package allocator

import (
	"errors"
	"sync"
	"testing"
	"time"
)

func TestFixedWindowBudgetLimitsEachRegionAndResets(t *testing.T) {
	now := time.Unix(1000, 0).UTC()
	budget, err := NewFixedWindowBudget(2, time.Minute)
	if err != nil {
		t.Fatal(err)
	}
	for i := 0; i < 2; i++ {
		if err := budget.Allow("EU", now); err != nil {
			t.Fatalf("EU attempt %d: %v", i, err)
		}
	}
	if err := budget.Allow("EU", now); !errors.Is(err, ErrAllocationBudgetExceeded) {
		t.Fatalf("third EU attempt = %v, want budget error", err)
	}
	if err := budget.Allow("NA", now); err != nil {
		t.Fatalf("NA should have an independent budget: %v", err)
	}
	if err := budget.Allow("EU", now.Add(time.Minute)); err != nil {
		t.Fatalf("EU after window: %v", err)
	}
}

func TestFixedWindowBudgetIsAtomicUnderConcurrentAttempts(t *testing.T) {
	budget, err := NewFixedWindowBudget(7, time.Minute)
	if err != nil {
		t.Fatal(err)
	}
	now := time.Unix(1000, 0).UTC()
	var wg sync.WaitGroup
	var mu sync.Mutex
	allowed := 0
	for i := 0; i < 64; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			if budget.Allow("EU", now) == nil {
				mu.Lock()
				allowed++
				mu.Unlock()
			}
		}()
	}
	wg.Wait()
	if allowed != 7 {
		t.Fatalf("allowed=%d, want exactly 7", allowed)
	}
}

func TestFixedWindowBudgetRejectsInvalidConfigurationAndInput(t *testing.T) {
	if _, err := NewFixedWindowBudget(0, time.Minute); err == nil {
		t.Fatal("zero limit accepted")
	}
	if _, err := NewFixedWindowBudget(1, 0); err == nil {
		t.Fatal("zero window accepted")
	}
	budget, _ := NewFixedWindowBudget(1, time.Minute)
	if err := budget.Allow("APAC", time.Unix(1000, 0)); err == nil {
		t.Fatal("unknown region accepted")
	}
	if err := budget.Allow("EU", time.Time{}); err == nil {
		t.Fatal("zero time accepted")
	}
}