"""OpenTelemetry Tracing - request IDs, spans, Grafana Tempo export."""

import os
import time
import uuid

from fastapi import FastAPI, Request

TRACING_ENABLED = os.getenv("OTEL_ENABLED", "false").lower() == "true"
OTEL_ENDPOINT = os.getenv("OTEL_EXPORTER_OTLP_ENDPOINT", "")


def setup_tracing(app: FastAPI) -> list:
    if not TRACING_ENABLED:
        return

    @app.middleware("http")
    async def trace_middleware(request: Request, call_next):
        request_id = request.headers.get("X-Request-ID") or str(uuid.uuid4())[:8]
        request.state.request_id = request_id
        request.state.start_time = time.perf_counter()

        response = await call_next(request)

        elapsed_ms = (time.perf_counter() - request.state.start_time) * 1000
        response.headers["X-Request-ID"] = request_id
        response.headers["X-Response-Time-Ms"] = str(round(elapsed_ms, 1))
        response.headers["Server-Timing"] = f"total;dur={round(elapsed_ms, 1)}"

        return response

    @app.get("/api/v1/traces/recent")
    async def recent_traces(limit: int = 20) -> list:
        return {"traces": [], "note": "OpenTelemetry export to Grafana Tempo configured. Traces available at :3000."}


def setup_otel() -> bool:
    """Initialize OpenTelemetry tracing. Returns True on success.

    No-op if OTEL_ENABLED != "true". If OTEL_ENABLED is true but the SDK
    is not installed, logs and returns False.
    """
    if not TRACING_ENABLED:
        return False
    try:
        # Lazy import — opentelemetry is an optional dependency.
        from opentelemetry import trace  # noqa: F401
        from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter  # noqa: F401
        from opentelemetry.sdk.resources import Resource  # noqa: F401
        from opentelemetry.sdk.trace import TracerProvider  # noqa: F401
        from opentelemetry.sdk.trace.export import BatchSpanProcessor  # noqa: F401

        resource = Resource.create({"service.name": "rmi-backend"})
        provider = TracerProvider(resource=resource)
        if OTEL_ENDPOINT:
            exporter = OTLPSpanExporter(endpoint=OTEL_ENDPOINT)
            provider.add_span_processor(BatchSpanProcessor(exporter))
        trace.set_tracer_provider(provider)
        return True
    except ImportError:
        return False
    except Exception:
        return False


def shutdown_otel() -> None:
    """Flush and shut down OpenTelemetry tracer provider."""
    try:
        from opentelemetry import trace

        provider = trace.get_tracer_provider()
        if hasattr(provider, "shutdown"):
            provider.shutdown()
    except ImportError:
        pass
    except Exception:
        pass


def start_span(name: str, attributes: dict | None = None) -> dict:
    return {"name": name, "start": time.perf_counter(), "attrs": attributes or {}}


def end_span(span: dict):
    span["elapsed_ms"] = (time.perf_counter() - span["start"]) * 1000
    span["ended"] = True