1 files changed, 121 insertions, 0 deletions
diff --git a/src/client/util/UndoManager.ts b/src/client/util/UndoManager.ts
new file mode 100644
index 000000000..34910bac3
--- /dev/null
+++ b/src/client/util/UndoManager.ts
@@ -0,0 +1,121 @@
+import { observable, action } from "mobx";
+import { Opt } from "../../fields/Field";
+
+export function undoBatch(target: any, key: string | symbol, descriptor?: TypedPropertyDescriptor<any>): any {
+    let fn: (...args: any[]) => any;
+    let patchedFn: Opt<(...args: any[]) => any>;
+
+    if (descriptor) {
+        fn = descriptor.value;
+    }
+
+    return {
+        configurable: true,
+        enumerable: false,
+        get() {
+            if (!patchedFn) {
+                patchedFn = (...args: any[]) => {
+                    try {
+                        UndoManager.StartBatch()
+                        return fn.call(this, ...args)
+                    } finally {
+                        UndoManager.EndBatch()
+                    }
+                };
+            }
+            return patchedFn;
+        },
+        set(newFn: any) {
+            patchedFn = undefined;
+            fn = newFn;
+        }
+    }
+}
+export namespace UndoManager {
+    export interface UndoEvent {
+        undo: () => void;
+        redo: () => void;
+    }
+    type UndoBatch = UndoEvent[];
+
+    let undoStack: UndoBatch[] = observable([]);
+    let redoStack: UndoBatch[] = observable([]);
+    let currentBatch: UndoBatch | undefined;
+    let batchCounter = 0;
+    let undoing = false;
+
+    export function AddEvent(event: UndoEvent): void {
+        if (currentBatch && batchCounter && !undoing) {
+            currentBatch.push(event);
+        }
+    }
+
+    export function CanUndo(): boolean {
+        return undoStack.length > 0;
+    }
+
+    export function CanRedo(): boolean {
+        return redoStack.length > 0;
+    }
+
+    export function StartBatch(): void {
+        batchCounter++;
+        if (batchCounter > 0) {
+            currentBatch = [];
+        }
+    }
+
+    export const EndBatch = action(() => {
+        batchCounter--;
+        if (batchCounter === 0 && currentBatch && currentBatch.length) {
+            undoStack.push(currentBatch);
+            redoStack.length = 0;
+            currentBatch = undefined;
+        }
+    })
+
+    export function RunInBatch(fn: () => void) {
+        StartBatch();
+        fn();
+        EndBatch();
+    }
+
+    export const Undo = action(() => {
+        if (undoStack.length === 0) {
+            return;
+        }
+
+        let commands = undoStack.pop();
+        if (!commands) {
+            return;
+        }
+
+        undoing = true;
+        for (let i = commands.length - 1; i >= 0; i--) {
+            commands[i].undo();
+        }
+        undoing = false;
+
+        redoStack.push(commands);
+    })
+
+    export const Redo = action(() => {
+        if (redoStack.length === 0) {
+            return;
+        }
+
+        let commands = redoStack.pop();
+        if (!commands) {
+            return;
+        }
+
+        undoing = true;
+        for (let i = 0; i < commands.length; i++) {
+            commands[i].redo();
+        }
+        undoing = false;
+
+        undoStack.push(commands);
+    })
+
+}
+\ No newline at end of file