"""Chat API routes for session management and chat history."""

import logging
from datetime import datetime
from typing import Dict, Any, Optional

from flask import Blueprint, request, jsonify, current_app, g
from flask_limiter import Limiter
from flask_limiter.util import get_remote_address
import redis

from ..services.session_manager import SessionManager, SessionManagerError, SessionNotFoundError, SessionExpiredError
from ..services.chat_history import ChatHistoryManager, ChatHistoryError
from ..services.language_context import LanguageContextManager, LanguageContextError
from ..models.language_context import LanguageContext
from ..models.base import db
from .middleware import require_auth, validate_json_request, create_limiter


logger = logging.getLogger(__name__)

# Create blueprint
chat_bp = Blueprint('chat', __name__, url_prefix='/api/v1/chat')

# Initialize rate limiter (will be configured in app factory)
limiter = create_limiter()


class APIError(Exception):
    """Base API error class."""
    def __init__(self, message: str, status_code: int = 400, payload: Optional[Dict] = None):
        super().__init__()
        self.message = message
        self.status_code = status_code
        self.payload = payload


def handle_api_error(error: APIError):
    """Handle API errors and return JSON response."""
    response = {'error': error.message}
    if error.payload:
        response.update(error.payload)
    return jsonify(response), error.status_code


def get_services():
    """Get service instances from current app context."""
    redis_client = None
    redis_url = current_app.config.get('REDIS_URL')
    
    if redis_url and redis_url != 'None':
        try:
            redis_client = redis.from_url(redis_url)
            # Test the connection
            redis_client.ping()
        except Exception as e:
            logger.warning(f"Redis connection failed: {e}. Running without Redis cache.")
            redis_client = None
    else:
        logger.info("Redis disabled in configuration. Running without Redis cache.")
    
    session_manager = SessionManager(redis_client, current_app.config.get('SESSION_TIMEOUT', 3600))
    chat_history_manager = ChatHistoryManager(
        redis_client,
        current_app.config.get('MAX_CHAT_HISTORY', 20),
        current_app.config.get('CONTEXT_WINDOW_SIZE', 10)
    )
    language_context_manager = LanguageContextManager()
    
    return session_manager, chat_history_manager, language_context_manager


# Session Management Endpoints

@chat_bp.route('/sessions', methods=['POST'])
@limiter.limit("10 per minute")
@require_auth
@validate_json_request(['language'])
def create_session():
    """
    Create a new chat session.
    
    Request body:
    {
        "language": "python",
        "metadata": {"key": "value"}  // optional
    }
    """
    try:
        data = request.json_data
        language = data['language']
        metadata = data.get('metadata', {})
        
        # Validate language
        if not LanguageContext.is_supported_language(language):
            supported = LanguageContext.get_supported_languages()
            raise APIError(f'Unsupported language: {language}. Supported: {", ".join(supported)}', 400)
        
        session_manager, _, language_context_manager = get_services()
        
        # Create session
        session = session_manager.create_session(
            user_id=request.user_id,
            language=language,
            session_metadata=metadata
        )
        
        # Create language context
        language_context_manager.create_context(session.id, language)
        
        logger.info(f"Created session {session.id} for user {request.user_id}")
        
        return jsonify({
            'session_id': session.id,
            'user_id': session.user_id,
            'language': session.language,
            'created_at': session.created_at.isoformat(),
            'message_count': session.message_count,
            'metadata': session.session_metadata
        }), 201
        
    except (SessionManagerError, LanguageContextError) as e:
        logger.error(f"Error creating session: {e}")
        raise APIError(f'Failed to create session: {str(e)}', 500)
    except APIError:
        raise
    except Exception as e:
        logger.error(f"Unexpected error creating session: {e}")
        raise APIError('Internal server error', 500)


@chat_bp.route('/sessions/<session_id>', methods=['GET'])
@limiter.limit("30 per minute")
@require_auth
def get_session(session_id: str):
    """Get session information."""
    try:
        session_manager, _, _ = get_services()
        
        session = session_manager.get_session(session_id)
        
        # Check if user owns this session
        if session.user_id != request.user_id:
            raise APIError('Access denied', 403)
        
        return jsonify({
            'session_id': session.id,
            'user_id': session.user_id,
            'language': session.language,
            'created_at': session.created_at.isoformat(),
            'last_active': session.last_active.isoformat(),
            'message_count': session.message_count,
            'is_active': session.is_active,
            'metadata': session.session_metadata
        })
        
    except SessionNotFoundError:
        raise APIError('Session not found', 404)
    except SessionExpiredError:
        raise APIError('Session has expired', 410)
    except SessionManagerError as e:
        logger.error(f"Error getting session: {e}")
        raise APIError(f'Failed to get session: {str(e)}', 500)
    except APIError:
        raise
    except Exception as e:
        logger.error(f"Unexpected error getting session: {e}")
        raise APIError('Internal server error', 500)


