refactor: update inventory management to use a map for products

go/01-basics/inventory.go

@@ -1,6 +1,8 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+)
 
 // a new type named Category that can hold integer values
 type Category int
@@ -26,7 +28,6 @@ func (c Category) String() string {
 	}
 }
 
-// Struct for product details
 type Product struct {
 	Name     string
 	Price    float64
@@ -34,84 +35,86 @@ type Product struct {
 	Category Category
 }
 
-// Add a new product to the inventory
-func addProduct(inventory *[]Product, //pointer to the slice of of Products that shall be modified. In that way it can serve as in input/output parameter
-	name string, price float64, quantity int, category Category) {
-	// Check if the product already exists in the inventory
-	for _, product := range *inventory {
-		if product.Name == name {
-			fmt.Println("Product already exists.")
-			return
-		}
-	}
-	// Add the new product
-	*inventory = append(*inventory, Product{
-		Name:     name,
-		Price:    price,
-		Quantity: quantity,
-		Category: category,
-	})
-	fmt.Printf("Added product: %s\n", name)
+// implementation of the fmt.Stringer interface for printing products
+func (p Product) String() string {
+	return fmt.Sprintf("%s (%s, Price: $%.2f, Quantity: %d)", p.Name, p.Category, p.Price, p.Quantity)
 }
 
-// Remove a product from the inventory
-func removeProduct(inventory *[]Product, //pointer to the slice of of Products that shall be modified. In that way it can serve as in input/output parameter
-	name string) {
-	for i, product := range *inventory {
-		if product.Name == name {
-			*inventory = append((*inventory)[:i], (*inventory)[i+1:]...)
-			fmt.Printf("Removed product: %s\n", name)
-			return
-		}
+func addProduct(inventory map[string]Product, name string, price float64, quantity int, category Category) {
+
+	//do not create a new product in case a product with the name already exists
+	if _, exists := inventory[name]; exists {
+		fmt.Printf("Unable to add new Product %s: Product already exists.\n", name)
+		return
 	}
-	fmt.Println("Product not found.")
+
+	//create a new product...
+	p := Product{name, price, quantity, category}
+	inventory[name] = p // ...and insert it into the map
 }
 
-// Update the quantity of a product.
-func updateQuantity(inventory *[]Product, //pointer to the slice of of Products that shall be modified. In that way it can serve as in input/output parameter
-	name string, newQuantity int) {
-	for i, product := range *inventory {
-		if product.Name == name {
-			(*inventory)[i].Quantity = newQuantity
-			fmt.Printf("Updated quantity for %s: New Quantity = %d\n", name, newQuantity)
-			return
-		}
-	}
-	fmt.Println("Product not found.")
+func removeProduct(inventory map[string]Product, name string) {
+	//no checks required. Does nothing if the product doesn't exist.
+	delete(inventory, name)
 }
 
-// Display the inventory
-func displayInventory(inventory []Product) {
-	fmt.Println("Inventory:")
-	for _, product := range inventory { //iterating over a range returns pairs of index and the content of a container (here: inventory). Since we don't care about the index, we use _ as a placeholder.
-		fmt.Printf("%s - %s (Price: $%.2f, Quantity: %d)\n",
-			product.Name, product.Category, product.Price, product.Quantity)
+func updateQuantity(inventory map[string]Product, name string, newQuantity int) {
+	p := inventory[name]     //read from the map
+	p.Quantity = newQuantity //update value
+	inventory[name] = p      //store back into the map
+}
+
+func displayInventory(inventory map[string]Product) {
+	//Iterate over the inventory
+	i := 1
+	for _, p := range inventory { //don't care about the key (_), only the value (p) is relevant
+		fmt.Printf("%d. %s\n", i, p)
+		i++
 	}
 }
 
 func main() {
-	// Initialize inventory
-	inventory := []Product{
-		{Name: "Laptop", Price: 1000, Quantity: 5, Category: Electronics},
-		{Name: "Apples", Price: 2, Quantity: 50, Category: Groceries},
-		{Name: "T-shirt", Price: 10, Quantity: 20, Category: Clothes},
+
+	fmt.Println("Welcome to the Inventory Manager!")
+
+	// Store a fixed list of initial product names in an array.
+	initialProductNames := [...]string{"Laptop"}
+
+	// Convert the array into a slice so the inventory can grow or shrink dynamically.
+	productNames := initialProductNames[:]
+	productNames = append(productNames, "Apples", "T-shirt")
+
+	// Use a map to associate product names with details like quantity, price, and category.
+	prices := []float64{1000.0, 2.0, 10.0}
+	quantities := []int{5, 50, 20}
+	categories := []Category{Electronics, Groceries, Clothes}
+
+	inventory := make(map[string]Product)
+	for i, name := range productNames {
+		inventory[name] = Product{name, prices[i], quantities[i], categories[i]}
 	}
 
 	// Display initial inventory
+	fmt.Println("\nInitial Inventory:")
 	displayInventory(inventory)
 
 	// Add a new product
-	addProduct(&inventory, "Phone", 800, 10, Electronics)
+	fmt.Println("\nAdding a new product: Phone (Electronics, Price: $800, Quantity: 10)")
+	addProduct(inventory, "Phone", 800, 10, Electronics)
 
 	// Display updated inventory
+	fmt.Println("\nUpdated Inventory:")
 	displayInventory(inventory)
 
 	// Update the quantity of an existing product
-	updateQuantity(&inventory, "Apples", 30)
+	fmt.Println("\nUpdating quantity for Apples: New Quantity = 30")
+	updateQuantity(inventory, "Apples", 30)
 
 	// Remove a product
-	removeProduct(&inventory, "T-shirt")
+	fmt.Println("\nRemoving product: T-shirt")
+	removeProduct(inventory, "T-shirt")
 
 	// Display final inventory
+	fmt.Println("\nFinal Inventory:")
 	displayInventory(inventory)
 }