from __future__ import annotations

import secrets
from datetime import datetime, timedelta
from typing import Annotated

import jwt
from fastapi import Depends, Header, HTTPException, status
from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
from jwt.exceptions import PyJWTError as JWTError
from passlib.context import CryptContext
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from backend.app.core.database import async_session, get_db
from backend.app.models.api_key import APIKey
from backend.app.models.settings import Settings
from backend.app.models.user import User

# Password hashing
# Use pbkdf2_sha256 instead of bcrypt to avoid 72-byte limit and passlib initialization issues
# pbkdf2_sha256 is a secure password hashing algorithm without bcrypt's limitations
pwd_context = CryptContext(schemes=["pbkdf2_sha256"], deprecated="auto")

# JWT settings
SECRET_KEY = "bambuddy-secret-key-change-in-production"  # TODO: Move to settings/env
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 60 * 24 * 7  # 7 days

# HTTP Bearer token
security = HTTPBearer(auto_error=False)


def verify_password(plain_password: str, hashed_password: str) -> bool:
    """Verify a password against a hash.

    Uses pbkdf2_sha256 which handles long passwords automatically.
    """
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password: str) -> str:
    """Hash a password.

    Uses pbkdf2_sha256 which is secure and has no password length limit.
    """
    return pwd_context.hash(password)


def create_access_token(data: dict, expires_delta: timedelta | None = None) -> str:
    """Create a JWT access token."""
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.utcnow() + expires_delta
    else:
        expire = datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_user_by_username(db: AsyncSession, username: str) -> User | None:
    """Get a user by username."""
    result = await db.execute(select(User).where(User.username == username))
    return result.scalar_one_or_none()


async def authenticate_user(db: AsyncSession, username: str, password: str) -> User | None:
    """Authenticate a user by username and password."""
    user = await get_user_by_username(db, username)
    if not user:
        return None
    if not verify_password(password, user.password_hash):
        return None
    if not user.is_active:
        return None
    return user


async def is_auth_enabled(db: AsyncSession) -> bool:
    """Check if authentication is enabled."""
    try:
        result = await db.execute(select(Settings).where(Settings.key == "auth_enabled"))
        setting = result.scalar_one_or_none()
        if setting is None:
            return False
        return setting.value.lower() == "true"
    except Exception:
        # If settings table doesn't exist or query fails, assume auth is disabled
        return False


async def get_current_user_optional(
    credentials: Annotated[HTTPAuthorizationCredentials | None, Depends(security)] = None,
) -> User | None:
    """Get the current authenticated user from JWT token, or None if not authenticated."""
    if credentials is None:
        return None

    try:
        token = credentials.credentials
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            return None
    except JWTError:
        return None

    async with async_session() as db:
        user = await get_user_by_username(db, username)
        if user is None or not user.is_active:
            return None
        return user


async def get_current_user(
    credentials: Annotated[HTTPAuthorizationCredentials | None, Depends(security)] = None,
) -> User:
    """Get the current authenticated user from JWT token."""
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    if credentials is None:
        raise credentials_exception
    try:
        token = credentials.credentials
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception

    async with async_session() as db:
        user = await get_user_by_username(db, username)
        if user is None:
            raise credentials_exception
        if not user.is_active:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail="User account is disabled",
            )
        return user


async def get_current_active_user(current_user: Annotated[User, Depends(get_current_user)]) -> User:
    """Get the current active user (alias for clarity)."""
    return current_user


async def require_auth_if_enabled(
    credentials: Annotated[HTTPAuthorizationCredentials | None, Depends(security)] = None,
) -> User | None:
    """Require authentication if auth is enabled, otherwise return None."""
    async with async_session() as db:
        auth_enabled = await is_auth_enabled(db)
        if not auth_enabled:
            return None

        if credentials is None:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Authentication required",
                headers={"WWW-Authenticate": "Bearer"},
            )

        try:
            token = credentials.credentials
            payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
            username: str = payload.get("sub")
            if username is None:
                raise HTTPException(
                    status_code=status.HTTP_401_UNAUTHORIZED,
                    detail="Could not validate credentials",
                    headers={"WWW-Authenticate": "Bearer"},
                )
        except JWTError:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Could not validate credentials",
                headers={"WWW-Authenticate": "Bearer"},
            )

        user = await get_user_by_username(db, username)
        if user is None or not user.is_active:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Could not validate credentials",
                headers={"WWW-Authenticate": "Bearer"},
            )
        return user


def require_role(required_role: str):
    """Dependency factory for role-based access control."""

