400 lines
15 KiB
Python
400 lines
15 KiB
Python
"""Direct-message (DM) chat router.
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docs/planning/social.md §4/§5 (US-4). Builds the send/list REST surface on
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top of ``app/models/chat.py`` (Conversation/ConversationParticipant/Message,
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already merged), ``app/services/text_filter.py`` (already merged), and
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``app/rate_limit.py`` (already merged).
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Endpoints:
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- POST /api/chat/dm/{user_id}/messages -- send a DM to ``user_id``
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- GET /api/chat/dm/{user_id}/messages -- paginated history with ``user_id``
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- GET /api/chat/dm/conversations -- list the caller's conversations
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Scope/boundaries (per task): REST send/list only, no WebSocket/real-time
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delivery (separate task), no world/room chat (separate sibling task; that
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uses the same ``Message`` table but with ``world_id``/``room_id`` set and
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``conversation_id`` null).
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Design decisions this task owns:
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- **Blocking.** A block in *either* direction (blocker->blockee or
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blockee->blocker) hard-prevents *sending* a new DM between the pair (403).
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It does not hide history the pair already has -- ``GET .../messages``
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still returns previously-exchanged messages after a block, consistent
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with the "preserve history" convention documented in
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``app/models/chat.py``'s module docstring. Only sending is blocked.
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- **Text filtering.** Every DM body is run through the module-level
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``TextFilter`` (the deterministic default, ``ListBasedTextFilter`` in
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``FilterMode.REDACT``) before storing:
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- ALLOW -> store the body as-is, ``filtered=False``.
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- REDACT -> store ``filtered_text`` (matched spans starred out),
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``filtered=True``.
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- REJECT -> nothing is stored; the sender gets a 422 explaining the
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message was rejected by the content filter. (The bundled default
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filter is configured in REDACT mode, so REJECT only fires for a
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deployment that swaps in a stricter-configured filter -- the handling
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is here regardless so that swap needs no router change.)
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- **Rate limiting.** Sending is capped via
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``rate_limit("chat_dm_send", max_hits=20, window_seconds=60)`` -- 20
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DM sends/minute/client-IP, generous for real chat use and painful for a
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spam bot. A no-op when ``settings.RATE_LIMIT_ENABLED`` is false (see
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``app/rate_limit.py``), matching every other rate-limited endpoint.
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- **Unread tracking.** A last-read timestamp per participant
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(``ConversationParticipant.last_read_at``, migration 0010). Fetching a
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conversation's *latest* page of history (``GET .../messages`` with no
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``before`` cursor) bumps the caller's own ``last_read_at`` to now; paging
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into older history does not. ``GET /conversations`` computes each
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conversation's ``unread_count`` as the number of messages from the peer
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(``sender_id != caller``) with ``created_at > last_read_at`` (or all of
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them, if the caller has never read the conversation).
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- **Pagination.**
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- History (``GET {user_id}/messages``): cursor-based, newest-first.
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``limit`` (default 50, max 100) plus an optional ``before`` cursor (a
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message id) that returns only messages older than that id. Response
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includes ``next_cursor`` (the oldest returned message's id, to pass as
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the next page's ``before``; null when there's no older history left).
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- Conversation list (``GET /conversations``): plain ``offset``/``limit``
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(default 20, max 100), ordered by ``Conversation.updated_at`` desc
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(bumped on every new message in that conversation, not just via the
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column's own ``onupdate`` -- see ``_touch_conversation`` below).
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- Both list endpoints are inherently scoped to the caller: the history
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endpoint only ever resolves the conversation between the caller and the
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path's ``user_id`` (no raw conversation id is ever accepted from the
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client), and the conversation list only ever queries
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``ConversationParticipant.user_id == caller``. There is no way for a
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client to address another pair's conversation.
