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// Copyright 2010 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//      http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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 * @fileoverview Factories for common path types.
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 * @author [email protected] (Nick Santos)
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 */
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goog.provide('goog.math.paths');
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goog.require('goog.math.Coordinate');
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goog.require('goog.math.Path');
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/**
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 * Defines a regular n-gon by specifing the center, a vertex, and the total
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 * number of vertices.
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 * @param {goog.math.Coordinate} center The center point.
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 * @param {goog.math.Coordinate} vertex The vertex, which implicitly defines
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 *     a radius as well.
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 * @param {number} n The number of vertices.
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 * @return {!goog.math.Path} The path.
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 */
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goog.math.paths.createRegularNGon = function(center, vertex, n) {
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  var path = new goog.math.Path();
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  path.moveTo(vertex.x, vertex.y);
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  var startAngle = Math.atan2(vertex.y - center.y, vertex.x - center.x);
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  var radius = goog.math.Coordinate.distance(center, vertex);
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  for (var i = 1; i < n; i++) {
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    var angle = startAngle + 2 * Math.PI * (i / n);
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    path.lineTo(
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        center.x + radius * Math.cos(angle),
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        center.y + radius * Math.sin(angle));
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  }
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  path.close();
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  return path;
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};
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/**
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 * Defines an arrow.
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 * @param {goog.math.Coordinate} a Point A.
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 * @param {goog.math.Coordinate} b Point B.
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 * @param {?number} aHead The size of the arrow head at point A.
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 *     0 omits the head.
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 * @param {?number} bHead The size of the arrow head at point B.
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 *     0 omits the head.
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 * @return {!goog.math.Path} The path.
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 */
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goog.math.paths.createArrow = function(a, b, aHead, bHead) {
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  var path = new goog.math.Path();
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  path.moveTo(a.x, a.y);
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  path.lineTo(b.x, b.y);
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  var angle = Math.atan2(b.y - a.y, b.x - a.x);
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  if (aHead) {
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    path.appendPath(
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        goog.math.paths.createRegularNGon(
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            new goog.math.Coordinate(
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                a.x + aHead * Math.cos(angle), a.y + aHead * Math.sin(angle)),
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            a, 3));
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  }
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  if (bHead) {
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    path.appendPath(
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        goog.math.paths.createRegularNGon(
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            new goog.math.Coordinate(
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                b.x + bHead * Math.cos(angle + Math.PI),
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                b.y + bHead * Math.sin(angle + Math.PI)),
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            b, 3));
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  }
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  return path;
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};
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