//SVG validator: http://validator.w3.org/
//SVG viewer: http://svg-edit.googlecode.com/svn/branches/2.6/editor/svg-editor.html
function saveToSvg() {
  var lastX = 0, lastY = 0, lastIsMove;
  var svg = '';

  var boundsWidth = doodleBounds[2] - doodleBounds[0];
  var boundsHeight = doodleBounds[3] - doodleBounds[1];

  svg += '<?xml version="1.0" standalone="no"?>\n';
  svg += '<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">\n';
  svg += '<svg width="' + boundsWidth + '" height="' + boundsHeight + '" version="1.1" xmlns="http://www.w3.org/2000/svg">\n';
  svg += '\t<desc>Doodle 3D sketch</desc>\n';

  var data = '';
  for (var i = 0; i < _points.length; ++i) {
    var x = _points[i][0], y = _points[i][1], isMove = _points[i][2];
    var dx = x - lastX, dy = y - lastY;

    if (i == 0)
      data += 'M'; //emit absolute move on first pair of coordinates
    else if (isMove != lastIsMove)
      data += isMove ? 'm' : 'l';

    data += dx + ',' + dy + ' ';

    lastX = x;
    lastY = y;
    lastIsMove = isMove;
  }

  svg += '\t<path transform="translate(' + -doodleBounds[0] + ',' + -doodleBounds[1] + ')" d="' + data + '" fill="none" stroke="black" stroke-width="2" />\n';

  var fields = JSON.stringify({'height': numLayers, 'outlineShape': VERTICALSHAPE, 'twist': rStep});
  svg += '\t<!--<![CDATA[d3d-keys ' + fields + ']]>-->\n';

  svg += '</svg>\n';

  return svg;
}


//TODO: use local variables instead of _points,numLayers,VERTICALSHAPE and rStep so we can leave a current doodle in tact if an error occurs while parsing
function loadFromSvg(svgData) {
  var mode = '', x = 0, y = 0;

  console.log("loading " + svgData.length + " bytes of data...");

  clearDoodle();

  var p = svgData.indexOf("<path");
  if (p == -1) { console.log("loadFromSvg: could not find parsing start point"); return false; }
  p = svgData.indexOf('d="', p);
  if (p == -1) { console.log("loadFromSvg: could not find parsing start point"); return false; }
  p += 3; //skip 'd="'

  var skipSpace = function() { while (svgData.charAt(p) == ' ') p++; }
  var parseCommand = function() {
    while (true) {
      skipSpace();
      var c = svgData.charAt(p);
      if (c == 'M' || c == 'm' || c == 'l') { //new command letter
        mode = c;
      } else if (c == '"') { //end of command chain
        return true;
      } else { //something else, must be a pair of coordinates...
        var tx = 0, ty = 0, numberEnd = 0, len = 0;
        numberEnd = svgData.indexOf(',', p);
        if (numberEnd == -1) { console.log("could not find comma in coordinate pair"); return false; }
        len = numberEnd - p;
        tx = parseInt(svgData.substr(p, len));
        p += len + 1;
        skipSpace();
        numberEnd = svgData.indexOf(' ', p);
        if (numberEnd == -1) { console.log("could not find space after coordinate pair"); return false; }
        len = numberEnd - p;
        ty = parseInt(svgData.substr(p, len));
        p += len;

        if (mode == 'M' || mode == 'L') {
          x = tx; y = ty;
        } else if (mode == 'm' || mode == 'l') {
          x += tx; y += ty;
        } else {
          console.log("loadFromSvg: found coordinate pair but mode was never set");
          return false;
        }

        var isMove = mode == 'm' || mode == 'M';

        //TODO: create script-wide function for adding points?
        //console.log("inserting "+x+","+y+" ",isMove);
        updatePrevX = x;
        updatePrevY = y;
        _points.push([x, y, isMove]);
        adjustBounds(x, y);
        adjustPreviewTransformation();

        if (isMove) draw(x, y, .5);
        else draw(x, y);
      }
      p++;
    }

    return true;
  };

  parseCommand(); //depends on value of p, so don't move this without taking that into consideration

  const fieldDefMarker = "<!--<![CDATA[d3d-keys";
  p = svgData.indexOf(fieldDefMarker);
  if (p == -1) { console.log("loadFromSvg: could not find metadata marker"); return false; }
  p += fieldDefMarker.length;
  skipSpace();

  var endP = svgData.indexOf("]]>-->", p);
  if (endP == -1) { console.log("loadFromSvg: could not find metadata end-marker"); return false; }
  var metaFields = JSON.parse(svgData.substr(p, endP - p));
  //TODO: log error and return false if parsing failed
  for (var k in metaFields) {
    var v = metaFields[k];
    switch (k) {
      case "height": numLayers = v; break;
      case "outlineShape": VERTICALSHAPE = v; break;
      case "twist": rStep = v; break;
    }
  }

  renderToImageDataPreview();

  return true;
}