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class InputHistory { |
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constructor() { |
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this.states = []; |
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this.currentIndex = 0; |
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} |
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get currentState() { |
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return this.states[this.currentIndex]; |
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} |
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get isEmpty() { |
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return this.states.length === 0; |
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} |
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push(state) { |
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// if current index points before the last element then remove the future |
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if (this.currentIndex < this.states.length - 1) this.states.length = this.currentIndex + 1; |
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this.states.push(state); |
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if (this.states.length > InputHistory.MAX_LENGTH) this.states.shift(); |
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this.currentIndex = this.states.length - 1; |
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} |
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go(steps) { |
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this.currentIndex = Math.min(Math.max(this.currentIndex + steps, 0), this.states.length - 1); |
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return this.currentState; |
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} |
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undo() { |
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return this.go(-1); |
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} |
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redo() { |
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return this.go(+1); |
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} |
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clear() { |
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this.states.length = 0; |
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this.currentIndex = 0; |
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} |
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} |
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InputHistory.MAX_LENGTH = 100; |
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|
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export { InputHistory as default }; |
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