package main

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"math/rand"
	"sort"
	"time"
)

func main() {

	trialset := []int{}
	numtrials := 100
	for i := 0; i < numtrials; i++ {
		trialset = append(trialset, hashTrial())
	}

	fmt.Println("Mean Trials: " + fmt.Sprint(mean(trialset)))
	fmt.Println()
	fmt.Println("Median Trials: " + fmt.Sprint(median(trialset)))
	fmt.Println()

}

func median(numbers []int) float64 {
	sort.Ints(numbers)
	n := len(numbers)
	if n%2 == 0 {
		return float64(numbers[n/2-1]+numbers[n/2]) / 2
	}
	return float64(numbers[n/2])
}

func mean(numbers []int) float64 {
	var sum int
	for _, n := range numbers {
		sum += n
	}
	return float64(sum) / float64(len(numbers))
}

func hashTrial() int {

	// puzzle difficulty
	difficulty := 5

	// string to match leading zeros
	m := ""
	for i := 0; i < difficulty; i++ {
		m += "0"
	}

	// counter for number of trials
	trials := 1

	// original message to hash
	s := "Hello"

	// random seed using time and generation of a nonce
	rand.Seed(time.Now().UnixNano())
	nonce := rand.Intn(1000000)

	// compute first sha256
	h := sha256.New()
	p := string(s) + " " + fmt.Sprint(nonce)

	h.Write([]byte(p))

	fmt.Println()
	fmt.Println(s)
	fmt.Println()
	fmt.Println(p)
	fmt.Println()
	fmt.Println(hex.EncodeToString(h.Sum(nil)))
	fmt.Println()

	// compute sha256 until leading zeros are found
	for string(hex.EncodeToString(h.Sum(nil))[:difficulty]) != m {

		h.Reset()

		nonce++
		p = string(s) + " " + fmt.Sprint(nonce)
		h.Write([]byte(p))

		fmt.Println(p)
		fmt.Println()
		fmt.Println(hex.EncodeToString(h.Sum(nil)))
		fmt.Println()

		trials++

	}

	fmt.Println("Trials: " + fmt.Sprint(trials))
	fmt.Println()

	return trials

}