"""Centralized runtime OpenTelemetry tracing bootstrap."""

from fastapi import FastAPI
from opentelemetry import trace
from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import OTLPSpanExporter
from opentelemetry.instrumentation.fastapi import FastAPIInstrumentor
from opentelemetry.instrumentation.httpx import HTTPXClientInstrumentor
from opentelemetry.instrumentation.redis import RedisInstrumentor
from opentelemetry.sdk.resources import Resource
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import BatchSpanProcessor

from app.config import ObservabilityConfig

_HTTPX_INSTRUMENTOR = HTTPXClientInstrumentor()
_REDIS_INSTRUMENTOR = RedisInstrumentor()
_TRACER_PROVIDER: TracerProvider | None = None


def configure_tracing(app: FastAPI, observability: ObservabilityConfig) -> None:
    if not observability.enabled:
        return

    tracer_provider = _get_or_create_tracer_provider(observability)
    _instrument_fastapi_app(app, tracer_provider=tracer_provider)
    _instrument_httpx(tracer_provider=tracer_provider)
    _instrument_redis(tracer_provider=tracer_provider)


def _get_or_create_tracer_provider(observability: ObservabilityConfig) -> TracerProvider:
    global _TRACER_PROVIDER

    if _TRACER_PROVIDER is not None:
        return _TRACER_PROVIDER

    tracer_provider = _build_tracer_provider(observability)
    trace.set_tracer_provider(tracer_provider)
    _TRACER_PROVIDER = tracer_provider
    return tracer_provider


def _build_tracer_provider(observability: ObservabilityConfig) -> TracerProvider:
    exporter = _build_span_exporter(observability)
    tracer_provider = TracerProvider(resource=_build_resource(observability))
    tracer_provider.add_span_processor(BatchSpanProcessor(exporter))
    return tracer_provider


def _build_span_exporter(observability: ObservabilityConfig) -> OTLPSpanExporter:
    return OTLPSpanExporter(
        endpoint=observability.otlp_endpoint,
        insecure=observability.otlp_insecure,
    )


def _build_resource(observability: ObservabilityConfig) -> Resource:
    return Resource.create({"service.name": observability.service_name})


def _instrument_fastapi_app(app: FastAPI, *, tracer_provider: TracerProvider) -> None:
    if getattr(app, "_is_instrumented_by_opentelemetry", False):
        return
    FastAPIInstrumentor.instrument_app(app, tracer_provider=tracer_provider)


def _instrument_httpx(*, tracer_provider: TracerProvider) -> None:
    if _HTTPX_INSTRUMENTOR.is_instrumented_by_opentelemetry:
        return
    _HTTPX_INSTRUMENTOR.instrument(tracer_provider=tracer_provider)


def _instrument_redis(*, tracer_provider: TracerProvider) -> None:
    if _REDIS_INSTRUMENTOR.is_instrumented_by_opentelemetry:
        return
    _REDIS_INSTRUMENTOR.instrument(tracer_provider=tracer_provider)