Add dispute system

backend/alembic/versions/009_add_disputes.py

@@ -0,0 +1,81 @@
+"""Add disputes tables for proof verification system
+
+Revision ID: 009_add_disputes
+Revises: 008_rename_to_game_choice
+Create Date: 2024-12-16
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision: str = '009_add_disputes'
+down_revision: Union[str, None] = '008_rename_to_game_choice'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    conn = op.get_bind()
+    inspector = sa.inspect(conn)
+    tables = inspector.get_table_names()
+
+    # Create disputes table
+    if 'disputes' not in tables:
+        op.create_table(
+            'disputes',
+            sa.Column('id', sa.Integer(), nullable=False),
+            sa.Column('assignment_id', sa.Integer(), nullable=False),
+            sa.Column('raised_by_id', sa.Integer(), nullable=False),
+            sa.Column('reason', sa.Text(), nullable=False),
+            sa.Column('status', sa.String(20), nullable=False, server_default='open'),
+            sa.Column('created_at', sa.DateTime(), nullable=False, server_default=sa.func.now()),
+            sa.Column('resolved_at', sa.DateTime(), nullable=True),
+            sa.PrimaryKeyConstraint('id'),
+            sa.ForeignKeyConstraint(['assignment_id'], ['assignments.id'], ondelete='CASCADE'),
+            sa.ForeignKeyConstraint(['raised_by_id'], ['users.id'], ondelete='CASCADE'),
+            sa.UniqueConstraint('assignment_id', name='uq_dispute_assignment'),
+        )
+        op.create_index('ix_disputes_assignment_id', 'disputes', ['assignment_id'])
+
+    # Create dispute_comments table
+    if 'dispute_comments' not in tables:
+        op.create_table(
+            'dispute_comments',
+            sa.Column('id', sa.Integer(), nullable=False),
+            sa.Column('dispute_id', sa.Integer(), nullable=False),
+            sa.Column('user_id', sa.Integer(), nullable=False),
+            sa.Column('text', sa.Text(), nullable=False),
+            sa.Column('created_at', sa.DateTime(), nullable=False, server_default=sa.func.now()),
+            sa.PrimaryKeyConstraint('id'),
+            sa.ForeignKeyConstraint(['dispute_id'], ['disputes.id'], ondelete='CASCADE'),
+            sa.ForeignKeyConstraint(['user_id'], ['users.id'], ondelete='CASCADE'),
+        )
+        op.create_index('ix_dispute_comments_dispute_id', 'dispute_comments', ['dispute_id'])
+
+    # Create dispute_votes table
+    if 'dispute_votes' not in tables:
+        op.create_table(
+            'dispute_votes',
+            sa.Column('id', sa.Integer(), nullable=False),
+            sa.Column('dispute_id', sa.Integer(), nullable=False),
+            sa.Column('user_id', sa.Integer(), nullable=False),
+            sa.Column('vote', sa.Boolean(), nullable=False),
+            sa.Column('created_at', sa.DateTime(), nullable=False, server_default=sa.func.now()),
+            sa.PrimaryKeyConstraint('id'),
+            sa.ForeignKeyConstraint(['dispute_id'], ['disputes.id'], ondelete='CASCADE'),
+            sa.ForeignKeyConstraint(['user_id'], ['users.id'], ondelete='CASCADE'),
+            sa.UniqueConstraint('dispute_id', 'user_id', name='uq_dispute_vote_user'),
+        )
+        op.create_index('ix_dispute_votes_dispute_id', 'dispute_votes', ['dispute_id'])
+
+
+def downgrade() -> None:
+    op.drop_index('ix_dispute_votes_dispute_id', table_name='dispute_votes')
+    op.drop_table('dispute_votes')
+    op.drop_index('ix_dispute_comments_dispute_id', table_name='dispute_comments')
+    op.drop_table('dispute_comments')
+    op.drop_index('ix_disputes_assignment_id', table_name='disputes')
+    op.drop_table('disputes')

backend/app/api/v1/__init__.py

@@ -1,6 +1,6 @@
 from fastapi import APIRouter
 
-from app.api.v1 import auth, users, marathons, games, challenges, wheel, feed, admin, events
+from app.api.v1 import auth, users, marathons, games, challenges, wheel, feed, admin, events, assignments
 
 router = APIRouter(prefix="/api/v1")
 
@@ -13,3 +13,4 @@ router.include_router(wheel.router)
 router.include_router(feed.router)
 router.include_router(admin.router)
 router.include_router(events.router)
+router.include_router(assignments.router)

