package tracing

// Tests for tracing initialization, config parsing, and helper wrappers.

import (
	"context"
	"errors"
	"testing"

	"github.com/stretchr/testify/require"
)

// TestNewTracer_Disabled verifies disabled mode initializes and safely starts spans.
func TestNewTracer_Disabled(t *testing.T) {
	cfg := DefaultConfig()
	cfg.Enabled = false

	tracer, err := NewTracer(cfg)
	require.NoError(t, err)
	require.NotNil(t, tracer)

	ctx, span := tracer.StartSpan(context.Background(), "test")
	require.NotNil(t, ctx)
	require.NotNil(t, span)
	require.NotPanics(t, func() {
		span.SetAttribute("k", "v")
		span.RecordError(errors.New("boom"))
		span.End()
	})
}

// TestNewTracer_Enabled verifies enabled mode initializes tracer components.
func TestNewTracer_Enabled(t *testing.T) {
	cfg := DefaultConfig()
	cfg.Enabled = true

	tracer, err := NewTracer(cfg)
	require.NoError(t, err)
	require.NotNil(t, tracer)
	require.NoError(t, tracer.Shutdown(context.Background()))
}

// TestShutdown_Disabled verifies shutdown is a no-op when tracing is disabled.
func TestShutdown_Disabled(t *testing.T) {
	tracer, err := NewTracer(DefaultConfig())
	require.NoError(t, err)

	err = tracer.Shutdown(context.Background())
	require.NoError(t, err)
}

// TestTraceServiceOperation verifies tracing wraps a service operation and returns errors.
func TestTraceServiceOperation(t *testing.T) {
	tracer, err := NewTracer(DefaultConfig())
	require.NoError(t, err)

	expected := errors.New("boom")
	err = TraceServiceOperation(context.Background(), tracer, "svc", "op", func(ctx context.Context) error {
		return expected
	})
	require.Equal(t, expected, err)
}

// TestTraceDatabaseOperation verifies tracing wraps a database operation and calls the function.
func TestTraceDatabaseOperation(t *testing.T) {
	tracer, err := NewTracer(DefaultConfig())
	require.NoError(t, err)

	called := false
	err = TraceDatabaseOperation(context.Background(), tracer, "select", "users", func(ctx context.Context) error {
		called = true
		return nil
	})
	require.NoError(t, err)
	require.True(t, called)
}

// TestConfigFromEnvDefaults verifies defaults are used when env vars are absent or empty.
func TestConfigFromEnvDefaults(t *testing.T) {
	t.Setenv("TRACING_ENABLED", "")
	t.Setenv("TRACING_SERVICE_NAME", "")
	t.Setenv("TRACING_SERVICE_VERSION", "")
	t.Setenv("TRACING_ENVIRONMENT", "")
	t.Setenv("TRACING_OTLP_ENDPOINT", "")
	t.Setenv("TRACING_JAEGER_ENDPOINT", "")
	t.Setenv("TRACING_SAMPLE_RATE", "")

	cfg := ConfigFromEnv()
	def := DefaultConfig()

	require.Equal(t, def, cfg)
}

// TestConfigFromEnvOverrides verifies valid env vars override defaults.
func TestConfigFromEnvOverrides(t *testing.T) {
	t.Setenv("TRACING_ENABLED", "true")
	t.Setenv("TRACING_SERVICE_NAME", "gateway")
	t.Setenv("TRACING_SERVICE_VERSION", "1.2.3")
	t.Setenv("TRACING_ENVIRONMENT", "production")
	t.Setenv("TRACING_OTLP_ENDPOINT", "https://otel-collector:4318/v1/traces")
	t.Setenv("TRACING_JAEGER_ENDPOINT", "http://jaeger:14268/api/traces")
	t.Setenv("TRACING_SAMPLE_RATE", "0.25")

	cfg := ConfigFromEnv()
	require.True(t, cfg.Enabled)
	require.Equal(t, "gateway", cfg.ServiceName)
	require.Equal(t, "1.2.3", cfg.ServiceVersion)
	require.Equal(t, "production", cfg.Environment)
	require.Equal(t, "https://otel-collector:4318/v1/traces", cfg.OTLPEndpoint)
	require.Equal(t, "http://jaeger:14268/api/traces", cfg.JaegerEndpoint)
	require.Equal(t, 0.25, cfg.SampleRate)
}

// TestConfigFromEnvInvalidSampleRate verifies invalid sample rate falls back to default.
func TestConfigFromEnvInvalidSampleRate(t *testing.T) {
	t.Setenv("TRACING_SAMPLE_RATE", "not-a-float")

	cfg := ConfigFromEnv()
	require.Equal(t, DefaultConfig().SampleRate, cfg.SampleRate)
}

// TestConfigFromEnvLegacyEndpointFallback verifies legacy env var is used when OTLP endpoint is unset.
func TestConfigFromEnvLegacyEndpointFallback(t *testing.T) {
	t.Setenv("TRACING_OTLP_ENDPOINT", "")
	t.Setenv("TRACING_JAEGER_ENDPOINT", "http://legacy:14268/api/traces")

	cfg := ConfigFromEnv()
	require.Equal(t, "http://legacy:14268/api/traces", cfg.OTLPEndpoint)
	require.Equal(t, "http://legacy:14268/api/traces", cfg.JaegerEndpoint)
}

// TestConfigFromEnvEndpointPrecedence verifies OTLP endpoint has precedence over legacy Jaeger endpoint.
func TestConfigFromEnvEndpointPrecedence(t *testing.T) {
	t.Setenv("TRACING_OTLP_ENDPOINT", "https://collector:4318/v1/traces")
	t.Setenv("TRACING_JAEGER_ENDPOINT", "http://legacy:14268/api/traces")

	cfg := ConfigFromEnv()
	require.Equal(t, "https://collector:4318/v1/traces", cfg.OTLPEndpoint)
	require.Equal(t, "http://legacy:14268/api/traces", cfg.JaegerEndpoint)
}