Merge pull request #131 from shotstack/derk/eng-721-canundo-canredo-getters

feat: expose canUndo/canRedo on the Edit class

Author: dazzatronus

src/core/edit-session.ts

@@ -1045,6 +1045,16 @@ export class Edit {
 			}
 		});
 	}
+	/** True when there is a command to undo (the history pointer is not before the first command). */
+	public get canUndo(): boolean {
+		return this.commandIndex >= 0;
+	}
+
+	/** True when there is a command ahead to redo (the history pointer is not at the latest command). */
+	public get canRedo(): boolean {
+		return this.commandIndex < this.commandHistory.length - 1;
+	}
+
 	/** @internal */
 	public setUpdatedClip(clip: Player, initialClipConfig: ResolvedClip | null = null, finalClipConfig: ResolvedClip | null = null): void {
 		// Find track and clip indices

tests/edit-commands.test.ts

@@ -654,6 +654,61 @@ describe("Edit Command History", () => {
 		});
 	});
 
+	describe("canUndo / canRedo getters", () => {
+		it("are both false on a freshly loaded edit (load is not a command)", () => {
+			expect(getCommandState(edit).index).toBe(-1);
+			expect(edit.canUndo).toBe(false);
+			expect(edit.canRedo).toBe(false);
+		});
+
+		it("canUndo turns true after a command; canRedo stays false", async () => {
+			await edit.executeEditCommand(new TestCommand());
+			expect(edit.canUndo).toBe(true);
+			expect(edit.canRedo).toBe(false);
+		});
+
+		it("undo turns canRedo on and, back at the start, canUndo off", async () => {
+			await edit.executeEditCommand(new TestCommand());
+			await edit.undo();
+			expect(edit.canUndo).toBe(false);
+			expect(edit.canRedo).toBe(true);
+		});
+
+		it("redo turns canUndo back on and, at the end, canRedo off", async () => {
+			await edit.executeEditCommand(new TestCommand());
+			await edit.undo();
+			await edit.redo();
+			expect(edit.canUndo).toBe(true);
+			expect(edit.canRedo).toBe(false);
+		});
+
+		it("both are true mid-stack", async () => {
+			await edit.executeEditCommand(new TestCommand());
+			await edit.executeEditCommand(new TestCommand());
+			await edit.undo();
+			expect(edit.canUndo).toBe(true);
+			expect(edit.canRedo).toBe(true);
+		});
+
+		it("a new command after undo truncates redo (canRedo false)", async () => {
+			await edit.executeEditCommand(new TestCommand());
+			await edit.executeEditCommand(new TestCommand());
+			await edit.undo();
+			await edit.executeEditCommand(new TestCommand());
+			expect(edit.canUndo).toBe(true);
+			expect(edit.canRedo).toBe(false);
+		});
+
+		it("track the underlying commandIndex bounds", async () => {
+			await edit.executeEditCommand(new TestCommand());
+			await edit.executeEditCommand(new TestCommand());
+			await edit.undo();
+			const { history, index } = getCommandState(edit);
+			expect(edit.canUndo).toBe(index >= 0);
+			expect(edit.canRedo).toBe(index < history.length - 1);
+		});
+	});
+
 	describe("state restoration", () => {
 		it("undo restores previous state via command.undo()", async () => {
 			// Use a command that tracks state changes