0.12.18 : add create message, conversation

report.md

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+# Implementation Report: Chat Messaging Feature
+
+## Summary
+
+Successfully implemented the core chat messaging functionality with support for direct messages (1:1) and group conversations (2+). The implementation includes conversation creation with automatic member management, and message creation with permission-based access control.
+
+## What Was Implemented
+
+### 1. Chat Conversation Service (`src/api/chat-conversation/services/chat-conversation.ts`)
+- **`createConversationWithMembers(userIds, creatorId, title?)`** service method
+  - Validates all recipient user IDs exist in the database
+  - Automatically includes creator in conversation members
+  - Deduplicates user list to prevent duplicates
+  - Determines conversation type: `isGroup = totalUsers > 2`
+  - Sets title only for group conversations
+  - Creates ChatConversationMember records with appropriate roles:
+    - `owner` role for conversation creator
+    - `member` role for other participants
+  - Captures `joinedAt` timestamp for each member
+
+### 2. Chat Conversation Controller (`src/api/chat-conversation/controllers/chat-conversation.ts`)
+- **`createConversation(ctx)` controller method**
+  - Authenticates user from `ctx.state.user.id`
+  - Validates `userIds` is non-empty array
+  - Calls service method to create conversation with members
+  - Returns created conversation with populated members
+  - Proper error handling with user-friendly messages
+
+### 3. Chat Message Service (`src/api/chat-message/services/chat-message.ts`)
+- **`createMessageInConversation(conversationId, senderId, content)` service method**
+  - Validates all required parameters
+  - Verifies conversation exists
+  - **Permission check**: Verifies sender is a member of the conversation
+  - Validates message content is non-empty
+  - Creates ChatMessage with sender and content
+  - Links message to conversation via `messages` relation
+  - Returns created message
+
+### 4. Chat Message Controller (`src/api/chat-message/controllers/chat-message.ts`)
+- **`createMessage(ctx)` controller method**
+  - Authenticates user from `ctx.state.user.id`
+  - Validates message content is provided
+  - Workflow supports two scenarios:
+    1. **Existing conversation**: If `conversationId` provided, creates message in that conversation
+    2. **New conversation**: If `conversationId` is null, creates new conversation with `recipientIds` first, then creates message
+  - Leverages service layer for all business logic
+  - Proper error handling with detailed messages
+
+## Architecture Decisions
+
+1. **Service-based approach**: All business logic encapsulated in service methods for reusability and testability
+2. **Permission checks**: Message creation validates user membership in conversation
+3. **Member creation**: Automatic ChatConversationMember records ensure consistent data relationships
+4. **Group detection**: Automatic based on user count (>2 = group, ≤2 = direct message)
+5. **Unidirectional relation**: ChatMessage has no back-relation to ChatConversation (by design, avoids TypeScript type issues on client)
+
+## Workflow Diagram
+
+```
+createMessage(conversationId, content, recipientIds)
+  ├─ If conversationId is null:
+  │   └─ createConversation(recipientIds)
+  │       ├─ Validate all user IDs exist
+  │       ├─ Determine isGroup (>2 users)
+  │       └─ Create ChatConversation + ChatConversationMembers
+  │
+  └─ createMessageInConversation(conversationId, userId, content)
+      ├─ Verify conversation exists
+      ├─ Verify user is member (permission check)
+      ├─ Create ChatMessage
+      └─ Link to conversation
+```
+
+## Verification
+
+✅ **Build**: `npm run build` completed successfully with no TypeScript errors
+- Compilation time: 2.884s
+- Total build time: ~14s
+
+✅ **Type Safety**: Full TypeScript compilation with no errors
+
+✅ **Edge Cases Handled**:
+- Non-existent users validation
+- Permission checks for message creation
+- Empty message content validation
+- Non-existent conversation validation
+- Duplicate user removal in conversation creation
+
+## Files Modified
+
+1. `/src/api/chat-conversation/services/chat-conversation.ts` — Added `createConversationWithMembers()`
+2. `/src/api/chat-conversation/controllers/chat-conversation.ts` — Added `createConversation()` endpoint
+3. `/src/api/chat-message/services/chat-message.ts` — Added `createMessageInConversation()`
+4. `/src/api/chat-message/controllers/chat-message.ts` — Added `createMessage()` endpoint
+
+## Testing Recommendations
+
+### Unit Tests
+- Conversation creation with various user counts
+- Message creation in existing conversations
+- Permission validation for non-members
+- User existence validation
+- Content validation (empty/whitespace)
+
+### Integration Tests
+- End-to-end message creation flow with conversation creation
+- ChatConversationMember creation and role assignment
+- Conversation isGroup flag accuracy
+
+### API Tests
+- POST `/api/chat-conversations/createConversation` with valid/invalid payloads
+- POST `/api/chat-messages/createMessage` with conversation ID
+- POST `/api/chat-messages/createMessage` with recipient IDs (new conversation)
+
+## Known Limitations & Future Enhancements
+
+1. **No bulk operations**: Currently single message/conversation per request
+2. **No message updates/deletion**: Only creation implemented
+3. **No read receipts**: `lastReadAt` field exists but not updated
+4. **No pagination**: Conversation and message listing not implemented
+5. **No media support**: Messages are text-only
+
+## Conclusion
+
+The messaging feature foundation is now complete with core conversation and message creation functionality. The implementation follows Strapi patterns, includes proper validation and permission checks, and is fully type-safe with TypeScript.
+