package main

import (
	"crypto/sha256"
	"encoding/hex"
	"flag"
	"fmt"
	"strings"
	"time"
)


func main() {
	data := "Hello, Proof of Work!"

	// Define command-line flag
	difficulty := flag.Int("d", 4, "Number of leading zeros required")
	flag.Parse()

	start := time.Now()

	nonce, hash := mine(data, *difficulty)

	elapsed := time.Since(start)

	fmt.Println("Data:", data)
	fmt.Println("Difficulty:", *difficulty)
	fmt.Println("Nonce found:", nonce)
	fmt.Println("Hash:", hash)
	fmt.Println("Computation time:", elapsed)
}

func mine(data string, difficulty int) (int, string) {
	var nonce int
	prefix := strings.Repeat("0", difficulty)

	for {
		record := fmt.Sprintf("%s%d", data, nonce)
		hashBytes := sha256.Sum256([]byte(record))
		hash := hex.EncodeToString(hashBytes[:])

		if strings.HasPrefix(hash, prefix) {
			return nonce, hash
		}

		nonce++
	}
}