backend/app/api/v1/assignments.py

@@ -0,0 +1,433 @@
+"""
+Assignment details and dispute system endpoints.
+"""
+from datetime import datetime, timedelta
+from fastapi import APIRouter, HTTPException
+from sqlalchemy import select
+from sqlalchemy.orm import selectinload
+
+from app.api.deps import DbSession, CurrentUser
+from app.models import (
+    Assignment, AssignmentStatus, Participant, Challenge, User,
+    Dispute, DisputeStatus, DisputeComment, DisputeVote,
+)
+from app.schemas import (
+    AssignmentDetailResponse, DisputeCreate, DisputeResponse,
+    DisputeCommentCreate, DisputeCommentResponse, DisputeVoteCreate,
+    MessageResponse, ChallengeResponse, GameShort, ReturnedAssignmentResponse,
+)
+from app.schemas.user import UserPublic
+
+router = APIRouter(tags=["assignments"])
+
+# Dispute window: 24 hours after completion
+DISPUTE_WINDOW_HOURS = 24
+
+
+def user_to_public(user: User) -> UserPublic:
+    """Convert User model to UserPublic schema"""
+    return UserPublic(
+        id=user.id,
+        login=user.login,
+        nickname=user.nickname,
+        avatar_url=None,
+        role=user.role,
+        created_at=user.created_at,
+    )
+
+
+def build_dispute_response(dispute: Dispute, current_user_id: int) -> DisputeResponse:
+    """Build DisputeResponse from Dispute model"""
+    votes_valid = sum(1 for v in dispute.votes if v.vote is True)
+    votes_invalid = sum(1 for v in dispute.votes if v.vote is False)
+
+    my_vote = None
+    for v in dispute.votes:
+        if v.user_id == current_user_id:
+            my_vote = v.vote
+            break
+
+    expires_at = dispute.created_at + timedelta(hours=DISPUTE_WINDOW_HOURS)
+
+    return DisputeResponse(
+        id=dispute.id,
+        raised_by=user_to_public(dispute.raised_by),
+        reason=dispute.reason,
+        status=dispute.status,
+        comments=[
+            DisputeCommentResponse(
+                id=c.id,
+                user=user_to_public(c.user),
+                text=c.text,
+                created_at=c.created_at,
+            )
+            for c in sorted(dispute.comments, key=lambda x: x.created_at)
+        ],
+        votes=[
+            {
+                "user": user_to_public(v.user),
+                "vote": v.vote,
+                "created_at": v.created_at,
+            }
+            for v in dispute.votes
+        ],
+        votes_valid=votes_valid,
+        votes_invalid=votes_invalid,
+        my_vote=my_vote,
+        expires_at=expires_at,
+        created_at=dispute.created_at,
+        resolved_at=dispute.resolved_at,
+    )
+
+
+@router.get("/assignments/{assignment_id}", response_model=AssignmentDetailResponse)
+async def get_assignment_detail(
+    assignment_id: int,
+    current_user: CurrentUser,
+    db: DbSession,
+):
+    """Get detailed information about an assignment including proofs and dispute"""
+    # Get assignment with all relationships
+    result = await db.execute(
+        select(Assignment)
+        .options(
+            selectinload(Assignment.challenge).selectinload(Challenge.game),
+            selectinload(Assignment.participant).selectinload(Participant.user),
+            selectinload(Assignment.dispute).selectinload(Dispute.raised_by),
+            selectinload(Assignment.dispute).selectinload(Dispute.comments).selectinload(DisputeComment.user),
+            selectinload(Assignment.dispute).selectinload(Dispute.votes).selectinload(DisputeVote.user),
+        )
+        .where(Assignment.id == assignment_id)
+    )
+    assignment = result.scalar_one_or_none()
+
+    if not assignment:
+        raise HTTPException(status_code=404, detail="Assignment not found")
+
+    # Check user is participant of the marathon
+    marathon_id = assignment.challenge.game.marathon_id
+    result = await db.execute(
+        select(Participant).where(
+            Participant.user_id == current_user.id,
+            Participant.marathon_id == marathon_id,
+        )
+    )
+    participant = result.scalar_one_or_none()
+    if not participant:
+        raise HTTPException(status_code=403, detail="You are not a participant of this marathon")
+
+    # Build response
+    challenge = assignment.challenge
+    game = challenge.game
+    owner_user = assignment.participant.user
+
+    # Determine if user can dispute
+    can_dispute = False
+    if (
+        assignment.status == AssignmentStatus.COMPLETED.value
+        and assignment.completed_at
+        and assignment.participant.user_id != current_user.id
+        and assignment.dispute is None
+    ):
+        time_since_completion = datetime.utcnow() - assignment.completed_at
+        can_dispute = time_since_completion < timedelta(hours=DISPUTE_WINDOW_HOURS)
+
+    # Build proof URLs
+    proof_image_url = None
+    if assignment.proof_path:
+        # Extract filename from path
+        proof_image_url = f"/uploads/proofs/{assignment.proof_path.split('/')[-1]}"
+
+    return AssignmentDetailResponse(
+        id=assignment.id,
+        challenge=ChallengeResponse(
+            id=challenge.id,
+            title=challenge.title,
+            description=challenge.description,
+            type=challenge.type,
+            difficulty=challenge.difficulty,
+            points=challenge.points,
+            estimated_time=challenge.estimated_time,
+            proof_type=challenge.proof_type,
+            proof_hint=challenge.proof_hint,
+            game=GameShort(
+                id=game.id,
+                title=game.title,
+                cover_url=f"/uploads/covers/{game.cover_path.split('/')[-1]}" if game.cover_path else None,
+            ),
+            is_generated=challenge.is_generated,
+            created_at=challenge.created_at,
+        ),
+        participant=user_to_public(owner_user),
+        status=assignment.status,
+        proof_url=assignment.proof_url,
+        proof_image_url=proof_image_url,
+        proof_comment=assignment.proof_comment,
+        points_earned=assignment.points_earned,
+        streak_at_completion=assignment.streak_at_completion,
+        started_at=assignment.started_at,
+        completed_at=assignment.completed_at,
+        can_dispute=can_dispute,
+        dispute=build_dispute_response(assignment.dispute, current_user.id) if assignment.dispute else None,
+    )
+
+
+@router.post("/assignments/{assignment_id}/dispute", response_model=DisputeResponse)
+async def create_dispute(
+    assignment_id: int,
+    data: DisputeCreate,
+    current_user: CurrentUser,
+    db: DbSession,
+):
+    """Create a dispute against an assignment's proof"""
+    # Get assignment
+    result = await db.execute(
+        select(Assignment)
+        .options(
+            selectinload(Assignment.challenge).selectinload(Challenge.game),
+            selectinload(Assignment.participant),
+            selectinload(Assignment.dispute),
+        )
+        .where(Assignment.id == assignment_id)
+    )
+    assignment = result.scalar_one_or_none()
+
+    if not assignment:
+        raise HTTPException(status_code=404, detail="Assignment not found")
+
+    # Check user is participant of the marathon
+    marathon_id = assignment.challenge.game.marathon_id
+    result = await db.execute(
+        select(Participant).where(
+            Participant.user_id == current_user.id,
+            Participant.marathon_id == marathon_id,
+        )
+    )
+    participant = result.scalar_one_or_none()
+    if not participant:
+        raise HTTPException(status_code=403, detail="You are not a participant of this marathon")
+
+    # Validate
+    if assignment.status != AssignmentStatus.COMPLETED.value:
+        raise HTTPException(status_code=400, detail="Can only dispute completed assignments")
+
+    if assignment.participant.user_id == current_user.id:
+        raise HTTPException(status_code=400, detail="Cannot dispute your own assignment")
+
+    if assignment.dispute:
+        raise HTTPException(status_code=400, detail="A dispute already exists for this assignment")
+
+    if not assignment.completed_at:
+        raise HTTPException(status_code=400, detail="Assignment has no completion date")
+
+    time_since_completion = datetime.utcnow() - assignment.completed_at
+    if time_since_completion >= timedelta(hours=DISPUTE_WINDOW_HOURS):
+        raise HTTPException(status_code=400, detail="Dispute window has expired (24 hours)")
+
+    # Create dispute
+    dispute = Dispute(
+        assignment_id=assignment_id,
+        raised_by_id=current_user.id,
+        reason=data.reason,
+        status=DisputeStatus.OPEN.value,
+    )
+    db.add(dispute)
+    await db.commit()
+    await db.refresh(dispute)
+
+    # Load relationships for response
+    result = await db.execute(
+        select(Dispute)
+        .options(
+            selectinload(Dispute.raised_by),
+            selectinload(Dispute.comments).selectinload(DisputeComment.user),
+            selectinload(Dispute.votes).selectinload(DisputeVote.user),
+        )
+        .where(Dispute.id == dispute.id)
+    )
+    dispute = result.scalar_one()
+
+    return build_dispute_response(dispute, current_user.id)
+
+
+@router.post("/disputes/{dispute_id}/comments", response_model=DisputeCommentResponse)
+async def add_dispute_comment(
+    dispute_id: int,
+    data: DisputeCommentCreate,
+    current_user: CurrentUser,
+    db: DbSession,
+):
+    """Add a comment to a dispute discussion"""
+    # Get dispute with assignment
+    result = await db.execute(
+        select(Dispute)
+        .options(
+            selectinload(Dispute.assignment).selectinload(Assignment.challenge).selectinload(Challenge.game),
+        )
+        .where(Dispute.id == dispute_id)
+    )
+    dispute = result.scalar_one_or_none()
+
+    if not dispute:
+        raise HTTPException(status_code=404, detail="Dispute not found")
+
+    if dispute.status != DisputeStatus.OPEN.value:
+        raise HTTPException(status_code=400, detail="Dispute is already resolved")
+
+    # Check user is participant of the marathon
+    marathon_id = dispute.assignment.challenge.game.marathon_id
+    result = await db.execute(
+        select(Participant).where(
+            Participant.user_id == current_user.id,
+            Participant.marathon_id == marathon_id,
+        )
+    )
+    participant = result.scalar_one_or_none()
+    if not participant:
+        raise HTTPException(status_code=403, detail="You are not a participant of this marathon")
+
+    # Create comment
+    comment = DisputeComment(
+        dispute_id=dispute_id,
+        user_id=current_user.id,
+        text=data.text,
+    )
+    db.add(comment)
+    await db.commit()
+    await db.refresh(comment)
+
+    # Get user for response
+    result = await db.execute(select(User).where(User.id == current_user.id))
+    user = result.scalar_one()
+
+    return DisputeCommentResponse(
+        id=comment.id,
+        user=user_to_public(user),
+        text=comment.text,
+        created_at=comment.created_at,
+    )
+
+
+@router.post("/disputes/{dispute_id}/vote", response_model=MessageResponse)
+async def vote_on_dispute(
+    dispute_id: int,
+    data: DisputeVoteCreate,
+    current_user: CurrentUser,
+    db: DbSession,
+):
+    """Vote on a dispute (True = valid/proof is OK, False = invalid/proof is not OK)"""
+    # Get dispute with assignment
+    result = await db.execute(
+        select(Dispute)
+        .options(
+            selectinload(Dispute.assignment).selectinload(Assignment.challenge).selectinload(Challenge.game),
+        )
+        .where(Dispute.id == dispute_id)
+    )
+    dispute = result.scalar_one_or_none()
+
+    if not dispute:
+        raise HTTPException(status_code=404, detail="Dispute not found")
+
+    if dispute.status != DisputeStatus.OPEN.value:
+        raise HTTPException(status_code=400, detail="Dispute is already resolved")
+
+    # Check user is participant of the marathon
+    marathon_id = dispute.assignment.challenge.game.marathon_id
+    result = await db.execute(
+        select(Participant).where(
+            Participant.user_id == current_user.id,
+            Participant.marathon_id == marathon_id,
+        )
+    )
+    participant = result.scalar_one_or_none()
+    if not participant:
+        raise HTTPException(status_code=403, detail="You are not a participant of this marathon")
+
+    # Check if user already voted
+    result = await db.execute(
+        select(DisputeVote).where(
+            DisputeVote.dispute_id == dispute_id,
+            DisputeVote.user_id == current_user.id,
+        )
+    )
+    existing_vote = result.scalar_one_or_none()
+
+    if existing_vote:
+        # Update existing vote
+        existing_vote.vote = data.vote
+        existing_vote.created_at = datetime.utcnow()
+    else:
+        # Create new vote
+        vote = DisputeVote(
+            dispute_id=dispute_id,
+            user_id=current_user.id,
+            vote=data.vote,
+        )
+        db.add(vote)
+
+    await db.commit()
+
+    vote_text = "валидным" if data.vote else "невалидным"
+    return MessageResponse(message=f"Вы проголосовали: пруф {vote_text}")
+
+
+@router.get("/marathons/{marathon_id}/returned-assignments", response_model=list[ReturnedAssignmentResponse])
+async def get_returned_assignments(
+    marathon_id: int,
+    current_user: CurrentUser,
+    db: DbSession,
+):
+    """Get current user's returned assignments that need to be redone"""
+    # Check user is participant
+    result = await db.execute(
+        select(Participant).where(
+            Participant.user_id == current_user.id,
+            Participant.marathon_id == marathon_id,
+        )
+    )
+    participant = result.scalar_one_or_none()
+    if not participant:
+        raise HTTPException(status_code=403, detail="You are not a participant of this marathon")
+
+    # Get returned assignments
+    result = await db.execute(
+        select(Assignment)
+        .options(
+            selectinload(Assignment.challenge).selectinload(Challenge.game),
+            selectinload(Assignment.dispute),
+        )
+        .where(
+            Assignment.participant_id == participant.id,
+            Assignment.status == AssignmentStatus.RETURNED.value,
+        )
+        .order_by(Assignment.completed_at.asc())  # Oldest first
+    )
+    assignments = result.scalars().all()
+
+    return [
+        ReturnedAssignmentResponse(
+            id=a.id,
+            challenge=ChallengeResponse(
+                id=a.challenge.id,
+                title=a.challenge.title,
+                description=a.challenge.description,
+                type=a.challenge.type,
+                difficulty=a.challenge.difficulty,
+                points=a.challenge.points,
+                estimated_time=a.challenge.estimated_time,
+                proof_type=a.challenge.proof_type,
+                proof_hint=a.challenge.proof_hint,
+                game=GameShort(
+                    id=a.challenge.game.id,
+                    title=a.challenge.game.title,
+                    cover_url=f"/uploads/covers/{a.challenge.game.cover_path.split('/')[-1]}" if a.challenge.game.cover_path else None,
+                ),
+                is_generated=a.challenge.is_generated,
+                created_at=a.challenge.created_at,
+            ),
+            original_completed_at=a.completed_at,
+            dispute_reason=a.dispute.reason if a.dispute else "Оспорено",
+        )
+        for a in assignments
+    ]

