package internalhttp

import (
	"bytes"
	"context"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"testing"

	"galaxy/user/internal/service/authdirectory"
	usertelemetry "galaxy/user/internal/telemetry"

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

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

	logger, buffer := newObservedLogger()
	telemetryRuntime, reader, recorder := newObservedInternalTelemetryRuntime(t)
	handler := mustNewHandler(t, Dependencies{
		Logger:    logger,
		Telemetry: telemetryRuntime,
		ExistsByUserID: existsByUserIDFunc(func(context.Context, authdirectory.ExistsByUserIDInput) (authdirectory.ExistsByUserIDResult, error) {
			return authdirectory.ExistsByUserIDResult{Exists: true}, nil
		}),
	})

	recorderHTTP := httptest.NewRecorder()
	request := httptest.NewRequest(http.MethodGet, "/api/v1/internal/users/user-123/exists", nil)
	request.Header.Set("traceparent", "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01")

	handler.ServeHTTP(recorderHTTP, request)

	require.Equal(t, http.StatusOK, recorderHTTP.Code)
	require.NotEmpty(t, recorder.Ended())
	assert.Contains(t, buffer.String(), "otel_trace_id")
	assert.Contains(t, buffer.String(), "otel_span_id")

	assertMetricCount(t, reader, "user.internal_http.requests", map[string]string{
		"route":        "/api/v1/internal/users/:user_id/exists",
		"method":       http.MethodGet,
		"edge_outcome": "success",
	}, 1)
}

func newObservedInternalTelemetryRuntime(t *testing.T) (*usertelemetry.Runtime, *sdkmetric.ManualReader, *tracetest.SpanRecorder) {
	t.Helper()

	reader := sdkmetric.NewManualReader()
	meterProvider := sdkmetric.NewMeterProvider(sdkmetric.WithReader(reader))
	recorder := tracetest.NewSpanRecorder()
	tracerProvider := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(recorder))

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

	return runtime, reader, recorder
}

func newObservedLogger() (*slog.Logger, *bytes.Buffer) {
	buffer := &bytes.Buffer{}
	return slog.New(slog.NewJSONHandler(buffer, &slog.HandlerOptions{Level: slog.LevelDebug})), buffer
}

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 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
}