--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/development/plugins/undo.js	Thu Aug 04 15:21:29 2022 -0600
@@ -0,0 +1,362 @@
+(function (sceditor) {
+	'use strict';
+
+	sceditor.plugins.undo = function () {
+		var base = this;
+		var sourceEditor;
+		var editor;
+		var body;
+		var lastInputType = '';
+		var charChangedCount = 0;
+		var isInPatchedFn = false;
+		/**
+		 * If currently restoring a state
+		 * Should ignore events while it's happening
+		 */
+		var isApplying = false;
+		/**
+		 * If current selection change event has already been stored
+		 */
+		var isSelectionChangeHandled = false;
+
+		var undoLimit  = 50;
+		var undoStates = [];
+		var redoPosition = 0;
+		var lastState;
+
+		/**
+		 * Sets the editor to the specified state.
+		 * @param  {Object} state
+		 * @private
+		 */
+		function applyState(state) {
+			isApplying = true;
+			editor.sourceMode(state.sourceMode);
+
+			if (state.sourceMode) {
+				editor.val(state.value, false);
+				editor.sourceEditorCaret(state.caret);
+			} else {
+				editor.getBody().innerHTML = state.value;
+
+				var range = editor.getRangeHelper().selectedRange();
+				setRangePositions(range, state.caret);
+				editor.getRangeHelper().selectRange(range);
+			}
+
+			editor.focus();
+			isApplying = false;
+		};
+
+		/**
+		 * Patches a function on the object to call store() after invocation
+		 * @param {Object} obj
+		 * @param {string} fn
+		 */
+		function patch(obj, fn) {
+			var origFn = obj[fn];
+			obj[fn] = function () {
+				// sourceMode calls other patched methods so need to ignore them
+				var ignore = isInPatchedFn;
+
+				// Store caret position before any change is made
+				if (!ignore && !isApplying && lastState &&
+						editor.getRangeHelper().hasSelection()) {
+					updateLastState();
+				}
+
+				isInPatchedFn = true;
+				origFn.apply(this, arguments);
+
+				if (!ignore) {
+					isInPatchedFn = false;
+
+					if (!isApplying) {
+						storeState();
+						lastInputType = '';
+					}
+				}
+			};
+		}
+
+		/**
+		 * Stores the editors current state
+		 */
+		function storeState() {
+			if (redoPosition) {
+				undoStates.length -= redoPosition;
+				redoPosition = 0;
+			}
+
+			if (undoLimit > 0 && undoStates.length > undoLimit) {
+				undoStates.shift();
+			}
+
+			lastState = {};
+			updateLastState();
+			undoStates.push(lastState);
+		}
+
+		/**
+		 * Updates the last saved state with the editors current state
+		 */
+		function updateLastState() {
+			var sourceMode = editor.sourceMode();
+			lastState.caret = sourceMode ? editor.sourceEditorCaret() :
+				getRangePositions(editor.getRangeHelper().selectedRange());
+			lastState.sourceMode = sourceMode;
+			lastState.value = sourceMode ?
+				editor.getSourceEditorValue(false) :
+				editor.getBody().innerHTML;
+		}
+
+		base.init = function () {
+			// The this variable will be set to the instance of the editor
+			// calling it, hence why the plugins "this" is saved to the base
+			// variable.
+			editor = this;
+
+			undoLimit = editor.undoLimit || undoLimit;
+
+			editor.addShortcut('ctrl+z', base.undo);
+			editor.addShortcut('ctrl+shift+z', base.redo);
+			editor.addShortcut('ctrl+y', base.redo);
+		};
+
+		function documentSelectionChangeHandler() {
+			if (sourceEditor === document.activeElement) {
+				base.signalSelectionchangedEvent();
+			}
+		}
+
+		base.signalReady = function () {
+			sourceEditor = editor.getContentAreaContainer().nextSibling;
+			body = editor.getBody();
+
+			// Store initial state
+			storeState();
+
+			// Patch methods that allow inserting content into the editor
+			// programmatically
+			// TODO: remove this when there is a built in event to handle it
+			patch(editor, 'setWysiwygEditorValue');
+			patch(editor, 'setSourceEditorValue');
+			patch(editor, 'sourceEditorInsertText');
+			patch(editor.getRangeHelper(), 'insertNode');
+			patch(editor, 'toggleSourceMode');
+
+			/**
+			 * Handles the before input event so can override built in
+			 * undo / redo
+			 * @param {InputEvent} e
+			 */
+			function beforeInputHandler(e) {
+				if (e.inputType === 'historyUndo') {
+					base.undo();
+					e.preventDefault();
+				} else if (e.inputType === 'historyRedo') {
+					base.redo();
+					e.preventDefault();
+				}
+			}
+
+			body.addEventListener('beforeinput', beforeInputHandler);
+			sourceEditor.addEventListener('beforeinput', beforeInputHandler);
+
+			/**
+			 * Should always store state at the end of composing
+			 */
+			function compositionHandler() {
+				lastInputType = '';
+				storeState();
+			}
+			body.addEventListener('compositionend', compositionHandler);
+			sourceEditor.addEventListener('compositionend', compositionHandler);
+
+			// Chrome doesn't trigger selectionchange on textarea so need to
