mirror of https://github.com/status-im/codimd.git
112 lines
3.5 KiB
JavaScript
112 lines
3.5 KiB
JavaScript
if (typeof ot === 'undefined') {
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// Export for browsers
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var ot = {};
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}
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ot.UndoManager = (function () {
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'use strict';
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var NORMAL_STATE = 'normal';
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var UNDOING_STATE = 'undoing';
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var REDOING_STATE = 'redoing';
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// Create a new UndoManager with an optional maximum history size.
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function UndoManager (maxItems) {
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this.maxItems = maxItems || 50;
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this.state = NORMAL_STATE;
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this.dontCompose = false;
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this.undoStack = [];
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this.redoStack = [];
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}
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// Add an operation to the undo or redo stack, depending on the current state
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// of the UndoManager. The operation added must be the inverse of the last
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// edit. When `compose` is true, compose the operation with the last operation
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// unless the last operation was alread pushed on the redo stack or was hidden
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// by a newer operation on the undo stack.
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UndoManager.prototype.add = function (operation, compose) {
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if (this.state === UNDOING_STATE) {
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this.redoStack.push(operation);
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this.dontCompose = true;
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} else if (this.state === REDOING_STATE) {
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this.undoStack.push(operation);
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this.dontCompose = true;
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} else {
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var undoStack = this.undoStack;
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if (!this.dontCompose && compose && undoStack.length > 0) {
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undoStack.push(operation.compose(undoStack.pop()));
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} else {
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undoStack.push(operation);
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if (undoStack.length > this.maxItems) { undoStack.shift(); }
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}
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this.dontCompose = false;
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this.redoStack = [];
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}
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};
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function transformStack (stack, operation) {
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var newStack = [];
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var Operation = operation.constructor;
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for (var i = stack.length - 1; i >= 0; i--) {
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var pair = Operation.transform(stack[i], operation);
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if (typeof pair[0].isNoop !== 'function' || !pair[0].isNoop()) {
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newStack.push(pair[0]);
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}
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operation = pair[1];
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}
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return newStack.reverse();
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}
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// Transform the undo and redo stacks against a operation by another client.
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UndoManager.prototype.transform = function (operation) {
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this.undoStack = transformStack(this.undoStack, operation);
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this.redoStack = transformStack(this.redoStack, operation);
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};
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// Perform an undo by calling a function with the latest operation on the undo
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// stack. The function is expected to call the `add` method with the inverse
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// of the operation, which pushes the inverse on the redo stack.
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UndoManager.prototype.performUndo = function (fn) {
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this.state = UNDOING_STATE;
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if (this.undoStack.length === 0) { throw new Error("undo not possible"); }
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fn(this.undoStack.pop());
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this.state = NORMAL_STATE;
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};
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// The inverse of `performUndo`.
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UndoManager.prototype.performRedo = function (fn) {
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this.state = REDOING_STATE;
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if (this.redoStack.length === 0) { throw new Error("redo not possible"); }
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fn(this.redoStack.pop());
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this.state = NORMAL_STATE;
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};
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// Is the undo stack not empty?
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UndoManager.prototype.canUndo = function () {
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return this.undoStack.length !== 0;
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};
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// Is the redo stack not empty?
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UndoManager.prototype.canRedo = function () {
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return this.redoStack.length !== 0;
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};
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// Whether the UndoManager is currently performing an undo.
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UndoManager.prototype.isUndoing = function () {
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return this.state === UNDOING_STATE;
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};
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// Whether the UndoManager is currently performing a redo.
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UndoManager.prototype.isRedoing = function () {
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return this.state === REDOING_STATE;
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};
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return UndoManager;
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}());
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// Export for CommonJS
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if (typeof module === 'object') {
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module.exports = ot.UndoManager;
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}
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