from uuid import UUID
from typing import Optional
from datetime import datetime, timezone
from decimal import Decimal
from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy import select, or_, and_, func, desc, Integer, case
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.database import get_db
from app.api.deps import get_current_active_user, require_engineer_or_admin
from app.core.permissions import can_view_step, can_edit_step
from app.models.user import User
from app.models.step_library import StepLibrary, StepRating
from app.models.step_category import StepCategory
from app.schemas.step_library import (
    StepLibraryCreate,
    StepLibraryUpdate,
    StepLibraryResponse,
    StepLibraryListResponse,
    StepRatingCreate,
    StepRatingUpdate,
    StepRatingResponse,
    PopularTagResponse,
)

router = APIRouter(prefix="/steps", tags=["steps"])


async def get_step_or_404(
    step_id: UUID,
    db: AsyncSession,
    current_user: User,
    check_view: bool = True,
    check_edit: bool = False
) -> StepLibrary:
    """Get step by ID with permission checks."""
    result = await db.execute(
        select(StepLibrary).where(
            StepLibrary.id == step_id,
            StepLibrary.is_active == True
        )
    )
    step = result.scalar_one_or_none()
    if not step:
        raise HTTPException(status_code=404, detail="Step not found")

    if check_view and not can_view_step(current_user, step):
        raise HTTPException(status_code=403, detail="Not authorized to view this step")

    if check_edit and not can_edit_step(current_user, step):
        raise HTTPException(status_code=403, detail="Not authorized to modify this step")

    return step


def build_visibility_filter(user: User):
    """Build SQLAlchemy filter for step visibility based on user."""
    if user.team_id:
        return or_(
            StepLibrary.visibility == 'public',
            and_(StepLibrary.visibility == 'team', StepLibrary.team_id == user.team_id),
            StepLibrary.created_by == user.id  # Own private steps
        )
    else:
        return or_(
            StepLibrary.visibility == 'public',
            StepLibrary.created_by == user.id
        )


@router.get("", response_model=list[StepLibraryListResponse])
async def list_steps(
    visibility: Optional[str] = Query(None, regex="^(private|team|public)$"),
    category_id: Optional[UUID] = None,
    tags: Optional[list[str]] = Query(None),
    min_rating: Optional[float] = Query(None, ge=0, le=5),
    step_type: Optional[str] = Query(None, regex="^(decision|action|solution)$"),
    sort_by: str = Query("recent", regex="^(recent|popular|highest_rated|most_used)$"),
    limit: int = Query(20, ge=1, le=100),
    offset: int = Query(0, ge=0),
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """List steps with filters and pagination."""
    query = select(StepLibrary).where(
        StepLibrary.is_active == True,
        build_visibility_filter(current_user)
    )

    # Apply filters
    if visibility:
        query = query.where(StepLibrary.visibility == visibility)
    if category_id:
        query = query.where(StepLibrary.category_id == category_id)
    if tags:
        # Match any of the provided tags
        query = query.where(StepLibrary.tags.overlap(tags))
    if min_rating is not None:
        query = query.where(StepLibrary.rating_average >= Decimal(str(min_rating)))
    if step_type:
        query = query.where(StepLibrary.step_type == step_type)

    # Apply sorting
    if sort_by == "recent":
        query = query.order_by(desc(StepLibrary.created_at))
    elif sort_by == "popular" or sort_by == "most_used":
        query = query.order_by(desc(StepLibrary.usage_count))
    elif sort_by == "highest_rated":
        query = query.order_by(desc(StepLibrary.rating_average), desc(StepLibrary.rating_count))

    # Apply pagination
    query = query.offset(offset).limit(limit)

    result = await db.execute(query)
    steps = result.scalars().all()

    # Fetch category names and author names
    response = []
    for step in steps:
        step_dict = {
            "id": step.id,
            "title": step.title,
            "step_type": step.step_type,
            "visibility": step.visibility,
            "category_id": step.category_id,
            "tags": step.tags,
            "usage_count": step.usage_count,
            "rating_average": step.rating_average,
            "rating_count": step.rating_count,
            "is_featured": step.is_featured,
            "created_by": step.created_by,
            "created_at": step.created_at,
        }

        # Get category name if exists
        if step.category_id:
            cat_result = await db.execute(
                select(StepCategory.name).where(StepCategory.id == step.category_id)
            )
            cat_name = cat_result.scalar_one_or_none()
            step_dict["category_name"] = cat_name

