package main

import (
	"flag"
	"fmt"
	"math"
	"os"
	"strings"
)

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

func main() {

	var charsets map[string]string
	var usedCharsets[] string
	var possibleSymbols int = 0

	var passphrase string
	var words int

	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"

	flag.StringVar(&passphrase, "diceware", "", "a diceware passphrase")
	flag.IntVar(&words, "words", 0, "How many words")
	flag.StringVar(&passphrase, "random", "", "a random string password")
	flag.StringVar(&passphrase, "insecure", "", "a human invented password")

	flag.Parse()

	seen := make(map[string]bool)
	flag.Visit(func(f *flag.Flag) { seen[f.Name] = true })

	if len(seen) == 0 {
		flag.PrintDefaults()
		os.Exit(2) // the same exit code flag.Parse uses
	}

	fmt.Println("\nEvaluated string:", passphrase)

	if dice := seen["diceware"]; dice {
		if dice := !seen["words"]; dice {
			os.Exit(2)
		} else {
			entropy := math.Log2(math.Pow(float64(7776), float64(words)))
			fmt.Println("\nPassphrase entropy:", entropy)
		}
	} else if rnd := seen["random"]; rnd {
		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)
	}
}