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"""
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from __future__ import annotations
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from datetime import datetime, timezone
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from typing import Annotated
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from fastapi import APIRouter, Depends, HTTPException, Query, status
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from pydantic import BaseModel, Field
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from sqlalchemy import and_, func, or_, select
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from sqlalchemy.ext.asyncio import AsyncSession
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from app.database import get_db
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from app.dependencies import CurrentUser
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from app.models.chat import Conversation, ConversationParticipant, Message
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from app.models.social import Block
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from app.models.user import User
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from app.rate_limit import rate_limit
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from app.services.chat_pubsub import publish_dm_chat_event
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from app.services.text_filter import FilterAction, default_text_filter
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router = APIRouter()
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DbDep = Annotated[AsyncSession, Depends(get_db)]
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_text_filter = default_text_filter()
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chat_dm_send_rate_limit = rate_limit("chat_dm_send", max_hits=20, window_seconds=60)
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_BODY_MAX_LEN = 4000
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# ──────────────────────────── Pydantic schemas ────────────────────────────
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class SendDMRequest(BaseModel):
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body: str = Field(..., min_length=1, max_length=_BODY_MAX_LEN)
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class DMMessageResponse(BaseModel):
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id: int
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conversation_id: int
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sender_id: int
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recipient_id: int
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body: str
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filtered: bool
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created_at: datetime
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model_config = {"from_attributes": True}
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class DMMessageListResponse(BaseModel):
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messages: list[DMMessageResponse]
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next_cursor: int | None = None
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class DMConversationSummary(BaseModel):
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conversation_id: int
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peer_id: int
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peer_username: str
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last_message: DMMessageResponse | None
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unread_count: int
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updated_at: datetime
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class DMConversationListResponse(BaseModel):
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conversations: list[DMConversationSummary]
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total: int
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# ──────────────────────────────── Helpers ──────────────────────────────────
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async def _get_target_user(db: AsyncSession, user_id: int) -> User:
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result = await db.execute(select(User).where(User.id == user_id))
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user = result.scalar_one_or_none()
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if user is None:
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raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
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return user
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async def _is_blocked_either_direction(db: AsyncSession, user_a: int, user_b: int) -> bool:
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result = await db.execute(
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select(Block.id).where(
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or_(
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and_(Block.blocker_id == user_a, Block.blocked_id == user_b),
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and_(Block.blocker_id == user_b, Block.blocked_id == user_a),
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)
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).limit(1)
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)
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return result.scalar_one_or_none() is not None
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async def _get_or_create_conversation(
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db: AsyncSession, user_a_id: int, user_b_id: int
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) -> Conversation:
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lo, hi = sorted((user_a_id, user_b_id))
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result = await db.execute(
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select(Conversation).where(
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Conversation.user_a_id == lo, Conversation.user_b_id == hi
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)
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)
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conversation = result.scalar_one_or_none()
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if conversation is not None:
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return conversation
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conversation = Conversation(user_a_id=lo, user_b_id=hi)
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db.add(conversation)
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await db.flush() # assign conversation.id
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db.add(ConversationParticipant(conversation_id=conversation.id, user_id=lo))
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db.add(ConversationParticipant(conversation_id=conversation.id, user_id=hi))
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await db.flush()
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return conversation
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async def _get_participant(
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db: AsyncSession, conversation_id: int, user_id: int
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) -> ConversationParticipant | None:
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result = await db.execute(
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select(ConversationParticipant).where(
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ConversationParticipant.conversation_id == conversation_id,
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ConversationParticipant.user_id == user_id,
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)
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)
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return result.scalar_one_or_none()
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def _peer_id(conversation: Conversation, self_id: int) -> int:
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return conversation.user_b_id if conversation.user_a_id == self_id else conversation.user_a_id
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def _touch_conversation(conversation: Conversation) -> None:
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"""Bump ``updated_at`` explicitly.
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``Conversation.updated_at`` has ``onupdate=func.now()``, but that only
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fires when an UPDATE statement touches the ``conversations`` row itself
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-- inserting a ``Message`` row alone never does. Explicitly dirtying the
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column here is what actually keeps "most recently active conversation"
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ordering correct for ``GET /conversations``.
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"""
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conversation.updated_at = datetime.now(timezone.utc)
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def _to_message_response(message: Message, recipient_id: int) -> DMMessageResponse:
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return DMMessageResponse(
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id=message.id,
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conversation_id=message.conversation_id,
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sender_id=message.sender_id,
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recipient_id=recipient_id,
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body=message.body,
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filtered=message.filtered,
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created_at=message.created_at,
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)
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# ──────────────────────────────── Endpoints ────────────────────────────────
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@router.post(
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"/{user_id}/messages",
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response_model=DMMessageResponse,
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status_code=status.HTTP_201_CREATED,
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dependencies=[Depends(chat_dm_send_rate_limit)],
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)
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async def send_dm(
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user_id: int,
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body: SendDMRequest,
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current_user: CurrentUser,
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db: DbDep,
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):
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"""Send a DM to ``user_id``."""
