package main

import "fmt"

const GlobalLimit = 100
const MaxCacheSize = 10 * GlobalLimit
const (
  CacheKeyBook = "book_"
  CacheKeyCD   = "cd_"
)

var cache map[string]string

func cacheGet(key string) string {
  return cache[key]
}

func cacheSet(key, val string) {
  if len(cache)+1 >= MaxCacheSize {
    return
  }
  cache[key] = val
}

func getBook(isbn string) string {
  return cacheGet(CacheKeyBook + isbn)
}

func setBook(isbn, name string) {
  cacheSet(CacheKeyBook+isbn, name)
}

func getCD(sku string) string {
  return cacheGet(CacheKeyCD + sku)
}

func setCD(sku, title string) {
  cacheSet(CacheKeyCD+sku, title)
}

func main() {

  cache = make(map[string]string)

  setBook("1234-5678", "Get ready to Go")
  setCD("1234-5678", "Get ready to Go audio book")

  fmt.Println("Book:", getBook("1234-5678"))
  fmt.Println("CD  :", getCD("1234-5678"))

}