import os
import base64
from opentelemetry import trace
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import BatchSpanProcessor
from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter
from opentelemetry.sdk.resources import Resource

def setup_telemetry():
    """
    Configures OpenTelemetry to export traces to Langfuse.
    Dependencies: langfuse, opentelemetry-sdk, opentelemetry-exporter-otlp
    """
    
    # helper to check if vars exist
    secret_key = os.environ.get("LANGFUSE_SECRET_KEY")
    public_key = os.environ.get("LANGFUSE_PUBLIC_KEY")
    base_url = os.environ.get("LANGFUSE_BASE_URL", "https://cloud.langfuse.com")
    
    if not (secret_key and public_key):
        print("⚠ Langfuse credentials not found. Telemetry disabled.")
        return

    print(f"Initializing Langfuse Telemetry at {base_url}...")

    # Auth Header for Langfuse (Basic Auth)
    auth_str = f"{public_key}:{secret_key}"
    auth_bytes = auth_str.encode("ascii")
    base64_auth = base64.b64encode(auth_bytes).decode("ascii")
    
    # Configure OTLP HTTP Exporter
    # Langfuse OTLP HTTP endpoint: /api/public/otel/v1/traces
    
    # Construct endpoint
    # Remove trailing slash from base
    clean_base_url = base_url.rstrip("/")
    # Note: OTLPSpanExporter (HTTP) does NOT automatically append /v1/traces in all versions
    # or if we provide a full URL. Best to be explicit for Langfuse.
    endpoint = f"{clean_base_url}/api/public/otel/v1/traces"

    exporter = OTLPSpanExporter(
        endpoint=endpoint,
        headers={"Authorization": f"Basic {base64_auth}"}
    )

    # Resource
    resource = Resource.create(attributes={
        "service.name": "fraud_model_explainability_assistant",
        "service.version": "1.0.0"
    })

    # Provider
    provider = TracerProvider(resource=resource)
    processor = BatchSpanProcessor(exporter)
    provider.add_span_processor(processor)

    # Set global provider
    trace.set_tracer_provider(provider)
    
    print("✅ Langfuse Telemetry configured.")