from flask import Blueprint, request, jsonify, current_app, g
from db.model import User, Course, Enrollment, Chat, db
import uuid
from sqlalchemy import select, and_
from datetime import datetime

chat = Blueprint('chat', __name__)

@chat.route('/<uuid:course_id>/messages', methods=['GET'])
def get_course_messages(course_id: uuid.UUID):
    """
    Fetch chat messages for a specific course.
    Only enrolled users can access the messages.
    """
    try:
        current_user: User = g.current_user
        
        # Verify user's enrollment
        enrollment = db.session.execute(
            select(Enrollment).where(
                and_(
                    Enrollment.courseID == course_id,
                    Enrollment.userID == current_user.id
                )
            )
        ).scalar()
        
        if not enrollment:
            return jsonify({'message': 'You are not enrolled in this course'}), 401
            
        # Get chat messages for the course
        messages = db.session.execute(
            select(Chat)
            .where(Chat.courseID == course_id)
            .order_by(Chat.chatDate.desc())
        ).scalars()
        
        # Format messages
        chat_messages = [{
            'id': str(msg.id),
            'text': msg.textContent,
            'userId': str(msg.userID),
            'username': msg.user.username,
            'timestamp': msg.chatDate.isoformat()
        } for msg in messages]
        
        return jsonify({'messages': chat_messages}), 200
        
    except Exception as e:
        return jsonify({'message': f'An error occurred: {str(e)}'}), 500

@chat.route('/<uuid:course_id>/send', methods=['POST'])
def send_message(course_id: uuid.UUID):
    """
    Send a new chat message in a course.
    Only enrolled users can send messages.
    """
    try:
        current_user: User = g.current_user
        message_text = request.json.get('message')
        
        if not message_text or not message_text.strip():
            return jsonify({'message': 'Message content is required'}), 400
            
        # Verify user's enrollment
        enrollment = db.session.execute(
            select(Enrollment).where(
                and_(
                    Enrollment.courseID == course_id,
                    Enrollment.userID == current_user.id
                )
            )
        ).scalar()
        
        if not enrollment:
            return jsonify({'message': 'You are not enrolled in this course'}), 401
            
        # Create new chat message
        new_message = Chat(
            textContent=message_text,
            userID=current_user.id,
            courseID=course_id,
            chatDate=datetime.now()
        )
        
        db.session.add(new_message)
        
        # Update last activity in enrollment
        enrollment.lastActivity = datetime.now()
        
        db.session.commit()
        
        return jsonify({
            'message': 'Message sent successfully',
            'messageId': str(new_message.id),
            'timestamp': new_message.chatDate.isoformat()
        }), 201
        
    except Exception as e:
        db.session.rollback()
        return jsonify({'message': f'An error occurred: {str(e)}'}), 500

@chat.route('/<uuid:course_id>/participants', methods=['GET'])
def get_chat_participants(course_id: uuid.UUID):
    """
    Get list of active participants in a course chat.
    Returns only enrolled users with recent activity.
    """
    try:
        current_user: User = g.current_user
        
        # Verify requesting user's enrollment
        user_enrollment = db.session.execute(
            select(Enrollment).where(
                and_(
                    Enrollment.courseID == course_id,
                    Enrollment.userID == current_user.id
                )
            )
        ).scalar()
        
        if not user_enrollment:
            return jsonify({'message': 'You are not enrolled in this course'}), 401
            
        # Get enrolled users
        enrollments = db.session.execute(
            select(Enrollment)
            .where(Enrollment.courseID == course_id)
            .join(User)
        ).scalars()
        
        # Return participant information
        participants = [{
            'id': str(enrollment.userID),
            'username': enrollment.user.username,
            'lastActivity': enrollment.lastActivity.isoformat()
        } for enrollment in enrollments]
        
        return jsonify({'participants': participants}), 200
        
    except Exception as e:
        return jsonify({'message': f'An error occurred: {str(e)}'}), 500