
      keystr = c.charCodeAt(0).toString(16);
  }
  else if (c == '\n')
    keystr = "0a";
  else if (c == '\t')
    keystr = "09";
  else if (c == '\b')
    keystr = "08";
  else if (c == ' ')
    keystr = "20";
  else if (c in charshifts) {
    if (termemu.shiftp())
      keystr = charshifts[c];
    else
      keystr = c.charCodeAt(0).toString(16);
  }
  else
    return;
  //writeData("Sending " + keystr);
  var formdata = {"t": "d", "n": nsend++, "d": keystr};
  var datareq = new XMLHttpRequest();
  datareq.onreadystatechange = postResponseHandler;
  datareq.open('POST', '/feed', true);
  datareq.send(JSON.stringify(formdata));
  return;
}

function setup() {
  keyHexCodes.init();
  termemu.init("termwrap", 24, 80);
  setTitle("Not connected.");
  return;
}

function toggleshift() {
  termemu.toggleshift();
  keydiv = document.getElementById("shiftkey");
  if (termemu.shiftp())
    keydiv.className = "keysel";
  else
    keydiv.className = "key";
  return;
}

function togglectrl() {
  termemu.togglectrl();
  keydiv = document.getElementById("ctrlkey");
  if (termemu.ctrlp())
    keydiv.className = "keysel";
  else
    keydiv.className = "key";
  return;
}

function login(h, w) {
  if (isalive)
    return;
  params = {"login": true, "h": h, "w": w};
  var req = new XMLHttpRequest();
  req.onreadystatechange = function () {
    if (req.readyState == 4 && req.status == 200) {
      var logindict = JSON.parse(req.responseText);
      if (logindict.login) {
        /* Success */
        termemu.resize(logindict.h, logindict.w);
        isalive = true;
        nsend = 0;
        nrecv = 0;
	setTitle("Logged in");
        debug(1, "Logged in with id " + logindict.id);
        getData();
        return;
      }
      return;
    }
  };
  req.open('POST', '/login', true);
  req.send(JSON.stringify(params));
  //req.send("login=login&h=" + String(h) + "&w=" + String(w));
  return;
}

function stop() {
  var req = new XMLHttpRequest();
  req.onreadystatechange = function () {
    if (req.readyState == 4 && req.status == 200) {
      /* Figure out whether or not it worked. */
      /* FIXME the server might respond with output. */
      isalive = false;
      return;
    }
  };
  req.open('POST', '/feed', true);
  req.send(JSON.stringify({"t": "q", "n": nsend++}));
  return;
}

function setTitle(tstr) {
  var titlespan = document.getElementById("ttitle");
  var tnode = document.createTextNode(tstr);
  if (titlespan.childNodes.length == 0)
    titlespan.appendChild(tnode);
  else
    titlespan.replaceChild(tnode, titlespan.childNodes[0]);
  return;
}

function debug(level, msg) {
  if (level < debugSuppress)
    return;
  var msgdiv = document.createElement("div");
  var msgtext = document.createTextNode(msg);
  msgdiv.appendChild(msgtext);
  document.getElementById("debug").appendChild(msgdiv);
  return;
}

/* This should be a termemu method. */
function textsize(larger) {
  var cssSize = document.getElementById("term").style.fontSize;
  if (!cssSize)
    return;
  var match = cssSize.match(/\d*/);
  if (!match)
    return;
  var csize = Number(match[0]);
  var nsize;
  if (larger) {
    if (csize >= 48)
      nsize = 48;
    else if (csize >= 20)
      nsize = csize + 4;
    else if (csize >= 12)
      nsize = csize + 2;
    else if (csize >= 8)
      nsize = csize + 1;
    else
      nsize = 8;
  }
  else {
    if (csize <= 8)
      nsize = 8;
    else if (csize <= 12)
      nsize = csize - 1;
    else if (csize <= 20)
      nsize = csize - 2;
    else if (csize <= 48)
      nsize = csize - 4;
    else
      nsize = 48;
  }
  document.getElementById("term").style.fontSize = nsize.toString() + "px";
  termemu.fixsize();
  debug(1, "Changing font size to " + nsize.toString());
  return;
}

function bell(on) {
  var imgnode = document.getElementById("bell");
  if (on) {
    imgnode.style.visibility = "visible";
    window.setTimeout(bell, 1500, false);
  }
  else
    imgnode.style.visibility = "hidden";
  return;
}

function dkey(codestr) {
  var dstr = "Keystring: ";
  for (var i = 0; i < codestr.length; i += 2) {
    code = Number("0x" + codestr.substr(i, 2));
    if (code < 32 || (code >= 127 && code < 160))
      dstr += "\\x" + code.toString(16);
    else
      dstr += String.fromCharCode(code);
  }
  debug(1, dstr);
  return;
}