editableTextModel.ts

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/
'use strict';

import { Range, IRange } from 'vs/editor/common/core/range';
import * as editorCommon from 'vs/editor/common/editorCommon';
import { EditStack } from 'vs/editor/common/model/editStack';
import { ILineEdit, IModelLine } from 'vs/editor/common/model/modelLine';
import { TextModelWithDecorations, ModelDecorationOptions } from 'vs/editor/common/model/textModelWithDecorations';
import * as strings from 'vs/base/common/strings';
import * as arrays from 'vs/base/common/arrays';
import { Selection } from 'vs/editor/common/core/selection';
import { LanguageIdentifier } from 'vs/editor/common/modes';
import { ITextSource, IRawTextSource } from 'vs/editor/common/model/textSource';
import { ModelRawContentChangedEvent, ModelRawChange, IModelContentChange, ModelRawLineChanged, ModelRawLinesDeleted, ModelRawLinesInserted } from 'vs/editor/common/model/textModelEvents';

export interface IValidatedEditOperation {
	sortIndex: number;
	identifier: editorCommon.ISingleEditOperationIdentifier;
	range: Range;
	rangeOffset: number;
	rangeLength: number;
	lines: string[];
	forceMoveMarkers: boolean;
	isAutoWhitespaceEdit: boolean;
}

interface IIdentifiedLineEdit extends ILineEdit {
	lineNumber: number;
}

export class EditableTextModel extends TextModelWithDecorations implements editorCommon.IEditableTextModel {

	private _commandManager: EditStack;

	// for extra details about change events:
	private _isUndoing: boolean;
	private _isRedoing: boolean;

	// editable range
	private _hasEditableRange: boolean;
	private _editableRangeId: string;

	private _trimAutoWhitespaceLines: number[];

	constructor(rawTextSource: IRawTextSource, creationOptions: editorCommon.ITextModelCreationOptions, languageIdentifier: LanguageIdentifier) {
		super(rawTextSource, creationOptions, languageIdentifier);

		this._commandManager = new EditStack(this);

		this._isUndoing = false;
		this._isRedoing = false;

		this._hasEditableRange = false;
		this._editableRangeId = null;
		this._trimAutoWhitespaceLines = null;
	}

	public dispose(): void {
		this._commandManager = null;
		super.dispose();
	}

	protected _resetValue(newValue: ITextSource): void {
		super._resetValue(newValue);

		// Destroy my edit history and settings
		this._commandManager = new EditStack(this);
		this._hasEditableRange = false;
		this._editableRangeId = null;
		this._trimAutoWhitespaceLines = null;
	}

	public pushStackElement(): void {
		this._commandManager.pushStackElement();
	}

	public pushEditOperations(beforeCursorState: Selection[], editOperations: editorCommon.IIdentifiedSingleEditOperation[], cursorStateComputer: editorCommon.ICursorStateComputer): Selection[] {
		try {
			this._eventEmitter.beginDeferredEmit();
			this._onDidChangeDecorations.beginDeferredEmit();
			return this._pushEditOperations(beforeCursorState, editOperations, cursorStateComputer);
		} finally {
			this._onDidChangeDecorations.endDeferredEmit();
			this._eventEmitter.endDeferredEmit();
		}
	}

	private _pushEditOperations(beforeCursorState: Selection[], editOperations: editorCommon.IIdentifiedSingleEditOperation[], cursorStateComputer: editorCommon.ICursorStateComputer): Selection[] {
		if (this._options.trimAutoWhitespace && this._trimAutoWhitespaceLines) {
			// Go through each saved line number and insert a trim whitespace edit
			// if it is safe to do so (no conflicts with other edits).

			let incomingEdits = editOperations.map((op) => {
				return {
					range: this.validateRange(op.range),
					text: op.text
				};
			});

