// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package prometheus

import (
	"fmt"
	"testing"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/stretchr/testify/require"

	"go.opentelemetry.io/otel/sdk/metric"
)

func run(n int) func(b *testing.B) {
	return func(b *testing.B) {
		ctx := b.Context()
		registry := prometheus.NewRegistry()
		exporter, err := New(WithRegisterer(registry))
		require.NoError(b, err)
		provider := metric.NewMeterProvider(metric.WithReader(exporter))
		meter := provider.Meter("testmeter")

		for i := range n {
			counter, err := meter.Float64Counter(fmt.Sprintf("foo_%d", i))
			require.NoError(b, err)
			counter.Add(ctx, float64(i))
		}

		b.ReportAllocs()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			_, err := registry.Gather()
			require.NoError(b, err)
		}
	}
}

func benchmarkCollect(b *testing.B, n int) {
	b.Run("ObservabilityDisabled", run(n))
	b.Run("ObservabilityEnabled", func(b *testing.B) {
		b.Setenv("OTEL_GO_X_OBSERVABILITY", "true")
		bmark := run(n)
		bmark(b)
	})
}

func BenchmarkCollect1(b *testing.B)     { benchmarkCollect(b, 1) }
func BenchmarkCollect10(b *testing.B)    { benchmarkCollect(b, 10) }
func BenchmarkCollect100(b *testing.B)   { benchmarkCollect(b, 100) }
func BenchmarkCollect1000(b *testing.B)  { benchmarkCollect(b, 1000) }
func BenchmarkCollect10000(b *testing.B) { benchmarkCollect(b, 10000) }