@chat_bp.route('/sessions/<session_id>', methods=['DELETE'])
@limiter.limit("5 per minute")
@require_auth
def delete_session(session_id: str):
    """Delete a chat session."""
    try:
        session_manager, chat_history_manager, _ = get_services()
        
        # Get session to check ownership
        session = session_manager.get_session(session_id)
        
        # Check if user owns this session
        if session.user_id != request.user_id:
            raise APIError('Access denied', 403)
        
        # Clear chat history
        message_count = chat_history_manager.clear_session_history(session_id)
        
        # Delete session
        session_manager.delete_session(session_id)
        
        logger.info(f"Deleted session {session_id} with {message_count} messages")
        
        return jsonify({
            'message': 'Session deleted successfully',
            'session_id': session_id,
            'messages_deleted': message_count
        })
        
    except SessionNotFoundError:
        raise APIError('Session not found', 404)
    except (SessionManagerError, ChatHistoryError) as e:
        logger.error(f"Error deleting session: {e}")
        raise APIError(f'Failed to delete session: {str(e)}', 500)
    except APIError:
        raise
    except Exception as e:
        logger.error(f"Unexpected error deleting session: {e}")
        raise APIError('Internal server error', 500)


@chat_bp.route('/sessions', methods=['GET'])
@limiter.limit("20 per minute")
@require_auth
def list_user_sessions():
    """List all sessions for the authenticated user."""
    try:
        active_only = request.args.get('active_only', 'true').lower() == 'true'
        
        session_manager, _, _ = get_services()
        
        sessions = session_manager.get_user_sessions(request.user_id, active_only)
        
        session_list = []
        for session in sessions:
            session_list.append({
                'session_id': session.id,
                'language': session.language,
                'created_at': session.created_at.isoformat(),
                'last_active': session.last_active.isoformat(),
                'message_count': session.message_count,
                'is_active': session.is_active,
                'metadata': session.session_metadata
            })
        
        return jsonify({
            'sessions': session_list,
            'total_count': len(session_list),
            'active_only': active_only
        })
        
    except SessionManagerError as e:
        logger.error(f"Error listing sessions: {e}")
        raise APIError(f'Failed to list sessions: {str(e)}', 500)
    except Exception as e:
        logger.error(f"Unexpected error listing sessions: {e}")
        raise APIError('Internal server error', 500)


# Chat History Endpoints

@chat_bp.route('/sessions/<session_id>/history', methods=['GET'])
@limiter.limit("30 per minute")
@require_auth
def get_chat_history(session_id: str):
    """Get chat history for a session."""
    try:
        # Validate session ownership
        session_manager, chat_history_manager, _ = get_services()
        session = session_manager.get_session(session_id)
        
        if session.user_id != request.user_id:
            raise APIError('Access denied', 403)
        
        # Get pagination parameters
        page = int(request.args.get('page', 1))
        page_size = min(int(request.args.get('page_size', 50)), 100)  # Max 100 messages per page
        recent_only = request.args.get('recent_only', 'false').lower() == 'true'
        
        if recent_only:
            # Get recent messages for context
            limit = min(int(request.args.get('limit', 10)), 50)  # Max 50 recent messages
            messages = chat_history_manager.get_recent_history(session_id, limit)
            total_count = len(messages)
        else:
            # Get paginated full history
            messages = chat_history_manager.get_full_history(session_id, page, page_size)
            total_count = chat_history_manager.get_message_count(session_id)
        
        message_list = []
        for message in messages:
            message_list.append({
                'id': message.id,
                'role': message.role,
                'content': message.content,
                'language': message.language,
                'timestamp': message.timestamp.isoformat(),
                'metadata': message.message_metadata
            })
        
        response_data = {
            'messages': message_list,
            'session_id': session_id,
            'total_count': total_count
        }
        
        if not recent_only:
            response_data.update({
                'page': page,
                'page_size': page_size,
                'total_pages': (total_count + page_size - 1) // page_size
            })
        
        return jsonify(response_data)
        
    except SessionNotFoundError:
        raise APIError('Session not found', 404)
    except SessionExpiredError:
        raise APIError('Session has expired', 410)
    except ChatHistoryError as e:
        logger.error(f"Error getting chat history: {e}")
        raise APIError(f'Failed to get chat history: {str(e)}', 500)
    except APIError:
        raise
    except Exception as e:
        logger.error(f"Unexpected error getting chat history: {e}")
        raise APIError('Internal server error', 500)


