Feat offline support body

[gewenyu99]

What does this PR do?

Adds body to offline support PR.

Details to be filled are marked TODO.

Test Plan

(Write your test plan here. If you changed any code, please provide us with clear instructions on how you verified your changes work.)

Related PRs and Issues

(If this PR is related to any other PR or resolves any issue or related to any issue link all related PR and issues here.)

Have you read the Contributing Guidelines on issues?

(Write your answer here.)

[stnguyen90]

Sounds good so far. Just some tweaks.

[gewenyu99]

Proposing additions to getting started guides later.

[stnguyen90]

I added the content you requested. Let me know if there's anything else you need.

[stnguyen90]

For Flutter, it'll be:

client.setOfflinePersistency(status: true);

[stnguyen90]

This will be:

client.setOfflineCacheSize(40000); // 40MB

[stnguyen90]

Using await like:

    final document = await databases.createDocument(
      databaseId: '[DATABASE_ID]',
      collectionId: '[COLLECTION_ID]',
      documentId: ID.unique(),
      data: {},
    );

will block execution.

[stnguyen90]

Updated with more info about state:

  void blockingSubmitTodo() async {
    if (inputController.text.isEmpty || isLoading) return;
    final messenger = ScaffoldMessenger.of(context);
    final newTodo = Todo(
      content: inputController.text,
      id: ID.unique(),
    );

    try {
      await _databases.createDocument(
        databaseId: '[DATABASE_ID]',
        collectionId: '[COLLECTION_ID]',
        documentId: newTodo.id,
        data: {
          "content": newTodo.content,
          "isComplete": newTodo.isComplete,
        },
      );
      inputController.text = '';
      todos.add(newTodo);
    } catch (e) {
      messenger.showSnackBar(createErrorSnackBar(e.toString()));
    }

    setState(() {
      isLoading = false;
    });
  }

[stnguyen90]

To avoid blocking, don't await

    final document = databases.createDocument(
      databaseId: '[DATABASE_ID]',
      collectionId: '[COLLECTION_ID]',
      documentId: ID.unique(),
      data: {},
    );

[gewenyu99]

@stnguyen90 I was really hoping to show an illustrative example where we also show updating local state/ui optimistically to make the point clear.

Is this something we can do?

[stnguyen90]

Updated with more info about state:

  void nonBlockingSubmitTodo() async {
    if (inputController.text.isEmpty || isLoading) return;
    final messenger = ScaffoldMessenger.of(context);
    final newTodo = Todo(
      content: inputController.text,
      id: ID.unique(),
    );

    _databases.createDocument(
      databaseId: '[DATABASE_ID]',
      collectionId: '[COLLECTION_ID]',
      documentId: newTodo.id,
      data: {
        "content": newTodo.content,
        "isComplete": newTodo.isComplete,
      },
    ).catchError((e) {
      messenger.showSnackBar(createErrorSnackBar(e.toString()));
      todos.remove(newTodo);
    });

    setState(() {
      inputController.text = '';
      todos.add(newTodo);
      isLoading = false;
    });
  }

[stnguyen90]

When a locally queued request is sent to the server, it will include the timestamp when the request was queued in the X-Appwrite-Timestamp header. Appwrite will compare that request timestamp with the document's $updatedAt timestamp and return a status 409 error if the document's $updatedAt timestamp is newer than the request timestamp. The SDK will revert the changes in the local cache, and then the client can try the request again.

[gewenyu99]

@stnguyen90 I was also thinking if there could be a short, self contained code example we can show at the end? might be cool.

[stnguyen90]

@stnguyen90 I was also thinking if there could be a short, self contained code example we can show at the end? might be cool.

You wouldn't really put everything in 1 self-contained file so I'm not sure if it's good to show that. Maybe we can link to a repo or something once we have the sample app built?

[gewenyu99]

@stnguyen90 I was also thinking if there could be a short, self contained code example we can show at the end? might be cool.

You wouldn't really put everything in 1 self-contained file so I'm not sure if it's good to show that. Maybe we can link to a repo or something once we have the sample app built?

Can we add it to the playground app?

:OOOO

[stnguyen90]

Can we add it to the playground app?

@gewenyu99, we plan on updating the todo app to showcase relationships and offline support.