"""API Token Authentication utilities for REST API"""

from functools import wraps
from flask import request, jsonify, g, current_app
from app.models import ApiToken, User
from app import db
from datetime import datetime


def extract_token_from_request():
    """Extract API token from request headers

    Supports multiple formats:
    - Authorization: Bearer <token>
    - Authorization: Token <token>
    - X-API-Key: <token>

    Returns:
        str or None: The token if found
    """
    # Check Authorization header
    auth_header = request.headers.get("Authorization", "")
    if auth_header:
        parts = auth_header.split()
        if len(parts) == 2:
            scheme = parts[0].lower()
            if scheme in ("bearer", "token"):
                return parts[1]

    # Check X-API-Key header
    api_key = request.headers.get("X-API-Key")
    if api_key:
        return api_key

    return None


def authenticate_token(token_string):
    """Authenticate an API token and return the associated user

    Args:
        token_string: The plain token string

    Returns:
        tuple: (User, ApiToken, error_message) if invalid, (User, ApiToken, None) if valid
    """
    if not token_string or not token_string.startswith("tt_"):
        return None, None, "Invalid token format"

    # Get token hash
    token_hash = ApiToken.hash_token(token_string)

    # Find token in database
    api_token = ApiToken.query.filter_by(token_hash=token_hash).first()

    if not api_token:
        return None, None, "Token not found"

    # Check if token is active
    if not api_token.is_active:
        return None, None, "Token has been revoked"

    # Check expiration
    if api_token.expires_at and api_token.expires_at < datetime.utcnow():
        return None, None, "Token has expired"

    # Check IP whitelist if configured
    if api_token.ip_whitelist:
        client_ip = request.remote_addr
        allowed_ips = [ip.strip() for ip in api_token.ip_whitelist.split(",") if ip.strip()]

        # Simple IP matching (can be enhanced with CIDR support)
        if client_ip not in allowed_ips:
            # Check CIDR blocks if any
            from ipaddress import ip_address, ip_network

            ip_allowed = False
            for allowed in allowed_ips:
                try:
                    if "/" in allowed:
                        # CIDR block
                        if ip_address(client_ip) in ip_network(allowed, strict=False):
                            ip_allowed = True
                            break
                    elif client_ip == allowed:
                        ip_allowed = True
                        break
                except ValueError:
                    # Invalid IP format, skip
                    continue

            if not ip_allowed:
                current_app.logger.warning(f"API token {api_token.token_prefix}... access denied from IP {client_ip}")
                return None, None, "Access denied from this IP address"

    # Get associated user
    user = User.query.get(api_token.user_id)
    if not user or not user.is_active:
        return None, None, "User account is inactive"

    # Record usage
    try:
        api_token.record_usage(request.remote_addr)
    except Exception as e:
        current_app.logger.warning(f"Failed to record API token usage: {e}")

    return user, api_token, None


def require_api_token(required_scope=None):
    """Decorator to require API token authentication

    Args:
        required_scope: Optional scope required for this endpoint (e.g., 'read:projects')

    Usage:
        @require_api_token('read:projects')
        def get_projects():
            # Access authenticated user via g.api_user
            # Access token via g.api_token
            pass
    """

    def decorator(f):
        @wraps(f)
        def decorated_function(*args, **kwargs):
            # Extract token from request
            token_string = extract_token_from_request()

            if not token_string:
                return (
                    jsonify(
                        {
                            "error": "Authentication required",
                            "message": "API token must be provided in Authorization header or X-API-Key header",
                        }
                    ),
                    401,
                )

            # Authenticate token
            user, api_token, error_msg = authenticate_token(token_string)

            if not user or not api_token:
                message = error_msg or "The provided API token is invalid or expired"
                return (
                    jsonify({"error": "Invalid token", "message": message}),
                    401,
                )

            # Check scope if required
            if required_scope and not api_token.has_scope(required_scope):
                return (
                    jsonify(
                        {
                            "error": "Insufficient permissions",
                            "message": f'This endpoint requires the "{required_scope}" scope',
                            "required_scope": required_scope,
                            "available_scopes": api_token.scopes.split(",") if api_token.scopes else [],
                        }
                    ),
                    403,
                )

            # Store in request context
            g.api_user = user
            g.api_token = api_token

            return f(*args, **kwargs)

        return decorated_function

    return decorator


def optional_api_token():
    """Decorator that allows both session-based and token-based authentication

    Useful for endpoints that can be accessed via web UI or API

    Usage:
        @optional_api_token()
        @login_required  # Will be satisfied by API token if present
        def get_data():
            # Access user via current_user (session) or g.api_user (token)
            pass
    """

    def decorator(f):
        @wraps(f)
        def decorated_function(*args, **kwargs):
            # Try to extract and authenticate token
            token_string = extract_token_from_request()

            if token_string:
                user, api_token, error_msg = authenticate_token(token_string)
                if user and api_token:
                    g.api_user = user
                    g.api_token = api_token

            return f(*args, **kwargs)

        return decorated_function

    return decorator