@chat_bp.route('/sessions/<session_id>/history/search', methods=['GET'])
@limiter.limit("20 per minute")
@require_auth
def search_chat_history(session_id: str):
    """Search chat history for a session."""
    try:
        query = request.args.get('q', '').strip()
        if not query:
            raise APIError('Search query is required', 400)
        
        if len(query) < 3:
            raise APIError('Search query must be at least 3 characters', 400)
        
        # Validate session ownership
        session_manager, chat_history_manager, _ = get_services()
        session = session_manager.get_session(session_id)
        
        if session.user_id != request.user_id:
            raise APIError('Access denied', 403)
        
        limit = min(int(request.args.get('limit', 20)), 50)  # Max 50 results
        
        messages = chat_history_manager.search_messages(session_id, query, limit)
        
        message_list = []
        for message in messages:
            message_list.append({
                'id': message.id,
                'role': message.role,
                'content': message.content,
                'language': message.language,
                'timestamp': message.timestamp.isoformat(),
                'metadata': message.message_metadata
            })
        
        return jsonify({
            'messages': message_list,
            'session_id': session_id,
            'query': query,
            'result_count': len(message_list)
        })
        
    except SessionNotFoundError:
        raise APIError('Session not found', 404)
    except SessionExpiredError:
        raise APIError('Session has expired', 410)
    except ChatHistoryError as e:
        logger.error(f"Error searching chat history: {e}")
        raise APIError(f'Failed to search chat history: {str(e)}', 500)
    except APIError:
        raise
    except Exception as e:
        logger.error(f"Unexpected error searching chat history: {e}")
        raise APIError('Internal server error', 500)


# Language Context Endpoints

@chat_bp.route('/sessions/<session_id>/language', methods=['GET'])
@limiter.limit("30 per minute")
@require_auth
def get_language_context(session_id: str):
    """Get language context for a session."""
    try:
        # Validate session ownership
        session_manager, _, language_context_manager = get_services()
        session = session_manager.get_session(session_id)
        
        if session.user_id != request.user_id:
            raise APIError('Access denied', 403)
        
        context = language_context_manager.get_context(session_id)
        
        return jsonify({
            'session_id': session_id,
            'language': context.language,
            'prompt_template': context.get_prompt_template(),
            'syntax_highlighting': context.get_syntax_highlighting(),
            'language_info': context.get_language_info(),
            'updated_at': context.updated_at.isoformat()
        })
        
    except SessionNotFoundError:
        raise APIError('Session not found', 404)
    except SessionExpiredError:
        raise APIError('Session has expired', 410)
    except LanguageContextError as e:
        logger.error(f"Error getting language context: {e}")
        raise APIError(f'Failed to get language context: {str(e)}', 500)
    except APIError:
        raise
    except Exception as e:
        logger.error(f"Unexpected error getting language context: {e}")
        raise APIError('Internal server error', 500)


@chat_bp.route('/sessions/<session_id>/language', methods=['PUT'])
@limiter.limit("10 per minute")
@require_auth
@validate_json_request(['language'])
def update_language_context(session_id: str):
    """Update language context for a session."""
    try:
        data = request.json_data
        language = data['language']
        
        # Validate language
        if not LanguageContext.is_supported_language(language):
            supported = LanguageContext.get_supported_languages()
            raise APIError(f'Unsupported language: {language}. Supported: {", ".join(supported)}', 400)
        
        # Validate session ownership
        session_manager, _, language_context_manager = get_services()
        session = session_manager.get_session(session_id)
        
        if session.user_id != request.user_id:
            raise APIError('Access denied', 403)
        
        # Update language context
        context = language_context_manager.set_language(session_id, language)
        
        # Update session language
        session_manager.set_session_language(session_id, language)
        
        logger.info(f"Updated language to {language} for session {session_id}")
        
        return jsonify({
            'session_id': session_id,
            'language': context.language,
            'prompt_template': context.get_prompt_template(),
            'syntax_highlighting': context.get_syntax_highlighting(),
            'language_info': context.get_language_info(),
            'updated_at': context.updated_at.isoformat()
        })
        
    except SessionNotFoundError:
        raise APIError('Session not found', 404)
    except SessionExpiredError:
        raise APIError('Session has expired', 410)
    except (SessionManagerError, LanguageContextError) as e:
        logger.error(f"Error updating language context: {e}")
        raise APIError(f'Failed to update language context: {str(e)}', 500)
    except APIError:
        raise
    except Exception as e:
        logger.error(f"Unexpected error updating language context: {e}")
        raise APIError('Internal server error', 500)