    async def role_checker(current_user: Annotated[User, Depends(get_current_user)]) -> User:
        if current_user.role != required_role:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=f"Requires {required_role} role",
            )
        return current_user

    return role_checker


def require_admin_if_auth_enabled():
    """Dependency factory that requires admin role if auth is enabled."""

    async def admin_checker(
        current_user: Annotated[User | None, Depends(require_auth_if_enabled)] = None,
    ) -> User | None:
        if current_user is None:
            return None  # Auth not enabled, allow access
        if current_user.role != "admin":
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail="Requires admin role",
            )
        return current_user

    return admin_checker


def generate_api_key() -> tuple[str, str, str]:
    """Generate a new API key.

    Returns:
        tuple: (full_key, key_hash, key_prefix)
            - full_key: The complete API key (only shown once on creation)
            - key_hash: Hashed version for storage and verification
            - key_prefix: First 8 characters for display purposes
    """
    # Generate a secure random API key (32 bytes = 64 hex characters)
    full_key = f"bb_{secrets.token_urlsafe(32)}"
    key_hash = get_password_hash(full_key)
    key_prefix = full_key[:8] + "..." if len(full_key) > 8 else full_key
    return full_key, key_hash, key_prefix


async def get_api_key(
    authorization: Annotated[str | None, Header(alias="Authorization")] = None,
    x_api_key: Annotated[str | None, Header(alias="X-API-Key")] = None,
    db: AsyncSession = Depends(get_db),
) -> APIKey:
    """Get and validate API key from request headers.

    Checks both 'Authorization: Bearer <key>' and 'X-API-Key: <key>' headers.
    """
    api_key_value = None
    if x_api_key:
        api_key_value = x_api_key
    elif authorization and authorization.startswith("Bearer "):
        api_key_value = authorization.replace("Bearer ", "")

    if not api_key_value:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="API key required. Provide 'X-API-Key' header or 'Authorization: Bearer <key>'",
        )

    # Get all API keys and check them
    result = await db.execute(select(APIKey).where(APIKey.enabled.is_(True)))
    api_keys = result.scalars().all()

    for api_key in api_keys:
        # Check if key matches (verify against hash)
        if verify_password(api_key_value, api_key.key_hash):
            # Check expiration
            if api_key.expires_at and api_key.expires_at < datetime.now():
                raise HTTPException(
                    status_code=status.HTTP_401_UNAUTHORIZED,
                    detail="API key has expired",
                )
            # Update last_used timestamp
            api_key.last_used = datetime.now()
            await db.commit()
            return api_key

    raise HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Invalid API key",
    )


def check_permission(api_key: APIKey, permission: str) -> None:
    """Check if API key has the required permission.

    Args:
        api_key: The API key object
        permission: One of 'queue', 'control_printer', 'read_status'

    Raises:
        HTTPException: If permission is not granted
    """
    permission_map = {
        "queue": "can_queue",
        "control_printer": "can_control_printer",
        "read_status": "can_read_status",
    }

    if permission not in permission_map:
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Unknown permission: {permission}",
        )

    attr_name = permission_map[permission]
    if not getattr(api_key, attr_name, False):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail=f"API key does not have '{permission}' permission",
        )


def check_printer_access(api_key: APIKey, printer_id: int) -> None:
    """Check if API key has access to the specified printer.

    Args:
        api_key: The API key object
        printer_id: The printer ID to check access for

    Raises:
        HTTPException: If access is denied
    """
    # If printer_ids is None or empty, access to all printers
    if api_key.printer_ids is None or len(api_key.printer_ids) == 0:
        return

    # Check if printer_id is in allowed list
    if printer_id not in api_key.printer_ids:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail=f"API key does not have access to printer {printer_id}",
        )


# Convenience dependencies - these are functions that return Depends objects
def RequireAdmin():
    """Dependency that requires admin role."""
    return Depends(require_role("admin"))


def RequireAdminIfAuthEnabled():
    """Dependency that requires admin role if auth is enabled."""
    return Depends(require_admin_if_auth_enabled())