package inventory

import (
	"context"
	"testing"
	"time"
)

// ── Tests ────────────────────────────────────────────────────────────────

func TestInMemoryReserveAndRelease(t *testing.T) {
	ctx := context.Background()
	p := NewInMemoryReservationPolicy(
		SKU("ABC-1"), LocationID("se"), int64(10),
		SKU("ABC-1"), LocationID("no"), int64(5),
	)

	// Reserve available stock
	err := p.Reserve(ctx, CartReserveRequest{
		InventoryReference: &InventoryReference{SKU: "ABC-1", LocationID: "se"},
		CartID:             "cart-1",
		Quantity:           3,
		TTL:                15 * time.Minute,
	})
	if err != nil {
		t.Fatalf("Reserve: %v", err)
	}
	avail, _ := p.Available(ctx, "ABC-1", "se")
	if avail != 7 {
		t.Fatalf("after reserve 3 of 10, expected 7 available, got %d", avail)
	}

	// Release
	if err := p.Release(ctx, "ABC-1", "se", "cart-1"); err != nil {
		t.Fatalf("Release: %v", err)
	}
	avail, _ = p.Available(ctx, "ABC-1", "se")
	if avail != 10 {
		t.Fatalf("after release, expected 10 available, got %d", avail)
	}
}

func TestInMemoryInsufficientStock(t *testing.T) {
	ctx := context.Background()
	p := NewInMemoryReservationPolicy(
		SKU("ABC-1"), LocationID("se"), int64(2),
	)

	err := p.Reserve(ctx, CartReserveRequest{
		InventoryReference: &InventoryReference{SKU: "ABC-1", LocationID: "se"},
		CartID:             "cart-1",
		Quantity:           5,
		TTL:                15 * time.Minute,
	})
	if err == nil {
		t.Fatal("expected insufficient stock error, got nil")
	}
}

func TestInMemoryConcurrentReserves(t *testing.T) {
	ctx := context.Background()
	p := NewInMemoryReservationPolicy(
		SKU("ABC-1"), LocationID("se"), int64(100),
	)

	errs := make(chan error, 10)
	for i := 0; i < 10; i++ {
		go func(n int) {
			errs <- p.Reserve(ctx, CartReserveRequest{
				InventoryReference: &InventoryReference{SKU: "ABC-1", LocationID: "se"},
				CartID:             CartID(string(rune('0' + n))),
				Quantity:           10,
				TTL:                15 * time.Minute,
			})
		}(i)
	}

	for i := 0; i < 10; i++ {
		if err := <-errs; err != nil {
			t.Errorf("concurrent reserve %d: %v", i, err)
		}
	}

	avail, _ := p.Available(ctx, "ABC-1", "se")
	if avail != 0 {
		t.Fatalf("after 10×10 reserves from 100, expected 0 available, got %d", avail)
	}
}