;(function(w, d) {

  var screenBuffer = "", inputBuffer = "", screenDom, inputRes = "",
      floader, vm

  /* screen rendering routine */
  function renderScreen() {
    screenDom.textContent = screenBuffer + inputBuffer + "\u258f"
    screenDom.scrollTop = screenDom.scrollHeight
  }

  /* external program loading routine */
  function loadProgFileHandler(e) {
    if(e.target.files.length > 0) {
      var fobj = e.target.files[0], rdr = new FileReader()
      rdr.onload = function() {
        var progsrc = rdr.result
        if(progsrc.length > 0) {
          var instrs = progsrc.split(/\s+/), i, l = instrs.length,
              instr, lno, cmd, x, y, z, icount = 0
          for(i=0;i<l;i++) {
            instr = parseInt(instrs[i] || 0)
            if(icount == 0) lno = instr
            else if(icount == 1) cmd = instr
            else if(icount == 2) x = instr
            else if(icount == 3) y = instr
            else if(icount == 4) z = instr
            icount++
            if(icount == 5) {
              vm.ilenter(lno, cmd, x, y, z)
              icount = 0
            }
          }
          lineOut("\nProgram " + fobj.name + " loaded successfully\n> ")
        }
      }
      if(fobj) rdr.readAsText(fobj)
    }
  }

  /* main input routine:
   * digits 0 to 9, 10 is space,
   * 11 is minus/backspace, 12 is enter, 13 is decimal point,
   * 14 is program load action */
  function doInput(number) {
    if(number >= 0 && number < 10) /* normal digit */
      inputBuffer += ("" + number)
    else if(number == 10) /* space */
      inputBuffer += " "
    else if(number == 11) { /* backspace or minus */
      if(inputBuffer.length == 0)
        inputBuffer += "-"
      else
        inputBuffer = inputBuffer.slice(0, inputBuffer.length - 1)
    } else if(number == 12) { /* enter */
      screenBuffer += inputBuffer + "\n"
      inputRes = inputBuffer
      inputBuffer = ""
    } else if(number == 13) /* decimal point */
      inputBuffer += "."
    else if(number == 14) floader.click() /* trigger program loader */
    renderScreen()
  }

  function setupInput() {
    /* setup physical keys */
    w.addEventListener("keydown", function(e) {
      switch(e.key) {
        case "0":
        case "1":
        case "2":
        case "3":
        case "4":
        case "5":
        case "6":
        case "7":
        case "8":
        case "9":
          e.preventDefault()
          doInput(parseInt(e.key))
          break
        case "+":
        case "/":
        case " ":
        case "Call":
        case "ArrowDown":
          e.preventDefault()
          doInput(10)
          break
        case "Backspace":
        case "Back":
        case "ArrowLeft":
        case "Delete":
        case "-":
          e.preventDefault()
          e.stopPropagation()
          doInput(11)
          break
        case "#":
        case "Enter":
          e.preventDefault()
          doInput(12)
          break
        case "*":
        case ",":
        case ".":
          e.preventDefault()
          doInput(13)
          break
        case "l":
        case "L":
        case "ArrowUp":
        case "SoftLeft":
          e.preventDefault()
          doInput(14)
          break
      }
    }, false)
    /* setup virtual keys */
    w.addEventListener("click", function(e) {
      switch(e.target.id) {
        case "b0":
        case "b1":
        case "b2":
        case "b3":
        case "b4":
        case "b5":
        case "b6":
        case "b7":
        case "b8":
        case "b9":
          e.preventDefault()
          doInput(parseInt(e.target.id.slice(1)))
          break
        case "bspc":
          e.preventDefault()
          doInput(10)
          break
        case "bbksp":
          e.preventDefault()
          doInput(11)
          break
        case "benter":
          e.preventDefault()
          doInput(12)
          break
        case "bpoint":
          e.preventDefault()
          doInput(13)
          break
        case "bprogload":
          e.preventDefault()
          doInput(14)
          break
      }
    }, false)
  }

  function lineOut(s) { /* line output routine */
    screenBuffer += s
    renderScreen()
  }

  function charOut(c) { /* character output routine */
    screenBuffer += String.fromCharCode(+c)
    renderScreen()
  }

  function lineIn(cb) {
    inputRes = ""
    var inv = setInterval(function resWait() {
      if(inputRes != "") {
        clearInterval(inv)
        cb(inputRes)
        inputRes = ""
      }
    }, 100)
  }

  function main() { /* UI entry point */
    screenDom = d.getElementById("screenfield")
    floader = d.getElementById("programloadfield")
    floader.addEventListener("change", loadProgFileHandler, false)
    setupInput()
    prompt = "> "
    vm = createmu808(lineOut, charOut, lineIn)
    lineOut("mu808 v1 by Luxferre\nPROGMEM: 16383 steps\nDATAMEM: 16384 floats\n")
    ;(function repl() {
      lineOut(prompt)
      lineIn(function(entryString) {
        var eparts = entryString.split(/[^\-0-9]+/).slice(0, 5),
            lno = parseInt(eparts[0] || 0),
            cmd = parseInt(eparts[1] || 0),
            x = parseInt(eparts[2] || 0),
            y = parseInt(eparts[3] || 0),
            z = parseInt(eparts[4] || 0)
        vm.ilenter(lno, cmd, x, y, z, repl)
      })
    })()
  }

  w.addEventListener("DOMContentLoaded", main, false)
})(window, document)