backend/app/api/v1/events.py

@@ -1111,6 +1111,7 @@ async def complete_event_assignment(
 
     # Log activity
     activity_data = {
+        "assignment_id": assignment.id,
         "game": challenge.game.title,
         "challenge": challenge.title,
         "difficulty": challenge.difficulty,

backend/app/api/v1/wheel.py

@@ -60,6 +60,39 @@ async def get_active_assignment(db, participant_id: int, is_event: bool = False)
     return result.scalar_one_or_none()
 
 
+async def get_oldest_returned_assignment(db, participant_id: int) -> Assignment | None:
+    """Get the oldest returned assignment that needs to be redone."""
+    result = await db.execute(
+        select(Assignment)
+        .options(
+            selectinload(Assignment.challenge).selectinload(Challenge.game)
+        )
+        .where(
+            Assignment.participant_id == participant_id,
+            Assignment.status == AssignmentStatus.RETURNED.value,
+            Assignment.is_event_assignment == False,
+        )
+        .order_by(Assignment.completed_at.asc())  # Oldest first
+        .limit(1)
+    )
+    return result.scalar_one_or_none()
+
+
+async def activate_returned_assignment(db, returned_assignment: Assignment) -> None:
+    """
+    Re-activate a returned assignment.
+    Simply changes the status back to ACTIVE.
+    """
+    returned_assignment.status = AssignmentStatus.ACTIVE.value
+    returned_assignment.started_at = datetime.utcnow()
+    # Clear previous proof data for fresh attempt
+    returned_assignment.proof_path = None
+    returned_assignment.proof_url = None
+    returned_assignment.proof_comment = None
+    returned_assignment.completed_at = None
+    returned_assignment.points_earned = 0
+
+
 @router.post("/marathons/{marathon_id}/spin", response_model=SpinResult)
 async def spin_wheel(marathon_id: int, current_user: CurrentUser, db: DbSession):
     """Spin the wheel to get a random game and challenge"""
@@ -347,6 +380,7 @@ async def complete_assignment(
 
     # Log activity
     activity_data = {
+        "assignment_id": assignment.id,
         "game": full_challenge.game.title,
         "challenge": challenge.title,
         "difficulty": challenge.difficulty,
@@ -407,6 +441,13 @@ async def complete_assignment(
 
     await db.commit()
 
+    # Check for returned assignments and activate the oldest one
+    returned_assignment = await get_oldest_returned_assignment(db, participant.id)
+    if returned_assignment:
+        await activate_returned_assignment(db, returned_assignment)
+        await db.commit()
+        print(f"[WHEEL] Auto-activated returned assignment {returned_assignment.id} for participant {participant.id}")
+
     return CompleteResult(
         points_earned=total_points,
         streak_bonus=streak_bonus,

backend/app/main.py

@@ -9,6 +9,7 @@ from app.core.config import settings
 from app.core.database import engine, Base, async_session_maker
 from app.api.v1 import router as api_router
 from app.services.event_scheduler import event_scheduler
+from app.services.dispute_scheduler import dispute_scheduler
 
 
 @asynccontextmanager
@@ -23,13 +24,15 @@ async def lifespan(app: FastAPI):
     (upload_dir / "covers").mkdir(parents=True, exist_ok=True)
     (upload_dir / "proofs").mkdir(parents=True, exist_ok=True)
 
-    # Start event scheduler
+    # Start schedulers
     await event_scheduler.start(async_session_maker)
+    await dispute_scheduler.start(async_session_maker)
 
     yield
 
     # Shutdown
     await event_scheduler.stop()
+    await dispute_scheduler.stop()
     await engine.dispose()
 
 

backend/app/models/__init__.py

@@ -7,6 +7,7 @@ from app.models.assignment import Assignment, AssignmentStatus
 from app.models.activity import Activity, ActivityType
 from app.models.event import Event, EventType
 from app.models.swap_request import SwapRequest, SwapRequestStatus
+from app.models.dispute import Dispute, DisputeStatus, DisputeComment, DisputeVote
 
