func Generate()

in cli/azd/pkg/password/generator.go [69:179]
97 lines of code
37 McCabe index (conditional complexity)

func Generate(config GenerateConfig) (string, error) {
	var minLower uint
	if config.MinLower != nil {
		minLower = *config.MinLower
	}
	var minUpper uint
	if config.MinUpper != nil {
		minUpper = *config.MinUpper
	}
	var minNumeric uint
	if config.MinNumeric != nil {
		minNumeric = *config.MinNumeric
	}
	var minSpecial uint
	if config.MinSpecial != nil {
		minSpecial = *config.MinSpecial
	}

	// a cluster is a group of characters that are required to be present in the password
	clustersLength := minLower + minUpper + minNumeric + minSpecial
	totalLength := config.Length
	if totalLength == 0 {
		totalLength = clustersLength
	}
	if clustersLength > totalLength {
		return "",
			fmt.Errorf("the sum of MinLower, MinUpper, MinNumeric, and MinSpecial must be less than or equal to the length")
	}
	if totalLength == 0 {
		return "", fmt.Errorf(
			"either Length or the sum of MinLower, MinUpper, MinNumeric, and MinSpecial must be greater than 0")
	}

	unassignedClusterSize := totalLength - clustersLength
	var generated string

	genCluster := func(minClusterSize uint, disallowedCluster *bool, alphabet string, appendTo *string) error {
		if disallowedCluster != nil && *disallowedCluster {
			if minClusterSize > 0 {
				return fmt.Errorf("cluster size is greater than 0 but the condition is false")
			}
			return nil
		}
		if minClusterSize > 0 {
			gen, err := FromAlphabet(alphabet, minClusterSize)
			if err != nil {
				return fmt.Errorf("generating fixed size cluster: %w", err)
			}
			*appendTo += gen
		}
		return nil
	}
	if err := genCluster(minLower, config.NoLower, LowercaseLetters, &generated); err != nil {
		return "", err
	}
	if err := genCluster(minUpper, config.NoUpper, UppercaseLetters, &generated); err != nil {
		return "", err
	}
	if err := genCluster(minNumeric, config.NoNumeric, Digits, &generated); err != nil {
		return "", err
	}
	if err := genCluster(minSpecial, config.NoSpecial, Symbols, &generated); err != nil {
		return "", err
	}

	// Strategy for generating remaining characters:
	// 1. If all characters are disallowed, return an error
	// 2. For each character that needs to be generated, generate a charset picking one random char for each allowed cluster
	// 3. Use the generated charset to pick a random character for the char
	// This strategy gives the same changes for each character to be picked from any cluster, regardless of the cluster size
	// For example, picking a char from lowercase letters and numbers should not give more changes to get a lowercase letter
	// just because there are more lower case letters than numbers.
	for unassignedClusterSize > 0 {
		var combinedAlphabet string
		var noDisallow bool
		if config.NoLower == nil || (config.NoLower != nil && !*config.NoLower) {
			if err := genCluster(1, &noDisallow, LowercaseLetters, &combinedAlphabet); err != nil {
				return "", err
			}
		}
		if config.NoUpper == nil || (config.NoUpper != nil && !*config.NoUpper) {
			if err := genCluster(1, &noDisallow, UppercaseLetters, &combinedAlphabet); err != nil {
				return "", err
			}
		}
		if config.NoNumeric == nil || (config.NoNumeric != nil && !*config.NoNumeric) {
			if err := genCluster(1, &noDisallow, Digits, &combinedAlphabet); err != nil {
				return "", err
			}
		}
		if config.NoSpecial == nil || (config.NoSpecial != nil && !*config.NoSpecial) {
			if err := genCluster(1, &noDisallow, Symbols, &combinedAlphabet); err != nil {
				return "", err
			}
		}
		if combinedAlphabet == "" {
			return "", fmt.Errorf("can't generate if all characters are disallowed (noLower, noUpper, noNumeric, noSpecial)")
		}
		if err := genCluster(1, &noDisallow, combinedAlphabet, &generated); err != nil {
			return "", err
		}
		unassignedClusterSize--
	}

	fixedSizeClustersStringChars := strings.Split(generated, "")
	if err := Shuffle(fixedSizeClustersStringChars); err != nil {
		return "", fmt.Errorf("shuffling fixed size cluster: %w", err)
	}

	return strings.Join(fixedSizeClustersStringChars, ""), nil
}