"""
Top List endpoints for API v1.

Provides CRUD operations for user-created ranked lists.
Users can create lists of parks, rides, or coasters with custom rankings and notes.
"""
from typing import List, Optional
from uuid import UUID
from django.shortcuts import get_object_or_404
from django.db.models import Q, Max
from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import ValidationError
from django.db import transaction
from ninja import Router, Query
from ninja.pagination import paginate, PageNumberPagination
import logging

from apps.users.models import UserTopList, UserTopListItem, User
from apps.entities.models import Park, Ride
from apps.users.permissions import jwt_auth, require_auth
from ..schemas import (
    TopListCreateSchema,
    TopListUpdateSchema,
    TopListItemCreateSchema,
    TopListItemUpdateSchema,
    TopListOut,
    TopListDetailOut,
    TopListListOut,
    TopListItemOut,
    ErrorResponse,
    UserSchema,
)

router = Router(tags=["Top Lists"])
logger = logging.getLogger(__name__)


class TopListPagination(PageNumberPagination):
    """Custom pagination for top lists."""
    page_size = 50


def _get_entity(entity_type: str, entity_id: UUID):
    """Helper to get and validate entity (Park or Ride)."""
    if entity_type == 'park':
        return get_object_or_404(Park, id=entity_id), ContentType.objects.get_for_model(Park)
    elif entity_type == 'ride':
        return get_object_or_404(Ride, id=entity_id), ContentType.objects.get_for_model(Ride)
    else:
        raise ValidationError(f"Invalid entity_type: {entity_type}")


def _serialize_list_item(item: UserTopListItem) -> dict:
    """Serialize top list item with computed fields."""
    entity = item.content_object
    
    data = {
        'id': item.id,
        'position': item.position,
        'entity_type': item.content_type.model,
        'entity_id': str(item.object_id),
        'entity_name': entity.name if entity else 'Unknown',
        'entity_slug': entity.slug if entity and hasattr(entity, 'slug') else '',
        'entity_image_url': None,  # TODO: Get from entity
        'park_name': None,
        'notes': item.notes or '',
        'created': item.created,
        'modified': item.modified,
    }
    
    # If entity is a ride, add park name
    if item.content_type.model == 'ride' and entity and hasattr(entity, 'park'):
        data['park_name'] = entity.park.name if entity.park else None
    
    return data


def _serialize_top_list(top_list: UserTopList, include_items: bool = False) -> dict:
    """Serialize top list with optional items."""
    data = {
        'id': top_list.id,
        'user': UserSchema(
            id=top_list.user.id,
            username=top_list.user.username,
            display_name=top_list.user.display_name,
            avatar_url=top_list.user.avatar_url,
            reputation_score=top_list.user.reputation_score,
        ),
        'list_type': top_list.list_type,
        'title': top_list.title,
        'description': top_list.description or '',
        'is_public': top_list.is_public,
        'item_count': top_list.item_count,
        'created': top_list.created,
        'modified': top_list.modified,
    }
    
    if include_items:
        items = top_list.items.select_related('content_type').order_by('position')
        data['items'] = [_serialize_list_item(item) for item in items]
    
    return data


# ============================================================================
# Main Top List CRUD Endpoints
# ============================================================================

@router.post("/", response={201: TopListOut, 400: ErrorResponse}, auth=jwt_auth)
@require_auth
def create_top_list(request, data: TopListCreateSchema):
    """
    Create a new top list.
    
    **Authentication:** Required
    
    **Parameters:**
    - list_type: "parks", "rides", or "coasters"
    - title: List title
    - description: List description (optional)
    - is_public: Whether list is publicly visible (default: true)
    
    **Returns:** Created top list
    """
    try:
        user = request.auth
        
        # Create list
        top_list = UserTopList.objects.create(
            user=user,
            list_type=data.list_type,
            title=data.title,
            description=data.description or '',
            is_public=data.is_public,
        )
        
        logger.info(f"Top list created: {top_list.id} by {user.email}")
        
        list_data = _serialize_top_list(top_list)
        return 201, list_data
        
    except Exception as e:
        logger.error(f"Error creating top list: {e}")
        return 400, {'detail': str(e)}


@router.get("/", response={200: List[TopListOut]})
@paginate(TopListPagination)
def list_top_lists(
    request,
    list_type: Optional[str] = Query(None, description="Filter by list type"),
    user_id: Optional[UUID] = Query(None, description="Filter by user ID"),
    ordering: Optional[str] = Query("-created", description="Sort by field")
):
    """
    List accessible top lists.
    