        # Get author name
        author_result = await db.execute(
            select(User.name).where(User.id == step.created_by)
        )
        author_name = author_result.scalar_one_or_none()
        step_dict["author_name"] = author_name

        response.append(StepLibraryListResponse(**step_dict))

    return response


@router.get("/search", response_model=list[StepLibraryListResponse])
async def search_steps(
    q: str = Query(..., min_length=1),
    limit: int = Query(20, ge=1, le=100),
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Full-text search for steps."""
    # Use PostgreSQL full-text search
    search_query = func.to_tsquery('english', q.replace(' ', ' & '))

    query = select(StepLibrary).where(
        StepLibrary.is_active == True,
        build_visibility_filter(current_user),
        func.to_tsvector('english', StepLibrary.title).match(search_query)
    ).order_by(desc(StepLibrary.rating_average)).limit(limit)

    result = await db.execute(query)
    steps = result.scalars().all()

    response = []
    for step in steps:
        step_dict = {
            "id": step.id,
            "title": step.title,
            "step_type": step.step_type,
            "visibility": step.visibility,
            "category_id": step.category_id,
            "tags": step.tags,
            "usage_count": step.usage_count,
            "rating_average": step.rating_average,
            "rating_count": step.rating_count,
            "is_featured": step.is_featured,
            "created_by": step.created_by,
            "created_at": step.created_at,
        }

        if step.category_id:
            cat_result = await db.execute(
                select(StepCategory.name).where(StepCategory.id == step.category_id)
            )
            step_dict["category_name"] = cat_result.scalar_one_or_none()

        author_result = await db.execute(
            select(User.name).where(User.id == step.created_by)
        )
        step_dict["author_name"] = author_result.scalar_one_or_none()

        response.append(StepLibraryListResponse(**step_dict))

    return response


@router.get("/tags/popular", response_model=list[PopularTagResponse])
async def get_popular_tags(
    limit: int = Query(20, ge=1, le=50),
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Get popular tags with usage counts."""
    # Use unnest to expand arrays and count occurrences
    query = select(
        func.unnest(StepLibrary.tags).label('tag'),
        func.count().label('count')
    ).where(
        StepLibrary.is_active == True,
        build_visibility_filter(current_user)
    ).group_by(
        func.unnest(StepLibrary.tags)
    ).order_by(
        desc(func.count())
    ).limit(limit)

    result = await db.execute(query)
    tags = result.all()

    return [PopularTagResponse(tag=row.tag, count=row.count) for row in tags]


@router.get("/{step_id}", response_model=StepLibraryResponse)
async def get_step(
    step_id: UUID,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Get a step by ID."""
    step = await get_step_or_404(step_id, db, current_user, check_view=True)

    response_dict = {
        "id": step.id,
        "title": step.title,
        "step_type": step.step_type,
        "content": step.content,
        "category_id": step.category_id,
        "tags": step.tags,
        "visibility": step.visibility,
        "created_by": step.created_by,
        "team_id": step.team_id,
        "usage_count": step.usage_count,
        "rating_average": step.rating_average,
        "rating_count": step.rating_count,
        "helpful_yes": step.helpful_yes,
        "helpful_no": step.helpful_no,
        "is_featured": step.is_featured,
        "is_verified": step.is_verified,
        "is_active": step.is_active,
        "created_at": step.created_at,
        "updated_at": step.updated_at,
    }

    # Get category name if exists
    if step.category_id:
        cat_result = await db.execute(
            select(StepCategory.name).where(StepCategory.id == step.category_id)
        )
        response_dict["category_name"] = cat_result.scalar_one_or_none()

    # Get author name
    author_result = await db.execute(
        select(User.name).where(User.id == step.created_by)
    )
    response_dict["author_name"] = author_result.scalar_one_or_none()

    return StepLibraryResponse(**response_dict)


@router.post("", response_model=StepLibraryResponse, status_code=201)
async def create_step(
    step_data: StepLibraryCreate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(require_engineer_or_admin)
):
    """Create a new step (engineers and admins only, not viewers)."""
    # Validate category if provided
    if step_data.category_id:
        cat_result = await db.execute(
            select(StepCategory).where(
                StepCategory.id == step_data.category_id,
                StepCategory.is_active == True
            )
        )
        if not cat_result.scalar_one_or_none():
            raise HTTPException(status_code=400, detail="Invalid category")