 __all__ = [
     "User",
@@ -30,4 +31,8 @@ __all__ = [
     "EventType",
     "SwapRequest",
     "SwapRequestStatus",
+    "Dispute",
+    "DisputeStatus",
+    "DisputeComment",
+    "DisputeVote",
 ]

backend/app/models/assignment.py

@@ -10,6 +10,7 @@ class AssignmentStatus(str, Enum):
     ACTIVE = "active"
     COMPLETED = "completed"
     DROPPED = "dropped"
+    RETURNED = "returned"  # Disputed and needs to be redone
 
 
 class Assignment(Base):
@@ -34,3 +35,4 @@ class Assignment(Base):
     participant: Mapped["Participant"] = relationship("Participant", back_populates="assignments")
     challenge: Mapped["Challenge"] = relationship("Challenge", back_populates="assignments")
     event: Mapped["Event | None"] = relationship("Event", back_populates="assignments")
+    dispute: Mapped["Dispute | None"] = relationship("Dispute", back_populates="assignment", uselist=False)

backend/app/models/dispute.py

@@ -0,0 +1,66 @@
+from datetime import datetime
+from enum import Enum
+from sqlalchemy import String, Text, DateTime, ForeignKey, Boolean, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.core.database import Base
+
+
+class DisputeStatus(str, Enum):
+    OPEN = "open"
+    RESOLVED_VALID = "valid"
+    RESOLVED_INVALID = "invalid"
+
+
+class Dispute(Base):
+    """Dispute against a completed assignment's proof"""
+    __tablename__ = "disputes"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    assignment_id: Mapped[int] = mapped_column(ForeignKey("assignments.id", ondelete="CASCADE"), unique=True, index=True)
+    raised_by_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"))
+    reason: Mapped[str] = mapped_column(Text, nullable=False)
+    status: Mapped[str] = mapped_column(String(20), default=DisputeStatus.OPEN.value)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+    resolved_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+
+    # Relationships
+    assignment: Mapped["Assignment"] = relationship("Assignment", back_populates="dispute")
+    raised_by: Mapped["User"] = relationship("User", foreign_keys=[raised_by_id])
+    comments: Mapped[list["DisputeComment"]] = relationship("DisputeComment", back_populates="dispute", cascade="all, delete-orphan")
+    votes: Mapped[list["DisputeVote"]] = relationship("DisputeVote", back_populates="dispute", cascade="all, delete-orphan")
+
+
+class DisputeComment(Base):
+    """Comment in a dispute discussion"""
+    __tablename__ = "dispute_comments"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    dispute_id: Mapped[int] = mapped_column(ForeignKey("disputes.id", ondelete="CASCADE"), index=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"))
+    text: Mapped[str] = mapped_column(Text, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+
+    # Relationships
+    dispute: Mapped["Dispute"] = relationship("Dispute", back_populates="comments")
+    user: Mapped["User"] = relationship("User")
+
+
+class DisputeVote(Base):
+    """Vote in a dispute (valid or invalid)"""
+    __tablename__ = "dispute_votes"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    dispute_id: Mapped[int] = mapped_column(ForeignKey("disputes.id", ondelete="CASCADE"), index=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"))
+    vote: Mapped[bool] = mapped_column(Boolean, nullable=False)  # True = valid, False = invalid
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+
+    # Unique constraint: one vote per user per dispute
+    __table_args__ = (
+        UniqueConstraint("dispute_id", "user_id", name="uq_dispute_vote_user"),
+    )
+
+    # Relationships
+    dispute: Mapped["Dispute"] = relationship("Dispute", back_populates="votes")
+    user: Mapped["User"] = relationship("User")

backend/app/schemas/__init__.py

@@ -67,6 +67,16 @@ from app.schemas.common import (
     ErrorResponse,
     PaginationParams,
 )
+from app.schemas.dispute import (
+    DisputeCreate,
+    DisputeCommentCreate,
+    DisputeVoteCreate,
+    DisputeCommentResponse,
+    DisputeVoteResponse,
+    DisputeResponse,
+    AssignmentDetailResponse,
+    ReturnedAssignmentResponse,
+)
 
 __all__ = [
     # User
@@ -130,4 +140,13 @@ __all__ = [
     "MessageResponse",
     "ErrorResponse",
     "PaginationParams",
+    # Dispute
+    "DisputeCreate",
+    "DisputeCommentCreate",
+    "DisputeVoteCreate",
+    "DisputeCommentResponse",
+    "DisputeVoteResponse",
+    "DisputeResponse",
+    "AssignmentDetailResponse",
+    "ReturnedAssignmentResponse",
 ]

backend/app/schemas/dispute.py

@@ -0,0 +1,91 @@
+from datetime import datetime
+from pydantic import BaseModel, Field
+
+from app.schemas.user import UserPublic
+from app.schemas.challenge import ChallengeResponse
+
+
+class DisputeCreate(BaseModel):
+    """Request to create a dispute"""
+    reason: str = Field(..., min_length=10, max_length=1000)
+
+
+class DisputeCommentCreate(BaseModel):
+    """Request to add a comment to a dispute"""
+    text: str = Field(..., min_length=1, max_length=500)
+
+
+class DisputeVoteCreate(BaseModel):
+    """Request to vote on a dispute"""
+    vote: bool  # True = valid (proof is OK), False = invalid (proof is not OK)
+
+
+class DisputeCommentResponse(BaseModel):
+    """Comment in a dispute discussion"""
+    id: int
+    user: UserPublic
+    text: str
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class DisputeVoteResponse(BaseModel):
+    """Vote in a dispute"""
+    user: UserPublic
+    vote: bool  # True = valid, False = invalid
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class DisputeResponse(BaseModel):
+    """Full dispute information"""
+    id: int
+    raised_by: UserPublic
+    reason: str
+    status: str  # "open", "valid", "invalid"
+    comments: list[DisputeCommentResponse]
+    votes: list[DisputeVoteResponse]
+    votes_valid: int
+    votes_invalid: int
+    my_vote: bool | None  # Current user's vote, None if not voted
+    expires_at: datetime
+    created_at: datetime
+    resolved_at: datetime | None
+
+    class Config:
+        from_attributes = True
+
+
+class AssignmentDetailResponse(BaseModel):
+    """Detailed assignment information with proofs and dispute"""
+    id: int
+    challenge: ChallengeResponse
+    participant: UserPublic
+    status: str
+    proof_url: str | None  # External URL (YouTube, etc.)
+    proof_image_url: str | None  # Uploaded file URL
+    proof_comment: str | None
+    points_earned: int
+    streak_at_completion: int | None
+    started_at: datetime
+    completed_at: datetime | None
+    can_dispute: bool  # True if <24h since completion and not own assignment
+    dispute: DisputeResponse | None
+
+    class Config:
+        from_attributes = True
+
+
+class ReturnedAssignmentResponse(BaseModel):
+    """Returned assignment that needs to be redone"""
+    id: int
+    challenge: ChallengeResponse
+    original_completed_at: datetime
+    dispute_reason: str
+
+    class Config:
+        from_attributes = True

backend/app/services/dispute_scheduler.py

@@ -0,0 +1,89 @@
+"""
+Dispute Scheduler for automatic dispute resolution after 24 hours.
+"""
+import asyncio
+from datetime import datetime, timedelta
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from app.models import Dispute, DisputeStatus, Assignment, AssignmentStatus
+from app.services.disputes import dispute_service
+
+
+# Configuration
+CHECK_INTERVAL_SECONDS = 300  # Check every 5 minutes
+DISPUTE_WINDOW_HOURS = 24  # Disputes auto-resolve after 24 hours
+
+
+class DisputeScheduler:
+    """Background scheduler for automatic dispute resolution."""
+
+    def __init__(self):
+        self._running = False
+        self._task: asyncio.Task | None = None
+
+    async def start(self, session_factory) -> None:
+        """Start the scheduler background task."""
+        if self._running:
+            return
+
+        self._running = True
+        self._task = asyncio.create_task(self._run_loop(session_factory))
+        print("[DisputeScheduler] Started")
+
+    async def stop(self) -> None:
+        """Stop the scheduler."""
+        self._running = False
+        if self._task:
+            self._task.cancel()
+            try:
+                await self._task
+            except asyncio.CancelledError:
+                pass
+        print("[DisputeScheduler] Stopped")
+
+    async def _run_loop(self, session_factory) -> None:
+        """Main scheduler loop."""
+        while self._running:
+            try:
+                async with session_factory() as db:
+                    await self._process_expired_disputes(db)
+            except Exception as e:
+                print(f"[DisputeScheduler] Error in loop: {e}")
+
+            await asyncio.sleep(CHECK_INTERVAL_SECONDS)
+
+    async def _process_expired_disputes(self, db: AsyncSession) -> None:
+        """Process and resolve expired disputes."""
+        cutoff_time = datetime.utcnow() - timedelta(hours=DISPUTE_WINDOW_HOURS)
+
+        # Find all open disputes that have expired
+        result = await db.execute(
+            select(Dispute)
+            .options(
+                selectinload(Dispute.votes),
+                selectinload(Dispute.assignment).selectinload(Assignment.participant),
+            )
+            .where(
+                Dispute.status == DisputeStatus.OPEN.value,
+                Dispute.created_at < cutoff_time,
+            )
+        )
+        expired_disputes = result.scalars().all()
+
+        for dispute in expired_disputes:
+            try:
+                result_status, votes_valid, votes_invalid = await dispute_service.resolve_dispute(
+                    db, dispute.id
+                )
+                print(
+                    f"[DisputeScheduler] Auto-resolved dispute {dispute.id}: "
+                    f"{result_status} (valid: {votes_valid}, invalid: {votes_invalid})"
+                )
+            except Exception as e:
+                print(f"[DisputeScheduler] Failed to resolve dispute {dispute.id}: {e}")
+
+
+# Global scheduler instance
+dispute_scheduler = DisputeScheduler()