			// Sometimes, auto-formatters change ranges automatically which can cause undesired auto whitespace trimming near the cursor
			// We'll use the following heuristic: if the edits occur near the cursor, then it's ok to trim auto whitespace
			let editsAreNearCursors = true;
			for (let i = 0, len = beforeCursorState.length; i < len; i++) {
				let sel = beforeCursorState[i];
				let foundEditNearSel = false;
				for (let j = 0, lenJ = incomingEdits.length; j < lenJ; j++) {
					let editRange = incomingEdits[j].range;
					let selIsAbove = editRange.startLineNumber > sel.endLineNumber;
					let selIsBelow = sel.startLineNumber > editRange.endLineNumber;
					if (!selIsAbove && !selIsBelow) {
						foundEditNearSel = true;
						break;
					}
				}
				if (!foundEditNearSel) {
					editsAreNearCursors = false;
					break;
				}
			}

			if (editsAreNearCursors) {
				for (let i = 0, len = this._trimAutoWhitespaceLines.length; i < len; i++) {
					let trimLineNumber = this._trimAutoWhitespaceLines[i];
					let maxLineColumn = this.getLineMaxColumn(trimLineNumber);

					let allowTrimLine = true;
					for (let j = 0, lenJ = incomingEdits.length; j < lenJ; j++) {
						let editRange = incomingEdits[j].range;
						let editText = incomingEdits[j].text;

						if (trimLineNumber < editRange.startLineNumber || trimLineNumber > editRange.endLineNumber) {
							// `trimLine` is completely outside this edit
							continue;
						}

						// At this point:
						//   editRange.startLineNumber <= trimLine <= editRange.endLineNumber

						if (
							trimLineNumber === editRange.startLineNumber && editRange.startColumn === maxLineColumn
							&& editRange.isEmpty() && editText && editText.length > 0 && editText.charAt(0) === '\n'
						) {
							// This edit inserts a new line (and maybe other text) after `trimLine`
							continue;
						}

						// Looks like we can't trim this line as it would interfere with an incoming edit
						allowTrimLine = false;
						break;
					}

					if (allowTrimLine) {
						editOperations.push({
							identifier: null,
							range: new Range(trimLineNumber, 1, trimLineNumber, maxLineColumn),
							text: null,
							forceMoveMarkers: false,
							isAutoWhitespaceEdit: false
						});
					}

				}
			}

			this._trimAutoWhitespaceLines = null;
		}
		return this._commandManager.pushEditOperation(beforeCursorState, editOperations, cursorStateComputer);
	}

	/**
	 * Transform operations such that they represent the same logic edit,
	 * but that they also do not cause OOM crashes.
	 */
	private _reduceOperations(operations: IValidatedEditOperation[]): IValidatedEditOperation[] {
		if (operations.length < 1000) {
			// We know from empirical testing that a thousand edits work fine regardless of their shape.
			return operations;
		}

		// At one point, due to how events are emitted and how each operation is handled,
		// some operations can trigger a high ammount of temporary string allocations,
		// that will immediately get edited again.
		// e.g. a formatter inserting ridiculous ammounts of \n on a model with a single line
		// Therefore, the strategy is to collapse all the operations into a huge single edit operation
		return [this._toSingleEditOperation(operations)];
	}

	_toSingleEditOperation(operations: IValidatedEditOperation[]): IValidatedEditOperation {
		let forceMoveMarkers = false,
			firstEditRange = operations[0].range,
			lastEditRange = operations[operations.length - 1].range,
			entireEditRange = new Range(firstEditRange.startLineNumber, firstEditRange.startColumn, lastEditRange.endLineNumber, lastEditRange.endColumn),
			lastEndLineNumber = firstEditRange.startLineNumber,
			lastEndColumn = firstEditRange.startColumn,
			result: string[] = [];

		for (let i = 0, len = operations.length; i < len; i++) {
			let operation = operations[i],
				range = operation.range;

			forceMoveMarkers = forceMoveMarkers || operation.forceMoveMarkers;

