/*globals svgedit*/
/*jslint vars: true, eqeq: true */
/**
 * Package: svgedit.history
 *
 * Licensed under the MIT License
 *
 * Copyright(c) 2011 Jeff Schiller
 * Copyright(c) 2016 Flint O'Brien
 */

// Dependencies:
// 1) svgedit.js
// 2) draw.js

(function() {
	'use strict';

if (!svgedit.draw) {
  svgedit.draw = {};
}
var NS = svgedit.NS;


/**
 * This class encapsulates the concept of a layer in the drawing. It can be constructed with
 * an existing group element or, with three parameters, will create a new layer group element.
 * @param {string} name - Layer name
 * @param {SVGGElement} group - SVG group element that constitutes the layer or null if a group should be created and added to the DOM..
 * @param {SVGGElement} svgElem - The SVG DOM element. If defined, use this to add
 * 		a new layer to the document.
 */
var Layer = svgedit.draw.Layer = function(name, group, svgElem) {
  this.name_ = name;
  this.group_ = group;

  if (!group) {
    // Create a group element with title and add it to the DOM.
    var svgdoc = svgElem.ownerDocument;
    this.group_ = svgdoc.createElementNS(NS.SVG, "g");
    var layer_title = svgdoc.createElementNS(NS.SVG, "title");
    layer_title.textContent = name;
    this.group_.appendChild(layer_title);
    svgElem.appendChild(this.group_);
  }

  addLayerClass(this.group_);
  svgedit.utilities.walkTree(this.group_, function(e){e.setAttribute("style", "pointer-events:inherit");});

  this.group_.setAttribute("style", svgElem ? "pointer-events:all" : "pointer-events:none");
};

/**
 * @type {string} CLASS_NAME - class attribute assigned to all layer groups.
 */
Layer.CLASS_NAME = 'layer';

/**
 * @type {RegExp} CLASS_REGEX - Used to test presence of class Layer.CLASS_NAME
 */
Layer.CLASS_REGEX = new RegExp('(\\s|^)' + Layer.CLASS_NAME + '(\\s|$)');


/**
 * Get the layer's name.
 * @returns {string} The layer name
 */
Layer.prototype.getName = function() {
  return this.name_;
};

/**
 * Get the group element for this layer.
 * @returns {SVGGElement} The layer SVG group
 */
Layer.prototype.getGroup = function() {
  return this.group_;
};

/**
 * Active this layer so it takes pointer events.
 */
Layer.prototype.activate = function() {
  this.group_.setAttribute("style", "pointer-events:all");
};

/**
 * Deactive this layer so it does NOT take pointer events.
 */
Layer.prototype.deactivate = function() {
  this.group_.setAttribute("style", "pointer-events:none");
};

/**
 * Set this layer visible or hidden based on 'visible' parameter.
 * @param {boolean} visible - If true, make visible; otherwise, hide it.
 */
Layer.prototype.setVisible = function(visible) {
  var expected = visible === undefined || visible ? "inline" : "none";
  var oldDisplay = this.group_.getAttribute("display");
  if (oldDisplay !== expected) {
    this.group_.setAttribute("display", expected);
  }
};

/**
 * Is this layer visible?
 * @returns {boolean} True if visible.
 */
Layer.prototype.isVisible = function() {
  return this.group_.getAttribute('display') !== 'none';
};

/**
 * Get layer opacity.
 * @returns {number} Opacity value.
 */
Layer.prototype.getOpacity = function() {
  var opacity = this.group_.getAttribute('opacity');
  if (opacity === null || opacity === undefined) {
    return 1;
  }
  return parseFloat(opacity);
};

/**
 * Sets the opacity of this layer. If opacity is not a value between 0.0 and 1.0,
 * nothing happens.
 * @param {number} opacity - A float value in the range 0.0-1.0
 */
Layer.prototype.setOpacity = function(opacity) {
  if (typeof opacity === 'number' && opacity >= 0.0 && opacity <= 1.0) {
    this.group_.setAttribute('opacity', opacity);
  }
};

/**
 * Append children to this layer.
 * @param {SVGGElement} children - The children to append to this layer.
 */
Layer.prototype.appendChildren = function(children) {
  for (var i = 0; i < children.length; ++i) {
    this.group_.appendChild(children[i]);
  }
};

Layer.prototype.getTitleElement = function() {
  var len = this.group_.childNodes.length;
  for (var i = 0; i < len; ++i) {
    var child = this.group_.childNodes.item(i);
    if (child && child.tagName === 'title') {
      return child;
    }
  }
  return null;
};

Layer.prototype.setName = function(name) {
  var previousName = this.name_;
  name = svgedit.utilities.toXml(name);
  // now change the underlying title element contents
  var title = this.getTitleElement();
  if (title) {
    while (title.firstChild) { title.removeChild(title.firstChild); }
    title.textContent = name;
    this.name_ = name;
    return {title: title, previousName: previousName};
  }
  return null;
};

/**
 * Remove this layer's group from the DOM. No more functions on group can be called after this.
 * @param {SVGGElement} children - The children to append to this layer.
 * @returns {SVGGElement} The layer SVG group that was just removed.
 */
Layer.prototype.removeGroup = function() {
  var parent = this.group_.parentNode;
  var group = parent.removeChild(this.group_);
  this.group_ = undefined;
  return group;
};


/**
 * Add class Layer.CLASS_NAME to the element (usually class='layer').
 *
 * Parameters:
 * @param {SVGGElement} elem - The SVG element to update
 */
function addLayerClass(elem) {
  var classes = elem.getAttribute('class');
  if (classes === null || classes === undefined || classes.length === 0) {
    elem.setAttribute('class', Layer.CLASS_NAME);
  } else if (! Layer.CLASS_REGEX.test(classes)) {
    elem.setAttribute('class', classes + ' ' + Layer.CLASS_NAME);
  }
}

}());