package orders_test

import (
	"context"
	"errors"
	"testing"

	"github.com/google/uuid"

	"backend/internal/modules/orders"
	"backend/internal/modules/pricing"
	"backend/internal/modules/products"
	"backend/internal/modules/units"
)

// fakeRepository is an in-memory orders.Repository used to unit-test
// orders.Service without a real database.
type fakeRepository struct {
	orders map[uuid.UUID]*orders.Order
	items  map[uuid.UUID][]*orders.OrderItem
}

func newFakeRepository() *fakeRepository {
	return &fakeRepository{orders: map[uuid.UUID]*orders.Order{}, items: map[uuid.UUID][]*orders.OrderItem{}}
}

func (r *fakeRepository) Create(_ context.Context, order *orders.Order, items []*orders.OrderItem) error {
	cp := *order
	r.orders[order.ID] = &cp
	for _, item := range items {
		item.OrderID = order.ID
	}
	r.items[order.ID] = items
	return nil
}

func (r *fakeRepository) FindByID(_ context.Context, id uuid.UUID) (*orders.Order, []*orders.OrderItem, error) {
	o, ok := r.orders[id]
	if !ok {
		return nil, nil, orders.ErrNotFound
	}
	return o, r.items[id], nil
}

func (r *fakeRepository) List(_ context.Context, status string) ([]*orders.Order, error) {
	var list []*orders.Order
	for _, o := range r.orders {
		if status == "" || o.Status == status {
			list = append(list, o)
		}
	}
	return list, nil
}

func (r *fakeRepository) UpdateStatus(_ context.Context, id uuid.UUID, status string) (*orders.Order, error) {
	o, ok := r.orders[id]
	if !ok {
		return nil, orders.ErrNotFound
	}
	o.Status = status
	return o, nil
}

// fakeProducts / fakeUnits / fakePrices back the small consumer-defined
// interfaces orders.Service depends on.
type fakeProducts struct {
	byID map[uuid.UUID]*products.Product
}

func (f *fakeProducts) Get(_ context.Context, id uuid.UUID) (*products.Product, error) {
	p, ok := f.byID[id]
	if !ok {
		return nil, products.ErrNotFound
	}
	return p, nil
}

type fakeUnits struct {
	byID map[uuid.UUID]*units.Unit
}

func (f *fakeUnits) Get(_ context.Context, id uuid.UUID) (*units.Unit, error) {
	u, ok := f.byID[id]
	if !ok {
		return nil, units.ErrNotFound
	}
	return u, nil
}

type fakePrices struct {
	byID map[uuid.UUID]*pricing.PriceTier
}

func (f *fakePrices) PriceForQuantity(_ context.Context, tierID uuid.UUID, multiplier int64) (int64, *pricing.PriceTier, error) {
	t, ok := f.byID[tierID]
	if !ok {
		return 0, nil, pricing.ErrNotFound
	}
	if multiplier < 1 {
		multiplier = 1
	}
	return t.PriceCents * multiplier, t, nil
}

type fakeNotifier struct {
	newOrderCalls     []string
	statusChangeCalls []string
}

func (f *fakeNotifier) NotifyNewOrder(_ context.Context, summary string) {
	f.newOrderCalls = append(f.newOrderCalls, summary)
}

func (f *fakeNotifier) NotifyOrderStatusChange(_ context.Context, summary string) {
	f.statusChangeCalls = append(f.statusChangeCalls, summary)
}

// testFixture wires a full set of fakes with one product/unit/tier, ready
// for a service under test.
type testFixture struct {
	repo     *fakeRepository
	products *fakeProducts
	units    *fakeUnits
	prices   *fakePrices
	notifier *fakeNotifier

	productID uuid.UUID
	unitID    uuid.UUID
	tierID    uuid.UUID
}

func newFixture() *testFixture {
	productID := uuid.New()
	unitID := uuid.New()
	tierID := uuid.New()