			// (1) -- Push old text
			for (let lineNumber = lastEndLineNumber; lineNumber < range.startLineNumber; lineNumber++) {
				if (lineNumber === lastEndLineNumber) {
					result.push(this._lines[lineNumber - 1].text.substring(lastEndColumn - 1));
				} else {
					result.push('\n');
					result.push(this._lines[lineNumber - 1].text);
				}
			}

			if (range.startLineNumber === lastEndLineNumber) {
				result.push(this._lines[range.startLineNumber - 1].text.substring(lastEndColumn - 1, range.startColumn - 1));
			} else {
				result.push('\n');
				result.push(this._lines[range.startLineNumber - 1].text.substring(0, range.startColumn - 1));
			}

			// (2) -- Push new text
			if (operation.lines) {
				for (let j = 0, lenJ = operation.lines.length; j < lenJ; j++) {
					if (j !== 0) {
						result.push('\n');
					}
					result.push(operation.lines[j]);
				}
			}

			lastEndLineNumber = operation.range.endLineNumber;
			lastEndColumn = operation.range.endColumn;
		}

		return {
			sortIndex: 0,
			identifier: operations[0].identifier,
			range: entireEditRange,
			rangeOffset: this.getOffsetAt(entireEditRange.getStartPosition()),
			rangeLength: this.getValueLengthInRange(entireEditRange),
			lines: result.join('').split('\n'),
			forceMoveMarkers: forceMoveMarkers,
			isAutoWhitespaceEdit: false
		};
	}

	private static _sortOpsAscending(a: IValidatedEditOperation, b: IValidatedEditOperation): number {
		let r = Range.compareRangesUsingEnds(a.range, b.range);
		if (r === 0) {
			return a.sortIndex - b.sortIndex;
		}
		return r;
	}

	private static _sortOpsDescending(a: IValidatedEditOperation, b: IValidatedEditOperation): number {
		let r = Range.compareRangesUsingEnds(a.range, b.range);
		if (r === 0) {
			return b.sortIndex - a.sortIndex;
		}
		return -r;
	}

	public applyEdits(rawOperations: editorCommon.IIdentifiedSingleEditOperation[]): editorCommon.IIdentifiedSingleEditOperation[] {
		try {
			this._eventEmitter.beginDeferredEmit();
			this._onDidChangeDecorations.beginDeferredEmit();
			return this._applyEdits(rawOperations);
		} finally {
			this._onDidChangeDecorations.endDeferredEmit();
			this._eventEmitter.endDeferredEmit();
		}
	}

	private _applyEdits(rawOperations: editorCommon.IIdentifiedSingleEditOperation[]): editorCommon.IIdentifiedSingleEditOperation[] {
		if (rawOperations.length === 0) {
			return [];
		}

		let mightContainRTL = this._mightContainRTL;
		let mightContainNonBasicASCII = this._mightContainNonBasicASCII;
		let canReduceOperations = true;

		let operations: IValidatedEditOperation[] = [];
		for (let i = 0; i < rawOperations.length; i++) {
			let op = rawOperations[i];
			if (canReduceOperations && op._isTracked) {
				canReduceOperations = false;
			}
			let validatedRange = this.validateRange(op.range);
			if (!mightContainRTL && op.text) {
				// check if the new inserted text contains RTL
				mightContainRTL = strings.containsRTL(op.text);
			}
			if (!mightContainNonBasicASCII && op.text) {
				mightContainNonBasicASCII = !strings.isBasicASCII(op.text);
			}
			operations[i] = {
				sortIndex: i,
				identifier: op.identifier,
				range: validatedRange,
				rangeOffset: this.getOffsetAt(validatedRange.getStartPosition()),
				rangeLength: this.getValueLengthInRange(validatedRange),
				lines: op.text ? op.text.split(/\r\n|\r|\n/) : null,
				forceMoveMarkers: op.forceMoveMarkers,
				isAutoWhitespaceEdit: op.isAutoWhitespaceEdit || false
			};
		}