    **Authentication:** Optional
    
    **Filters:**
    - list_type: parks, rides, or coasters
    - user_id: Lists by specific user
    - ordering: Sort field (default: -created)
    
    **Returns:** Paginated list of top lists
    
    **Note:** Shows public lists + user's own private lists if authenticated.
    """
    user = request.auth if hasattr(request, 'auth') else None
    
    # Base query
    queryset = UserTopList.objects.select_related('user')
    
    # Apply visibility filter
    if user:
        # Show public lists + user's own lists
        queryset = queryset.filter(Q(is_public=True) | Q(user=user))
    else:
        # Only public lists
        queryset = queryset.filter(is_public=True)
    
    # Apply list type filter
    if list_type:
        queryset = queryset.filter(list_type=list_type)
    
    # Apply user filter
    if user_id:
        queryset = queryset.filter(user_id=user_id)
    
    # Apply ordering
    valid_order_fields = ['created', 'modified', 'title']
    order_field = ordering.lstrip('-')
    if order_field in valid_order_fields:
        queryset = queryset.order_by(ordering)
    else:
        queryset = queryset.order_by('-created')
    
    # Serialize lists
    lists = [_serialize_top_list(tl) for tl in queryset]
    return lists


@router.get("/public", response={200: List[TopListOut]})
@paginate(TopListPagination)
def list_public_top_lists(
    request,
    list_type: Optional[str] = Query(None),
    user_id: Optional[UUID] = Query(None),
    ordering: Optional[str] = Query("-created")
):
    """
    List public top lists.
    
    **Authentication:** Optional
    
    **Parameters:**
    - list_type: Filter by type (optional)
    - user_id: Filter by user (optional)
    - ordering: Sort field (default: -created)
    
    **Returns:** Paginated list of public top lists
    """
    queryset = UserTopList.objects.filter(is_public=True).select_related('user')
    
    if list_type:
        queryset = queryset.filter(list_type=list_type)
    
    if user_id:
        queryset = queryset.filter(user_id=user_id)
    
    valid_order_fields = ['created', 'modified', 'title']
    order_field = ordering.lstrip('-')
    if order_field in valid_order_fields:
        queryset = queryset.order_by(ordering)
    else:
        queryset = queryset.order_by('-created')
    
    lists = [_serialize_top_list(tl) for tl in queryset]
    return lists


@router.get("/{list_id}", response={200: TopListDetailOut, 403: ErrorResponse, 404: ErrorResponse})
def get_top_list(request, list_id: UUID):
    """
    Get a specific top list with all items.
    
    **Authentication:** Optional
    
    **Parameters:**
    - list_id: List UUID
    
    **Returns:** Top list with all items
    
    **Note:** Private lists only accessible to owner.
    """
    user = request.auth if hasattr(request, 'auth') else None
    
    top_list = get_object_or_404(
        UserTopList.objects.select_related('user'),
        id=list_id
    )
    
    # Check access
    if not top_list.is_public:
        if not user or top_list.user != user:
            return 403, {'detail': 'This list is private'}
    
    list_data = _serialize_top_list(top_list, include_items=True)
    return 200, list_data


@router.put("/{list_id}", response={200: TopListOut, 403: ErrorResponse, 404: ErrorResponse}, auth=jwt_auth)
@require_auth
def update_top_list(request, list_id: UUID, data: TopListUpdateSchema):
    """
    Update a top list.
    