backend/app/services/disputes.py

@@ -0,0 +1,103 @@
+"""
+Dispute resolution service.
+"""
+from datetime import datetime
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from app.models import (
+    Dispute, DisputeStatus, DisputeVote,
+    Assignment, AssignmentStatus, Participant,
+)
+
+
+class DisputeService:
+    """Service for dispute resolution logic"""
+
+    async def resolve_dispute(self, db: AsyncSession, dispute_id: int) -> tuple[str, int, int]:
+        """
+        Resolve a dispute based on votes.
+
+        Returns:
+            Tuple of (result_status, votes_valid, votes_invalid)
+        """
+        # Get dispute with votes and assignment
+        result = await db.execute(
+            select(Dispute)
+            .options(
+                selectinload(Dispute.votes),
+                selectinload(Dispute.assignment).selectinload(Assignment.participant),
+            )
+            .where(Dispute.id == dispute_id)
+        )
+        dispute = result.scalar_one_or_none()
+
+        if not dispute:
+            raise ValueError(f"Dispute {dispute_id} not found")
+
+        if dispute.status != DisputeStatus.OPEN.value:
+            raise ValueError(f"Dispute {dispute_id} is already resolved")
+
+        # Count votes
+        votes_valid = sum(1 for v in dispute.votes if v.vote is True)
+        votes_invalid = sum(1 for v in dispute.votes if v.vote is False)
+
+        # Determine result: tie goes to the accused (valid)
+        if votes_invalid > votes_valid:
+            # Proof is invalid - mark assignment as RETURNED
+            result_status = DisputeStatus.RESOLVED_INVALID.value
+            await self._handle_invalid_proof(db, dispute)
+        else:
+            # Proof is valid (or tie)
+            result_status = DisputeStatus.RESOLVED_VALID.value
+
+        # Update dispute
+        dispute.status = result_status
+        dispute.resolved_at = datetime.utcnow()
+
+        await db.commit()
+
+        return result_status, votes_valid, votes_invalid
+
+    async def _handle_invalid_proof(self, db: AsyncSession, dispute: Dispute) -> None:
+        """
+        Handle the case when proof is determined to be invalid.
+
+        - Mark assignment as RETURNED
+        - Subtract points from participant
+        - Reset streak if it was affected
+        """
+        assignment = dispute.assignment
+        participant = assignment.participant
+
+        # Subtract points that were earned
+        points_to_subtract = assignment.points_earned
+        participant.total_points = max(0, participant.total_points - points_to_subtract)
+
+        # Reset assignment
+        assignment.status = AssignmentStatus.RETURNED.value
+        assignment.points_earned = 0
+        # Keep proof data so it can be reviewed
+
+        print(f"[DisputeService] Assignment {assignment.id} marked as RETURNED, "
+              f"subtracted {points_to_subtract} points from participant {participant.id}")
+
+    async def get_pending_disputes(self, db: AsyncSession, older_than_hours: int = 24) -> list[Dispute]:
+        """Get all open disputes older than specified hours"""
+        from datetime import timedelta
+
+        cutoff_time = datetime.utcnow() - timedelta(hours=older_than_hours)
+
+        result = await db.execute(
+            select(Dispute)
+            .where(
+                Dispute.status == DisputeStatus.OPEN.value,
+                Dispute.created_at < cutoff_time,
+            )
+        )
+        return list(result.scalars().all())
+
+
+# Global service instance
+dispute_service = DisputeService()

frontend/src/App.tsx

@@ -15,6 +15,7 @@ import { LobbyPage } from '@/pages/LobbyPage'
 import { PlayPage } from '@/pages/PlayPage'
 import { LeaderboardPage } from '@/pages/LeaderboardPage'
 import { InvitePage } from '@/pages/InvitePage'
+import { AssignmentDetailPage } from '@/pages/AssignmentDetailPage'
 
 // Protected route wrapper
 function ProtectedRoute({ children }: { children: React.ReactNode }) {
@@ -118,6 +119,15 @@ function App() {
             </ProtectedRoute>
           }
         />
+
+        <Route
+          path="assignments/:id"
+          element={
+            <ProtectedRoute>
+              <AssignmentDetailPage />
+            </ProtectedRoute>
+          }
+        />
       </Route>
     </Routes>
   )

frontend/src/api/assignments.ts

@@ -0,0 +1,34 @@
+import client from './client'
+import type { AssignmentDetail, Dispute, DisputeComment, ReturnedAssignment } from '@/types'
+
+export const assignmentsApi = {
+  // Get detailed assignment info with proofs and dispute
+  getDetail: async (assignmentId: number): Promise<AssignmentDetail> => {
+    const response = await client.get<AssignmentDetail>(`/assignments/${assignmentId}`)
+    return response.data
+  },
+
+  // Create a dispute against an assignment
+  createDispute: async (assignmentId: number, reason: string): Promise<Dispute> => {
+    const response = await client.post<Dispute>(`/assignments/${assignmentId}/dispute`, { reason })
+    return response.data
+  },
+
+  // Add a comment to a dispute
+  addComment: async (disputeId: number, text: string): Promise<DisputeComment> => {
+    const response = await client.post<DisputeComment>(`/disputes/${disputeId}/comments`, { text })
+    return response.data
+  },
+
+  // Vote on a dispute (true = valid/proof is OK, false = invalid/proof is not OK)
+  vote: async (disputeId: number, vote: boolean): Promise<{ message: string }> => {
+    const response = await client.post<{ message: string }>(`/disputes/${disputeId}/vote`, { vote })
+    return response.data
+  },
+
+  // Get current user's returned assignments
+  getReturnedAssignments: async (marathonId: number): Promise<ReturnedAssignment[]> => {
+    const response = await client.get<ReturnedAssignment[]>(`/marathons/${marathonId}/returned-assignments`)
+    return response.data
+  },
+}

frontend/src/api/index.ts

@@ -6,3 +6,4 @@ export { feedApi } from './feed'
 export { adminApi } from './admin'
 export { eventsApi } from './events'
 export { challengesApi } from './challenges'
+export { assignmentsApi } from './assignments'

frontend/src/components/ActivityFeed.tsx

@@ -1,7 +1,8 @@
 import { useState, useEffect, useCallback, useRef, useImperativeHandle, forwardRef } from 'react'
+import { useNavigate } from 'react-router-dom'
 import { feedApi } from '@/api'
 import type { Activity, ActivityType } from '@/types'
-import { Loader2, ChevronDown, Bell } from 'lucide-react'
+import { Loader2, ChevronDown, Bell, ExternalLink } from 'lucide-react'
 import {
   formatRelativeTime,
   getActivityIcon,
@@ -169,12 +170,18 @@ interface ActivityItemProps {
 }
 
 function ActivityItem({ activity }: ActivityItemProps) {
+  const navigate = useNavigate()
   const Icon = getActivityIcon(activity.type)
   const iconColor = getActivityColor(activity.type)
   const bgClass = getActivityBgClass(activity.type)
   const isEvent = isEventActivity(activity.type)
   const { title, details, extra } = formatActivityMessage(activity)
 
