"""Health check endpoints for monitoring and load balancing."""

import time
import psutil
from datetime import datetime
from flask import Blueprint, jsonify, current_app
import redis
import psycopg2
from sqlalchemy import text

from chat_agent.models.base import db
from chat_agent.utils.error_handler import get_error_handler

health_bp = Blueprint('health', __name__, url_prefix='/health')


def check_database():
    """Check database connectivity and basic operations."""
    try:
        # Test basic database connection
        result = db.session.execute(text('SELECT 1'))
        result.fetchone()
        
        # Test if migrations table exists (indicates proper setup)
        result = db.session.execute(text(
            "SELECT COUNT(*) FROM information_schema.tables WHERE table_name = 'schema_migrations'"
        ))
        migrations_table_exists = result.fetchone()[0] > 0
        
        return {
            'status': 'healthy',
            'connection': 'ok',
            'migrations_table': 'exists' if migrations_table_exists else 'missing',
            'response_time_ms': 0  # Will be calculated by caller
        }
    except Exception as e:
        return {
            'status': 'unhealthy',
            'error': str(e),
            'connection': 'failed'
        }


def check_redis():
    """Check Redis connectivity and basic operations."""
    redis_url = current_app.config.get('REDIS_URL')
    if not redis_url or redis_url == 'None':
        return {
            'status': 'disabled',
            'message': 'Redis is disabled in configuration'
        }
    
    try:
        redis_client = redis.from_url(redis_url)
        
        # Test basic operations
        start_time = time.time()
        redis_client.ping()
        response_time = (time.time() - start_time) * 1000
        
        # Test set/get operation
        test_key = 'health_check_test'
        redis_client.set(test_key, 'test_value', ex=10)
        value = redis_client.get(test_key)
        redis_client.delete(test_key)
        
        return {
            'status': 'healthy',
            'connection': 'ok',
            'response_time_ms': round(response_time, 2),
            'operations': 'ok' if value == b'test_value' else 'failed'
        }
    except Exception as e:
        return {
            'status': 'unhealthy',
            'error': str(e),
            'connection': 'failed'
        }


def check_groq_api():
    """Check Groq API configuration and basic connectivity."""
    groq_api_key = current_app.config.get('GROQ_API_KEY')
    
    if not groq_api_key:
        return {
            'status': 'unhealthy',
            'error': 'GROQ_API_KEY not configured'
        }
    
    # Basic configuration check
    return {
        'status': 'configured',
        'api_key_present': bool(groq_api_key),
        'model': current_app.config.get('GROQ_MODEL', 'not_configured'),
        'note': 'API connectivity not tested in health check to avoid quota usage'
    }


def get_system_metrics():
    """Get basic system metrics."""
    try:
        return {
            'cpu_percent': psutil.cpu_percent(interval=1),
            'memory_percent': psutil.virtual_memory().percent,
            'disk_percent': psutil.disk_usage('/').percent,
            'load_average': psutil.getloadavg()[0] if hasattr(psutil, 'getloadavg') else None
        }
    except Exception as e:
        return {
            'error': f'Failed to get system metrics: {str(e)}'
        }


@health_bp.route('/')
@health_bp.route('/basic')
def basic_health():
    """Basic health check endpoint for load balancers."""
    return jsonify({
        'status': 'healthy',
        'timestamp': datetime.utcnow().isoformat(),
        'service': 'chat-agent',
        'version': '1.0.0'
    }), 200


@health_bp.route('/detailed')
def detailed_health():
    """Detailed health check with all dependencies."""
    start_time = time.time()
    
    # Check all components
    db_start = time.time()
    database_health = check_database()
    database_health['response_time_ms'] = round((time.time() - db_start) * 1000, 2)
    
    redis_health = check_redis()
    groq_health = check_groq_api()
    system_metrics = get_system_metrics()
    
    # Determine overall status
    overall_status = 'healthy'
    if database_health['status'] == 'unhealthy':
        overall_status = 'unhealthy'
    elif redis_health['status'] == 'unhealthy':
        overall_status = 'degraded'  # Redis failure is not critical
    elif groq_health['status'] == 'unhealthy':
        overall_status = 'degraded'  # Can still serve static content
    
    response = {
        'status': overall_status,
        'timestamp': datetime.utcnow().isoformat(),
        'service': 'chat-agent',
        'version': '1.0.0',
        'uptime_seconds': round(time.time() - start_time, 2),
        'components': {
            'database': database_health,
            'redis': redis_health,
            'groq_api': groq_health
        },
        'system': system_metrics,
        'config': {
            'environment': current_app.config.get('FLASK_ENV', 'unknown'),
            'debug': current_app.config.get('DEBUG', False),
            'default_language': current_app.config.get('DEFAULT_LANGUAGE', 'python')
        }
    }
    
    # Return appropriate HTTP status code
    status_code = 200
    if overall_status == 'unhealthy':
        status_code = 503
    elif overall_status == 'degraded':
        status_code = 200  # Still functional
    
    return jsonify(response), status_code


@health_bp.route('/ready')
def readiness():
    """Readiness probe for Kubernetes/container orchestration."""
    # Check critical dependencies only
    db_health = check_database()
    
    if db_health['status'] == 'healthy':
        return jsonify({
            'status': 'ready',
            'timestamp': datetime.utcnow().isoformat(),
            'database': 'connected'
        }), 200
    else:
        return jsonify({
            'status': 'not_ready',
            'timestamp': datetime.utcnow().isoformat(),
            'database': 'disconnected',
            'error': db_health.get('error', 'Database check failed')
        }), 503


@health_bp.route('/live')
def liveness():
    """Liveness probe for Kubernetes/container orchestration."""
    # Simple check that the application is running
    return jsonify({
        'status': 'alive',
        'timestamp': datetime.utcnow().isoformat(),
        'service': 'chat-agent'
    }), 200


@health_bp.route('/metrics')
def metrics():
    """Basic metrics endpoint for monitoring systems."""
    system_metrics = get_system_metrics()
    
    # Add application-specific metrics
    app_metrics = {
        'active_sessions': 0,  # TODO: Implement session counting
        'total_messages': 0,   # TODO: Implement message counting
        'cache_hit_rate': 0.0  # TODO: Implement cache metrics
    }
    
    return jsonify({
        'timestamp': datetime.utcnow().isoformat(),
        'system': system_metrics,
        'application': app_metrics
    }), 200


# Error handler for health check blueprint
@health_bp.errorhandler(Exception)
def handle_health_error(error):
    """Handle errors in health check endpoints."""
    error_handler = get_error_handler()
    if error_handler:
        error_handler.handle_error(error, context="health_check")
    
    return jsonify({
        'status': 'error',
        'timestamp': datetime.utcnow().isoformat(),
        'error': 'Health check failed',
        'message': str(error)
    }), 500