// cmd/loadtest : script de charge maison pour l'API control-plane (aucun
// outil externe type k6/locust — un seul binaire Go qui mesure latence et
// taux d'erreur sous charge concurrente sur un endpoint authentifié).
//
// Usage :
//
//	go run ./cmd/loadtest --url https://control-plane.example \
//	  --username admin --password *** \
//	  --endpoint /api/v1/demos --concurrency 20 --duration 30s
package main

import (
	"bytes"
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"sort"
	"sync"
	"sync/atomic"
	"time"
)

func main() {
	baseURL := flag.String("url", "http://localhost:8080", "URL de base de l'API")
	username := flag.String("username", "", "identifiant admin (pour /auth/login)")
	password := flag.String("password", "", "mot de passe admin")
	endpoint := flag.String("endpoint", "/api/v1/demos", "endpoint GET à charger (authentifié)")
	concurrency := flag.Int("concurrency", 10, "nombre de workers concurrents")
	duration := flag.Duration("duration", 30*time.Second, "durée du test")
	flag.Parse()

	if *username == "" || *password == "" {
		log.Fatal("--username et --password requis (compte admin)")
	}

	token, err := login(*baseURL, *username, *password)
	if err != nil {
		log.Fatalf("login: %v", err)
	}
	log.Printf("connecté — %d workers pendant %s sur %s%s", *concurrency, *duration, *baseURL, *endpoint)

	var (
		mu        sync.Mutex
		latencies []time.Duration
		okCount   int64
		errCount  int64
	)

	ctx, cancel := context.WithTimeout(context.Background(), *duration)
	defer cancel()

	client := &http.Client{Timeout: 10 * time.Second}
	var wg sync.WaitGroup
	for i := 0; i < *concurrency; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for {
				select {
				case <-ctx.Done():
					return
				default:
				}

				start := time.Now()
				req, err := http.NewRequestWithContext(ctx, http.MethodGet, *baseURL+*endpoint, nil)
				if err != nil {
					atomic.AddInt64(&errCount, 1)
					continue
				}
				req.Header.Set("Authorization", "Bearer "+token)

				resp, err := client.Do(req)
				elapsed := time.Since(start)
				if err != nil {
					atomic.AddInt64(&errCount, 1)
					continue
				}
				io.Copy(io.Discard, resp.Body)
				resp.Body.Close()

				if resp.StatusCode >= 400 {
					atomic.AddInt64(&errCount, 1)
					continue
				}
				atomic.AddInt64(&okCount, 1)
				mu.Lock()
				latencies = append(latencies, elapsed)
				mu.Unlock()
			}
		}()
	}
	wg.Wait()

	report(latencies, okCount, errCount, *duration)
}

func login(baseURL, username, password string) (string, error) {
	body, err := json.Marshal(map[string]string{"username": username, "password": password})
	if err != nil {
		return "", err
	}
	resp, err := http.Post(baseURL+"/api/v1/auth/login", "application/json", bytes.NewReader(body))
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		b, _ := io.ReadAll(resp.Body)
		return "", fmt.Errorf("statut %d: %s", resp.StatusCode, b)
	}
	var out struct {
		Token string `json:"token"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return "", err
	}
	return out.Token, nil
}

func report(latencies []time.Duration, ok, errs int64, duration time.Duration) {
	sort.Slice(latencies, func(i, j int) bool { return latencies[i] < latencies[j] })

	percentile := func(p float64) time.Duration {
		if len(latencies) == 0 {
			return 0
		}
		idx := int(float64(len(latencies)-1) * p)
		return latencies[idx]
	}

	total := ok + errs
	var errRate float64
	if total > 0 {
		errRate = 100 * float64(errs) / float64(total)
	}

	fmt.Println()
	fmt.Println("=== Résultat ===")
	fmt.Printf("Durée                 : %s\n", duration)
	fmt.Printf("Requêtes              : %d (%.1f req/s)\n", total, float64(total)/duration.Seconds())
	fmt.Printf("Succès / Erreurs      : %d / %d (%.2f%% d'erreurs)\n", ok, errs, errRate)
	if len(latencies) > 0 {
		fmt.Printf("Latence p50/p95/p99   : %s / %s / %s\n", percentile(0.50), percentile(0.95), percentile(0.99))
		fmt.Printf("Latence min/max       : %s / %s\n", latencies[0], latencies[len(latencies)-1])
	} else {
		fmt.Println("Aucune requête réussie — pas de statistiques de latence.")
	}
}