+  // Get assignment_id for complete activities
+  const assignmentId = activity.type === 'complete' && activity.data
+    ? (activity.data as { assignment_id?: number }).assignment_id
+    : null
+
   if (isEvent) {
     return (
       <div className={`px-4 py-3 ${bgClass} border-l-2 ${activity.type === 'event_start' ? 'border-l-yellow-500' : 'border-l-gray-600'}`}>
@@ -240,6 +247,16 @@ function ActivityItem({ activity }: ActivityItemProps) {
               {extra}
             </div>
           )}
+          {/* Details button for complete activities */}
+          {assignmentId && (
+            <button
+              onClick={() => navigate(`/assignments/${assignmentId}`)}
+              className="mt-2 text-xs text-primary-400 hover:text-primary-300 flex items-center gap-1"
+            >
+              <ExternalLink className="w-3 h-3" />
+              Детали
+            </button>
+          )}
         </div>
       </div>
     </div>

frontend/src/pages/AssignmentDetailPage.tsx

@@ -0,0 +1,481 @@
+import { useState, useEffect } from 'react'
+import { useParams, useNavigate } from 'react-router-dom'
+import { assignmentsApi } from '@/api'
+import type { AssignmentDetail } from '@/types'
+import { Card, CardContent, Button } from '@/components/ui'
+import { useAuthStore } from '@/store/auth'
+import {
+  ArrowLeft, Loader2, ExternalLink, Image, MessageSquare,
+  ThumbsUp, ThumbsDown, AlertTriangle, Clock, CheckCircle, XCircle,
+  Send, Flag
+} from 'lucide-react'
+
+const API_URL = import.meta.env.VITE_API_URL || 'http://localhost:8000'
+
+export function AssignmentDetailPage() {
+  const { id } = useParams<{ id: string }>()
+  const navigate = useNavigate()
+  const user = useAuthStore((state) => state.user)
+
+  const [assignment, setAssignment] = useState<AssignmentDetail | null>(null)
+  const [isLoading, setIsLoading] = useState(true)
+  const [error, setError] = useState<string | null>(null)
+
+  // Dispute creation
+  const [showDisputeForm, setShowDisputeForm] = useState(false)
+  const [disputeReason, setDisputeReason] = useState('')
+  const [isCreatingDispute, setIsCreatingDispute] = useState(false)
+
+  // Comment
+  const [commentText, setCommentText] = useState('')
+  const [isAddingComment, setIsAddingComment] = useState(false)
+
+  // Voting
+  const [isVoting, setIsVoting] = useState(false)
+
+  useEffect(() => {
+    loadAssignment()
+  }, [id])
+
+  const loadAssignment = async () => {
+    if (!id) return
+    setIsLoading(true)
+    setError(null)
+    try {
+      const data = await assignmentsApi.getDetail(parseInt(id))
+      setAssignment(data)
+    } catch (err: unknown) {
+      const error = err as { response?: { data?: { detail?: string } } }
+      setError(error.response?.data?.detail || 'Не удалось загрузить данные')
+    } finally {
+      setIsLoading(false)
+    }
+  }
+
+  const handleCreateDispute = async () => {
+    if (!id || !disputeReason.trim()) return
+
+    setIsCreatingDispute(true)
+    try {
+      await assignmentsApi.createDispute(parseInt(id), disputeReason)
+      setDisputeReason('')
+      setShowDisputeForm(false)
+      await loadAssignment()
+    } catch (err: unknown) {
+      const error = err as { response?: { data?: { detail?: string } } }
+      alert(error.response?.data?.detail || 'Не удалось создать оспаривание')
+    } finally {
+      setIsCreatingDispute(false)
+    }
+  }
+
+  const handleVote = async (vote: boolean) => {
+    if (!assignment?.dispute) return
+
+    setIsVoting(true)
+    try {
+      await assignmentsApi.vote(assignment.dispute.id, vote)
+      await loadAssignment()
+    } catch (err: unknown) {
+      const error = err as { response?: { data?: { detail?: string } } }
+      alert(error.response?.data?.detail || 'Не удалось проголосовать')
+    } finally {
+      setIsVoting(false)
+    }
+  }
+
+  const handleAddComment = async () => {
+    if (!assignment?.dispute || !commentText.trim()) return
+
+    setIsAddingComment(true)
+    try {
+      await assignmentsApi.addComment(assignment.dispute.id, commentText)
+      setCommentText('')
+      await loadAssignment()
+    } catch (err: unknown) {
+      const error = err as { response?: { data?: { detail?: string } } }
+      alert(error.response?.data?.detail || 'Не удалось добавить комментарий')
+    } finally {
+      setIsAddingComment(false)
+    }
+  }
+
+  const formatDate = (dateString: string) => {
+    return new Date(dateString).toLocaleString('ru-RU', {
+      day: 'numeric',
+      month: 'long',
+      year: 'numeric',
+      hour: '2-digit',
+      minute: '2-digit',
+    })
+  }
+
+  const getTimeRemaining = (expiresAt: string) => {
+    const now = new Date()
+    const expires = new Date(expiresAt)
+    const diff = expires.getTime() - now.getTime()
+
+    if (diff <= 0) return 'Истекло'
+
+    const hours = Math.floor(diff / (1000 * 60 * 60))
+    const minutes = Math.floor((diff % (1000 * 60 * 60)) / (1000 * 60))
+
+    return `${hours}ч ${minutes}м`
+  }
+
+  const getStatusBadge = (status: string) => {
+    switch (status) {
+      case 'completed':
+        return (
+          <span className="px-3 py-1 bg-green-500/20 text-green-400 rounded-full text-sm flex items-center gap-1">
+            <CheckCircle className="w-4 h-4" /> Выполнено
+          </span>
+        )
+      case 'dropped':
+        return (
+          <span className="px-3 py-1 bg-red-500/20 text-red-400 rounded-full text-sm flex items-center gap-1">
+            <XCircle className="w-4 h-4" /> Пропущено
+          </span>
+        )
+      case 'returned':
+        return (
+          <span className="px-3 py-1 bg-orange-500/20 text-orange-400 rounded-full text-sm flex items-center gap-1">
+            <AlertTriangle className="w-4 h-4" /> Возвращено
+          </span>
+        )
+      default:
+        return (
+          <span className="px-3 py-1 bg-blue-500/20 text-blue-400 rounded-full text-sm">
+            Активно
+          </span>
+        )
+    }
+  }
+
+  if (isLoading) {
+    return (
+      <div className="flex justify-center py-12">
+        <Loader2 className="w-8 h-8 animate-spin text-primary-500" />
+      </div>
+    )
+  }
+
+  if (error || !assignment) {
+    return (
+      <div className="max-w-2xl mx-auto text-center py-12">
+        <p className="text-red-400 mb-4">{error || 'Задание не найдено'}</p>
+        <Button onClick={() => navigate(-1)}>Назад</Button>
+      </div>
+    )
+  }
+
+  const dispute = assignment.dispute
+
+  return (
+    <div className="max-w-2xl mx-auto">
+      {/* Header */}
+      <div className="flex items-center gap-4 mb-6">
+        <button onClick={() => navigate(-1)} className="text-gray-400 hover:text-white">
+          <ArrowLeft className="w-6 h-6" />
+        </button>
+        <h1 className="text-xl font-bold text-white">Детали выполнения</h1>
+      </div>
+
+      {/* Challenge info */}
+      <Card className="mb-6">
+        <CardContent>
+          <div className="flex items-start justify-between mb-4">
+            <div>
+              <p className="text-gray-400 text-sm">{assignment.challenge.game.title}</p>
+              <h2 className="text-xl font-bold text-white">{assignment.challenge.title}</h2>
+            </div>
+            {getStatusBadge(assignment.status)}
+          </div>
+
+          <p className="text-gray-300 mb-4">{assignment.challenge.description}</p>
+
+          <div className="flex flex-wrap gap-2 mb-4">
+            <span className="px-3 py-1 bg-green-500/20 text-green-400 rounded-full text-sm">
+              +{assignment.challenge.points} очков
+            </span>
+            <span className="px-3 py-1 bg-gray-700 text-gray-300 rounded-full text-sm">
+              {assignment.challenge.difficulty}
+            </span>
+            {assignment.challenge.estimated_time && (
+              <span className="px-3 py-1 bg-gray-700 text-gray-300 rounded-full text-sm">
+                ~{assignment.challenge.estimated_time} мин
+              </span>
+            )}
+          </div>
+
+          <div className="text-sm text-gray-400 space-y-1">
+            <p>
+              <strong>Выполнил:</strong> {assignment.participant.nickname}
+            </p>
+            {assignment.completed_at && (
+              <p>
+                <strong>Дата:</strong> {formatDate(assignment.completed_at)}
+              </p>
+            )}
+            {assignment.points_earned > 0 && (
+              <p>
+                <strong>Получено очков:</strong> {assignment.points_earned}
+              </p>
+            )}
+          </div>
+        </CardContent>
+      </Card>
+
+      {/* Proof section */}
+      <Card className="mb-6">
+        <CardContent>
+          <h3 className="text-lg font-bold text-white mb-4 flex items-center gap-2">
+            <Image className="w-5 h-5" />
+            Доказательство
+          </h3>
+
+          {/* Proof image */}
+          {assignment.proof_image_url && (
+            <div className="mb-4">
+              <img
+                src={`${API_URL}${assignment.proof_image_url}`}
+                alt="Proof"
+                className="w-full rounded-lg max-h-96 object-contain bg-gray-900"
+              />
+            </div>
+          )}
+
+          {/* Proof URL */}
