module VestalVersions
  # Allows version creation to occur conditionally based on given <tt>:if</tt> and/or
  # <tt>:unless</tt> options.
  module Conditions
    extend ActiveSupport::Concern

    # Class methods on ActiveRecord::Base to prepare the <tt>:if</tt> and <tt>:unless</tt> options.
    module ClassMethods
      # After the original +prepare_versioned_options+ method cleans the given options, this alias
      # also extracts the <tt>:if</tt> and <tt>:unless</tt> options, chaning them into arrays
      # and converting any symbols to procs. Procs are called with the ActiveRecord model instance
      # as the sole argument.
      #
      # If all of the <tt>:if</tt> conditions are met and none of the <tt>:unless</tt> conditions
      # are unmet, than version creation will proceed, assuming all other conditions are also met.
      def prepare_versioned_options(options)
        result = super(options)

        vestal_versions_options[:if] = Array(options.delete(:if)).map(&:to_proc)
        vestal_versions_options[:unless] = Array(options.delete(:unless)).map(&:to_proc)

        result
      end
    end

    # Instance methods that determine based on the <tt>:if</tt> and <tt>:unless</tt> conditions,
    # whether a version is to be create or updated.
    
    
    private
      # After first determining whether the <tt>:if</tt> and <tt>:unless</tt> conditions are
      # satisfied, the original, unaliased +create_version?+ method is called to determine
      # whether a new version should be created upon update of the ActiveRecord::Base instance.
      def create_version?
        version_conditions_met? && super
      end

      # After first determining whether the <tt>:if</tt> and <tt>:unless</tt> conditions are
      # satisfied, the original, unaliased +update_version?+ method is called to determine
      # whther the last version should be updated to include changes merged from the current
      # ActiveRecord::Base instance update.
      #
      # The overridden +update_version?+ method simply returns false, effectively delegating
      # the decision to whether the <tt>:if</tt> and <tt>:unless</tt> conditions are met.
      def update_version?
        version_conditions_met? && super
      end

      # Simply checks whether the <tt>:if</tt> and <tt>:unless</tt> conditions given in the
      # +versioned+ options are met: meaning that all procs in the <tt>:if</tt> array must
      # evaluate to a non-false, non-nil value and that all procs in the <tt>:unless</tt> array
      # must all evaluate to either false or nil.
      def version_conditions_met?
        vestal_versions_options[:if].all?{|p| p.call(self) } && !vestal_versions_options[:unless].any?{|p| p.call(self) }
      end
  end
end