"""FastAPI dependencies for Mantimon TCG API.

This module provides dependency injection functions for authentication
and database access in API endpoints.

Usage:
    from app.api.deps import get_current_user, get_db

    @router.get("/me")
    async def get_me(
        user: User = Depends(get_current_user),
        db: AsyncSession = Depends(get_db),
    ):
        return user

Dependencies:
    - get_db: Async database session
    - get_current_user: Authenticated user from JWT (required)
    - get_optional_user: Authenticated user or None
    - get_current_premium_user: User with active premium
"""

from typing import Annotated

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from sqlalchemy.ext.asyncio import AsyncSession

from app.db import get_session
from app.db.models import User
from app.services.jwt_service import verify_access_token
from app.services.user_service import user_service

# OAuth2 scheme for extracting Bearer token from Authorization header
# tokenUrl is for OpenAPI docs - points to where tokens are obtained
oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="/api/auth/token",  # For OpenAPI docs
    auto_error=True,  # Raise 401 if no token
)

oauth2_scheme_optional = OAuth2PasswordBearer(
    tokenUrl="/api/auth/token",
    auto_error=False,  # Return None if no token
)


async def get_db() -> AsyncSession:
    """Get async database session.

    Yields:
        AsyncSession for database operations.

    Example:
        @router.get("/items")
        async def get_items(db: AsyncSession = Depends(get_db)):
            ...
    """
    async with get_session() as session:
        yield session


async def get_current_user(
    token: Annotated[str, Depends(oauth2_scheme)],
    db: Annotated[AsyncSession, Depends(get_db)],
) -> User:
    """Get the current authenticated user from JWT token.

    Validates the access token and fetches the user from database.

    Args:
        token: JWT access token from Authorization header.
        db: Database session.

    Returns:
        The authenticated User.

    Raises:
        HTTPException: 401 if token is invalid or user not found.

    Example:
        @router.get("/me")
        async def get_me(user: User = Depends(get_current_user)):
            return {"email": user.email}
    """
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )

    # Verify token and extract user ID
    user_id = verify_access_token(token)
    if user_id is None:
        raise credentials_exception

    # Fetch user from database
    user = await user_service.get_by_id(db, user_id)
    if user is None:
        raise credentials_exception

    return user


async def get_optional_user(
    token: Annotated[str | None, Depends(oauth2_scheme_optional)],
    db: Annotated[AsyncSession, Depends(get_db)],
) -> User | None:
    """Get the current user if authenticated, or None.

    Useful for endpoints that work both with and without authentication,
    but may provide additional features for authenticated users.

    Args:
        token: JWT access token or None.
        db: Database session.

    Returns:
        The authenticated User, or None if not authenticated.

    Example:
        @router.get("/cards")
        async def get_cards(user: User | None = Depends(get_optional_user)):
            if user:
                # Show user's collection
            else:
                # Show public cards
    """
    if token is None:
        return None

    user_id = verify_access_token(token)
    if user_id is None:
        return None

    return await user_service.get_by_id(db, user_id)


async def get_current_premium_user(
    user: Annotated[User, Depends(get_current_user)],
) -> User:
    """Get the current user and verify they have premium.

    Args:
        user: The authenticated user.

    Returns:
        The authenticated User with active premium.

    Raises:
        HTTPException: 403 if user doesn't have active premium.

    Example:
        @router.post("/decks")
        async def create_unlimited_decks(
            user: User = Depends(get_current_premium_user)
        ):
            # Only premium users can have unlimited decks
            ...
    """
    if not user.has_active_premium:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Premium subscription required",
        )
    return user


# Type aliases for cleaner endpoint signatures
CurrentUser = Annotated[User, Depends(get_current_user)]
OptionalUser = Annotated[User | None, Depends(get_optional_user)]
PremiumUser = Annotated[User, Depends(get_current_premium_user)]
DbSession = Annotated[AsyncSession, Depends(get_db)]