inventory.go

package main

import (
	"fmt"
	"sort"
)

type Item struct {
	ID       string //英文名
	Name     string //中文名
	Quantity int
}

type Inventory struct {
	items map[string]Item
}

func removeItem(inventory map[string]Item, id string, quantity int) error {
	if quantity <= 0 {
		return fmt.Errorf("quantity must be greater than 0")
	}

	item, exists := inventory[id]
	if !exists {
		return fmt.Errorf("item %s does not exist", id)
	}
	if item.Quantity < quantity {
		return fmt.Errorf("quantity %d not enough for item %s", quantity, id)
	}

	if item.Quantity == quantity {
		delete(inventory, id)
	} else {
		item.Quantity -= quantity
		inventory[id] = item
	}

	return nil
}

func NewInventory() *Inventory {
	return &Inventory{
		items: make(map[string]Item),
	}
}

func (inventory *Inventory) Add(id string, name string, quantity int) error {
	return addItem(inventory.items, id, name, quantity)
}

func (inventory *Inventory) Get(id string) (Item, bool) {
	item, exists := inventory.items[id]
	return item, exists
}

func addItem(inventory map[string]Item, id string, name string, quantity int) error {
	if quantity <= 0 {
		return fmt.Errorf("quantity must be greater than 0")
	}
	item, exists := inventory[id]
	if !exists {
		item = Item{
			ID:   id,
			Name: name,
		}
		inventory[id] = item
	}

	item.Quantity += quantity
	inventory[id] = item

	return nil

}

func (inventory *Inventory) Remove(id string, quantity int) error {
	return removeItem(inventory.items, id, quantity)
}

func (inventory *Inventory) List() []Item {
	if len(inventory.items) == 0 {
		return []Item{}
	}
	items := make([]Item, 0)
	ids := make([]string, 0)
	for id := range inventory.items {
		ids = append(ids, id)
	}
	sort.Strings(ids)
	for i := 0; i < len(ids); i++ {
		items = append(items, inventory.items[ids[i]])
	}
	return items
}

func (inventory *Inventory) TotalQuantity() int {
	total := 0
	items := inventory.List()
	for _, item := range items {
		total += item.Quantity
	}
	return total
}