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
}