package store

import (
	"encoding/json"
	"fmt"
	"orchestra/internal/authz"
	"orchestra/internal/domain"
	"sort"
	"testing"
	"time"
)

// Append includes the fsynced event-log write and sparse projection-cache
// checkpoint. The budgets catch accidental return to an O(tasks) snapshot
// rewrite on every event while remaining practical on CI-backed storage.
const (
	appendP95Budget1K  = 10 * time.Second
	appendP95Budget10K = 90 * time.Second
)

func BenchmarkAppend1K(b *testing.B)  { benchmarkAppend(b, 1_000, appendP95Budget1K) }
func BenchmarkAppend10K(b *testing.B) { benchmarkAppend(b, 10_000, appendP95Budget10K) }

func benchmarkAppend(b *testing.B, events int, budget time.Duration) {
	b.Helper()
	samples := make([]time.Duration, 0, b.N)
	b.ResetTimer()
	for sample := 0; sample < b.N; sample++ {
		b.StopTimer()
		s, err := Open(b.TempDir())
		if err != nil {
			b.Fatal(err)
		}
		b.StartTimer()
		started := time.Now()
		for i := 0; i < events; i++ {
			id := fmt.Sprintf("task-%d", i)
			payload, _ := json.Marshal(map[string]any{"source": "benchmark", "external_id": id, "project": "p"})
			if err := s.Append(domain.Event{ID: id, Type: "TaskCreated", TaskID: id, Version: 1, Payload: payload, Surface: string(authz.System)}); err != nil {
				b.Fatal(err)
			}
		}
		samples = append(samples, time.Since(started))
		b.StopTimer()
	}
	p95 := appendDurationP95(samples)
	b.ReportMetric(float64(p95.Microseconds()), "append_p95_us")
	if p95 > budget {
		b.Fatalf("append p95 %s exceeds budget %s for %d events", p95, budget, events)
	}
}

func appendDurationP95(samples []time.Duration) time.Duration {
	if len(samples) == 0 {
		return 0
	}
	sorted := append([]time.Duration(nil), samples...)
	sort.Slice(sorted, func(i, j int) bool { return sorted[i] < sorted[j] })
	return sorted[(len(sorted)*95+99)/100-1]
}