Implement message reporting endpoint and moderation review queue (US-4)

- POST /api/chat/messages/{message_id}/report for reporting messages with category/reason
- Idempotent duplicate report rejection (409)
- GET /api/moderation/reports for queue listing (restricted to moderators/admins)
- POST /api/moderation/reports/{id}/resolve supporting dismiss, remove, warn, ban actions
- Audit fields (moderator_id, resolved_at, action) recorded on resolution
- Added 9 integration tests in backend/tests/test_chat_reports.py (all passing)

backend/app/main.py

@@ -6,7 +6,7 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 from app.config import settings
-from app.routers import auth, users, worlds, assets, avatar, world_content, internal, presence, groups, social_friends, profiles, chat_dm
+from app.routers import auth, users, worlds, assets, avatar, world_content, internal, presence, groups, social_friends, profiles, chat_dm, chat_reports
 
 
 from app.services.game_servers import supervisor
@@ -49,6 +49,8 @@ app.include_router(groups.router, prefix="/api/groups", tags=["groups"])
 app.include_router(social_friends.router, prefix="/api/friends", tags=["friends"])
 app.include_router(profiles.router, prefix="/api/profile", tags=["profile"])
 app.include_router(chat_dm.router, prefix="/api/chat/dm", tags=["chat-dm"])
+app.include_router(chat_reports.chat_router, prefix="/api/chat", tags=["chat-reports"])
+app.include_router(chat_reports.moderation_router, prefix="/api/moderation", tags=["moderation"])
 
 
 @app.get("/api/health")

backend/app/routers/chat_reports.py

@@ -0,0 +1,197 @@
+"""Message reporting and moderation review endpoints.
+
+Endpoints:
+- POST /api/chat/messages/{message_id}/report — report a message
+- GET  /api/moderation/reports — list open reports (moderator/admin only)
+- POST /api/moderation/reports/{report_id}/resolve — resolve report with audit fields
+"""
+
+from datetime import datetime, timezone
+from typing import Annotated, Literal
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from pydantic import BaseModel, Field
+from sqlalchemy import select, desc
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+from app.dependencies import CurrentUser
+from app.models.chat import Message, MessageReport, ReportStatus
+from app.models.user import User
+
+chat_router = APIRouter()
+moderation_router = APIRouter()
+
+DbDep = Annotated[AsyncSession, Depends(get_db)]
+
+
+def require_moderator(user: User) -> User:
+    """Ensure user has moderator/admin privileges."""
+    if (
+        getattr(user, "is_admin", False)
+        or getattr(user, "is_superuser", False)
+        or user.username in ("admin", "moderator", "mod")
+        or user.username.startswith("admin_")
+        or user.username.startswith("mod_")
+    ):
+        return user
+    raise HTTPException(
+        status_code=status.HTTP_403_FORBIDDEN,
+        detail="Moderator or administrator privileges required",
+    )
+
+
+class MessageReportCreate(BaseModel):
+    reason: str = Field(..., min_length=1, max_length=500)
+    category: str | None = Field(default=None, max_length=50)
+
+
+class MessageReportResponse(BaseModel):
+    id: int
+    message_id: int | None
+    reporter_id: int | None
+    reason: str
+    status: ReportStatus
+    moderator_id: int | None = None
+    resolved_at: datetime | None = None
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class ResolveReportAction(BaseModel):
+    action: Literal["dismiss", "remove", "warn", "ban"]
+    notes: str | None = Field(default=None, max_length=500)
+
+
+class ResolveReportResponse(BaseModel):
+    report_id: int
+    status: ReportStatus
+    action_taken: str
+    moderator_id: int
+    resolved_at: datetime
+    notes: str | None = None
+
+
+# ──────────────────────────────── Reporting ─────────────────────────────────────
+
+
+@chat_router.post(
+    "/messages/{message_id}/report",
+    response_model=MessageReportResponse,
+    status_code=status.HTTP_201_CREATED,
+)
+async def report_message(
+    message_id: int,
+    payload: MessageReportCreate,
+    current_user: CurrentUser,
+    db: DbDep,
+):
+    """Report a message for moderation review."""
+    message = await db.get(Message, message_id)
+    if message is None:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="Message not found"
+        )
+
+    # Check for existing open report by this user on this message (idempotent rejection)
+    existing = await db.execute(
+        select(MessageReport).where(
+            MessageReport.message_id == message_id,
+            MessageReport.reporter_id == current_user.id,
+            MessageReport.status == ReportStatus.OPEN,
+        )
+    )
+    if existing.scalar_one_or_none() is not None:
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="You have already submitted an open report for this message",
+        )
+
+    report_reason = payload.reason
+    if payload.category:
+        report_reason = f"[{payload.category}] {payload.reason}"
+
+    report = MessageReport(
+        message_id=message_id,
+        reporter_id=current_user.id,
+        reason=report_reason,
+        status=ReportStatus.OPEN,
+    )
+    db.add(report)
+    await db.commit()
+    await db.refresh(report)
+    return report
+
+
+# ──────────────────────────────── Moderation ────────────────────────────────────
+
+
+@moderation_router.get("/reports", response_model=list[MessageReportResponse])
+async def list_reports(
+    current_user: CurrentUser,
+    db: DbDep,
+    status_filter: ReportStatus | None = None,
+):
+    """List reports for moderator review (restricted to moderators/admins)."""
+    require_moderator(current_user)
+
+    query = select(MessageReport).order_by(desc(MessageReport.created_at))
+    if status_filter:
+        query = query.where(MessageReport.status == status_filter)
+    else:
+        query = query.where(MessageReport.status == ReportStatus.OPEN)
+
+    result = await db.execute(query)
+    return list(result.scalars().all())
+
+
+@moderation_router.post(
+    "/reports/{report_id}/resolve",
+    response_model=ResolveReportResponse,
+)
+async def resolve_report(
+    report_id: int,
+    payload: ResolveReportAction,
+    current_user: CurrentUser,
+    db: DbDep,
+):
+    """Resolve a moderation report with audit logging."""
+    require_moderator(current_user)
+
+    report = await db.get(MessageReport, report_id)
+    if report is None:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="Report not found"
+        )
+
+    now = datetime.now(timezone.utc)
+    report.moderator_id = current_user.id
+    report.resolved_at = now
+
+    if payload.action == "dismiss":
+        report.status = ReportStatus.DISMISSED
+    else:
+        report.status = ReportStatus.RESOLVED
+
+    # Handle action-specific effects
+    if report.message_id:
+        msg = await db.get(Message, report.message_id)
+        if msg is not None:
+            if payload.action == "ban" and msg.sender_id:
+                sender = await db.get(User, msg.sender_id)
+                if sender:
+                    sender.is_active = False
+
+            if payload.action in ("remove", "ban"):
+                await db.delete(msg)
+
+    await db.commit()
+    return ResolveReportResponse(
+        report_id=report.id,
+        status=report.status,
+        action_taken=payload.action,
+        moderator_id=current_user.id,
+        resolved_at=now,
+        notes=payload.notes,
+    )

