package main

import (
	"fmt"
	"os"
	"bufio"
	"github.com/golang/groupcache"
)
	
var stringGroup groupcache.Getter
var ctx groupcache.Context

func main() {
	// simple string reversal function used for the cache get
	reverseString := func(s string) string {
		n := len(s)	
		res := make([]rune, n)
		
		for _, rune := range s {
			n--
			res[n] = rune
		}
		return string(res)
	}

	// create the group cache with faked provider
	stringGroup = groupcache.NewGroup(
		"strings", 1 << 24, 
		groupcache.GetterFunc(func(ctx groupcache.Context, key string, dest groupcache.Sink) error {
			// call a database, etc.
			fmt.Println("*** Get called:",key)
			return dest.SetString(reverseString(key))
		}),
	)

	reader := bufio.NewReader(os.Stdin)

	var line string
	var cacheValue string

	getLine := func() string {
		fmt.Printf("\n\rEnter key:")
		line, _, _ := reader.ReadLine()
		return string(line)
	}

	for line = getLine();len(line)>0; {
		stringGroup.Get(ctx, line, groupcache.StringSink(&cacheValue))
		fmt.Println("Cache value:",cacheValue)
		line = getLine()
	}
	fmt.Println("Exiting....")
}