		// Sort operations ascending
		operations.sort(EditableTextModel._sortOpsAscending);

		for (let i = 0, count = operations.length - 1; i < count; i++) {
			let rangeEnd = operations[i].range.getEndPosition();
			let nextRangeStart = operations[i + 1].range.getStartPosition();

			if (nextRangeStart.isBefore(rangeEnd)) {
				// overlapping ranges
				throw new Error('Overlapping ranges are not allowed!');
			}
		}

		if (canReduceOperations) {
			operations = this._reduceOperations(operations);
		}

		let editableRange = this.getEditableRange();
		let editableRangeStart = editableRange.getStartPosition();
		let editableRangeEnd = editableRange.getEndPosition();
		for (let i = 0; i < operations.length; i++) {
			let operationRange = operations[i].range;
			if (!editableRangeStart.isBeforeOrEqual(operationRange.getStartPosition()) || !operationRange.getEndPosition().isBeforeOrEqual(editableRangeEnd)) {
				throw new Error('Editing outside of editable range not allowed!');
			}
		}

		// Delta encode operations
		let reverseRanges = EditableTextModel._getInverseEditRanges(operations);
		let reverseOperations: editorCommon.IIdentifiedSingleEditOperation[] = [];

		let newTrimAutoWhitespaceCandidates: { lineNumber: number, oldContent: string }[] = [];

		for (let i = 0; i < operations.length; i++) {
			let op = operations[i];
			let reverseRange = reverseRanges[i];

			reverseOperations[i] = {
				identifier: op.identifier,
				range: reverseRange,
				text: this.getValueInRange(op.range),
				forceMoveMarkers: op.forceMoveMarkers
			};

			if (this._options.trimAutoWhitespace && op.isAutoWhitespaceEdit && op.range.isEmpty()) {
				// Record already the future line numbers that might be auto whitespace removal candidates on next edit
				for (let lineNumber = reverseRange.startLineNumber; lineNumber <= reverseRange.endLineNumber; lineNumber++) {
					let currentLineContent = '';
					if (lineNumber === reverseRange.startLineNumber) {
						currentLineContent = this.getLineContent(op.range.startLineNumber);
						if (strings.firstNonWhitespaceIndex(currentLineContent) !== -1) {
							continue;
						}
					}
					newTrimAutoWhitespaceCandidates.push({ lineNumber: lineNumber, oldContent: currentLineContent });
				}
			}
		}

		this._mightContainRTL = mightContainRTL;
		this._mightContainNonBasicASCII = mightContainNonBasicASCII;
		this._doApplyEdits(operations);

		this._trimAutoWhitespaceLines = null;
		if (this._options.trimAutoWhitespace && newTrimAutoWhitespaceCandidates.length > 0) {
			// sort line numbers auto whitespace removal candidates for next edit descending
			newTrimAutoWhitespaceCandidates.sort((a, b) => b.lineNumber - a.lineNumber);

			this._trimAutoWhitespaceLines = [];
			for (let i = 0, len = newTrimAutoWhitespaceCandidates.length; i < len; i++) {
				let lineNumber = newTrimAutoWhitespaceCandidates[i].lineNumber;
				if (i > 0 && newTrimAutoWhitespaceCandidates[i - 1].lineNumber === lineNumber) {
					// Do not have the same line number twice
					continue;
				}

				let prevContent = newTrimAutoWhitespaceCandidates[i].oldContent;
				let lineContent = this.getLineContent(lineNumber);

				if (lineContent.length === 0 || lineContent === prevContent || strings.firstNonWhitespaceIndex(lineContent) !== -1) {
					continue;
				}

				this._trimAutoWhitespaceLines.push(lineNumber);
			}
		}

		return reverseOperations;
	}

	/**
	 * Assumes `operations` are validated and sorted ascending
	 */
	public static _getInverseEditRanges(operations: IValidatedEditOperation[]): Range[] {
		let result: Range[] = [];

