102 lines
3.1 KiB
JavaScript
102 lines
3.1 KiB
JavaScript
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/*
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Copyright 2019 The Matrix.org Foundation C.I.C.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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export default class HistoryManager {
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constructor() {
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this._stack = [];
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this._newlyTypedCharCount = 0;
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this._currentIndex = -1;
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this._changedSinceLastPush = false;
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this._lastCaret = null;
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}
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_shouldPush(inputType, diff) {
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if (inputType === "insertText") {
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if (diff.removed) {
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// always append when removing text
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return true;
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}
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if (diff.added) {
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// only append after every 5th keystroke while typing
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this._newlyTypedCharCount += diff.added.length;
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return this._newlyTypedCharCount > 5;
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}
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} else {
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return true;
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}
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}
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_pushState(model, caret) {
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// remove all steps after current step
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while (this._currentIndex < (this._stack.length - 1)) {
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this._stack.pop();
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}
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const parts = model.serializeParts();
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this._stack.push({parts, caret});
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this._currentIndex = this._stack.length - 1;
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this._lastCaret = null;
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this._changedSinceLastPush = false;
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this._newlyTypedCharCount = 0;
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}
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// needs to persist parts and caret position
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tryPush(model, caret, inputType, diff) {
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// ignore state restoration echos.
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// these respect the inputType values of the input event,
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// but are actually passed in from MessageEditor calling model.reset()
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// in the keydown event handler.
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if (inputType === "historyUndo" || inputType === "historyRedo") {
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return false;
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}
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const shouldPush = this._shouldPush(inputType, diff);
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if (shouldPush) {
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this._pushState(model, caret);
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} else {
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this._lastCaret = caret;
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this._changedSinceLastPush = true;
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}
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return shouldPush;
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}
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canUndo() {
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return this._currentIndex >= 1 || this._changedSinceLastPush;
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}
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canRedo() {
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return this._currentIndex < (this._stack.length - 1);
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}
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// returns state that should be applied to model
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undo(model) {
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if (this.canUndo()) {
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if (this._changedSinceLastPush) {
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this._pushState(model, this._lastCaret);
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}
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this._currentIndex -= 1;
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return this._stack[this._currentIndex];
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}
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}
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// returns state that should be applied to model
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redo() {
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if (this.canRedo()) {
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this._changedSinceLastPush = false;
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this._currentIndex += 1;
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return this._stack[this._currentIndex];
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}
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}
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}
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