proceed to learn go!

bookstore/bookstore.go

@@ -0,0 +1,81 @@
+package bookstore
+
+import (
+	"errors"
+	"fmt"
+)
+
+type Category int
+
+const (
+	CategoryAutobiography Category = iota
+	CategoryLargePrintRomance
+	CategoryParticlePhysics
+)
+
+var validCategory = map[Category]bool{
+	CategoryAutobiography:     true,
+	CategoryLargePrintRomance: true,
+	CategoryParticlePhysics:   true,
+}
+
+type Book struct {
+	Title string
+	Author string
+	Copies int
+	ID int
+	PriceCents int
+	DiscountPercents int
+	category Category
+}
+
+type Catalog map[int]Book
+
+func Buy(b Book) (Book, error) {
+	if b.Copies == 0 {
+		return Book{}, errors.New("no copies left")
+	}
+	b.Copies --
+	return b, nil
+}
+
+func (c Catalog) GetAllBooks() []Book {
+	result := []Book{}
+	for _,b := range c {
+		result = append(result, b)
+	}
+	return  result
+}
+
+func (c Catalog) GetBook(ID int) (Book, error) {
+	b, ok := c[ID]
+	if !ok {
+		return Book{}, fmt.Errorf("book with ID %d not found", ID)
+	}
+	return b, nil
+}
+
+func (b Book) NetPriceCents() int{
+	saving := b.PriceCents * b.DiscountPercents/100
+	return  b.PriceCents - saving
+}
+
+func (b *Book) SetPriceCents(price int) (error) {
+	if price < 0 {
+		return fmt.Errorf("negative price %d", price)
+	}
+	b.PriceCents = price
+	return nil
+}
+
+func (b *Book) SetCategory(category Category) error {
+	if !validCategory[category] {
+		return fmt.Errorf("unknown category %q", category)
+	}
+	b.category = category
+	return  nil
+}
+
+func (b Book) Category() Category {
+	return b.category
+}

bookstore/bookstore_test.go

@@ -0,0 +1,134 @@
+package bookstore_test
+
+import (
+	"bookstore"
+	"testing"
+	"sort"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+)
+
+func TestBuy(t *testing.T) {
+	t.Parallel()
+	b := bookstore.Book{
+		Title: "Lol",
+		Author: "KEK",
+		Copies: 2,
+	}
+	want := 1
+	result,err := bookstore.Buy(b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := result.Copies
+	if want != got {
+		t.Errorf("Want %d but got %d", want,got)
+	}
+}
+
+func TestBuyOutOfStock(t *testing.T) {
+	t.Parallel()
+	b := bookstore.Book{
+		Title: "Lol",
+		Author: "KEK",
+		Copies: 0,
+	}
+	_,err := bookstore.Buy(b)
+	if err == nil {
+		t.Error("Book is out of stock")
+	}
+}
+
+func TestGetAllBooks(t *testing.T) {
+	t.Parallel()
+	catalog := bookstore.Catalog{
+		1: {ID: 1, Title: "For the Love of Go"},
+		2: {ID: 2, Title: "The Power of Go: Tools"},
+	}
+	want := []bookstore.Book{
+		{ID: 1, Title: "For the Love of Go"},
+		{ID: 2, Title: "The Power of Go: Tools"},
+	}
+	got := catalog.GetAllBooks()
+	sort.Slice(got, func(i, j int) bool {
+		return got[i].ID < got[j].ID
+	})
+	if !cmp.Equal(want, got,cmpopts.IgnoreUnexported(bookstore.Book{})) {
+		t.Error(cmp.Diff(want, got,))
+	}
+}
+func TestGetBook(t *testing.T) {
+	t.Parallel()
+	catalog := bookstore.Catalog{
+		1: {ID: 1, Title: "For the Love of Go"},
+		2: {ID: 2, Title: "The Power of Go: Tools"},
+	}
+    // want := bookstore.Book{ID: 2, Title: "The Power of Go: Tools"}
+	_, err := catalog.GetBook(2)
+	if err != nil {
+        t.Fatal("want error for non-existent ID, got nil")
+    } 
+}
+func TestNetPriceCents(t *testing.T) {
+	t.Parallel()
+	b := bookstore.Book {
+		Title: "For the love of Go",
+		PriceCents: 4000,
+		DiscountPercents: 25,
+	}
+	want := 3000
+	got := b.NetPriceCents()
+	if want != got {
+		t.Errorf("want %d, got %d",want,got)
+	}
+}
+func TestSetPriceCents(t *testing.T) {
+    t.Parallel()
+    b := bookstore.Book{
+        Title: "For the Love of Go",
+        PriceCents: 4000,
+    }
+    want := 3000
+    err := b.SetPriceCents(want)
+    if err != nil {
+        t.Fatal(err)
+    }
+    got := b.PriceCents
+	if want != got {
+    	t.Errorf("want updated price %d, got %d", want, got)
+    }
+}
+func TestSetCategory(t *testing.T) {
+	t.Parallel()
+	b := bookstore.Book{
+		Title: "For the Love of Go",
+	}
+	cats := []bookstore.Category {
+		bookstore.CategoryAutobiography,
+        bookstore.CategoryLargePrintRomance,
+        bookstore.CategoryParticlePhysics,
+	}
+	for _, cat := range cats {
+	err := b.SetCategory(cat)
+	if err != nil {
+		t.Fatal(err)
+		}
+	got := b.Category()
+	if cat != got {
+		t.Errorf("want category %q, got %q", cat, got)
+		}
+	}
+}
+
+
+func TestSetCategoryInvalid(t *testing.T) {
+	t.Parallel()
+	b := bookstore.Book{
+		Title: "For the Love of Go",
+	}
+	err := b.SetCategory(999)
+	if err == nil {
+		t.Fatal("want error for invalid category, got nil")
+	}
+}

bookstore/go.mod

@@ -0,0 +1,5 @@
+module bookstore
+
+go 1.24.4
+
+require github.com/google/go-cmp v0.7.0

bookstore/go.sum

@@ -0,0 +1,2 @@
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=

bookstore/kek.out

@@ -0,0 +1,4 @@
+mode: set
+bookstore/bookstore.go:13.32,14.19 1 1
+bookstore/bookstore.go:14.19,16.3 1 1
+bookstore/bookstore.go:17.2,18.15 2 1