"""
Session Manager - Handles automatic session timeout for HIPAA compliance
"""
import jwt
from datetime import datetime, timedelta
from functools import wraps
from flask import request, jsonify
import os
import logging

logger = logging.getLogger(__name__)

class SessionManager:
    """
    Manages user sessions with automatic timeout for HIPAA compliance
    """

    # Inactivity timeout - 2 hours for better UX while still being secure
    # Note: HIPAA recommends 15 minutes for clinical workstations with direct PHI access,
    # but web apps with less sensitive access can use longer timeouts
    INACTIVITY_TIMEOUT = timedelta(hours=2)

    # Maximum session duration - 24 hours (user must re-login daily)
    MAX_SESSION_DURATION = timedelta(hours=24)

    @staticmethod
    def create_token(user_id, role):
        """
        Create a JWT token with session management
        """
        now = datetime.utcnow()

        # Token expires after inactivity timeout
        expiration = now + SessionManager.INACTIVITY_TIMEOUT

        # But never exceed max session duration
        max_expiration = now + SessionManager.MAX_SESSION_DURATION
        if expiration > max_expiration:
            expiration = max_expiration

        payload = {
            'sub': str(user_id),
            'role': role,
            'iat': now,
            'exp': expiration,
            'last_activity': now.timestamp(),
            'session_start': now.timestamp()
        }

        token = jwt.encode(
            payload,
            os.environ.get('JWT_SECRET_KEY', 'your-secret-key-change-this'),
            algorithm='HS256'
        )

        logger.info(f"Session created for user {user_id} with role {role}")
        return token

    @staticmethod
    def refresh_token(token):
        """
        Refresh token on activity to extend session
        """
        try:
            # Decode without verification first to get payload
            payload = jwt.decode(
                token,
                os.environ.get('JWT_SECRET_KEY', 'your-secret-key-change-this'),
                algorithms=['HS256'],
                options={"verify_exp": False}
            )

            now = datetime.utcnow()
            session_start = datetime.fromtimestamp(payload['session_start'])

            # Check if session has exceeded maximum duration
            if now - session_start > SessionManager.MAX_SESSION_DURATION:
                logger.warning(f"Session exceeded maximum duration for user {payload['sub']}")
                return None

            # Check if session has been inactive too long
            last_activity = datetime.fromtimestamp(payload['last_activity'])
            if now - last_activity > SessionManager.INACTIVITY_TIMEOUT:
                logger.warning(f"Session timeout due to inactivity for user {payload['sub']}")
                return None

            # Create refreshed token
            new_expiration = now + SessionManager.INACTIVITY_TIMEOUT
            max_expiration = session_start + SessionManager.MAX_SESSION_DURATION

            if new_expiration > max_expiration:
                new_expiration = max_expiration

            payload['exp'] = new_expiration
            payload['last_activity'] = now.timestamp()

            new_token = jwt.encode(
                payload,
                os.environ.get('JWT_SECRET_KEY', 'your-secret-key-change-this'),
                algorithm='HS256'
            )

            return new_token

        except jwt.ExpiredSignatureError:
            logger.warning("Token expired during refresh attempt")
            return None
        except Exception as e:
            logger.error(f"Error refreshing token: {str(e)}")
            return None

    @staticmethod
    def validate_session(token):
        """
        Validate if session is still active
        """
        try:
            payload = jwt.decode(
                token,
                os.environ.get('JWT_SECRET_KEY', 'your-secret-key-change-this'),
                algorithms=['HS256']
            )

            now = datetime.utcnow()
            last_activity = datetime.fromtimestamp(payload.get('last_activity', 0))

            # Check inactivity timeout
            if now - last_activity > SessionManager.INACTIVITY_TIMEOUT:
                return False, "Session expired due to inactivity"

            return True, "Session valid"

        except jwt.ExpiredSignatureError:
            return False, "Session expired"
        except Exception as e:
            logger.error(f"Session validation error: {str(e)}")
            return False, "Invalid session"

def require_active_session(f):
    """
    Decorator to ensure session is active and refresh it on activity
    """
    @wraps(f)
    def decorated_function(*args, **kwargs):
        auth_header = request.headers.get('Authorization')

        if not auth_header or not auth_header.startswith('Bearer '):
            return jsonify({'error': 'No valid authorization header'}), 401

        token = auth_header.split(' ')[1]

        # Validate session
        is_valid, message = SessionManager.validate_session(token)
        if not is_valid:
            logger.warning(f"Session validation failed: {message}")
            return jsonify({'error': message, 'session_expired': True}), 401

        # Refresh token on activity
        new_token = SessionManager.refresh_token(token)
        if not new_token:
            return jsonify({'error': 'Session expired', 'session_expired': True}), 401

        # Add new token to response headers
        response = f(*args, **kwargs)
        if hasattr(response, 'headers'):
            response.headers['X-New-Token'] = new_token

        return response

    return decorated_function

def get_session_info(token):
    """
    Get information about current session
    """
    try:
        payload = jwt.decode(
            token,
            os.environ.get('JWT_SECRET_KEY', 'your-secret-key-change-this'),
            algorithms=['HS256'],
            options={"verify_exp": False}
        )

        now = datetime.utcnow()
        last_activity = datetime.fromtimestamp(payload.get('last_activity', 0))
        session_start = datetime.fromtimestamp(payload.get('session_start', 0))

        time_until_timeout = SessionManager.INACTIVITY_TIMEOUT - (now - last_activity)
        session_duration = now - session_start

        return {
            'user_id': payload['sub'],
            'role': payload['role'],
            'session_start': session_start.isoformat(),
            'last_activity': last_activity.isoformat(),
            'time_until_timeout': max(0, time_until_timeout.total_seconds()),
            'session_duration': session_duration.total_seconds(),
            'max_session_duration': SessionManager.MAX_SESSION_DURATION.total_seconds()
        }
    except Exception as e:
        logger.error(f"Error getting session info: {str(e)}")
        return None