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if user_id == current_user.id:
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raise HTTPException(
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status_code=status.HTTP_400_BAD_REQUEST, detail="Cannot send a DM to yourself"
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)
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await _get_target_user(db, user_id)
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if await _is_blocked_either_direction(db, current_user.id, user_id):
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raise HTTPException(
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status_code=status.HTTP_403_FORBIDDEN,
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detail="Cannot message this user",
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)
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result = _text_filter.check(body.body)
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if result.action is FilterAction.REJECT:
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raise HTTPException(
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status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
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detail="Message rejected by the content filter.",
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)
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conversation = await _get_or_create_conversation(db, current_user.id, user_id)
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message = Message(
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sender_id=current_user.id,
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conversation_id=conversation.id,
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body=result.filtered_text,
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filtered=(result.action is FilterAction.REDACT),
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)
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db.add(message)
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_touch_conversation(conversation)
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await db.commit()
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await db.refresh(message)
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resp = _to_message_response(message, recipient_id=user_id)
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await publish_dm_chat_event(conversation.id, resp.model_dump(mode="json"))
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return resp
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@router.get("/{user_id}/messages", response_model=DMMessageListResponse)
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async def get_dm_history(
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user_id: int,
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current_user: CurrentUser,
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db: DbDep,
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limit: int = Query(50, ge=1, le=100),
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before: int | None = Query(
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None, description="Return messages older than this message id (pagination cursor)."
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),
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):
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"""Paginated DM history between the caller and ``user_id``, newest first.
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Marks the conversation as read (bumps the caller's ``last_read_at``) only
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when fetching the first page (``before`` omitted) -- paging into older
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history doesn't affect unread state.
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"""
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await _get_target_user(db, user_id)
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lo, hi = sorted((current_user.id, user_id))
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conv_result = await db.execute(
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select(Conversation).where(Conversation.user_a_id == lo, Conversation.user_b_id == hi)
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)
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conversation = conv_result.scalar_one_or_none()
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if conversation is None:
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# No conversation yet -- nothing exchanged, not an error.
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return DMMessageListResponse(messages=[], next_cursor=None)
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stmt = select(Message).where(Message.conversation_id == conversation.id)
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if before is not None:
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stmt = stmt.where(Message.id < before)
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stmt = stmt.order_by(Message.id.desc()).limit(limit + 1)
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rows = (await db.execute(stmt)).scalars().all()
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has_more = len(rows) > limit
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page = rows[:limit]
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next_cursor = page[-1].id if has_more and page else None
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if before is None:
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participant = await _get_participant(db, conversation.id, current_user.id)
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if participant is not None:
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participant.last_read_at = datetime.now(timezone.utc)
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await db.commit()
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return DMMessageListResponse(
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messages=[_to_message_response(m, recipient_id=user_id) for m in page],
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next_cursor=next_cursor,
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)
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@router.get("/conversations", response_model=DMConversationListResponse)
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async def list_conversations(
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current_user: CurrentUser,
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db: DbDep,
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limit: int = Query(20, ge=1, le=100),
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offset: int = Query(0, ge=0),
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):
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"""List the caller's DM conversations, most recently active first."""
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total_result = await db.execute(
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select(func.count())
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.select_from(ConversationParticipant)
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.where(ConversationParticipant.user_id == current_user.id)
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)
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total = total_result.scalar_one()
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stmt = (
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select(Conversation, ConversationParticipant)
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.join(
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ConversationParticipant,
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ConversationParticipant.conversation_id == Conversation.id,
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)
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.where(ConversationParticipant.user_id == current_user.id)
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.order_by(Conversation.updated_at.desc())
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.offset(offset)
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.limit(limit)
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)
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rows = (await db.execute(stmt)).all()
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summaries: list[DMConversationSummary] = []
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for conversation, participant in rows:
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peer_id = _peer_id(conversation, current_user.id)
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peer = (
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await db.execute(select(User).where(User.id == peer_id))
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).scalar_one_or_none()
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peer_username = peer.username if peer is not None else "(deleted user)"
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last_message_row = (
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await db.execute(
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select(Message)
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.where(Message.conversation_id == conversation.id)
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.order_by(Message.id.desc())
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.limit(1)
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)
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).scalar_one_or_none()
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last_message = (
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_to_message_response(
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last_message_row,
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recipient_id=(
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peer_id if last_message_row.sender_id == current_user.id else current_user.id
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),
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)
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if last_message_row is not None
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else None
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)
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unread_filters = [
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Message.conversation_id == conversation.id,
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Message.sender_id != current_user.id,
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]
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if participant.last_read_at is not None:
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unread_filters.append(Message.created_at > participant.last_read_at)
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unread_count = (
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await db.execute(select(func.count()).select_from(Message).where(*unread_filters))
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).scalar_one()
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summaries.append(
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DMConversationSummary(
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conversation_id=conversation.id,
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peer_id=peer_id,
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peer_username=peer_username,
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last_message=last_message,
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unread_count=unread_count,
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updated_at=conversation.updated_at,
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)
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)
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return DMConversationListResponse(conversations=summaries, total=total)
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