"""
Observability module for Langfuse v3 integration with OpenTelemetry support.

This module provides:
- Single global CallbackHandler for LangChain integration
- Root span management for user requests
- Session and user tracking
- Background flushing for async operations
"""

import os
import base64
from typing import Optional, Dict, Any
from contextlib import contextmanager
from dotenv import load_dotenv

# Langfuse v3 imports
from langfuse import get_client
from langfuse.langchain import CallbackHandler

# OpenTelemetry imports for v3 compatibility  
from opentelemetry import trace
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import SimpleSpanProcessor
from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter

# Load environment variables
load_dotenv("env.local")

# Global callback handler instance (singleton)
_langfuse_handler: Optional[CallbackHandler] = None
_tracer_provider: Optional[TracerProvider] = None

def initialize_observability() -> bool:
    """
    Initialize Langfuse observability with OTEL integration.
    
    Returns:
        bool: True if initialization successful, False otherwise
    """
    global _langfuse_handler, _tracer_provider
    
    try:
        # Check required environment variables
        required_vars = ["LANGFUSE_PUBLIC_KEY", "LANGFUSE_SECRET_KEY", "LANGFUSE_HOST"]
        missing_vars = [var for var in required_vars if not os.getenv(var)]
        
        if missing_vars:
            print(f"Warning: Missing required environment variables: {missing_vars}")
            return False
        
        # Setup OTEL integration for Langfuse v3
        langfuse_auth = base64.b64encode(
            f"{os.getenv('LANGFUSE_PUBLIC_KEY')}:{os.getenv('LANGFUSE_SECRET_KEY')}".encode()
        ).decode()
        
        # Configure OTEL environment
        os.environ['OTEL_EXPORTER_OTLP_ENDPOINT'] = f"{os.getenv('LANGFUSE_HOST')}/api/public/otel"
        os.environ['OTEL_EXPORTER_OTLP_HEADERS'] = f"Authorization=Basic {langfuse_auth}"
        
        # Setup OpenTelemetry tracer provider
        _tracer_provider = TracerProvider()
        _tracer_provider.add_span_processor(SimpleSpanProcessor(OTLPSpanExporter()))
        trace.set_tracer_provider(_tracer_provider)
        
        # Create single global callback handler
        _langfuse_handler = CallbackHandler()
        
        print("✅ Langfuse observability initialized successfully")
        return True
        
    except Exception as e:
        print(f"❌ Failed to initialize observability: {e}")
        return False

def get_callback_handler() -> Optional[CallbackHandler]:
    """
    Get the global Langfuse callback handler.
    
    Returns:
        CallbackHandler or None if not initialized
    """
    global _langfuse_handler
    
    if _langfuse_handler is None:
        if initialize_observability():
            return _langfuse_handler
        return None
    
    return _langfuse_handler

@contextmanager
def start_root_span(
    name: str,
    user_id: str,
    session_id: str,
    metadata: Optional[Dict[str, Any]] = None
):
    """
    Context manager for creating root spans with user and session tracking.
    
    Args:
        name: Span name (e.g., "user-request")
        user_id: User identifier for session tracking
        session_id: Session identifier for conversation continuity
        metadata: Optional additional metadata
        
    Yields:
        Langfuse span context or None if creation fails
    """
    span = None
    try:
        # Create root span with v3 API
        client = get_client()
        span = client.start_as_current_span(name=name)
        span_context = span.__enter__()
        
        # Update trace with user and session information
        span_context.update_trace(
            user_id=user_id,
            session_id=session_id,
            tags=[
                os.getenv("ENV", "dev"),  # Environment tag
                "multi-agent-system"      # System identifier
            ]
        )
        
        # Add metadata if provided
        if metadata:
            span_context.update_trace(metadata=metadata)
        
        yield span_context
        
    except Exception as e:
        print(f"Warning: Failed to create root span: {e}")
        # Yield None so code doesn't break
        yield None
    finally:
        # Ensure proper cleanup
        if span is not None:
            try:
                span.__exit__(None, None, None)
            except Exception as e:
                print(f"Warning: Error closing span: {e}")

def flush_traces(background: bool = True) -> None:
    """
    Flush pending traces to Langfuse.
    
    Args:
        background: Whether to flush in background (non-blocking)
    """
    try:
        client = get_client()
        client.flush()
    except Exception as e:
        print(f"Warning: Failed to flush traces: {e}")

def shutdown_observability() -> None:
    """
    Clean shutdown of observability components.
    """
    global _tracer_provider
    
    try:
        # Flush any remaining traces
        flush_traces(background=False)
        
        # Shutdown tracer provider
        if _tracer_provider:
            _tracer_provider.shutdown()
            
    except Exception as e:
        print(f"Warning: Error during observability shutdown: {e}")

# Agent span helpers for consistent naming
@contextmanager
def agent_span(agent_name: str, metadata: Optional[Dict[str, Any]] = None):
    """
    Context manager for agent-level spans.
    
    Args:
        agent_name: Name of the agent (e.g., "lead", "research", "code")
        metadata: Optional metadata for the span
    """
    span_name = f"agent/{agent_name}"
    span = None
    
    try:
        client = get_client()
        span = client.start_as_current_span(name=span_name)
        span_context = span.__enter__()
        
        if metadata:
            span_context.update_trace(metadata=metadata)
        yield span_context
    except Exception as e:
        print(f"Warning: Failed to create agent span for {agent_name}: {e}")
        yield None
    finally:
        if span is not None:
            try:
                span.__exit__(None, None, None)
            except Exception as e:
                print(f"Warning: Error closing agent span: {e}")

@contextmanager  
def tool_span(tool_name: str, metadata: Optional[Dict[str, Any]] = None):
    """
    Context manager for tool-level spans.
    
    Args:
        tool_name: Name of the tool (e.g., "tavily_search", "calculator")
        metadata: Optional metadata for the span
    """
    span_name = f"tool/{tool_name}"
    span = None
    
    try:
        client = get_client()
        span = client.start_as_current_span(name=span_name)
        span_context = span.__enter__()
        
        if metadata:
            span_context.update_trace(metadata=metadata)
        yield span_context
    except Exception as e:
        print(f"Warning: Failed to create tool span for {tool_name}: {e}")
        yield None
    finally:
        if span is not None:
            try:
                span.__exit__(None, None, None)
            except Exception as e:
                print(f"Warning: Error closing tool span: {e}")