+			// listen to global event
+			document.addEventListener('selectionchange',
+				documentSelectionChangeHandler);
+		};
+
+		base.destroy = function () {
+			document.removeEventListener('selectionchange',
+				documentSelectionChangeHandler);
+		};
+
+		base.undo = function () {
+			lastState = null;
+
+			if (redoPosition < undoStates.length - 1) {
+				redoPosition++;
+				applyState(undoStates[undoStates.length - 1 - redoPosition]);
+			}
+
+			return false;
+		};
+
+		base.redo = function () {
+			if (redoPosition > 0) {
+				redoPosition--;
+				applyState(undoStates[undoStates.length - 1 - redoPosition]);
+			}
+
+			return false;
+		};
+
+		/**
+		 * Handle the selectionchanged event so can store the last caret
+		 * position before the input so undoing places it in the right place
+		 */
+		base.signalSelectionchangedEvent = function () {
+			if (isApplying || isSelectionChangeHandled) {
+				isSelectionChangeHandled = false;
+				return;
+			}
+			if (lastState) {
+				updateLastState();
+			}
+			lastInputType = '';
+		};
+
+		/**
+		 * Handles the input event
+		 * @param {InputEvent} e
+		 */
+		base.signalInputEvent = function (e) {
+			// InputType is one of
+			// https://rawgit.com/w3c/input-events/v1/index.html#interface-InputEvent-Attributes
+			// Most should cause a full undo item to be added so only need to
+			// handle a few of them
+			var inputType = e.inputType;
+
+			// Should ignore selection changes that occur because of input
+			// events as already handling them
+			isSelectionChangeHandled = true;
+
+			// inputType should be supported by all supported browsers
+			// except IE 11 in runWithoutWysiwygSupport. Shouldn't be an issue
+			// as native handling will mostly work there.
+			// Ignore if composing as will handle composition end instead
+			if (!inputType || e.isComposing) {
+				return;
+			}
+
+			switch (e.inputType) {
+				case 'deleteContentBackward':
+					if (lastState && lastInputType === inputType &&
+						charChangedCount < 20) {
+						updateLastState();
+					} else {
+						storeState();
+						charChangedCount = 0;
+					}
+
+					lastInputType = inputType;
+					break;
+
+				case 'insertText':
+					charChangedCount += e.data ? e.data.length : 1;
+
+					if (lastState && lastInputType === inputType &&
+							charChangedCount < 20 && !/\s$/.test(e.data)) {
+						updateLastState();
+					} else {
+						storeState();
+						charChangedCount = 0;
+					}
+
+					lastInputType = inputType;
+					break;
+				default:
+					lastInputType = 'sce-misc';
+					charChangedCount = 0;
+					storeState();
+					break;
+			}
+		};
+
+		/**
+		 * Creates a positions object form passed range
+		 * @param {Range} range
+		 * @return {Object<string, Array<number>}
+		 */
+		function getRangePositions(range) {
+			// Merge any adjacent text nodes as it will be done by innerHTML
+			// which would cause positions to be off if not done
+			body.normalize();
+
+			return {
+				startPositions:
+					nodeToPositions(range.startContainer, range.startOffset),
+				endPositions:
+					nodeToPositions(range.endContainer, range.endOffset)
+			};
+		}
+
+		/**
+		 * Sets the range start/end based on the positions object
+		 * @param {Range} range
+		 * @param {Object<string, Array<number>>} positions
+		 */
+		function setRangePositions(range, positions) {
+			try {
+				var startPositions = positions.startPositions;
+				var endPositions = positions.endPositions;
+
+				range.setStart(positionsToNode(body, startPositions),
+					startPositions[0]);
+				range.setEnd(positionsToNode(body, endPositions),
+					endPositions[0]);
+			} catch (e) {
+				if (console && console.warn) {
+					console.warn('[SCEditor] Undo plugin lost caret', e);
+				}
+			}
+		}
+
+		/**
+		 * Converts the passed container and offset into positions array
+		 * @param {Node} container
+		 * @param {number} offset
+		 * @returns {Array<number>}
+		 */
+		function nodeToPositions(container, offset) {
+			var positions = [offset];
+			var node = container;
+
+			while (node && node.tagName !== 'BODY') {
+				positions.push(nodeIndex(node));
+				node = node.parentNode;
+			}
+
+			return positions;
+		}
+
+		/**
+		 * Returns index of passed node
+		 * @param {Node} node
+		 * @returns {number}
+		 */
+		function nodeIndex(node) {
+			var i = 0;
+			while ((node = node.previousSibling)) {
+				i++;
+			}
+			return i;
+		}
+
+		/**
+		 * Gets the container node from the positions array
+		 * @param {Node} node
+		 * @param {Array<number>} positions
+		 * @returns {Node}
+		 */
+		function positionsToNode(node, positions) {
+			for (var i = positions.length - 1; node && i > 0; i--) {
+				node = node.childNodes[positions[i]];
+			}
+			return node;
+		}
+	};
+}(sceditor));