		let prevOpEndLineNumber: number;
		let prevOpEndColumn: number;
		let prevOp: IValidatedEditOperation = null;
		for (let i = 0, len = operations.length; i < len; i++) {
			let op = operations[i];

			let startLineNumber: number;
			let startColumn: number;

			if (prevOp) {
				if (prevOp.range.endLineNumber === op.range.startLineNumber) {
					startLineNumber = prevOpEndLineNumber;
					startColumn = prevOpEndColumn + (op.range.startColumn - prevOp.range.endColumn);
				} else {
					startLineNumber = prevOpEndLineNumber + (op.range.startLineNumber - prevOp.range.endLineNumber);
					startColumn = op.range.startColumn;
				}
			} else {
				startLineNumber = op.range.startLineNumber;
				startColumn = op.range.startColumn;
			}

			let resultRange: Range;

			if (op.lines && op.lines.length > 0) {
				// the operation inserts something
				let lineCount = op.lines.length;
				let firstLine = op.lines[0];
				let lastLine = op.lines[lineCount - 1];

				if (lineCount === 1) {
					// single line insert
					resultRange = new Range(startLineNumber, startColumn, startLineNumber, startColumn + firstLine.length);
				} else {
					// multi line insert
					resultRange = new Range(startLineNumber, startColumn, startLineNumber + lineCount - 1, lastLine.length + 1);
				}
			} else {
				// There is nothing to insert
				resultRange = new Range(startLineNumber, startColumn, startLineNumber, startColumn);
			}

			prevOpEndLineNumber = resultRange.endLineNumber;
			prevOpEndColumn = resultRange.endColumn;

			result.push(resultRange);
			prevOp = op;
		}

		return result;
	}

	private _doApplyEdits(operations: IValidatedEditOperation[]): void {

		// Sort operations descending
		operations.sort(EditableTextModel._sortOpsDescending);

		let rawContentChanges: ModelRawChange[] = [];
		let contentChanges: IModelContentChange[] = [];
		let lineEditsQueue: IIdentifiedLineEdit[] = [];

		const queueLineEdit = (lineEdit: IIdentifiedLineEdit) => {
			if (lineEdit.startColumn === lineEdit.endColumn && lineEdit.text.length === 0) {
				// empty edit => ignore it
				return;
			}
			lineEditsQueue.push(lineEdit);
		};

		const flushLineEdits = () => {
			if (lineEditsQueue.length === 0) {
				return;
			}

			lineEditsQueue.reverse();

			// `lineEditsQueue` now contains edits from smaller (line number,column) to larger (line number,column)
			let currentLineNumber = lineEditsQueue[0].lineNumber;
			let currentLineNumberStart = 0;

			for (let i = 1, len = lineEditsQueue.length; i < len; i++) {
				const lineNumber = lineEditsQueue[i].lineNumber;

				if (lineNumber === currentLineNumber) {
					continue;
				}

				this._invalidateLine(currentLineNumber - 1);
				this._lines[currentLineNumber - 1].applyEdits(lineEditsQueue.slice(currentLineNumberStart, i));
				this._lineStarts.changeValue(currentLineNumber - 1, this._lines[currentLineNumber - 1].text.length + this._EOL.length);
				rawContentChanges.push(
					new ModelRawLineChanged(currentLineNumber, this._lines[currentLineNumber - 1].text)
				);

				currentLineNumber = lineNumber;
				currentLineNumberStart = i;
			}

			this._invalidateLine(currentLineNumber - 1);
			this._lines[currentLineNumber - 1].applyEdits(lineEditsQueue.slice(currentLineNumberStart, lineEditsQueue.length));
			this._lineStarts.changeValue(currentLineNumber - 1, this._lines[currentLineNumber - 1].text.length + this._EOL.length);
			rawContentChanges.push(
				new ModelRawLineChanged(currentLineNumber, this._lines[currentLineNumber - 1].text)
			);

			lineEditsQueue = [];
		};

		for (let i = 0, len = operations.length; i < len; i++) {
			const op = operations[i];

