diff --git a/docs/DeveloperGuide.md b/docs/DeveloperGuide.md index 1e250ff1765..fe8ddeaeda8 100644 --- a/docs/DeveloperGuide.md +++ b/docs/DeveloperGuide.md @@ -161,104 +161,6 @@ Classes used by multiple components are in the `seedu.address.commons` package. This section describes some noteworthy details on how certain features are implemented. -### \[Proposed\] Undo/redo feature - -#### Proposed Implementation - -The proposed undo/redo mechanism is facilitated by `VersionedAddressBook`. It extends `AddressBook` with an undo/redo history, stored internally as an `addressBookStateList` and `currentStatePointer`. Additionally, it implements the following operations: - -- `VersionedAddressBook#commit()` — Saves the current address book state in its history. -- `VersionedAddressBook#undo()` — Restores the previous address book state from its history. -- `VersionedAddressBook#redo()` — Restores a previously undone address book state from its history. - -These operations are exposed in the `Model` interface as `Model#commitAddressBook()`, `Model#undoAddressBook()` and `Model#redoAddressBook()` respectively. - -Given below is an example usage scenario and how the undo/redo mechanism behaves at each step. - -Step 1. The user launches the application for the first time. The `VersionedAddressBook` will be initialized with the initial address book state, and the `currentStatePointer` pointing to that single address book state. - - - -Step 2. The user executes `delete 5` command to delete the 5th person in the address book. The `delete` command calls `Model#commitAddressBook()`, causing the modified state of the address book after the `delete 5` command executes to be saved in the `addressBookStateList`, and the `currentStatePointer` is shifted to the newly inserted address book state. - - - -Step 3. The user executes `add n/David …​` to add a new person. The `add` command also calls `Model#commitAddressBook()`, causing another modified address book state to be saved into the `addressBookStateList`. - - - - - -**Note:** If a command fails its execution, it will not call `Model#commitAddressBook()`, so the address book state will not be saved into the `addressBookStateList`. - - - -Step 4. The user now decides that adding the person was a mistake, and decides to undo that action by executing the `undo` command. The `undo` command will call `Model#undoAddressBook()`, which will shift the `currentStatePointer` once to the left, pointing it to the previous address book state, and restores the address book to that state. - - - - - - -**Note:** If the `currentStatePointer` is at index 0, pointing to the initial AddressBook state, then there are no previous AddressBook states to restore. The `undo` command uses `Model#canUndoAddressBook()` to check if this is the case. If so, it will return an error to the user rather -than attempting to perform the undo. - - - -The following sequence diagram shows how an undo operation goes through the `Logic` component: - - - - - -**Note:** The lifeline for `UndoCommand` should end at the destroy marker (X) but due to a limitation of PlantUML, the lifeline reaches the end of diagram. - - - -Similarly, how an undo operation goes through the `Model` component is shown below: - - - -The `redo` command does the opposite — it calls `Model#redoAddressBook()`, which shifts the `currentStatePointer` once to the right, pointing to the previously undone state, and restores the address book to that state. - - - -**Note:** If the `currentStatePointer` is at index `addressBookStateList.size() - 1`, pointing to the latest address book state, then there are no undone AddressBook states to restore. The `redo` command uses `Model#canRedoAddressBook()` to check if this is the case. If so, it will return an error to the user rather than attempting to perform the redo. - - - -Step 5. The user then decides to execute the command `list`. Commands that do not modify the address book, such as `list`, will usually not call `Model#commitAddressBook()`, `Model#undoAddressBook()` or `Model#redoAddressBook()`. Thus, the `addressBookStateList` remains unchanged. - - - -Step 6. The user executes `clear`, which calls `Model#commitAddressBook()`. Since the `currentStatePointer` is not pointing at the end of the `addressBookStateList`, all address book states after the `currentStatePointer` will be purged. Reason: It no longer makes sense to redo the `add n/David …​` command. This is the behavior that most modern desktop applications follow. - - - -The following activity diagram summarizes what happens when a user executes a new command: - - - -#### Design considerations: - -**Aspect: How undo & redo executes:** - -- **Alternative 1 (current choice):** Saves the entire address book. - - - Pros: Easy to implement. - - Cons: May have performance issues in terms of memory usage. - -- **Alternative 2:** Individual command knows how to undo/redo by - itself. - - Pros: Will use less memory (e.g. for `delete`, just save the person being deleted). - - Cons: We must ensure that the implementation of each individual command are correct. - -_{more aspects and alternatives to be added}_ - -### \[Proposed\] Data archiving - -_{Explain here how the data archiving feature will be implemented}_ - --- ## **Documentation, logging, testing, configuration, dev-ops**