package main

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"math"
	"math/big"
)

const (
	AuditSeed  = "5d1d88ae4cc8c868372ed48d5e8eb84767212f3c984e6b9bd30940b2ca17e17b"
	GameSeed   = "dc26e42bcdf464b1cd88b84e1a77a23991dd577d935e28b1ea950c9868aba53b"
	ClientSeed = "scenic makeshift rock"
)

func main() {

    roll := uint64(590)

    result := GameResult(AuditSeed, GameSeed, ClientSeed, roll)

    fmt.Println(result)

}

func GameResult(auditSeed, gameSeed, clientSeed string, nonce uint64) uint {
	const nBits = 52

	auditWagerSeed := hmacSha256(auditSeed, fmt.Sprint(nonce))
	gameHashString := hmacSha256(fmt.Sprintf("%s|%s|%d", gameSeed, clientSeed, nonce), auditWagerSeed)
	gameHash, err := hex.DecodeString(gameHashString)
	if err != nil {
		panic(err)
	}

	random := new(big.Int).SetBytes(gameHash)
	random.Rsh(random, sha256.Size*8-nBits)
	r := random.Uint64()

	X := float64(r) / math.Pow(2, nBits) // uniformly distributed in [0; 1)

	result := math.Floor(99 / (1 - X))
	result = math.Max(100, math.Min(result, 100000000))
	return uint(result)
}

func hmacSha256(key, message string) string {
	hash := hmac.New(sha256.New, []byte(key))
	hash.Write([]byte(message))
	return hex.EncodeToString(hash.Sum(nil))
}