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package main

import (
	"context"
	"encoding/json"
	"io"
	"net/http"
	"net/http/httptest"
	"os"
	"testing"

	"go.opentelemetry.io/otel/trace"
)

// TestOTLPJSONShape drives a real tracer provider through the exporter and
// checks the bytes that go on the wire.
//
// This is the test that justifies hand-writing the exporter instead of pulling
// in otlptracehttp (and with it grpc, genproto and grpc-gateway): if the JSON
// shape is right, the dependency is unnecessary.
func TestOTLPJSONShape(t *testing.T) {
	var captured []byte
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if got := r.Header.Get("Content-Type"); got != "application/json" {
			t.Errorf("Content-Type = %q, want application/json", got)
		}
		b, _ := io.ReadAll(r.Body)
		captured = b
		w.WriteHeader(http.StatusOK)
	}))
	defer srv.Close()

	t.Setenv("OTEL_EXPORTER_OTLP_ENDPOINT", srv.URL)
	t.Setenv("OTEL_SERVICE_NAME", "whatcd-resolver-test")
	os.Unsetenv("WHATCD_RESOLVER_DISABLE_TRACING")

	ctx := context.Background()
	shutdown, err := initTracing(ctx)
	if err != nil {
		t.Fatal(err)
	}

	err = inSpan(ctx, "outer", func(ctx context.Context, span trace.Span) error {
		attr(span, "artist-redacted-id", 2785)
		attr(span, "artist.name", "Kirinji")
		event(span, "did a thing")
		return inSpan(ctx, "inner", func(ctx context.Context, span trace.Span) error {
			attr(span, "nested", true)
			return nil
		})
	})
	if err != nil {
		t.Fatal(err)
	}

	// Flush.
	if err := shutdown(ctx); err != nil {
		t.Fatal(err)
	}
	if captured == nil {
		t.Fatal("exporter never posted anything")
	}

	// Optionally dump the exact wire bytes so they can be replayed against a
	// real collector (see the manpage, section TRACING).
	if dst := os.Getenv("WHATCD_RESOLVER_OTLP_DUMP"); dst != "" {
		if err := os.WriteFile(dst, captured, 0o644); err != nil {
			t.Fatal(err)
		}
	}

	var payload otlpPayload
	if err := json.Unmarshal(captured, &payload); err != nil {
		t.Fatalf("payload is not valid JSON: %v\n%s", err, captured)
	}
	if len(payload.ResourceSpans) != 1 {
		t.Fatalf("got %d resourceSpans, want 1", len(payload.ResourceSpans))
	}
	rs := payload.ResourceSpans[0]

	// service.name must be on the resource, otherwise Jaeger files the trace
	// under "unknown_service".
	var svc string
	for _, a := range rs.Resource.Attributes {
		if a.Key == "service.name" && a.Value.StringValue != nil {
			svc = *a.Value.StringValue
		}
	}
	if svc != "whatcd-resolver-test" {
		t.Errorf("service.name = %q, want whatcd-resolver-test", svc)
	}

	spans := map[string]otlpSpan{}
	for _, ss := range rs.ScopeSpans {
		for _, s := range ss.Spans {
			spans[s.Name] = s
		}
	}
	outer, ok := spans["outer"]
	if !ok {
		t.Fatalf("no span named outer, got %v", spans)
	}
	inner, ok := spans["inner"]
	if !ok {
		t.Fatalf("no span named inner, got %v", spans)
	}

	// IDs must be hex of the right length, timestamps decimal strings.
	if len(outer.TraceID) != 32 {
		t.Errorf("traceId = %q, want 32 hex chars", outer.TraceID)
	}
	if len(outer.SpanID) != 16 {
		t.Errorf("spanId = %q, want 16 hex chars", outer.SpanID)
	}
	if outer.StartTimeUnixNano == "" || outer.EndTimeUnixNano == "" {
		t.Error("timestamps must be set")
	}

	// Parent/child linkage is what makes the trace a tree in the UI.
	if inner.ParentSpanID != outer.SpanID {
		t.Errorf("inner.parentSpanId = %q, want outer.spanId %q", inner.ParentSpanID, outer.SpanID)
	}
	if inner.TraceID != outer.TraceID {
		t.Error("inner and outer must share a traceId")
	}

	// Attributes keep the "_." prefix the Haskell version used.
	attrs := map[string]otlpValue{}
	for _, a := range outer.Attributes {
		attrs[a.Key] = a.Value
	}
	if v, ok := attrs["_.artist-redacted-id"]; !ok {
		t.Errorf("missing _.artist-redacted-id, have %v", attrs)
	} else if v.IntValue == nil || *v.IntValue != "2785" {
		// int64 must be a *string* in OTLP JSON, not a number.
		t.Errorf("_.artist-redacted-id = %+v, want intValue \"2785\"", v)
	}
	if v, ok := attrs["_.artist.name"]; !ok || v.StringValue == nil || *v.StringValue != "Kirinji" {
		t.Errorf("_.artist.name = %+v, want stringValue Kirinji", v)
	}
	if len(outer.Events) != 1 || outer.Events[0].Name != "did a thing" {
		t.Errorf("events = %+v, want one named 'did a thing'", outer.Events)
	}
}

// TestOTLPErrorStatus checks that a failing operation is marked as an error, so
// it shows up red in Jaeger like the Haskell recordError did.
func TestOTLPErrorStatus(t *testing.T) {
	var captured []byte
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		b, _ := io.ReadAll(r.Body)
		captured = b
		w.WriteHeader(http.StatusOK)
	}))
	defer srv.Close()

	t.Setenv("OTEL_EXPORTER_OTLP_ENDPOINT", srv.URL)
	ctx := context.Background()
	shutdown, err := initTracing(ctx)
	if err != nil {
		t.Fatal(err)
	}
	_ = inSpan(ctx, "failing", func(ctx context.Context, span trace.Span) error {
		return io.ErrUnexpectedEOF
	})
	if err := shutdown(ctx); err != nil {
		t.Fatal(err)
	}

	var payload otlpPayload
	if err := json.Unmarshal(captured, &payload); err != nil {
		t.Fatal(err)
	}
	s := payload.ResourceSpans[0].ScopeSpans[0].Spans[0]
	if s.Status.Code != 2 {
		t.Errorf("status.code = %d, want 2 (ERROR)", s.Status.Code)
	}
	if s.Status.Message == "" {
		t.Error("status.message should carry the error text")
	}
	// An exception event is recorded by RecordError.
	found := false
	for _, ev := range s.Events {
		if ev.Name == "exception" {
			found = true
		}
	}
	if !found {
		t.Errorf("expected an 'exception' event, got %+v", s.Events)
	}
}

// TestTracingDisabled makes sure the kill switch works and that spans are still
// safe to use when tracing is off.
func TestTracingDisabled(t *testing.T) {
	t.Setenv("WHATCD_RESOLVER_DISABLE_TRACING", "1")
	ctx := context.Background()
	shutdown, err := initTracing(ctx)
	if err != nil {
		t.Fatal(err)
	}
	if err := inSpan(ctx, "noop", func(ctx context.Context, span trace.Span) error {
		attr(span, "x", 1)
		return nil
	}); err != nil {
		t.Fatal(err)
	}
	if err := shutdown(ctx); err != nil {
		t.Fatal(err)
	}
}