Ponder

Messaging Feature

Thread, message, encryption, polling, and chat_write behavior.

Purpose

Messaging provides 1:1 threads between accepted friends. It supports text messages and article-share messages with inline article previews.

Tables

Primary tables:

• threads
• thread_messages

Supporting tables:

• friendships for accepted-friend authorization.
• shares for article-share inbox rows.
• content for inline article previews.
• users for thread participant display names and avatars.

Thread Model

ThreadModel reads:

• row ID as id
• pairKey
• participantIds
• createdAt
• lastMessageAt

If pairKey is absent, the model derives it by sorting and joining participantIds with :.

Thread creation writes:

• pairKey: sorted participant IDs joined by :
• contentId: dm:{pairKey} for compatibility
• participantIds
• createdAt

Message Model

ThreadMessageModel reads:

• threadId
• authorId
• type: text or article
• body
• optional contentId
• sentAt

If typed article columns are absent, it can parse legacy article messages from body values beginning with __ponder_article__: followed by content ID and optional caption.

Encryption

FriendsService uses ThreadMessageCipher before writes and after reads:

• Text message bodies are encrypted before postMessage.
• Optional share messages are encrypted before shareArticle.
• Retrieved message and share bodies are decrypted before models reach the UI.

ThreadMessageCipher uses AES-GCM with 256-bit keys and HKDF/HMAC-SHA256. Encrypted values are prefixed with __ponder_encrypted_v1__: and store base64-url encoded nonce, ciphertext, and MAC bytes. The derived key context is based on sorted participant IDs, with a legacy thread-ID context fallback during decryption.

Function Write Path

chat_write is the preferred write path for:

• getOrCreateThread
• postMessage
• shareArticle

The function validates:

• POST method.
• Signed-in Appwrite execution user.
• Required fields for each action.
• Distinct participants.
• Accepted friendship.
• Thread participation for message posting.
• Message length limits.

It writes row permissions for participants and authors where row security applies.

Read Path

ThreadScreen watches threadMessagesProvider(threadId).

threadMessagesProvider:

1. Fetches messages immediately.
2. Emits the message list.
3. Waits for threadMessagesPollingIntervalProvider, currently two seconds.
4. Repeats until disposed.

Message reads use FriendsService.getThreadMessages, which queries thread_messages by threadId, orders by sentAt ascending, fetches the thread, decrypts rows, and maps them to ThreadMessageModel.

UI

ThreadScreen:

• Shows the other user’s avatar and title in the app bar.
• Displays current-user messages aligned right and other-user messages aligned left.
• Shows inline article cards for article messages with contentId.
• Lets the user send multi-line text messages.
• Scrolls to the end after new messages arrive or a send succeeds.

Compatibility

The code intentionally supports current and legacy schemas. Current rows use pairKey, type, and contentId; legacy fallbacks use contentId thread lookup and encoded article-message bodies.