Refactor validations into Rules

[beechnut]

Having a collection of validation functions and a collection of associated error messages has been fine, and the defensive style of the codebase has made it even more fine.

But when you think of a validation with an error message, it's messy, and it's becoming clear that a new noun is needed—a Rule.

This issue can be closed when:

• Validations are organized into subclasses of Rule. Folder structure probably looks like lib/rule/acronym and lib/rule/term.
• Rule defines an abstract method for validating and an error class or error-raising action, and it's left to subclasses to implement.
• Instead of referencing a predefined list of methods, acronyms validate by referencing all loaded subclasses of Acronym Rule (probably Rule::Acronym if we're following Rails conventions with the folder structure, but I wouldn't be too picky about it). Terms do the same with all loaded subclasses of Term Rule.

Ideas:

# lib/validate.rb

require 'lib/rule/term/specific_term_validation'
require 'lib/rule/term/specific_acronym_validation'
# ... and so forth

...

def validate_term(term_data) # I'd love to also make Term an object here so we can just reference the data
  Rule::Term.each { |rule| rule.validate(term_data) }
end

# lib/rule/term/has_description.rb
class Rule::Term::HasDescription < Rule::BaseTerm
  def rule_logic(key, values)
    desc = values[:description]
    if desc.nil?
      reminders << "add a description for \"#{values[:longform] || key}\""
    elsif desc.is_a?(String) && !desc.empty?
      true
    else
      false
    end
  end

  def error_class_name
    :TermMissingDescriptionError # just name the class here, we'll name it in the background
  end

  def message(params) # Define the error message here
    <<~ERR

      The term \"#{key}\" does not have a description.

      ... lines omitted
    ERR
  end

end

Rule::Term.register(Rule::Term::HasDescription) # Makes it accessible to Rule::Term.each

[beechnut]

It might be simpler to use a validation library like dry/validation.