    # Team validation: can only set team_id to own team
    team_id = step_data.team_id
    if team_id and team_id != current_user.team_id and not current_user.is_super_admin:
        raise HTTPException(status_code=403, detail="Cannot create step for another team")

    step = StepLibrary(
        title=step_data.title,
        step_type=step_data.step_type,
        content=step_data.content.model_dump(),
        category_id=step_data.category_id,
        tags=step_data.tags,
        visibility=step_data.visibility,
        created_by=current_user.id,
        team_id=team_id or current_user.team_id,
    )

    db.add(step)
    await db.commit()
    await db.refresh(step)

    # Build response
    response_dict = {
        "id": step.id,
        "title": step.title,
        "step_type": step.step_type,
        "content": step.content,
        "category_id": step.category_id,
        "tags": step.tags,
        "visibility": step.visibility,
        "created_by": step.created_by,
        "team_id": step.team_id,
        "usage_count": step.usage_count,
        "rating_average": step.rating_average,
        "rating_count": step.rating_count,
        "helpful_yes": step.helpful_yes,
        "helpful_no": step.helpful_no,
        "is_featured": step.is_featured,
        "is_verified": step.is_verified,
        "is_active": step.is_active,
        "created_at": step.created_at,
        "updated_at": step.updated_at,
        "author_name": current_user.name,
    }

    if step.category_id:
        cat_result = await db.execute(
            select(StepCategory.name).where(StepCategory.id == step.category_id)
        )
        response_dict["category_name"] = cat_result.scalar_one_or_none()

    return StepLibraryResponse(**response_dict)


@router.put("/{step_id}", response_model=StepLibraryResponse)
async def update_step(
    step_id: UUID,
    step_data: StepLibraryUpdate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Update a step (owner or admin only)."""
    step = await get_step_or_404(step_id, db, current_user, check_edit=True)

    # Validate category if being updated
    if step_data.category_id:
        cat_result = await db.execute(
            select(StepCategory).where(
                StepCategory.id == step_data.category_id,
                StepCategory.is_active == True
            )
        )
        if not cat_result.scalar_one_or_none():
            raise HTTPException(status_code=400, detail="Invalid category")

    # Apply updates
    update_data = step_data.model_dump(exclude_unset=True)
    if 'content' in update_data and update_data['content']:
        update_data['content'] = update_data['content'].model_dump() if hasattr(update_data['content'], 'model_dump') else update_data['content']

    for field, value in update_data.items():
        setattr(step, field, value)

    step.updated_at = datetime.now(timezone.utc)

    await db.commit()
    await db.refresh(step)

    # Build response
    response_dict = {
        "id": step.id,
        "title": step.title,
        "step_type": step.step_type,
        "content": step.content,
        "category_id": step.category_id,
        "tags": step.tags,
        "visibility": step.visibility,
        "created_by": step.created_by,
        "team_id": step.team_id,
        "usage_count": step.usage_count,
        "rating_average": step.rating_average,
        "rating_count": step.rating_count,
        "helpful_yes": step.helpful_yes,
        "helpful_no": step.helpful_no,
        "is_featured": step.is_featured,
        "is_verified": step.is_verified,
        "is_active": step.is_active,
        "created_at": step.created_at,
        "updated_at": step.updated_at,
    }

    if step.category_id:
        cat_result = await db.execute(
            select(StepCategory.name).where(StepCategory.id == step.category_id)
        )
        response_dict["category_name"] = cat_result.scalar_one_or_none()

    author_result = await db.execute(
        select(User.name).where(User.id == step.created_by)
    )
    response_dict["author_name"] = author_result.scalar_one_or_none()

    return StepLibraryResponse(**response_dict)


@router.delete("/{step_id}", status_code=204)
async def delete_step(
    step_id: UUID,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Soft delete a step (owner or admin only)."""
    step = await get_step_or_404(step_id, db, current_user, check_edit=True)

    step.is_active = False
    step.updated_at = datetime.now(timezone.utc)

    await db.commit()
    return None


# Rating endpoints
@router.post("/{step_id}/rate", response_model=StepRatingResponse, status_code=201)
async def rate_step(
    step_id: UUID,
    rating_data: StepRatingCreate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Rate a step (1-5 stars with optional review)."""
    step = await get_step_or_404(step_id, db, current_user, check_view=True)

    # Check if user already rated
    existing = await db.execute(
        select(StepRating).where(
            StepRating.step_id == step_id,
            StepRating.user_id == current_user.id
        )
    )
    if existing.scalar_one_or_none():
        raise HTTPException(status_code=400, detail="You have already rated this step. Use PUT to update.")

    rating = StepRating(
        step_id=step_id,
        user_id=current_user.id,
        rating=rating_data.rating,
        was_helpful=rating_data.was_helpful,
        review_text=rating_data.review_text,
        session_id=rating_data.session_id,
        is_verified_use=rating_data.session_id is not None,
    )

    db.add(rating)