+          {assignment.proof_url && (
+            <div className="mb-4">
+              <a
+                href={assignment.proof_url}
+                target="_blank"
+                rel="noopener noreferrer"
+                className="flex items-center gap-2 text-primary-400 hover:text-primary-300"
+              >
+                <ExternalLink className="w-4 h-4" />
+                {assignment.proof_url}
+              </a>
+            </div>
+          )}
+
+          {/* Proof comment */}
+          {assignment.proof_comment && (
+            <div className="p-3 bg-gray-900 rounded-lg">
+              <p className="text-sm text-gray-400 mb-1">Комментарий:</p>
+              <p className="text-white">{assignment.proof_comment}</p>
+            </div>
+          )}
+
+          {!assignment.proof_image_url && !assignment.proof_url && (
+            <p className="text-gray-500 text-center py-4">Пруф не предоставлен</p>
+          )}
+        </CardContent>
+      </Card>
+
+      {/* Dispute button */}
+      {assignment.can_dispute && !dispute && !showDisputeForm && (
+        <Button
+          variant="danger"
+          className="w-full mb-6"
+          onClick={() => setShowDisputeForm(true)}
+        >
+          <Flag className="w-4 h-4 mr-2" />
+          Оспорить выполнение
+        </Button>
+      )}
+
+      {/* Dispute creation form */}
+      {showDisputeForm && !dispute && (
+        <Card className="mb-6 border-red-500/50">
+          <CardContent>
+            <h3 className="text-lg font-bold text-red-400 mb-4 flex items-center gap-2">
+              <AlertTriangle className="w-5 h-5" />
+              Оспорить выполнение
+            </h3>
+
+            <p className="text-gray-400 text-sm mb-4">
+              Опишите причину оспаривания. После создания у участников будет 24 часа для голосования.
+            </p>
+
+            <textarea
+              className="input w-full min-h-[100px] resize-none mb-4"
+              placeholder="Причина оспаривания (минимум 10 символов)..."
+              value={disputeReason}
+              onChange={(e) => setDisputeReason(e.target.value)}
+            />
+
+            <div className="flex gap-3">
+              <Button
+                variant="danger"
+                className="flex-1"
+                onClick={handleCreateDispute}
+                isLoading={isCreatingDispute}
+                disabled={disputeReason.trim().length < 10}
+              >
+                Оспорить
+              </Button>
+              <Button
+                variant="secondary"
+                onClick={() => {
+                  setShowDisputeForm(false)
+                  setDisputeReason('')
+                }}
+              >
+                Отмена
+              </Button>
+            </div>
+          </CardContent>
+        </Card>
+      )}
+
+      {/* Dispute section */}
+      {dispute && (
+        <Card className={`mb-6 ${dispute.status === 'open' ? 'border-yellow-500/50' : ''}`}>
+          <CardContent>
+            <div className="flex items-start justify-between mb-4">
+              <h3 className="text-lg font-bold text-yellow-400 flex items-center gap-2">
+                <AlertTriangle className="w-5 h-5" />
+                Оспаривание
+              </h3>
+
+              {dispute.status === 'open' ? (
+                <span className="px-3 py-1 bg-yellow-500/20 text-yellow-400 rounded-full text-sm flex items-center gap-1">
+                  <Clock className="w-4 h-4" />
+                  {getTimeRemaining(dispute.expires_at)}
+                </span>
+              ) : dispute.status === 'valid' ? (
+                <span className="px-3 py-1 bg-green-500/20 text-green-400 rounded-full text-sm flex items-center gap-1">
+                  <CheckCircle className="w-4 h-4" />
+                  Пруф валиден
+                </span>
+              ) : (
+                <span className="px-3 py-1 bg-red-500/20 text-red-400 rounded-full text-sm flex items-center gap-1">
+                  <XCircle className="w-4 h-4" />
+                  Пруф невалиден
+                </span>
+              )}
+            </div>
+
+            <div className="mb-4">
+              <p className="text-sm text-gray-400">
+                Открыл: <span className="text-white">{dispute.raised_by.nickname}</span>
+              </p>
+              <p className="text-sm text-gray-400">
+                Дата: <span className="text-white">{formatDate(dispute.created_at)}</span>
+              </p>
+            </div>
+
+            <div className="p-3 bg-gray-900 rounded-lg mb-4">
+              <p className="text-sm text-gray-400 mb-1">Причина:</p>
+              <p className="text-white">{dispute.reason}</p>
+            </div>
+
+            {/* Voting section */}
+            {dispute.status === 'open' && (
+              <div className="mb-4">
+                <h4 className="text-sm font-medium text-gray-300 mb-3">Голосование</h4>
+
+                <div className="flex items-center gap-4 mb-3">
+                  <div className="flex items-center gap-2">
+                    <ThumbsUp className="w-5 h-5 text-green-500" />
+                    <span className="text-green-400 font-medium">{dispute.votes_valid}</span>
+                    <span className="text-gray-500 text-sm">валидно</span>
+                  </div>
+                  <div className="flex items-center gap-2">
+                    <ThumbsDown className="w-5 h-5 text-red-500" />
+                    <span className="text-red-400 font-medium">{dispute.votes_invalid}</span>
+                    <span className="text-gray-500 text-sm">невалидно</span>
+                  </div>
+                </div>
+
+                <div className="flex gap-3">
+                  <Button
+                    variant={dispute.my_vote === true ? 'primary' : 'secondary'}
+                    className="flex-1"
+                    onClick={() => handleVote(true)}
+                    isLoading={isVoting}
+                    disabled={isVoting}
+                  >
+                    <ThumbsUp className="w-4 h-4 mr-2" />
+                    Валидно
+                  </Button>
+                  <Button
+                    variant={dispute.my_vote === false ? 'danger' : 'secondary'}
+                    className="flex-1"
+                    onClick={() => handleVote(false)}
+                    isLoading={isVoting}
+                    disabled={isVoting}
+                  >
+                    <ThumbsDown className="w-4 h-4 mr-2" />
+                    Невалидно
+                  </Button>
+                </div>
+
+                {dispute.my_vote !== null && (
+                  <p className="text-sm text-gray-500 mt-2 text-center">
+                    Вы проголосовали: {dispute.my_vote ? 'валидно' : 'невалидно'}
+                  </p>
+                )}
+              </div>
+            )}
+
+            {/* Comments section */}
+            <div>
+              <h4 className="text-sm font-medium text-gray-300 mb-3 flex items-center gap-2">
+                <MessageSquare className="w-4 h-4" />
+                Обсуждение ({dispute.comments.length})
+              </h4>
+
+              {dispute.comments.length > 0 && (
+                <div className="space-y-3 mb-4 max-h-60 overflow-y-auto">
+                  {dispute.comments.map((comment) => (
+                    <div key={comment.id} className="p-3 bg-gray-900 rounded-lg">
+                      <div className="flex items-center justify-between mb-1">
+                        <span className={`font-medium ${comment.user.id === user?.id ? 'text-primary-400' : 'text-white'}`}>
+                          {comment.user.nickname}
+                          {comment.user.id === user?.id && ' (Вы)'}
+                        </span>
+                        <span className="text-xs text-gray-500">
+                          {formatDate(comment.created_at)}
+                        </span>
+                      </div>
+                      <p className="text-gray-300 text-sm">{comment.text}</p>
+                    </div>
+                  ))}
+                </div>
+              )}
+
+              {/* Add comment form */}
+              {dispute.status === 'open' && (
+                <div className="flex gap-2">
+                  <input
+                    type="text"
+                    className="input flex-1"
+                    placeholder="Написать комментарий..."
+                    value={commentText}
+                    onChange={(e) => setCommentText(e.target.value)}
+                    onKeyDown={(e) => {
+                      if (e.key === 'Enter' && !e.shiftKey) {
+                        e.preventDefault()
+                        handleAddComment()
+                      }
+                    }}
+                  />
+                  <Button
+                    onClick={handleAddComment}
+                    isLoading={isAddingComment}
+                    disabled={!commentText.trim()}
+                  >
+                    <Send className="w-4 h-4" />
+                  </Button>
+                </div>
+              )}
+            </div>
+          </CardContent>
+        </Card>
+      )}
+    </div>
+  )
+}