@chat_bp.route('/languages', methods=['GET'])
@limiter.limit("50 per minute")
def get_supported_languages():
    """Get list of supported programming languages."""
    try:
        languages = LanguageContext.get_supported_languages()
        language_names = LanguageContext.get_language_display_names()
        
        language_list = []
        for lang_code in languages:
            lang_info = LanguageContext.SUPPORTED_LANGUAGES[lang_code]
            language_list.append({
                'code': lang_code,
                'name': lang_info['name'],
                'syntax_highlighting': lang_info['syntax_highlighting'],
                'file_extensions': lang_info['file_extensions']
            })
        
        return jsonify({
            'languages': language_list,
            'default_language': 'python',
            'total_count': len(language_list)
        })
        
    except Exception as e:
        logger.error(f"Unexpected error getting supported languages: {e}")
        raise APIError('Internal server error', 500)


# Message Processing Endpoint

@chat_bp.route('/sessions/<session_id>/message', methods=['POST'])
@limiter.limit("30 per minute")
@require_auth
@validate_json_request(['content'])
def send_message(session_id: str):
    """Send a message to the chat agent and get a response."""
    try:
        data = request.json_data
        content = data['content'].strip()
        language = data.get('language')  # Optional language override
        
        if not content:
            raise APIError('Message content cannot be empty', 400)
        
        if len(content) > 5000:  # Reasonable message length limit
            raise APIError('Message too long (max 5000 characters)', 400)
        
        # Get services
        session_manager, chat_history_manager, language_context_manager = get_services()
        
        # Validate session ownership
        session = session_manager.get_session(session_id)
        if session.user_id != request.user_id:
            raise APIError('Access denied', 403)
        
        # Initialize chat agent
        from ..services.groq_client import GroqClient
        from ..services.chat_agent import ChatAgent
        from ..services.programming_assistance import ProgrammingAssistanceService
        
        groq_client = GroqClient()
        programming_assistance_service = ProgrammingAssistanceService()
        
        chat_agent = ChatAgent(
            groq_client=groq_client,
            language_context_manager=language_context_manager,
            session_manager=session_manager,
            chat_history_manager=chat_history_manager,
            programming_assistance_service=programming_assistance_service
        )
        
        # Process the message
        result = chat_agent.process_message(session_id, content, language)
        
        logger.info(f"Processed message for session {session_id}, response length: {len(result['response'])}")
        
        return jsonify({
            'response': result['response'],
            'message_id': result['message_id'],
            'session_id': session_id,
            'language': result['language'],
            'processing_time': result['processing_time'],
            'timestamp': result['timestamp']
        })
        
    except SessionNotFoundError:
        raise APIError('Session not found', 404)
    except SessionExpiredError:
        raise APIError('Session has expired', 410)
    except ChatAgentError as e:
        logger.error(f"Chat agent error: {e}")
        raise APIError(f'Failed to process message: {str(e)}', 500)
    except APIError:
        raise
    except Exception as e:
        logger.error(f"Unexpected error processing message: {e}")
        raise APIError('Internal server error', 500)


# Health Check Endpoint

@chat_bp.route('/health', methods=['GET'])
def health_check():
    """Health check endpoint for monitoring."""
    try:
        # Check database connection
        from sqlalchemy import text
        db.session.execute(text('SELECT 1'))
        
        # Check Redis connection (if configured)
        redis_status = "disabled"
        redis_url = current_app.config.get('REDIS_URL')
        if redis_url and redis_url != 'None':
            try:
                redis_client = redis.from_url(redis_url)
                redis_client.ping()
                redis_status = "connected"
            except Exception:
                redis_status = "disconnected"
        else:
            redis_status = "disabled"
        
        return jsonify({
            'status': 'healthy',
            'timestamp': datetime.utcnow().isoformat(),
            'services': {
                'database': 'connected',
                'redis': redis_status
            }
        })
        
    except Exception as e:
        logger.error(f"Health check failed: {e}")
        return jsonify({
            'status': 'unhealthy',
            'timestamp': datetime.utcnow().isoformat(),
            'error': str(e)
        }), 503


# Error handlers
@chat_bp.errorhandler(APIError)
def handle_api_error_handler(error):
    """Handle APIError exceptions."""
    return handle_api_error(error)


@chat_bp.errorhandler(400)
def handle_bad_request(error):
    """Handle bad request errors."""
    return jsonify({'error': 'Bad request'}), 400


@chat_bp.errorhandler(404)
def handle_not_found(error):
    """Handle not found errors."""
    return jsonify({'error': 'Not found'}), 404


@chat_bp.errorhandler(429)
def handle_rate_limit_exceeded(error):
    """Handle rate limit exceeded errors."""
    return jsonify({
        'error': 'Rate limit exceeded',
        'message': 'Too many requests. Please try again later.'
    }), 429


@chat_bp.errorhandler(500)
def handle_internal_error(error):
    """Handle internal server errors."""
    logger.error(f"Internal server error: {error}")
    return jsonify({'error': 'Internal server error'}), 500