	return &testFixture{
		repo: newFakeRepository(),
		products: &fakeProducts{byID: map[uuid.UUID]*products.Product{
			productID: {ID: productID, Name: "Honey jar", Slug: "honey-jar", IsActive: true},
		}},
		units: &fakeUnits{byID: map[uuid.UUID]*units.Unit{
			unitID: {ID: unitID, Name: "Kilogram", Symbol: "kg"},
		}},
		prices: &fakePrices{byID: map[uuid.UUID]*pricing.PriceTier{
			tierID: {ID: tierID, ProductID: productID, UnitID: unitID, Quantity: 5, PriceCents: 4500},
		}},
		notifier:  &fakeNotifier{},
		productID: productID,
		unitID:    unitID,
		tierID:    tierID,
	}
}

func (f *testFixture) service() *orders.Service {
	return orders.NewService(f.repo, f.products, f.units, f.prices, f.notifier)
}

func TestService_Create_ComputesTotalAndNotifies(t *testing.T) {
	f := newFixture()
	svc := f.service()

	order, items, err := svc.Create(context.Background(), orders.CreateInput{
		CustomerName:  "Alice",
		CustomerEmail: "alice@example.com",
		Items: []orders.ItemInput{
			{ProductID: f.productID, PriceTierID: f.tierID, Multiplier: 2},
		},
	})
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}
	if order.TotalCents != 9000 {
		t.Fatalf("Create() order.TotalCents = %d, want 9000 (2x 4500)", order.TotalCents)
	}
	if order.Status != orders.StatusPending {
		t.Fatalf("Create() order.Status = %q, want %q", order.Status, orders.StatusPending)
	}
	if len(items) != 1 || items[0].ProductName != "Honey jar" || items[0].UnitSymbol != "kg" {
		t.Fatalf("Create() items = %+v, want snapshot of product name/unit symbol", items)
	}
	if len(f.notifier.newOrderCalls) != 1 {
		t.Fatalf("Create() triggered %d new-order notifications, want exactly 1", len(f.notifier.newOrderCalls))
	}
}

func TestService_Create_RejectsEmptyOrder(t *testing.T) {
	f := newFixture()
	svc := f.service()

	_, _, err := svc.Create(context.Background(), orders.CreateInput{CustomerName: "Alice", CustomerEmail: "a@example.com"})
	if !errors.Is(err, orders.ErrEmptyOrder) {
		t.Fatalf("Create() error = %v, want ErrEmptyOrder", err)
	}
}

func TestService_Create_RejectsTierProductMismatch(t *testing.T) {
	f := newFixture()
	svc := f.service()

	otherProduct := uuid.New()
	f.products.byID[otherProduct] = &products.Product{ID: otherProduct, Name: "Other", Slug: "other", IsActive: true}

	_, _, err := svc.Create(context.Background(), orders.CreateInput{
		CustomerName:  "Alice",
		CustomerEmail: "alice@example.com",
		Items: []orders.ItemInput{
			// tierID actually belongs to f.productID, not otherProduct.
			{ProductID: otherProduct, PriceTierID: f.tierID, Multiplier: 1},
		},
	})
	if !errors.Is(err, orders.ErrProductMismatch) {
		t.Fatalf("Create() error = %v, want ErrProductMismatch", err)
	}
}

func TestService_UpdateStatus_ValidatesStatus(t *testing.T) {
	f := newFixture()
	svc := f.service()

	order, _, err := svc.Create(context.Background(), orders.CreateInput{
		CustomerName:  "Alice",
		CustomerEmail: "alice@example.com",
		Items:         []orders.ItemInput{{ProductID: f.productID, PriceTierID: f.tierID, Multiplier: 1}},
	})
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}

	if _, err := svc.UpdateStatus(context.Background(), order.ID, "not-a-real-status"); !errors.Is(err, orders.ErrInvalidStatus) {
		t.Fatalf("UpdateStatus() error = %v, want ErrInvalidStatus", err)
	}

	updated, err := svc.UpdateStatus(context.Background(), order.ID, orders.StatusConfirmed)
	if err != nil {
		t.Fatalf("UpdateStatus() error = %v", err)
	}
	if updated.Status != orders.StatusConfirmed {
		t.Fatalf("UpdateStatus() status = %q, want %q", updated.Status, orders.StatusConfirmed)
	}
	if len(f.notifier.statusChangeCalls) != 1 {
		t.Fatalf("UpdateStatus() triggered %d status-change notifications, want exactly 1", len(f.notifier.statusChangeCalls))
	}
}