AttributeMerger for Phlex Components

attribute_merger.rb

class AttributeMerger
    attr_reader :default_attrs, :user_attrs
    OVERRIDE_KEY = '!'.freeze

    def initialize(default_attrs, user_attrs)
        @default_attrs = flatten_hash(default_attrs)
        @user_attrs = flatten_hash(user_attrs)
    end

    def call
        merged_attrs = merge_hashes(default_attrs, non_override_attrs)
        mix(merged_attrs, override_attrs)
    end

    private

    # @return [Hash]
    def mix(*args)
        args.each_with_object({}) do |object, result|
            result.merge!(object) do |_key, old, new|
                case new
                when Hash
                    old.is_a?(Hash) ? mix(old, new) : new
                when Array
                    old.is_a?(Array) ? (old + new) : new
                when String
                    old.is_a?(String) ? "#{old} #{new}" : new
                else
                    new
                end
            end

            result.transform_keys! do |key|
                key.end_with?("!") ? key.name.chop.to_sym : key
            end
        end
    end

    def override_attrs
        user_attrs.select do |key, value|
            key.to_s.include?(OVERRIDE_KEY)
        end
    end

    def non_override_attrs
        user_attrs.reject do |key, value|
            key.to_s.include?(OVERRIDE_KEY)
        end
    end

    def flatten_hash(hash, parent_key = '', result_hash = {})
        hash.each do |key, value|
            new_key = parent_key.empty? ? key : "#{parent_key}_#{key}".to_sym
            if value.is_a? Hash
            flatten_hash(value, new_key, result_hash)
            else
            result_hash[new_key] = value
            end
        end
        result_hash
    end

    def merge_hashes(hash1, hash2)
        flat_hash1 = flatten_hash(hash1)
        flat_hash2 = flatten_hash(hash2)

        merged = flat_hash1.merge(flat_hash2) do |key, oldval, newval|
            "#{oldval} #{newval}"
        end

        merged
    end
end

index.rb

require 'attribute_merger'

AttributeMerger.new({class: 'bg-blue border py-2', data_action: 'click->accordion#open'}, {}).call
# => {class: 'bg-blue border py-2', data_action: 'click->accordion#open'}

AttributeMerger.new({class: 'bg-blue border py-2', data_action: 'click->accordion#open'}, {class: 'bg-black', 
data_action: 'mouseenter->accordion#open'}).call
# => {:class=>"bg-blue border py-2 bg-black", :data_action=>"click->accordion#open mouseenter->accordion#open"}

# Override attributes with '!' key values (eg. class!:)
AttributeMerger.new({
    class: 'bg-blue border py-2',
    data_action: 'click->accordion#open'
  }, 
  {
    class!: 'bg-black',
    data: {
      action!: 'mouseenter->accordion#open'
    }
  }
).call
# => {:class=>"bg-black", :data_action=>"mouseenter->accordion#open"}