Schema validation for Config structs.

Overview

This module validates all ExkPasswd.Config fields, ensuring configurations are valid before password generation begins. Invalid configurations fail fast with descriptive error messages.

Validation Rules

num_words

• Type: Integer
• Range: 1-10
• Purpose: Controls password length and entropy

word_length

• Type: Range (e.g., 4..8)
• Default bounds: 4-10 (English/Latin scripts)
• Custom bounds: Set word_length_bounds for other scripts
• Constraints: min >= 1, max <= 50, min <= max

case_transform

• Type: Atom
• Valid: :none, :alternate, :capitalize, :invert, :lower, :upper, :random
• Purpose: Controls word casing in output

separator

• Type: String
• Allowed: Symbols and punctuation only (no letters/numbers)
• Empty string: Disables word separation
• Unicode: Full Unicode symbol support

digits

• Type: Tuple {before, after}
• Range: 0-5 for each position
• Purpose: Adds numeric padding for complexity

padding

• Type: Map with keys :char, :before, :after, :to_length
• :char: Symbol string (same rules as separator)
• :before/:after: 0-5 repetitions
• :to_length: 0 (disabled) or 8-999 (minimum password length)

substitutions

• Type: Map of single-char strings
• Example: %{"a" => "@", "e" => "3"}
• Purpose: Leetspeak-style character replacement

substitution_mode

• Type: Atom
• Valid: :none, :always, :random
• Purpose: Controls when substitutions apply

dictionary

• Type: Atom
• Default: :eff (EFF word list)
• Custom: Any atom registered via Dictionary.load_custom/2

word_length_bounds

• Type: Range or nil
• Purpose: Override default 4-10 bounds for non-Latin scripts
• Example: 1..4 for Chinese, 1..50 for German compounds

Error Messages

All validation errors include:

• The field name that failed
• The invalid value received
• The valid range or options
• Suggestions for common mistakes

Examples

iex> alias ExkPasswd.Config.Schema
...> Schema.validate(%ExkPasswd.Config{num_words: 3})
:ok

iex> alias ExkPasswd.Config.Schema
...> {:error, msg} = Schema.validate(%ExkPasswd.Config{num_words: 0})
...> msg =~ "num_words must be between"
true

Symbol Validation

Separators and padding characters are restricted to prevent confusion:

• Letters and numbers are rejected (could be mistaken for password content)
• All Unicode symbols and punctuation are allowed
• Empty strings disable the feature