    # Update aggregated ratings on step
    await _update_step_ratings(db, step)

    await db.commit()
    await db.refresh(rating)

    return StepRatingResponse(
        id=rating.id,
        step_id=rating.step_id,
        user_id=rating.user_id,
        rating=rating.rating,
        was_helpful=rating.was_helpful,
        review_text=rating.review_text,
        is_verified_use=rating.is_verified_use,
        session_id=rating.session_id,
        is_visible=rating.is_visible,
        created_at=rating.created_at,
        updated_at=rating.updated_at,
        user_name=current_user.name,
    )


@router.put("/{step_id}/rate", response_model=StepRatingResponse)
async def update_rating(
    step_id: UUID,
    rating_data: StepRatingUpdate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Update your rating for a step."""
    step = await get_step_or_404(step_id, db, current_user, check_view=True)

    result = await db.execute(
        select(StepRating).where(
            StepRating.step_id == step_id,
            StepRating.user_id == current_user.id
        )
    )
    rating = result.scalar_one_or_none()
    if not rating:
        raise HTTPException(status_code=404, detail="Rating not found. Use POST to create.")

    update_data = rating_data.model_dump(exclude_unset=True)
    for field, value in update_data.items():
        setattr(rating, field, value)

    rating.updated_at = datetime.now(timezone.utc)

    # Update aggregated ratings on step
    await _update_step_ratings(db, step)

    await db.commit()
    await db.refresh(rating)

    return StepRatingResponse(
        id=rating.id,
        step_id=rating.step_id,
        user_id=rating.user_id,
        rating=rating.rating,
        was_helpful=rating.was_helpful,
        review_text=rating.review_text,
        is_verified_use=rating.is_verified_use,
        session_id=rating.session_id,
        is_visible=rating.is_visible,
        created_at=rating.created_at,
        updated_at=rating.updated_at,
        user_name=current_user.name,
    )


@router.delete("/{step_id}/rate", status_code=204)
async def delete_rating(
    step_id: UUID,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Delete your rating for a step."""
    step = await get_step_or_404(step_id, db, current_user, check_view=True)

    result = await db.execute(
        select(StepRating).where(
            StepRating.step_id == step_id,
            StepRating.user_id == current_user.id
        )
    )
    rating = result.scalar_one_or_none()
    if not rating:
        raise HTTPException(status_code=404, detail="Rating not found")

    await db.delete(rating)

    # Update aggregated ratings on step
    await _update_step_ratings(db, step)

    await db.commit()
    return None


@router.get("/{step_id}/reviews", response_model=list[StepRatingResponse])
async def get_reviews(
    step_id: UUID,
    limit: int = Query(20, ge=1, le=100),
    offset: int = Query(0, ge=0),
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    """Get reviews for a step."""
    await get_step_or_404(step_id, db, current_user, check_view=True)

    result = await db.execute(
        select(StepRating).where(
            StepRating.step_id == step_id,
            StepRating.is_visible == True,
            StepRating.review_text.isnot(None)
        ).order_by(desc(StepRating.created_at)).offset(offset).limit(limit)
    )
    ratings = result.scalars().all()

    response = []
    for rating in ratings:
        user_result = await db.execute(
            select(User.name).where(User.id == rating.user_id)
        )
        user_name = user_result.scalar_one_or_none()

        response.append(StepRatingResponse(
            id=rating.id,
            step_id=rating.step_id,
            user_id=rating.user_id,
            rating=rating.rating,
            was_helpful=rating.was_helpful,
            review_text=rating.review_text,
            is_verified_use=rating.is_verified_use,
            session_id=rating.session_id,
            is_visible=rating.is_visible,
            created_at=rating.created_at,
            updated_at=rating.updated_at,
            user_name=user_name,
        ))

    return response


async def _update_step_ratings(db: AsyncSession, step: StepLibrary):
    """Update aggregated rating fields on a step."""
    # Calculate new aggregates
    result = await db.execute(
        select(
            func.count(StepRating.id),
            func.avg(StepRating.rating),
            func.sum(case((StepRating.was_helpful == True, 1), else_=0)),
            func.sum(case((StepRating.was_helpful == False, 1), else_=0))
        ).where(StepRating.step_id == step.id)
    )
    row = result.one()

    step.rating_count = row[0] or 0
    step.rating_average = Decimal(str(round(row[1] or 0, 2)))
    step.helpful_yes = row[2] or 0
    step.helpful_no = row[3] or 0