import importlib

from fastapi import FastAPI

from app.config import ObservabilityConfig


def _reload_tracing_module():
    tracing_module = importlib.import_module("app.runtime.tracing")
    return importlib.reload(tracing_module)


def _make_observability_config(**overrides) -> ObservabilityConfig:
    payload = {
        "enabled": True,
        "service_name": "delivery-aggregator",
        "otlp_endpoint": "http://collector:4317",
        "otlp_insecure": True,
    }
    payload.update(overrides)
    return ObservabilityConfig(**payload)


def test_configure_tracing_skips_bootstrap_when_disabled(monkeypatch) -> None:
    tracing_module = _reload_tracing_module()
    calls = {"provider": 0, "fastapi": 0, "httpx": 0, "redis": 0}

    def fake_get_or_create_tracer_provider(_observability):
        calls["provider"] += 1
        return object()

    def fake_instrument_fastapi_app(_app, *, tracer_provider) -> None:
        del tracer_provider
        calls["fastapi"] += 1

    def fake_instrument_httpx(*, tracer_provider) -> None:
        del tracer_provider
        calls["httpx"] += 1

    def fake_instrument_redis(*, tracer_provider) -> None:
        del tracer_provider
        calls["redis"] += 1

    monkeypatch.setattr(
        tracing_module,
        "_get_or_create_tracer_provider",
        fake_get_or_create_tracer_provider,
    )
    monkeypatch.setattr(
        tracing_module,
        "_instrument_fastapi_app",
        fake_instrument_fastapi_app,
    )
    monkeypatch.setattr(tracing_module, "_instrument_httpx", fake_instrument_httpx)
    monkeypatch.setattr(tracing_module, "_instrument_redis", fake_instrument_redis)

    tracing_module.configure_tracing(
        FastAPI(),
        _make_observability_config(enabled=False),
    )

    assert calls == {"provider": 0, "fastapi": 0, "httpx": 0, "redis": 0}


def test_build_tracer_provider_uses_otlp_exporter_and_service_name(monkeypatch) -> None:
    tracing_module = _reload_tracing_module()
    created: dict[str, object] = {}

    class FakeExporter:
        def __init__(self, *, endpoint: str, insecure: bool) -> None:
            created["endpoint"] = endpoint
            created["insecure"] = insecure

    class FakeBatchSpanProcessor:
        def __init__(self, exporter: object) -> None:
            self.exporter = exporter
            created["processor_exporter"] = exporter

    class FakeTracerProvider:
        def __init__(self, *, resource) -> None:
            self.resource = resource
            self.span_processors: list[object] = []

        def add_span_processor(self, processor: object) -> None:
            self.span_processors.append(processor)

    monkeypatch.setattr(tracing_module, "OTLPSpanExporter", FakeExporter)
    monkeypatch.setattr(tracing_module, "BatchSpanProcessor", FakeBatchSpanProcessor)
    monkeypatch.setattr(tracing_module, "TracerProvider", FakeTracerProvider)

    provider = tracing_module._build_tracer_provider(
        _make_observability_config(
            service_name="g2s-aggregator",
            otlp_endpoint="http://trace-backend:4317",
            otlp_insecure=False,
        )
    )

    assert created["endpoint"] == "http://trace-backend:4317"
    assert created["insecure"] is False
    assert provider.resource.attributes["service.name"] == "g2s-aggregator"
    assert len(provider.span_processors) == 1
    assert created["processor_exporter"] is provider.span_processors[0].exporter


def test_configure_tracing_reuses_provider_and_global_instrumentation(monkeypatch) -> None:
    tracing_module = _reload_tracing_module()
    created = {
        "exporters": 0,
        "providers": 0,
        "set_provider_calls": 0,
        "fastapi_apps": [],
        "httpx_calls": 0,
        "redis_calls": 0,
    }

    class FakeExporter:
        def __init__(self, *, endpoint: str, insecure: bool) -> None:
            created["exporters"] += 1
            self.endpoint = endpoint
            self.insecure = insecure

    class FakeBatchSpanProcessor:
        def __init__(self, exporter: object) -> None:
            self.exporter = exporter

    class FakeTracerProvider:
        def __init__(self, *, resource) -> None:
            created["providers"] += 1
            self.resource = resource
            self.span_processors: list[object] = []

        def add_span_processor(self, processor: object) -> None:
            self.span_processors.append(processor)

    class FakeInstrumentor:
        def __init__(self, kind: str) -> None:
            self.kind = kind
            self.is_instrumented_by_opentelemetry = False

        def instrument(self, **kwargs) -> None:
            assert kwargs["tracer_provider"] is not None
            created[f"{self.kind}_calls"] += 1
            self.is_instrumented_by_opentelemetry = True

    class FakeFastAPIInstrumentor:
        @staticmethod
        def instrument_app(app: FastAPI, *, tracer_provider) -> None:
            assert tracer_provider is not None
            created["fastapi_apps"].append(app)
            app._is_instrumented_by_opentelemetry = True

    def fake_set_tracer_provider(_provider: object) -> None:
        created["set_provider_calls"] += 1

    monkeypatch.setattr(tracing_module, "OTLPSpanExporter", FakeExporter)
    monkeypatch.setattr(tracing_module, "BatchSpanProcessor", FakeBatchSpanProcessor)
    monkeypatch.setattr(tracing_module, "TracerProvider", FakeTracerProvider)
    monkeypatch.setattr(
        tracing_module,
        "_HTTPX_INSTRUMENTOR",
        FakeInstrumentor("httpx"),
    )
    monkeypatch.setattr(
        tracing_module,
        "_REDIS_INSTRUMENTOR",
        FakeInstrumentor("redis"),
    )
    monkeypatch.setattr(tracing_module, "FastAPIInstrumentor", FakeFastAPIInstrumentor)
    monkeypatch.setattr(tracing_module.trace, "set_tracer_provider", fake_set_tracer_provider)

    app_one = FastAPI()
    app_two = FastAPI()
    observability = _make_observability_config()

    tracing_module.configure_tracing(app_one, observability)
    tracing_module.configure_tracing(app_one, observability)
    tracing_module.configure_tracing(app_two, observability)

    assert created["exporters"] == 1
    assert created["providers"] == 1
    assert created["set_provider_calls"] == 1
    assert created["fastapi_apps"] == [app_one, app_two]
    assert created["httpx_calls"] == 1
    assert created["redis_calls"] == 1