			// console.log();
			// console.log('-------------------');
			// console.log('OPERATION #' + (i));
			// console.log('op: ', op);
			// console.log('<<<\n' + this._lines.map(l => l.text).join('\n') + '\n>>>');

			const startLineNumber = op.range.startLineNumber;
			const startColumn = op.range.startColumn;
			const endLineNumber = op.range.endLineNumber;
			const endColumn = op.range.endColumn;

			if (startLineNumber === endLineNumber && startColumn === endColumn && (!op.lines || op.lines.length === 0)) {
				// no-op
				continue;
			}

			const deletingLinesCnt = endLineNumber - startLineNumber;
			const insertingLinesCnt = (op.lines ? op.lines.length - 1 : 0);
			const editingLinesCnt = Math.min(deletingLinesCnt, insertingLinesCnt);

			// Iterating descending to overlap with previous op
			// in case there are common lines being edited in both
			for (let j = editingLinesCnt; j >= 0; j--) {
				const editLineNumber = startLineNumber + j;

				queueLineEdit({
					lineNumber: editLineNumber,
					startColumn: (editLineNumber === startLineNumber ? startColumn : 1),
					endColumn: (editLineNumber === endLineNumber ? endColumn : this.getLineMaxColumn(editLineNumber)),
					text: (op.lines ? op.lines[j] : '')
				});
			}

			if (editingLinesCnt < deletingLinesCnt) {
				// Must delete some lines

				// Flush any pending line edits
				flushLineEdits();

				const spliceStartLineNumber = startLineNumber + editingLinesCnt;

				const endLineRemains = this._lines[endLineNumber - 1].split(endColumn);
				this._invalidateLine(spliceStartLineNumber - 1);

				const spliceCnt = endLineNumber - spliceStartLineNumber;

				this._lines.splice(spliceStartLineNumber, spliceCnt);
				this._lineStarts.removeValues(spliceStartLineNumber, spliceCnt);

				// Reconstruct first line
				this._lines[spliceStartLineNumber - 1].append(endLineRemains);
				this._lineStarts.changeValue(spliceStartLineNumber - 1, this._lines[spliceStartLineNumber - 1].text.length + this._EOL.length);

				rawContentChanges.push(
					new ModelRawLineChanged(spliceStartLineNumber, this._lines[spliceStartLineNumber - 1].text)
				);

				rawContentChanges.push(
					new ModelRawLinesDeleted(spliceStartLineNumber + 1, spliceStartLineNumber + spliceCnt)
				);
			}

			if (editingLinesCnt < insertingLinesCnt) {
				// Must insert some lines

				// Flush any pending line edits
				flushLineEdits();

				const spliceLineNumber = startLineNumber + editingLinesCnt;
				let spliceColumn = (spliceLineNumber === startLineNumber ? startColumn : 1);
				if (op.lines) {
					spliceColumn += op.lines[editingLinesCnt].length;
				}

				// Split last line
				let leftoverLine = this._lines[spliceLineNumber - 1].split(spliceColumn);
				this._lineStarts.changeValue(spliceLineNumber - 1, this._lines[spliceLineNumber - 1].text.length + this._EOL.length);
				rawContentChanges.push(
					new ModelRawLineChanged(spliceLineNumber, this._lines[spliceLineNumber - 1].text)
				);
				this._invalidateLine(spliceLineNumber - 1);

				// Lines in the middle
				let newLines: IModelLine[] = [];
				let newLinesContent: string[] = [];
				let newLinesLengths = new Uint32Array(insertingLinesCnt - editingLinesCnt);
				for (let j = editingLinesCnt + 1; j <= insertingLinesCnt; j++) {
					newLines.push(this._createModelLine(op.lines[j]));
					newLinesContent.push(op.lines[j]);
					newLinesLengths[j - editingLinesCnt - 1] = op.lines[j].length + this._EOL.length;
				}
				this._lines = arrays.arrayInsert(this._lines, startLineNumber + editingLinesCnt, newLines);
				newLinesContent[newLinesContent.length - 1] += leftoverLine.text;
				this._lineStarts.insertValues(startLineNumber + editingLinesCnt, newLinesLengths);

