78 lines
1.7 KiB
JavaScript
78 lines
1.7 KiB
JavaScript
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/**
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* Represents the history of an object
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* @constructor
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*/
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var History = function() {
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/**
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* Stores the different states of the object
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* @type {Object[]}
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*/
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this.states = [];
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/**
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* Represents the position in the history we're at
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* @type {Number}
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*/
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this.index = -1;
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/**
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* Represents the number of elements in the history
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* @type {Number}
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*/
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this.size = 0;
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}
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/**
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* Appends a new state at the end of the history
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* @param {Object} state the state to append
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*/
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History.prototype.addState = function(state) {
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++this.index;
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this.size = this.index + 1;
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this.states[this.size-1] = state;
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}
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/**
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* Returns the previous state and change the index to the previous state (so you can redo)
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*/
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History.prototype.undo = function() {
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if (this.undoable()) {
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this.index--;
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return this.currentState();
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}
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}
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/**
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* Returns the next state and change the index to the next state (so you can re-undo)
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*/
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History.prototype.redo = function() {
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if (this.redoable()) {
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this.index++;
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return this.currentState();
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}
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}
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/**
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* Checks if there is a undo possibility
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* @returns {Boolean} true if undo is possible, false otherwise
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*/
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History.prototype.undoable = function() {
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return this.index > 0;
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}
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/**
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* Checks if there is a redo possibility
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* @returns {Boolean} true if redo is possible, false otherwise
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*/
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History.prototype.redoable = function() {
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return this.index < this.size - 1;
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}
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/**
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* Returns the current state in the history
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* @returns {Object} the current state in the history
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*/
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History.prototype.currentState = function() {
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return this.states[this.index];
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}
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