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 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(" insecure   Calculate entropy of an invented passphrase")
}

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

	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"

	dicewareCommand := flag.NewFlagSet("diceware", flag.ExitOnError)
	dicewarePassphraseFlag := dicewareCommand.String("passphrase", "", "the passphrase")
	wordsFlag := dicewareCommand.Int("words", 0, "number of words in passphrase")
	dictSizeFlag := dicewareCommand.Int("dictSize", 0, "number of words in dictionary")

	randomCommand := flag.NewFlagSet("random", flag.ExitOnError)
	randomPassphraseFlag := randomCommand.String("password", "", "the password")

	insecureCommand := flag.NewFlagSet("insecure", flag.ExitOnError)
	insecureWords := insecureCommand.Int("words", 0, "number of words in invented passphrase")

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

	switch os.Args[1] {
	case "diceware":
		dicewareCommand.Parse(os.Args[2:])
	case "random":
		randomCommand.Parse(os.Args[2:])
	case "insecure":
		insecureCommand.Parse(os.Args[2:])
	default:
		myUsage()
		fmt.Printf("\n%q is not valid command.\n", os.Args[1])
		os.Exit(2)
	}

	if dicewareCommand.Parsed() {
		if *dicewarePassphraseFlag == "" {
			dicewareCommand.Usage()
			return
		}
		if *wordsFlag == 0 {
			dicewareCommand.Usage()
			return
		}
		if *dictSizeFlag == 0 {
			dicewareCommand.Usage()
			return
		}
		entropy := math.Log2(math.Pow(float64(*dictSizeFlag), float64(*wordsFlag)))
		fmt.Println("\nPassphrase entropy:", entropy)
	}

	if randomCommand.Parsed() {
		if *randomPassphraseFlag == "" {
			randomCommand.Usage()
			return
		}
		passphraseLength := len(*randomPassphraseFlag)

		for key, value := range charsets {
			if strings.ContainsAny(*randomPassphraseFlag, 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)
	}

	if insecureCommand.Parsed() {
		if *insecureWords != 0 {
			insecureCommand.Usage()
			return
		}
	}
}