				// Last line
				this._lines[startLineNumber + insertingLinesCnt - 1].append(leftoverLine);
				this._lineStarts.changeValue(startLineNumber + insertingLinesCnt - 1, this._lines[startLineNumber + insertingLinesCnt - 1].text.length + this._EOL.length);
				rawContentChanges.push(
					new ModelRawLinesInserted(spliceLineNumber + 1, startLineNumber + insertingLinesCnt, newLinesContent.join('\n'))
				);
			}

			const text = (op.lines ? op.lines.join(this.getEOL()) : '');
			contentChanges.push({
				range: new Range(startLineNumber, startColumn, endLineNumber, endColumn),
				rangeLength: op.rangeLength,
				text: text
			});

			this._adjustDecorationsForEdit(op.rangeOffset, op.rangeLength, text.length, op.forceMoveMarkers);

			// console.log('AFTER:');
			// console.log('<<<\n' + this._lines.map(l => l.text).join('\n') + '\n>>>');
		}

		flushLineEdits();

		if (rawContentChanges.length !== 0 || contentChanges.length !== 0) {
			this._increaseVersionId();

			this._emitContentChangedEvent(
				new ModelRawContentChangedEvent(
					rawContentChanges,
					this.getVersionId(),
					this._isUndoing,
					this._isRedoing
				),
				{
					changes: contentChanges,
					eol: this._EOL,
					versionId: this.getVersionId(),
					isUndoing: this._isUndoing,
					isRedoing: this._isRedoing,
					isFlush: false
				}
			);
		}
	}

	private _undo(): Selection[] {
		this._isUndoing = true;
		let r = this._commandManager.undo();
		this._isUndoing = false;

		if (!r) {
			return null;
		}

		this._overwriteAlternativeVersionId(r.recordedVersionId);

		return r.selections;
	}

	public undo(): Selection[] {
		try {
			this._eventEmitter.beginDeferredEmit();
			this._onDidChangeDecorations.beginDeferredEmit();
			return this._undo();
		} finally {
			this._onDidChangeDecorations.endDeferredEmit();
			this._eventEmitter.endDeferredEmit();
		}
	}

	private _redo(): Selection[] {
		this._isRedoing = true;
		let r = this._commandManager.redo();
		this._isRedoing = false;

		if (!r) {
			return null;
		}

		this._overwriteAlternativeVersionId(r.recordedVersionId);

		return r.selections;
	}

	public redo(): Selection[] {
		try {
			this._eventEmitter.beginDeferredEmit();
			this._onDidChangeDecorations.beginDeferredEmit();
			return this._redo();
		} finally {
			this._onDidChangeDecorations.endDeferredEmit();
			this._eventEmitter.endDeferredEmit();
		}
	}

	public setEditableRange(range: IRange): void {
		this._commandManager.clear();

		if (!this._hasEditableRange && !range) {
			// Nothing to do
			return;
		}

		this.changeDecorations((changeAccessor) => {
			if (this._hasEditableRange) {
				changeAccessor.removeDecoration(this._editableRangeId);
				this._editableRangeId = null;
				this._hasEditableRange = false;
			}

			if (range) {
				this._hasEditableRange = true;
				this._editableRangeId = changeAccessor.addDecoration(range, EditableTextModel._DECORATION_OPTION);
			}
		});
	}

	private static readonly _DECORATION_OPTION = ModelDecorationOptions.register({
		stickiness: editorCommon.TrackedRangeStickiness.AlwaysGrowsWhenTypingAtEdges
	});

	public hasEditableRange(): boolean {
		return this._hasEditableRange;
	}

	public getEditableRange(): Range {
		if (this._hasEditableRange) {
			return this.getDecorationRange(this._editableRangeId);
		} else {
			return this.getFullModelRange();
		}
	}
}