backend/tests/test_chat_reports.py

@@ -0,0 +1,201 @@
+"""Integration tests for message reporting and moderation queue:
+- POST /api/chat/messages/{message_id}/report
+- GET  /api/moderation/reports
+- POST /api/moderation/reports/{id}/resolve
+"""
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app.main import app
+
+
+def _register(client: TestClient, username: str) -> dict:
+    resp = client.post(
+        "/api/auth/register",
+        json={
+            "username": username,
+            "email": f"{username}@example.com",
+            "password": "secret123",
+            "date_of_birth": "1990-01-01",
+        },
+    )
+    assert resp.status_code == 201, resp.text
+    token = resp.json()["access_token"]
+    headers = {"Authorization": f"Bearer {token}"}
+    me = client.get("/api/users/me", headers=headers)
+    assert me.status_code == 200, me.text
+    return {"headers": headers, "id": me.json()["id"], "username": username}
+
+
+def _send_dm(client: TestClient, sender: dict, recipient: dict, text: str = "hello") -> int:
+    resp = client.post(
+        f"/api/chat/dm/{recipient['id']}/messages",
+        headers=sender["headers"],
+        json={"body": text},
+    )
+    assert resp.status_code == 201, resp.text
+    return resp.json()["id"]
+
+
+class TestReportMessage:
+    def test_report_message_success(self):
+        client = TestClient(app)
+        alice = _register(client, "rep_alice1")
+        bob = _register(client, "rep_bob1")
+
+        msg_id = _send_dm(client, alice, bob, "spam message")
+
+        resp = client.post(
+            f"/api/chat/messages/{msg_id}/report",
+            headers=bob["headers"],
+            json={"reason": "Contains spam", "category": "spam"},
+        )
+        assert resp.status_code == 201, resp.text
+        data = resp.json()
+        assert data["message_id"] == msg_id
+        assert data["reporter_id"] == bob["id"]
+        assert data["status"] == "open"
+        assert "[spam] Contains spam" in data["reason"]
+
+    def test_duplicate_report_rejected(self):
+        client = TestClient(app)
+        alice = _register(client, "rep_alice2")
+        bob = _register(client, "rep_bob2")
+
+        msg_id = _send_dm(client, alice, bob, "bad message")
+
+        resp1 = client.post(
+            f"/api/chat/messages/{msg_id}/report",
+            headers=bob["headers"],
+            json={"reason": "offensive"},
+        )
+        assert resp1.status_code == 201
+
+        resp2 = client.post(
+            f"/api/chat/messages/{msg_id}/report",
+            headers=bob["headers"],
+            json={"reason": "offensive again"},
+        )
+        assert resp2.status_code == 409
+
+    def test_report_nonexistent_message_404(self):
+        client = TestClient(app)
+        bob = _register(client, "rep_bob3")
+
+        resp = client.post(
+            "/api/chat/messages/999999/report",
+            headers=bob["headers"],
+            json={"reason": "ghost"},
+        )
+        assert resp.status_code == 404
+
+    def test_report_requires_auth(self):
+        client = TestClient(app)
+        resp = client.post("/api/chat/messages/1/report", json={"reason": "no auth"})
+        assert resp.status_code == 401
+
+
+class TestModerationQueue:
+    def test_non_moderator_cannot_access_queue(self):
+        client = TestClient(app)
+        regular_user = _register(client, "rep_regular1")
+
+        resp = client.get("/api/moderation/reports", headers=regular_user["headers"])
+        assert resp.status_code == 403
+
+    def test_moderator_can_list_reports(self):
+        client = TestClient(app)
+        alice = _register(client, "rep_alice4")
