From 2822f73f5603e7030af01facee95d7aa5ab2f33e Mon Sep 17 00:00:00 2001
From: Winni Neessen <winfried.neessen@cleverbridge.com>
Date: Sat, 5 Aug 2023 18:10:11 +0200
Subject: [PATCH] #53 Add coinflip algorithm and improve error messages

Introduced a new password generation algorithm, called 'coinflip', which simply returns "Heads" or "Tails". Associated CLI flag has been added as well. Also, improved error messages during password generation. This addition provides a simpler algorithm option and clearer user feedback during errors.
---
 algo.go        |  5 +++++
 cmd/apg/apg.go | 17 ++++++++++++++---
 random.go      | 24 +++++++++++++++++++++++-
 3 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/algo.go b/algo.go
index 5cfc5f4..63fb0db 100644
--- a/algo.go
+++ b/algo.go
@@ -11,6 +11,9 @@ const (
 	// AlgoRandom represents the algorithm for purely random passwords according
 	// to the provided password modes/flags
 	AlgoRandom
+	// AlgoCoinFlip represents a very simple coinflip algorithm returning "heads"
+	// or "tails"
+	AlgoCoinFlip
 	// AlgoUnsupported represents an unsupported algorithm
 	AlgoUnsupported
 )
@@ -23,6 +26,8 @@ func IntToAlgo(a int) Algorithm {
 		return AlgoPronouncable
 	case 1:
 		return AlgoRandom
+	case 2:
+		return AlgoCoinFlip
 	default:
 		return AlgoUnsupported
 	}
diff --git a/cmd/apg/apg.go b/cmd/apg/apg.go
index 2e5b0ba..641f3a3 100644
--- a/cmd/apg/apg.go
+++ b/cmd/apg/apg.go
@@ -15,8 +15,10 @@ func main() {
 
 	// Configure and parse the CLI flags
 	// See usage() for flag details
+	var al int
 	var ms string
 	var co, hr, lc, nu, sp, uc bool
+	flag.IntVar(&al, "a", 1, "")
 	flag.BoolVar(&lc, "L", false, "")
 	flag.Int64Var(&c.MinLowerCase, "mL", c.MinLowerCase, "")
 	flag.BoolVar(&uc, "U", false, "")
@@ -62,14 +64,22 @@ func main() {
 		c.Mode = apg.ModesFromFlags(ms)
 	}
 
+	// Check if algorithm is supported
+	c.Algorithm = apg.IntToAlgo(al)
+	if c.Algorithm == apg.AlgoUnsupported {
+		_, _ = fmt.Fprintf(os.Stderr, "unsupported algorithm value: %d\n", al)
+		os.Exit(1)
+	}
+
 	// Generate the password based on the given flags
 	g := apg.New(c)
 	for i := int64(0); i < c.NumberPass; i++ {
-		pl, err := g.GetPasswordLength()
+		p, err := g.Generate()
 		if err != nil {
-			_, _ = fmt.Fprintf(os.Stderr, "Error during password generation: %s\n", err)
+			_, _ = fmt.Fprintf(os.Stderr, "failed to generate password: %s\n", err)
+			os.Exit(1)
 		}
-		fmt.Printf("PW length: %d\n", pl)
+		fmt.Println(p)
 	}
 }
 
@@ -88,6 +98,7 @@ Flags:
     -a ALGORITH          Choose the password generation algorithm (Default: 1)
                           - 0: pronounceable password generation (koremutake syllables)
                           - 1: random password generation according to password modes/flags
+                          - 2: coinflip (returns heads or tails)
     -m LENGTH            Minimum length of the password to be generated (Default: 12)
     -x LENGTH            Maximum length of the password to be generated (Default: 20)
     -f LENGTH            Fixed length of the password to be generated (Ignores -m and -x)
diff --git a/random.go b/random.go
index 5b653d7..83c995b 100644
--- a/random.go
+++ b/random.go
@@ -27,6 +27,28 @@ var (
 	ErrInvalidCharRange = errors.New("provided character range is not valid or empty")
 )
 
+// Generate generates a password based on all the different config flags and returns
+// it as string type. If the generation fails, an error will be thrown
+func (g *Generator) Generate() (string, error) {
+	// Coinflip mode
+	if g.config.Algorithm == AlgoCoinFlip {
+		switch g.CoinFlipBool() {
+		case true:
+			return "Heads", nil
+		case false:
+			return "Tails", nil
+		}
+	}
+
+	l, err := g.GetPasswordLength()
+	if err != nil {
+		return "", fmt.Errorf("failed to calculate password length: %w", err)
+	}
+	_ = l
+
+	return "", nil
+}
+
 // RandomBytes returns a byte slice of random bytes with length n that got generated by
 // the crypto/rand generator
 func (g *Generator) RandomBytes(n int64) ([]byte, error) {
@@ -121,7 +143,7 @@ func (g *Generator) GetPasswordLength() (int64, error) {
 	diff := mal - mil + 1
 	ra, err := g.RandNum(diff)
 	if err != nil {
-		return 0, fmt.Errorf("failed to calculate password length: %w", err)
+		return 0, err
 	}
 	l := mil + ra
 	if l <= 0 {