// FileDummy Sample Go File
package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"sync"
	"time"
)

// User represents a system user.
type User struct {
	ID        int       `json:"id"`
	Name      string    `json:"name"`
	Email     string    `json:"email"`
	Role      string    `json:"role"`
	CreatedAt time.Time `json:"created_at"`
}

// UserService manages users with thread-safe operations.
type UserService struct {
	mu      sync.RWMutex
	users   map[int]*User
	nextID  int
}

func NewUserService() *UserService {
	return &UserService{
		users:  make(map[int]*User),
		nextID: 1,
	}
}

func (s *UserService) Create(name, email, role string) *User {
	s.mu.Lock()
	defer s.mu.Unlock()

	user := &User{
		ID:        s.nextID,
		Name:      name,
		Email:     email,
		Role:      role,
		CreatedAt: time.Now(),
	}
	s.users[s.nextID] = user
	s.nextID++
	return user
}

func (s *UserService) Find(id int) (*User, bool) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	u, ok := s.users[id]
	return u, ok
}

func (s *UserService) List() []*User {
	s.mu.RLock()
	defer s.mu.RUnlock()
	result := make([]*User, 0, len(s.users))
	for _, u := range s.users {
		result = append(result, u)
	}
	return result
}

// ── HTTP Handler ─────────────────────────────
func handleUsers(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		json.NewEncoder(w).Encode(svc.List())
	case http.MethodPost:
		var u struct {
			Name  string `json:"name"`
			Email string `json:"email"`
		}
		if err := json.NewDecoder(r.Body).Decode(&u); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		json.NewEncoder(w).Encode(svc.Create(u.Name, u.Email, "user"))
	default:
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
	}
}

var svc = NewUserService()

func main() {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	_ = ctx // context used for graceful shutdown in real app

	svc.Create("Alice", "alice@example.com", "admin")
	svc.Create("Bob", "bob@example.com", "user")

	http.HandleFunc("/api/users", handleUsers)

	fmt.Println("Server starting on :8080...")
	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatal(err)
	}
}