app/utils/performance_monitor.py

"""
Performance monitoring utilities for tracking query execution times and database operations.
"""
import time
import logging
from functools import wraps
from typing import Dict, Any, Optional
from contextlib import asynccontextmanager

logger = logging.getLogger(__name__)

class PerformanceMetrics:
    """Class to track and store performance metrics."""
    
    def __init__(self):
        self.query_times = []
        self.slow_queries = []
        self.total_queries = 0
        self.total_time = 0.0
    
    def add_query_time(self, collection: str, pipeline_length: int, execution_time: float, query_type: str = "aggregation"):
        """Add a query execution time to metrics."""
        self.query_times.append({
            "collection": collection,
            "pipeline_length": pipeline_length,
            "execution_time": execution_time,
            "query_type": query_type,
            "timestamp": time.time()
        })
        
        self.total_queries += 1
        self.total_time += execution_time
        
        # Track slow queries (> 1 second)
        if execution_time > 1.0:
            self.slow_queries.append({
                "collection": collection,
                "pipeline_length": pipeline_length,
                "execution_time": execution_time,
                "query_type": query_type,
                "timestamp": time.time()
            })
            logger.warning(f"Slow query detected: {collection} took {execution_time:.3f}s")
    
    def get_average_time(self) -> float:
        """Get average query execution time."""
        return self.total_time / self.total_queries if self.total_queries > 0 else 0.0
    
    def get_slow_query_count(self) -> int:
        """Get count of slow queries."""
        return len(self.slow_queries)
    
    def get_metrics_summary(self) -> Dict[str, Any]:
        """Get a summary of performance metrics."""
        return {
            "total_queries": self.total_queries,
            "total_time": round(self.total_time, 3),
            "average_time": round(self.get_average_time(), 3),
            "slow_queries": self.get_slow_query_count(),
            "recent_queries": self.query_times[-10:] if self.query_times else []
        }

# Global performance metrics instance
performance_metrics = PerformanceMetrics()

def monitor_query_performance(func):
    """Decorator to monitor query performance."""
    @wraps(func)
    async def wrapper(*args, **kwargs):
        start_time = time.time()
        
        try:
            result = await func(*args, **kwargs)
            execution_time = time.time() - start_time
            
            # Extract collection and pipeline info from args
            collection = args[0] if args else "unknown"
            pipeline_length = len(args[1]) if len(args) > 1 and isinstance(args[1], list) else 0
            
            performance_metrics.add_query_time(
                collection=collection,
                pipeline_length=pipeline_length,
                execution_time=execution_time,
                query_type="aggregation"
            )
            
            logger.info(f"Query executed: {collection} in {execution_time:.3f}s (pipeline length: {pipeline_length})")
            
            return result
            
        except Exception as e:
            execution_time = time.time() - start_time
            logger.error(f"Query failed after {execution_time:.3f}s: {str(e)}")
            raise
    
    return wrapper

@asynccontextmanager
async def performance_timer(operation_name: str):
    """Context manager for timing operations."""
    start_time = time.time()
    try:
        yield
    finally:
        execution_time = time.time() - start_time
        logger.info(f"Operation '{operation_name}' completed in {execution_time:.3f}s")

def log_pipeline_complexity(pipeline: list, collection: str, operation: str):
    """Log pipeline complexity metrics."""
    complexity_score = 0
    stage_counts = {}
    
    for stage in pipeline:
        stage_type = list(stage.keys())[0] if stage else "unknown"
        stage_counts[stage_type] = stage_counts.get(stage_type, 0) + 1
        
        # Assign complexity scores to different stages
        complexity_weights = {
            "$match": 1,
            "$project": 1,
            "$sort": 2,
            "$group": 3,
            "$lookup": 4,
            "$facet": 5,
            "$unwind": 2,
            "$addFields": 1,
            "$limit": 1,
            "$skip": 1
        }
        
        complexity_score += complexity_weights.get(stage_type, 2)
    
    logger.info(f"Pipeline complexity for {operation} on {collection}: "
                f"score={complexity_score}, stages={len(pipeline)}, "
                f"breakdown={stage_counts}")
    
    # Warn about high complexity
    if complexity_score > 15:
        logger.warning(f"High complexity pipeline detected: {operation} on {collection} "
                      f"(score: {complexity_score})")
    
    return complexity_score

def get_performance_report() -> Dict[str, Any]:
    """Get a comprehensive performance report."""
    return {
        "metrics": performance_metrics.get_metrics_summary(),
        "recommendations": _generate_recommendations()
    }

def _generate_recommendations() -> list:
    """Generate performance recommendations based on metrics."""
    recommendations = []
    
    avg_time = performance_metrics.get_average_time()
    slow_query_count = performance_metrics.get_slow_query_count()
    
    if avg_time > 0.5:
        recommendations.append("Consider adding indexes for frequently queried fields")
    
    if slow_query_count > 0:
        recommendations.append(f"Optimize {slow_query_count} slow queries detected")
    
    if performance_metrics.total_queries > 100:
        recommendations.append("Consider implementing query result caching")
    
    return recommendations