    **Authentication:** Required (must be list owner)
    
    **Parameters:**
    - list_id: List UUID
    - data: Fields to update
    
    **Returns:** Updated list
    """
    user = request.auth
    
    top_list = get_object_or_404(UserTopList, id=list_id)
    
    # Check ownership
    if top_list.user != user:
        return 403, {'detail': 'You can only update your own lists'}
    
    # Update fields
    update_data = data.dict(exclude_unset=True)
    for key, value in update_data.items():
        setattr(top_list, key, value)
    
    top_list.save()
    
    logger.info(f"Top list updated: {top_list.id} by {user.email}")
    
    list_data = _serialize_top_list(top_list)
    return 200, list_data


@router.delete("/{list_id}", response={204: None, 403: ErrorResponse, 404: ErrorResponse}, auth=jwt_auth)
@require_auth
def delete_top_list(request, list_id: UUID):
    """
    Delete a top list.
    
    **Authentication:** Required (must be list owner)
    
    **Parameters:**
    - list_id: List UUID
    
    **Returns:** No content (204)
    
    **Note:** This also deletes all items in the list.
    """
    user = request.auth
    
    top_list = get_object_or_404(UserTopList, id=list_id)
    
    # Check ownership
    if top_list.user != user:
        return 403, {'detail': 'You can only delete your own lists'}
    
    logger.info(f"Top list deleted: {top_list.id} by {user.email}")
    top_list.delete()
    
    return 204, None


# ============================================================================
# List Item Endpoints
# ============================================================================

@router.post("/{list_id}/items", response={201: TopListItemOut, 400: ErrorResponse, 403: ErrorResponse}, auth=jwt_auth)
@require_auth
def add_list_item(request, list_id: UUID, data: TopListItemCreateSchema):
    """
    Add an item to a top list.
    
    **Authentication:** Required (must be list owner)
    
    **Parameters:**
    - list_id: List UUID
    - entity_type: "park" or "ride"
    - entity_id: Entity UUID
    - position: Position in list (optional, auto-assigned if not provided)
    - notes: Notes about this item (optional)
    
    **Returns:** Created list item
    """
    try:
        user = request.auth
        
        top_list = get_object_or_404(UserTopList, id=list_id)
        
        # Check ownership
        if top_list.user != user:
            return 403, {'detail': 'You can only modify your own lists'}
        
        # Validate entity
        entity, content_type = _get_entity(data.entity_type, data.entity_id)
        
        # Validate entity type matches list type
        if top_list.list_type == 'parks' and data.entity_type != 'park':
            return 400, {'detail': 'Can only add parks to a parks list'}
        elif top_list.list_type in ['rides', 'coasters']:
            if data.entity_type != 'ride':
                return 400, {'detail': f'Can only add rides to a {top_list.list_type} list'}
            if top_list.list_type == 'coasters' and not entity.is_coaster:
                return 400, {'detail': 'Can only add coasters to a coasters list'}
        
        # Determine position
        if data.position is None:
            # Auto-assign position (append to end)
            max_pos = top_list.items.aggregate(max_pos=Max('position'))['max_pos']
            position = (max_pos or 0) + 1
        else:
            position = data.position
            # Check if position is taken
            if top_list.items.filter(position=position).exists():
                return 400, {'detail': f'Position {position} is already taken'}
        
        # Create item
        with transaction.atomic():
            item = UserTopListItem.objects.create(
                top_list=top_list,
                content_type=content_type,
                object_id=entity.id,
                position=position,
                notes=data.notes or '',
            )
        
        logger.info(f"List item added: {item.id} to list {list_id}")
        
        item_data = _serialize_list_item(item)
        return 201, item_data
        
    except ValidationError as e:
        return 400, {'detail': str(e)}
    except Exception as e:
        logger.error(f"Error adding list item: {e}")
        return 400, {'detail': str(e)}


@router.put("/{list_id}/items/{position}", response={200: TopListItemOut, 400: ErrorResponse, 403: ErrorResponse, 404: ErrorResponse}, auth=jwt_auth)
@require_auth
def update_list_item(request, list_id: UUID, position: int, data: TopListItemUpdateSchema):
    """
    Update a list item.
    