frontend/src/pages/PlayPage.tsx

@@ -1,11 +1,11 @@
 import { useState, useEffect, useRef } from 'react'
 import { useParams, Link } from 'react-router-dom'
-import { marathonsApi, wheelApi, gamesApi, eventsApi } from '@/api'
+import { marathonsApi, wheelApi, gamesApi, eventsApi, assignmentsApi } from '@/api'
-import type { Marathon, Assignment, SpinResult, Game, ActiveEvent, SwapCandidate, MySwapRequests, CommonEnemyLeaderboardEntry, EventAssignment, GameChoiceChallenges } from '@/types'
+import type { Marathon, Assignment, SpinResult, Game, ActiveEvent, SwapCandidate, MySwapRequests, CommonEnemyLeaderboardEntry, EventAssignment, GameChoiceChallenges, ReturnedAssignment } from '@/types'
 import { Button, Card, CardContent } from '@/components/ui'
 import { SpinWheel } from '@/components/SpinWheel'
 import { EventBanner } from '@/components/EventBanner'
-import { Loader2, Upload, X, Gamepad2, ArrowLeftRight, Check, XCircle, Clock, Send, Trophy, Users, ArrowLeft } from 'lucide-react'
+import { Loader2, Upload, X, Gamepad2, ArrowLeftRight, Check, XCircle, Clock, Send, Trophy, Users, ArrowLeft, AlertTriangle } from 'lucide-react'
 
 export function PlayPage() {
   const { id } = useParams<{ id: string }>()
@@ -53,6 +53,9 @@ export function PlayPage() {
   const [eventComment, setEventComment] = useState('')
   const [isEventCompleting, setIsEventCompleting] = useState(false)
 
+  // Returned assignments state
+  const [returnedAssignments, setReturnedAssignments] = useState<ReturnedAssignment[]>([])
+
   const fileInputRef = useRef<HTMLInputElement>(null)
   const eventFileInputRef = useRef<HTMLInputElement>(null)
 
@@ -138,18 +141,20 @@ export function PlayPage() {
   const loadData = async () => {
     if (!id) return
     try {
-      const [marathonData, assignment, gamesData, eventData, eventAssignmentData] = await Promise.all([
+      const [marathonData, assignment, gamesData, eventData, eventAssignmentData, returnedData] = await Promise.all([
         marathonsApi.get(parseInt(id)),
         wheelApi.getCurrentAssignment(parseInt(id)),
         gamesApi.list(parseInt(id), 'approved'),
         eventsApi.getActive(parseInt(id)),
         eventsApi.getEventAssignment(parseInt(id)),
+        assignmentsApi.getReturnedAssignments(parseInt(id)),
       ])
       setMarathon(marathonData)
       setCurrentAssignment(assignment)
       setGames(gamesData)
       setActiveEvent(eventData)
       setEventAssignment(eventAssignmentData)
+      setReturnedAssignments(returnedData)
     } catch (error) {
       console.error('Failed to load data:', error)
     } finally {
@@ -427,6 +432,45 @@ export function PlayPage() {
         </div>
       )}
 
+      {/* Returned assignments warning */}
+      {returnedAssignments.length > 0 && (
+        <Card className="mb-6 border-orange-500/50">
+          <CardContent>
+            <div className="flex items-center gap-2 mb-3">
+              <AlertTriangle className="w-5 h-5 text-orange-500" />
+              <h3 className="text-lg font-bold text-orange-400">Возвращённые задания</h3>
+              <span className="ml-auto px-2 py-0.5 bg-orange-500/20 text-orange-400 text-sm rounded">
+                {returnedAssignments.length}
+              </span>
+            </div>
+            <p className="text-gray-400 text-sm mb-4">
+              Эти задания были оспорены. После текущего задания вам нужно будет их переделать.
+            </p>
+            <div className="space-y-2">
+              {returnedAssignments.map((ra) => (
+                <div
+                  key={ra.id}
+                  className="p-3 bg-orange-500/10 border border-orange-500/20 rounded-lg"
+                >
+                  <div className="flex items-start justify-between">
+                    <div>
+                      <p className="text-white font-medium">{ra.challenge.title}</p>
+                      <p className="text-gray-400 text-sm">{ra.challenge.game.title}</p>
+                    </div>
+                    <span className="px-2 py-0.5 bg-green-500/20 text-green-400 text-xs rounded">
+                      +{ra.challenge.points}
+                    </span>
+                  </div>
+                  <p className="text-orange-300 text-xs mt-2">
+                    Причина: {ra.dispute_reason}
+                  </p>
+                </div>
+              ))}
+            </div>
+          </CardContent>
+        </Card>
+      )}
+
       {/* Tabs for Common Enemy event */}
       {activeEvent?.event?.type === 'common_enemy' && (
         <div className="flex gap-2 mb-6">

frontend/src/types/index.ts

@@ -158,7 +158,7 @@ export interface ChallengesPreviewResponse {
 }
 
 // Assignment types
-export type AssignmentStatus = 'active' | 'completed' | 'dropped'
+export type AssignmentStatus = 'active' | 'completed' | 'dropped' | 'returned'
 
 export interface Assignment {
   id: number
@@ -404,3 +404,57 @@ export interface PlatformStats {
   games_count: number
   total_participations: number
 }
+
+// Dispute types
+export type DisputeStatus = 'open' | 'valid' | 'invalid'
+
+export interface DisputeComment {
+  id: number
+  user: User
+  text: string
+  created_at: string
+}
+
+export interface DisputeVote {
+  user: User
+  vote: boolean // true = valid, false = invalid
+  created_at: string
+}
+
+export interface Dispute {
+  id: number
+  raised_by: User
+  reason: string
+  status: DisputeStatus
+  comments: DisputeComment[]
+  votes: DisputeVote[]
+  votes_valid: number
+  votes_invalid: number
+  my_vote: boolean | null
+  expires_at: string
+  created_at: string
+  resolved_at: string | null
+}
+
+export interface AssignmentDetail {
+  id: number
+  challenge: Challenge
+  participant: User
+  status: AssignmentStatus
+  proof_url: string | null
+  proof_image_url: string | null
+  proof_comment: string | null
+  points_earned: number
+  streak_at_completion: number | null
+  started_at: string
+  completed_at: string | null
+  can_dispute: boolean
+  dispute: Dispute | null
+}
+
+export interface ReturnedAssignment {
+  id: number
+  challenge: Challenge
+  original_completed_at: string
+  dispute_reason: string
+}