"""Role-based access control definitions.

This module provides role and permission definitions for the application
along with utility functions and decorators for permission checking.
"""

from collections.abc import Callable
from enum import Enum
from functools import wraps
from typing import Any

from app.domain.exceptions import ForbiddenException


class Role(str, Enum):
    """User roles in the system.

    Defines the available user roles with hierarchical permissions.
    ADMIN has full access, USER has standard access, GUEST has read-only.

    Attributes:
        ADMIN: Administrator with full system access.
        USER: Regular authenticated user.
        GUEST: Unauthenticated or limited access user.

    Example:
        >>> if role == Role.ADMIN:
        ...     grant_full_access()
    """

    ADMIN = "admin"
    USER = "user"
    GUEST = "guest"


class Permission:
    """Permission definitions.

    Contains string constants for all available permissions in the system.
    Used for role-based access control checks.

    Example:
        >>> if has_permission(role, Permission.POST_CREATE):
        ...     allow_post_creation()
    """

    POST_CREATE = "post:create"
    POST_READ = "post:read"
    POST_READ_UNPUBLISHED = "post:read_unpublished"
    POST_UPDATE = "post:update"
    POST_DELETE = "post:delete"
    POST_PUBLISH = "post:publish"


ROLE_PERMISSIONS: dict[Role, list[str]] = {
    Role.ADMIN: [
        Permission.POST_CREATE,
        Permission.POST_READ,
        Permission.POST_READ_UNPUBLISHED,
        Permission.POST_UPDATE,
        Permission.POST_DELETE,
        Permission.POST_PUBLISH,
    ],
    Role.USER: [
        Permission.POST_CREATE,
        Permission.POST_READ,
        Permission.POST_UPDATE,
        Permission.POST_DELETE,
        Permission.POST_PUBLISH,
    ],
    Role.GUEST: [
        Permission.POST_READ,
    ],
}


def has_permission(role: Role, permission: str) -> bool:
    """Check if role has specific permission.

    Args:
        role: User role to check.
        permission: Permission string to verify.

    Returns:
        True if role has the permission, False otherwise.

    Example:
        >>> has_permission(Role.ADMIN, Permission.POST_DELETE)
        True
    """
    return permission in ROLE_PERMISSIONS.get(role, [])


def require_permission(
    permission: str,
) -> Callable[[Callable[..., Any]], Callable[..., Any]]:
    """Decorator to require specific permission.

    Creates a decorator that checks if the user has the required permission
    before executing the decorated function.

    Args:
        permission: Permission string required for execution.

    Returns:
        Decorator function for permission checking.

    Raises:
        ForbiddenException: If user lacks the required permission.

    Example:
        >>> @require_permission(Permission.POST_CREATE)
        ... async def create_post():
        ...     ...
    """

    def decorator(func: Callable[..., Any]) -> Callable[..., Any]:
        @wraps(func)
        async def wrapper(*args: Any, **kwargs: Any) -> Any:
            token_info = kwargs.get("token_info")
            if not token_info:
                raise ForbiddenException("Authentication required")

            roles = getattr(token_info, "roles", [])
            if Role.ADMIN.value in roles:
                role = Role.ADMIN
            elif Role.USER.value in roles:
                role = Role.USER
            else:
                role = Role.GUEST

            if not has_permission(role, permission):
                raise ForbiddenException(
                    f"Permission '{permission}' required for role '{role.value}'"
                )

            return await func(*args, **kwargs)

        return wrapper

    return decorator


def get_effective_role(roles: list[str]) -> Role:
    """Determine effective role from list of roles.

    Evaluates multiple roles and returns the highest privilege role.
    Priority order: admin > user > guest.

    Args:
        roles: List of role strings from token.

    Returns:
        Highest privilege Role enum value.

    Example:
        >>> get_effective_role(["user", "admin"])
        <Role.ADMIN: 'admin'>
    """
    if Role.ADMIN.value in roles:
        return Role.ADMIN
    elif Role.USER.value in roles:
        return Role.USER
    else:
        return Role.GUEST