package telemetry

import (
	"bytes"
	"context"
	"io"
	"log/slog"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"go.opentelemetry.io/otel/attribute"
	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/metric/metricdata"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
)

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

	runtime, err := newProcess(context.Background(), ProcessConfig{
		ServiceName:     "galaxy-user-test",
		TracesExporter:  processExporterNone,
		MetricsExporter: processExporterNone,
	}, slog.New(slog.NewTextHandler(io.Discard, nil)), io.Discard, io.Discard)
	require.NoError(t, err)

	assert.NotNil(t, runtime.TracerProvider())
	assert.NotNil(t, runtime.MeterProvider())
	assert.NotNil(t, runtime.Handler())
	require.NoError(t, runtime.Shutdown(context.Background()))
	require.NoError(t, runtime.Shutdown(context.Background()))
}

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

	traceBuffer := &bytes.Buffer{}
	metricBuffer := &bytes.Buffer{}

	runtime, err := newProcess(context.Background(), ProcessConfig{
		ServiceName:          "galaxy-user-test",
		TracesExporter:       processExporterNone,
		MetricsExporter:      processExporterNone,
		StdoutTracesEnabled:  true,
		StdoutMetricsEnabled: true,
	}, slog.New(slog.NewTextHandler(io.Discard, nil)), traceBuffer, metricBuffer)
	require.NoError(t, err)

	ctx, span := runtime.TracerProvider().Tracer("test").Start(context.Background(), "internal-request")
	runtime.RecordUserCreationOutcome(ctx, "created")
	span.End()

	require.NoError(t, runtime.Shutdown(context.Background()))
	assert.NotEmpty(t, traceBuffer.String())
	assert.NotEmpty(t, metricBuffer.String())
}

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

	reader := sdkmetric.NewManualReader()
	meterProvider := sdkmetric.NewMeterProvider(sdkmetric.WithReader(reader))
	tracerProvider := sdktrace.NewTracerProvider()

	runtime, err := NewWithProviders(meterProvider, tracerProvider)
	require.NoError(t, err)

	runtime.RecordInternalHTTPRequest(context.Background(), []attribute.KeyValue{
		attribute.String("route", "/api/v1/internal/users/:user_id/exists"),
		attribute.String("method", "GET"),
		attribute.String("edge_outcome", "success"),
	}, 125*time.Millisecond)
	runtime.RecordAuthResolutionOutcome(context.Background(), "resolve_by_email", "existing")
	runtime.RecordUserCreationOutcome(context.Background(), "created")
	runtime.RecordRaceNameReservationConflict(context.Background(), "update_my_profile")
	runtime.RecordEntitlementMutation(context.Background(), "grant", "success")
	runtime.RecordSanctionMutation(context.Background(), "apply", "conflict")
	runtime.RecordLimitMutation(context.Background(), "remove", "subject_not_found")
	runtime.RecordEventPublicationFailure(context.Background(), "user.profile.changed")

	assertMetricCount(t, reader, "user.internal_http.requests", map[string]string{
		"route":        "/api/v1/internal/users/:user_id/exists",
		"method":       "GET",
		"edge_outcome": "success",
	}, 1)
	assertHistogramCount(t, reader, "user.internal_http.duration", map[string]string{
		"route":        "/api/v1/internal/users/:user_id/exists",
		"method":       "GET",
		"edge_outcome": "success",
	}, 1)
	assertMetricCount(t, reader, "user.auth_resolution.outcomes", map[string]string{
		"operation": "resolve_by_email",
		"outcome":   "existing",
	}, 1)
	assertMetricCount(t, reader, "user.user_creation.outcomes", map[string]string{
		"outcome": "created",
	}, 1)
	assertMetricCount(t, reader, "user.race_name.reservation_conflicts", map[string]string{
		"operation": "update_my_profile",
	}, 1)
	assertMetricCount(t, reader, "user.entitlement.mutations", map[string]string{
		"command": "grant",
		"outcome": "success",
	}, 1)
	assertMetricCount(t, reader, "user.sanction.mutations", map[string]string{
		"command": "apply",
		"outcome": "conflict",
	}, 1)
	assertMetricCount(t, reader, "user.limit.mutations", map[string]string{
		"command": "remove",
		"outcome": "subject_not_found",
	}, 1)
	assertMetricCount(t, reader, "user.event_publication_failures", map[string]string{
		"event_type": "user.profile.changed",
	}, 1)
}

func assertMetricCount(t *testing.T, reader *sdkmetric.ManualReader, metricName string, wantAttrs map[string]string, wantValue int64) {
	t.Helper()

	var resourceMetrics metricdata.ResourceMetrics
	require.NoError(t, reader.Collect(context.Background(), &resourceMetrics))

	for _, scopeMetrics := range resourceMetrics.ScopeMetrics {
		for _, metric := range scopeMetrics.Metrics {
			if metric.Name != metricName {
				continue
			}

			sum, ok := metric.Data.(metricdata.Sum[int64])
			require.True(t, ok)

			for _, point := range sum.DataPoints {
				if hasMetricAttributes(point.Attributes.ToSlice(), wantAttrs) {
					assert.Equal(t, wantValue, point.Value)
					return
				}
			}
		}
	}

	require.Failf(t, "test failed", "metric %q with attrs %v not found", metricName, wantAttrs)
}

func assertHistogramCount(t *testing.T, reader *sdkmetric.ManualReader, metricName string, wantAttrs map[string]string, wantCount uint64) {
	t.Helper()

	var resourceMetrics metricdata.ResourceMetrics
	require.NoError(t, reader.Collect(context.Background(), &resourceMetrics))

	for _, scopeMetrics := range resourceMetrics.ScopeMetrics {
		for _, metric := range scopeMetrics.Metrics {
			if metric.Name != metricName {
				continue
			}

			histogram, ok := metric.Data.(metricdata.Histogram[float64])
			require.True(t, ok)

			for _, point := range histogram.DataPoints {
				if hasMetricAttributes(point.Attributes.ToSlice(), wantAttrs) {
					assert.Equal(t, wantCount, point.Count)
					return
				}
			}
		}
	}

	require.Failf(t, "test failed", "histogram %q with attrs %v not found", metricName, wantAttrs)
}

func hasMetricAttributes(values []attribute.KeyValue, want map[string]string) bool {
	if len(values) != len(want) {
		return false
	}

	for _, value := range values {
		if want[string(value.Key)] != value.Value.AsString() {
			return false
		}
	}

	return true
}