package telemetry

import (
	"context"
	"testing"
	"time"
)

// TestConfigValidate covers the supported and rejected exporter selections.
func TestConfigValidate(t *testing.T) {
	for _, exp := range []string{ExporterNone, ExporterStdout, ExporterOTLP} {
		c := DefaultConfig("svc")
		c.TracesExporter = exp
		c.MetricsExporter = exp
		if err := c.Validate(); err != nil {
			t.Errorf("exporter %q must be valid: %v", exp, err)
		}
	}
	bad := DefaultConfig("svc")
	bad.TracesExporter = "prometheus"
	if err := bad.Validate(); err == nil {
		t.Error("unsupported exporter must be rejected")
	}
	if err := DefaultConfig("").Validate(); err == nil {
		t.Error("empty service name must be rejected")
	}
}

// TestNewNoneAndStdout builds the providers with the none and stdout exporters,
// starts the runtime metrics and shuts them down.
func TestNewNoneAndStdout(t *testing.T) {
	for _, exp := range []string{ExporterNone, ExporterStdout} {
		cfg := DefaultConfig("svc")
		cfg.TracesExporter = exp
		cfg.MetricsExporter = exp
		rt, err := New(context.Background(), cfg)
		if err != nil {
			t.Fatalf("New(%q): %v", exp, err)
		}
		if rt.TracerProvider() == nil || rt.MeterProvider() == nil {
			t.Errorf("New(%q): nil provider", exp)
		}
		if err := rt.StartRuntimeMetrics(); err != nil {
			t.Errorf("StartRuntimeMetrics(%q): %v", exp, err)
		}
		if err := rt.Shutdown(context.Background()); err != nil {
			t.Errorf("Shutdown(%q): %v", exp, err)
		}
	}
}

// TestNewOTLPConstructs verifies the otlp exporter selection builds providers
// without a reachable collector (the gRPC exporters dial lazily). Shutdown is
// best-effort: with no collector the final export may error, so it is bounded and
// its result ignored.
func TestNewOTLPConstructs(t *testing.T) {
	cfg := DefaultConfig("svc")
	cfg.TracesExporter = ExporterOTLP
	cfg.MetricsExporter = ExporterOTLP
	rt, err := New(context.Background(), cfg)
	if err != nil {
		t.Fatalf("New(otlp): %v", err)
	}
	if rt.TracerProvider() == nil || rt.MeterProvider() == nil {
		t.Error("New(otlp): nil provider")
	}
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	_ = rt.Shutdown(ctx)
}

// TestNilRuntime checks the nil-receiver fallbacks used before initialisation.
func TestNilRuntime(t *testing.T) {
	var rt *Runtime
	if rt.TracerProvider() == nil {
		t.Error("nil runtime must fall back to the global tracer provider")
	}
	if rt.MeterProvider() == nil {
		t.Error("nil runtime must fall back to the global meter provider")
	}
	if err := rt.Shutdown(context.Background()); err != nil {
		t.Errorf("nil runtime Shutdown: %v", err)
	}
}