    **Authentication:** Required (must be list owner)
    
    **Parameters:**
    - list_id: List UUID
    - position: Current position
    - data: Fields to update (position, notes)
    
    **Returns:** Updated item
    
    **Note:** If changing position, items are reordered automatically.
    """
    try:
        user = request.auth
        
        top_list = get_object_or_404(UserTopList, id=list_id)
        
        # Check ownership
        if top_list.user != user:
            return 403, {'detail': 'You can only modify your own lists'}
        
        # Get item
        item = get_object_or_404(
            UserTopListItem.objects.select_related('content_type'),
            top_list=top_list,
            position=position
        )
        
        with transaction.atomic():
            # Handle position change
            if data.position is not None and data.position != position:
                new_position = data.position
                
                # Check if new position exists
                target_item = top_list.items.filter(position=new_position).first()
                
                if target_item:
                    # Swap positions
                    target_item.position = position
                    target_item.save()
                
                item.position = new_position
            
            # Update notes if provided
            if data.notes is not None:
                item.notes = data.notes
            
            item.save()
        
        logger.info(f"List item updated: {item.id}")
        
        item_data = _serialize_list_item(item)
        return 200, item_data
        
    except Exception as e:
        logger.error(f"Error updating list item: {e}")
        return 400, {'detail': str(e)}


@router.delete("/{list_id}/items/{position}", response={204: None, 403: ErrorResponse, 404: ErrorResponse}, auth=jwt_auth)
@require_auth
def delete_list_item(request, list_id: UUID, position: int):
    """
    Remove an item from a list.
    
    **Authentication:** Required (must be list owner)
    
    **Parameters:**
    - list_id: List UUID
    - position: Position of item to remove
    
    **Returns:** No content (204)
    
    **Note:** Remaining items are automatically reordered.
    """
    user = request.auth
    
    top_list = get_object_or_404(UserTopList, id=list_id)
    
    # Check ownership
    if top_list.user != user:
        return 403, {'detail': 'You can only modify your own lists'}
    
    # Get item
    item = get_object_or_404(
        UserTopListItem,
        top_list=top_list,
        position=position
    )
    
    with transaction.atomic():
        # Delete item
        item.delete()
        
        # Reorder remaining items
        items_to_reorder = top_list.items.filter(position__gt=position).order_by('position')
        for i, remaining_item in enumerate(items_to_reorder, start=position):
            remaining_item.position = i
            remaining_item.save()
    
    logger.info(f"List item deleted from list {list_id} at position {position}")
    
    return 204, None


# ============================================================================
# User-Specific Endpoints
# ============================================================================

@router.get("/users/{user_id}", response={200: List[TopListOut], 403: ErrorResponse})
@paginate(TopListPagination)
def get_user_top_lists(
    request,
    user_id: UUID,
    list_type: Optional[str] = Query(None),
    ordering: Optional[str] = Query("-created")
):
    """
    Get a user's top lists.
    
    **Authentication:** Optional
    
    **Parameters:**
    - user_id: User UUID
    - list_type: Filter by type (optional)
    - ordering: Sort field (default: -created)
    
    **Returns:** Paginated list of user's top lists
    
    **Note:** Only public lists visible unless viewing own lists.
    """
    target_user = get_object_or_404(User, id=user_id)
    
    # Check if current user
    current_user = request.auth if hasattr(request, 'auth') else None
    is_owner = current_user and current_user.id == target_user.id
    
    # Build query
    queryset = UserTopList.objects.filter(user=target_user).select_related('user')
    
    # Apply visibility filter
    if not is_owner:
        queryset = queryset.filter(is_public=True)
    
    # Apply list type filter
    if list_type:
        queryset = queryset.filter(list_type=list_type)
    
    # Apply ordering
    valid_order_fields = ['created', 'modified', 'title']
    order_field = ordering.lstrip('-')
    if order_field in valid_order_fields:
        queryset = queryset.order_by(ordering)
    else:
        queryset = queryset.order_by('-created')
    
    # Serialize lists
    lists = [_serialize_top_list(tl) for tl in queryset]
    return lists