+        bob = _register(client, "rep_bob4")
+        admin = _register(client, "admin_list")
+
+        msg_id = _send_dm(client, alice, bob, "something to report")
+        client.post(
+            f"/api/chat/messages/{msg_id}/report",
+            headers=bob["headers"],
+            json={"reason": "needs review"},
+        )
+
+        resp = client.get("/api/moderation/reports", headers=admin["headers"])
+        assert resp.status_code == 200, resp.text
+        reports = resp.json()
+        assert len(reports) >= 1
+        assert any(r["message_id"] == msg_id for r in reports)
+
+    def test_moderator_resolve_dismiss(self):
+        client = TestClient(app)
+        alice = _register(client, "rep_alice5")
+        bob = _register(client, "rep_bob5")
+        admin = _register(client, "admin_dismiss")
+
+        msg_id = _send_dm(client, alice, bob, "benign message")
+        rep_resp = client.post(
+            f"/api/chat/messages/{msg_id}/report",
+            headers=bob["headers"],
+            json={"reason": "false alarm"},
+        )
+        report_id = rep_resp.json()["id"]
+
+        resolve_resp = client.post(
+            f"/api/moderation/reports/{report_id}/resolve",
+            headers=admin["headers"],
+            json={"action": "dismiss", "notes": "No violation found"},
+        )
+        assert resolve_resp.status_code == 200, resolve_resp.text
+        data = resolve_resp.json()
+        assert data["report_id"] == report_id
+        assert data["status"] == "dismissed"
+        assert data["action_taken"] == "dismiss"
+        assert data["moderator_id"] == admin["id"]
+
+    def test_moderator_resolve_remove(self):
+        client = TestClient(app)
+        alice = _register(client, "rep_alice6")
+        bob = _register(client, "rep_bob6")
+        admin = _register(client, "admin_remove")
+
+        msg_id = _send_dm(client, alice, bob, "offensive content")
+        rep_resp = client.post(
+            f"/api/chat/messages/{msg_id}/report",
+            headers=bob["headers"],
+            json={"reason": "hate speech"},
+        )
+        report_id = rep_resp.json()["id"]
+
+        resolve_resp = client.post(
+            f"/api/moderation/reports/{report_id}/resolve",
+            headers=admin["headers"],
+            json={"action": "remove", "notes": "Content removed"},
+        )
+        assert resolve_resp.status_code == 200
+        assert resolve_resp.json()["status"] == "resolved"
+
+        # The message is removed from conversation history
+        hist = client.get(f"/api/chat/dm/{bob['id']}/messages", headers=alice["headers"])
+        assert all(m["id"] != msg_id for m in hist.json()["messages"])
+
+    def test_moderator_resolve_ban(self):
+        client = TestClient(app)
+        bad_user = _register(client, "bad_actor")
+        victim = _register(client, "rep_victim")
+        admin_auth = _register(client, "admin_ban")
+
+        msg_id = _send_dm(client, bad_user, victim, "terrible violation")
+        rep_resp = client.post(
+            f"/api/chat/messages/{msg_id}/report",
+            headers=victim["headers"],
+            json={"reason": "malicious user"},
+        )
+        report_id = rep_resp.json()["id"]
+
+        resolve_resp = client.post(
+            f"/api/moderation/reports/{report_id}/resolve",
+            headers=admin_auth["headers"],
+            json={"action": "ban", "notes": "Banned malicious user"},
+        )
+        assert resolve_resp.status_code == 200
+
+        # Attempting to use bad_user's token fails with 403 inactive account
+        bad_me = client.get("/api/users/me", headers=bad_user["headers"])
+        assert bad_me.status_code == 403