package tracing

import (
	"context"
	"io"
	"net/http"
	"net/http/httptest"
	"testing"

	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
	"go.opentelemetry.io/otel/trace"
)

func TestRestConfigWrapper_parentGated(t *testing.T) {
	t.Parallel()

	var gotTraceparent string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		gotTraceparent = r.Header.Get("traceparent")
		w.WriteHeader(http.StatusOK)
	}))
	t.Cleanup(srv.Close)

	sr := tracetest.NewSpanRecorder()
	tp := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(sr))
	t.Cleanup(func() { _ = tp.Shutdown(context.Background()) })

	rt := RestConfigWrapper(WithTracerProvider(tp))(http.DefaultTransport)
	do := func(ctx context.Context) {
		t.Helper()
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, srv.URL, nil)
		if err != nil {
			t.Fatal(err)
		}
		resp, err := rt.RoundTrip(req)
		if err != nil {
			t.Fatal(err)
		}
		_, _ = io.Copy(io.Discard, resp.Body)
		_ = resp.Body.Close()
	}

	// No parent span: informer watches, leader election. Must not trace.
	do(context.Background())
	if len(sr.Ended()) != 0 {
		t.Fatalf("request without parent span produced %d spans, want 0", len(sr.Ended()))
	}
	if gotTraceparent != "" {
		t.Fatalf("request without parent span injected traceparent %q", gotTraceparent)
	}

	// Under a parent span: one client child span, traceparent injected.
	ctx, parent := tp.Tracer("test").Start(context.Background(), "reconcile")
	do(ctx)
	parent.End()

	var client sdktrace.ReadOnlySpan
	for _, s := range sr.Ended() {
		if s.SpanKind() == trace.SpanKindClient {
			client = s
		}
	}
	if client == nil {
		t.Fatalf("no client span recorded, got %d spans", len(sr.Ended()))
	}
	if got := client.Parent().SpanID(); got != parent.SpanContext().SpanID() {
		t.Errorf("client span parent = %s, want %s", got, parent.SpanContext().SpanID())
	}
	if gotTraceparent == "" {
		t.Error("traceparent header not injected under a parent span")
	}
}