/*
* Timing of sorting in Go.
* Idea, build a struct of a string and a random number
* Then sort by either he string or the number
*
*@author ggtowell
* created: July 3, 2021
 */

package main

import (
	"bytes"
	"fmt"
	"math/rand"
	"sort"
	"time"
)

// a struct containing a random string and random number
type NumAndString struct {
	num int
	str string
}

// a slice containing the struct
type NumAndStringSlice []NumAndString
// Other than the name, the same as the prior type
type StringSlice NumAndStringSlice

// a global holding an instance of NumAndStirngSlice
var aaa NumAndStringSlice

// Associate three functions with the type NumAndStingSlice
// These will result in sorting on the number
// These three functions are required to implement sorting
// In Java parlance, you implement a interface of these three functions
func (p NumAndStringSlice) Len() int { return len(p) }
func (p NumAndStringSlice) Swap(i, j int) { p[i],p[j] = p[j],p[i] }
func (p NumAndStringSlice) Less(i, j int) bool { return p[i].num < p[j].num }


// Associate three functions with the type StingSlice
// These will result in sorting on the stirng
func (p StringSlice) Len() int { return len(p) }
func (p StringSlice) Swap(i, j int) { p[i],p[j] = p[j],p[i] }
func (p StringSlice) Less(i, j int) bool { return p[i].str < p[j].str }

/*
* Build a random string of the given length (lower case only)
*/
func randString(len int, r1 *rand.Rand) string {
	if len==0 { return "" }
	var buf bytes.Buffer
	for i := 0; i < len; i++ {
		buf.WriteString(string('a' + r1.Intn(26)))
	}
	return buf.String()
}

func main() {
	//Initialize the random number generatort
	s1 := rand.NewSource(time.Now().UnixNano())
    r1 := rand.New(s1)

	now := time.Now();
	doSort(10000000, r1, true)
	thn := time.Now();
	diff := thn.Sub(now)
	fmt.Println(diff);

}

/*
* Build the thing to be sorted, then sort it
* @param num -- the size of the thing to be sorted
* @param r1 -- an initialized instance of a random number generator
* @param stringSortP -- if true, sort on the stirng, else sort on the number
*/
func doSort(num int, r1 *rand.Rand, stringSortP bool) { 
	// initialized the slice
	aaa = make(NumAndStringSlice, num)
	// set the length of the string to be sorted
	strLen:=0
	if stringSortP {
		strLen = 6
	}
	// fill the slice
	for i := 0; i < num; i++ {
		aaa[i] = NumAndString{r1.Intn(num), randString(strLen,r1)}
	}

	// do the sort
	if !stringSortP {
		sort.Sort(aaa)
	} else {
		sort.Sort(StringSlice(aaa))
	}
	// show the first couple of items to verify that the sort worked
	for i:=0; i < 5; i++ {
		fmt.Printf("%v\n", aaa[i])
	}
}