Full refactor, remove dead code, remove math/rand, add version arg, remove symbol arg, help arg, and improve remove disallowed character argument

main.go

@@ -1,42 +1,66 @@
 // GoPass
 // Author: Maximilian Patterson
-// Version: 1.2.2
 package main
 
 import (
-	cryptorand "crypto/rand"
-	"encoding/binary"
+	"crypto/rand"
 	"fmt"
 	"math/big"
-	mathrand "math/rand"
 	"os"
 	"strconv"
+	"strings"
 )
 
 var allowedCharacters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890`~!@#$%^&*()_+[]\\{}|;':,./<>?")
 
-func main() {
-	// Take in all OS arg
-	args := os.Args[1:]
-	if len(args) < 1 {
-		println("No password length specified! (ex: ./gopass 16)")
-		return
+const (
+	Version = "1.3.0"
+	symbols = "`~!@#$%^&*()_+[]\\{}|;':,./<>?"
+)
+
+func matchArguments(args []string) string {
+	// If there are no arguments
+	if len(args) == 0 {
+		return "No password length specified! (ex: gopass 16)"
 	}
 
-	// Convert String arg to int
-	size, err := strconv.Atoi(args[0])
-	if err != nil {
-		println("First argument supplied must be an integer! (ex: 16)")
-		return
+	// First argument is special, must be an integer, -v, or -h
+	var size = 0 // Password length
+	err := error(nil)
+	if size, err = strconv.Atoi(args[0]); err == nil { // If first argument is an integer
+	} else if args[0] == "-v" {
+		return "GoPass version " + Version
+	} else if args[0] == "-h" {
+		return "GoPass - A simple password generator written in Go\n" +
+			"Usage: gopass [length] [disallowed characters] [optional remove symbols -s]\n" +
+			"     Example: gopass 16\n" +
+			"     Example: gopass 16 -r=abc123!@#\n" +
+			"     Example: gopass 16 -s\n" +
+			"\nFor help (this output): gopass -h\n" +
+			"For version: gopass -v\n"
 	}
 
-	// Grab second argument (if it exists) and use it as a disallowed character(s)
-	var disallowed []rune
-	if len(args) == 2 {
-		// Break apart the string into a slice of runes
-		disallowed = []rune(args[1])
+	for i := 1; i < len(args); i++ {
+		v := args[i]
+		if v == "-s" {
+			removeDisallowed([]rune(symbols))
+		} else if strings.HasPrefix(v, "-r=") { // If argument starts with -r=
+			// Remove all characters after the = until next whitespace
+			removeDisallowed([]rune(v[2:]))
+		} else {
+			return "Invalid argument (\"" + v + "\") supplied! (Type gopass -h for help)"
+		}
+	}
+
+	if size <= 0 {
+		return "No/invalid password length specified! (ex: gopass 16)"
+	} else {
+		return generatePassword(size)
+	}
+}
 
 // Remove all disallowed characters from the allowedCharacters slice
+func removeDisallowed(disallowed []rune) {
 	for _, r := range disallowed {
 		for i, v := range allowedCharacters {
 			if v == r {
@@ -46,29 +70,25 @@ func main() {
 	}
 }
 
+func generatePassword(size int) string {
 	// Make empty array of runes with size of size
 	pass := make([]rune, size)
 
-	// Seed rand with time
-	var b [8]byte
-	_, err = cryptorand.Read(b[:])
-	if err != nil {
-		println("Error securely seeding crypto/rand!")
-		return
-	}
-	mathrand.Seed(int64(binary.LittleEndian.Uint64(b[:])))
-
 	// Assign every slot of pass to a random allowedCharacter
 	for i := range pass {
 		// Generate a random int greater than 0 and not to exceed the length of allowedCharacters
-		index, err := cryptorand.Int(cryptorand.Reader, big.NewInt(int64(len(allowedCharacters))))
+		index, err := rand.Int(rand.Reader, big.NewInt(int64(len(allowedCharacters))))
 		if err != nil {
 			println("Error securely generating random character!")
-			return
+			return ""
 		}
 		pass[i] = allowedCharacters[index.Int64()]
 	}
 
-	// Print the password
-	fmt.Println(string(pass))
+	return string(pass)
+}
+
+func main() {
+	// Process arguments
+	fmt.Println(matchArguments(os.Args[1:]))
 }