// Inventory System -- package inventory (starter).
//
// Finish the TODOs so that main.go prints what the project page shows. As it
// is, the file compiles and the methods do nothing useful. Add "errors" to the
// import list when you need it.

package inventory

import "fmt"

// Item is one collectable thing. Make one with NewItem.
type Item struct {
	name   string
	weight float64
	value  int
}

// NewItem returns an item. The name must not be empty, and the weight and the
// value must not be below 0.
func NewItem(name string, weight float64, value int) (*Item, error) {
	// TODO: return nil and an error for each of the three bad cases.
	return &Item{name: name, weight: weight, value: value}, nil
}

// Name returns the item's name.
func (it *Item) Name() string {
	return it.name
}

// Describe returns a one-line summary such as "sword (3.5kg, 50g)".
func (it *Item) Describe() string {
	// TODO: use fmt.Sprintf. Replace this placeholder line:
	return "TODO: replace this line"
}

// Inventory is a container of items. Make one with New.
type Inventory struct {
	items []*Item
}

// New returns an empty inventory.
func New() *Inventory {
	return &Inventory{}
}

// Add puts an item in the inventory.
func (inv *Inventory) Add(item *Item) {
	// TODO: append item to inv.items.
}

// Remove takes out the first item with this name and returns it. It returns
// nil if no item has this name.
func (inv *Inventory) Remove(name string) *Item {
	// TODO: walk inv.items with range. If an item has this name, remove it
	// from the slice as in Chapter 22, and return it.
	return nil
}

// TotalWeight returns the sum of the weights.
func (inv *Inventory) TotalWeight() float64 {
	// TODO: add up the weights. Replace this placeholder value:
	return 0
}

// TotalValue returns the sum of the values.
func (inv *Inventory) TotalValue() int {
	// TODO: add up the values. Replace this placeholder value:
	return 0
}

// Counts returns how many items there are with each name.
func (inv *Inventory) Counts() map[string]int {
	// TODO: make a map and count the names. Replace this placeholder value:
	return map[string]int{}
}

// List prints each item on its own line, then a line of totals.
func (inv *Inventory) List() {
	// TODO: print "Inventory (N items):", then "  - " and Describe for each
	// item, then "  Totals: 8.70kg, 85g" with the real totals.
	fmt.Println("TODO: replace this line")
}