// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

var MINIMUM_EDGE_SEPARATION = 20;

function isEdgeInitiallyVisible(target, index, source, type) {
  return type == "control" && (target.cfg || source.cfg);
}

var Edge = function(target, index, source, type) {
  this.target = target;
  this.source = source;
  this.index = index;
  this.type = type;
  this.backEdgeNumber = 0;
  this.visible = isEdgeInitiallyVisible(target, index, source, type);
};

Edge.prototype.stringID = function() {
  return this.source.id + "," + this.index +  "," + this.target.id;
};

Edge.prototype.isVisible = function() {
  return this.visible && this.source.visible && this.target.visible;
};

Edge.prototype.getInputHorizontalPosition = function(graph) {
  if (this.backEdgeNumber > 0) {
    return graph.maxGraphNodeX + this.backEdgeNumber * MINIMUM_EDGE_SEPARATION;
  }
  var source = this.source;
  var target = this.target;
  var index = this.index;
  var input_x = target.x + target.getInputX(index);
  var inputApproach = target.getInputApproach(this.index);
  var outputApproach = source.getOutputApproach(graph);
  if (inputApproach > outputApproach) {
    return input_x;
  } else {
    var inputOffset = MINIMUM_EDGE_SEPARATION * (index + 1);
    return (target.x < source.x)
      ? (target.x + target.getTotalNodeWidth() + inputOffset)
      : (target.x - inputOffset)
  }
}

Edge.prototype.generatePath = function(graph) {
  var target = this.target;
  var source = this.source;
  var input_x = target.x + target.getInputX(this.index);
  var arrowheadHeight = 7;
  var input_y = target.y - 2 * DEFAULT_NODE_BUBBLE_RADIUS - arrowheadHeight;
  var output_x = source.x + source.getOutputX();
  var output_y = source.y + graph.getNodeHeight(source) + DEFAULT_NODE_BUBBLE_RADIUS;
  var inputApproach = target.getInputApproach(this.index);
  var outputApproach = source.getOutputApproach(graph);
  var horizontalPos = this.getInputHorizontalPosition(graph);

  var result = "M" + output_x + "," + output_y +
    "L" + output_x + "," + outputApproach +
    "L" + horizontalPos + "," + outputApproach;

  if (horizontalPos != input_x) {
    result += "L" + horizontalPos + "," + inputApproach;
  } else {
    if (inputApproach < outputApproach) {
      inputApproach = outputApproach;
    }
  }

  result += "L" + input_x + "," + inputApproach +
    "L" + input_x + "," + input_y;
  return result;
}

Edge.prototype.isBackEdge = function() {
  return this.target.hasBackEdges() && (this.target.rank < this.source.rank);
}