package main

import (
	"flag"
	"fmt"
	"github.com/trustelem/zxcvbn"
	"math"
	"os"
	"passphrase-entropy/packages/haveibeenpwned"
	"strings"
)

func contains(arr [3]string, str string) bool {
	for _, a := range arr {
		if a == str {
			return true
		}
	}
	return false
}

func myUsage() {
	fmt.Println("usage: passphrase-entropy <command> [<args>]")
	fmt.Println("Available commands are: ")
	fmt.Println(" diceware   Calculate entropy of a diceware passphrase")
	fmt.Println(" random     Calculate entropy of a random string")
	fmt.Println(" invented   Calculate entropy of an invented passphrase")
}

func secondsToHuman(guesses float64) (result string) {
	minute := float64(60)
	hour := minute * 60
	day := hour * 24
	month := day * 31
	year := month * 12
	century := year * 100
	if guesses < 1 {
		result = "< 1 second"
	} else if guesses < minute {
		result = fmt.Sprintf("%d seconds", int(math.Round(guesses)))
	} else if guesses < hour {
		result = fmt.Sprintf("%d minutes", int(math.Round(guesses / minute)))
	} else if guesses < day {
		result = fmt.Sprintf("%d hours", int(math.Round(guesses / hour)))
	} else if guesses < month {
		result = fmt.Sprintf("%d days", int(math.Round(guesses / day)))
	} else if guesses < year {
		result = fmt.Sprintf("%d months", int(math.Round(guesses / month)))
	} else if guesses < century {
		result = fmt.Sprintf("%d years", int(math.Round(guesses / year)))
	} else {
		result = fmt.Sprintf("Centuries")
	}
	return
}

func main() {
	var charsets map[string]string
	var usedCharsets[] string
	var possibleSymbols int = 0

	var haveIBeenPwned bool
	var passphrase string
	var pwnedFlag bool

	var err error

	charsets = make(map[string]string)
	charsets["Numbers"] = "0123456789"
	charsets["Lowercase"] = "abcdefghijklmnopqrstuvwxyz"
	charsets["Uppercase"] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	charsets["Common Special Characters"] = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"
	charsets["Space"] = " "
	charsets["Extended ASCII"] = "€‚ƒ„…†‡ˆ‰Š‹ŒŽ‘’“”•–—˜™š›œžŸ¡¢£¤¥¦§¨©ª«¬®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ"

	if len(os.Args) == 1 {
		myUsage()
		return
	}

	switch os.Args[1] {
	case "diceware":
		var words, dictSize int
		dicewareCommand := flag.NewFlagSet("diceware", flag.ExitOnError)
		dicewareCommand.IntVar(&words,"words", 0, "number of words in passphrase")
		dicewareCommand.IntVar(&dictSize,"dictSize", 0, "number of words in dictionary")
		dicewareCommand.Parse(os.Args[2:])
		if dicewareCommand.Parsed() {
			if words == 0 {
				dicewareCommand.Usage()
				return
			}
			if dictSize == 0 {
				dicewareCommand.Usage()
				return
			}

			entropy := math.Log2(math.Pow(float64(dictSize), float64(words)))
			fmt.Println("\nPassphrase entropy:", entropy)
		}
	case "random":
		var pwnedFlag bool
		randomCommand := flag.NewFlagSet("random", flag.ExitOnError)
		randomCommand.StringVar(&passphrase,"password", "", "the password")
		randomCommand.BoolVar(&pwnedFlag, "pwned", false, "check if password has been seen before")
		randomCommand.Parse(os.Args[2:])

		if randomCommand.Parsed() {
			if passphrase == "" {
				randomCommand.Usage()
				return
			}
			if pwnedFlag == true {
				haveIBeenPwned, err = pwned.IsPasswordCompromised(passphrase)
				if haveIBeenPwned == true {
					fmt.Println("This password does not have any entropy, because it has been compromised.")
					return
				}
			}
			passphraseLength := len(passphrase)

			for key, value := range charsets {
				if strings.ContainsAny(passphrase, value) {
					possibleSymbols += len(value)
					usedCharsets = append(usedCharsets, key)
				}
			}

			entropy := math.Log2(math.Pow(float64(possibleSymbols), float64(passphraseLength)))

			fmt.Println("\nNumber of characters:", passphraseLength)
			fmt.Println("\nUsed character sets:", strings.Join(usedCharsets, ", "))
			fmt.Println("\nPassphrase entropy:", entropy)
		}

	case "invented":
		var words string
		inventedCommand := flag.NewFlagSet("invented", flag.ExitOnError)
		inventedCommand.StringVar(&passphrase,"password", "", "the password")
		inventedCommand.StringVar(&words, "words", "", "used words")
		inventedCommand.BoolVar(&pwnedFlag, "pwned", false, "check if password has been seen before")
		inventedCommand.Parse(os.Args[2:])

		if inventedCommand.Parsed() {

			if pwnedFlag == true {
				haveIBeenPwned, err = pwned.IsPasswordCompromised(passphrase)
			}

			if err != nil {
				fmt.Println("Something went wrong.")
			} else if haveIBeenPwned == true {
				fmt.Println("This password does not have any entropy, because it has been compromised.")
				return
			} else {
				userInputs := strings.Fields(words)
				strength := zxcvbn.PasswordStrength(passphrase, userInputs)
				guesses := strength.Guesses
				fmt.Printf("\nPassword:\t\t%s\n", passphrase)

				fmt.Printf("Password strength:\t%d/4\n", strength.Score)

				fmt.Printf("Guesses Log10:\t\t%f\n", math.Log10(float64(guesses)))
				fmt.Println("\nGuess times")
				fmt.Printf("100 / h:\t\t%s\t(throttled online attack)\n",secondsToHuman(guesses * (3600 / 100)))
				fmt.Printf("10  / s:\t\t%s\t(unthrottled online attack)\n",secondsToHuman(guesses/10))
				fmt.Printf("10k / s:\t\t%s\t(offline attack, slow hash, many cores)\n",secondsToHuman(guesses / 1e4))
				fmt.Printf("10b / s:\t\t%s\t(offline attack, slow hash, many cores)\n",secondsToHuman(guesses / 1e10))
			}
		}
	default:
		myUsage()
		fmt.Printf("\n%q is not valid command.\n", os.Args[1])
		os.Exit(2)
	}
}