from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from sqlalchemy.orm import Session
from typing import Optional

from app.core.database import get_db
from app.core.security import decode_access_token
from app.core.redis import get_redis
from app.models.user import User

security = HTTPBearer()


async def get_current_user(
    credentials: HTTPAuthorizationCredentials = Depends(security),
    db: Session = Depends(get_db),
    redis_client=Depends(get_redis),
) -> User:
    """
    Dependency to get the current authenticated user.

    Validates the JWT token and checks session in Redis.
    """
    token = credentials.credentials

    # Decode and verify token
    payload = decode_access_token(token)
    if payload is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid or expired token",
            headers={"WWW-Authenticate": "Bearer"},
        )

    user_id = payload.get("sub")
    if user_id is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid token payload",
            headers={"WWW-Authenticate": "Bearer"},
        )

    # Check session in Redis
    stored_token = redis_client.get(f"session:{user_id}")
    if stored_token is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Session expired or invalid",
            headers={"WWW-Authenticate": "Bearer"},
        )
    # Handle Redis bytes type - decode if necessary
    if isinstance(stored_token, bytes):
        stored_token = stored_token.decode("utf-8")
    if stored_token != token:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Session expired or invalid",
            headers={"WWW-Authenticate": "Bearer"},
        )

    # Get user from database
    user = db.query(User).filter(User.id == user_id).first()
    if user is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="User not found",
            headers={"WWW-Authenticate": "Bearer"},
        )

    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: User = Depends(get_current_user),
) -> User:
    """
    Dependency to ensure user is active.
    """
    if not current_user.is_active:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Inactive user",
        )
    return current_user


def require_system_admin(
    current_user: User = Depends(get_current_user),
) -> User:
    """
    Dependency to require system admin privileges.
    """
    if not current_user.is_system_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="System admin privileges required",
        )
    return current_user


def require_permission(permission: str):
    """
    Decorator factory to require specific permission.

    Usage:
        @router.get("/protected")
        async def protected_route(user: User = Depends(require_permission("users.read"))):
            ...
    """
    def permission_checker(current_user: User = Depends(get_current_user)) -> User:
        # System admin has all permissions
        if current_user.is_system_admin:
            return current_user

        # Check role permissions
        if current_user.role is None:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail="No role assigned",
            )

        permissions = current_user.role.permissions or {}

        # Check for "all" permission
        if permissions.get("all"):
            return current_user

        # Check specific permission
        if not permissions.get(permission):
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=f"Permission '{permission}' required",
            )

        return current_user

    return permission_checker


def check_department_access(
    user: User,
    resource_department_id: Optional[str],
    resource_security_level: str = "department",
) -> bool:
    """
    Check if user has access to a resource based on department isolation.

    Args:
        user: The current user
        resource_department_id: Department ID of the resource
        resource_security_level: Security level ('public', 'department', 'confidential')

    Returns:
        bool: True if user has access, False otherwise
    """
    # System admin bypasses department isolation
    if user.is_system_admin:
        return True

    # Public resources are accessible to all
    if resource_security_level == "public":
        return True

    # No department specified on resource means accessible to all
    if resource_department_id is None:
        return True

    # User must be in the same department
    if user.department_id == resource_department_id:
        return True

    return False


def check_space_access(user: User, space) -> bool:
    """
    Check if user has access to a space.

    Currently all active users can see all spaces.
    Owner has edit/delete permissions.
    """
    # System admin has full access
    if user.is_system_admin:
        return True

    # All active users can view spaces
    return True


def check_space_edit_access(user: User, space) -> bool:
    """
    Check if user can edit/delete a space.
    """
    # System admin has full access
    if user.is_system_admin:
        return True

    # Only owner can edit
    return space.owner_id == user.id


def check_project_access(user: User, project) -> bool:
    """
    Check if user has access to a project based on security level and membership.

    Access is granted if any of the following conditions are met:
    1. User is a system admin
    2. User is the project owner
    3. User is an explicit project member (cross-department collaboration)
    4. Security level allows access:
       - public: All logged-in users
       - department: Same department users
       - confidential: Only owner/members/admin
    """
    # System admin bypasses all restrictions
    if user.is_system_admin:
        return True

    # Project owner always has access
    if project.owner_id == user.id:
        return True

    # Check if user is an explicit project member (for cross-department collaboration)
    # This allows users from other departments to access the project
    if hasattr(project, 'members') and project.members:
        for member in project.members:
            if member.user_id == user.id:
                return True

    # Check by security level
    security_level = project.security_level

    if security_level == "public":
        return True

    elif security_level == "department":
        # Same department has access
        if project.department_id and user.department_id == project.department_id:
            return True
        return False

    else:  # confidential
        # Only owner/members have access (already checked above)
        return False


def check_project_edit_access(user: User, project) -> bool:
    """
    Check if user can edit/delete a project.

    Edit access is granted if:
    1. User is a system admin
    2. User is the project owner
    3. User is a project member with 'admin' role
    """
    # System admin has full access
    if user.is_system_admin:
        return True

    # Owner can edit
    if project.owner_id == user.id:
        return True

    # Project member with admin role can edit
    if hasattr(project, 'members') and project.members:
        for member in project.members:
            if member.user_id == user.id and member.role == "admin":
                return True

    return False


def check_task_access(user: User, task, project) -> bool:
    """
    Check if user has access to a task.
    Task access is based on project access.
    """
    return check_project_access(user, project)


def check_task_edit_access(user: User, task, project) -> bool:
    """
    Check if user can edit a task.
    """
    # System admin has full access
    if user.is_system_admin:
        return True

    # Project owner can edit all tasks
    if project.owner_id == user.id:
        return True

    # Task creator can edit their own tasks
    if task.created_by == user.id:
        return True

    # Assignee can edit their assigned tasks
    if task.assignee_id == user.id:
        return True

    return False