class ReeHash::Merge

def call(first_hash, other_hash, deep: true, &block)
  recursively_merge(first_hash, other_hash, deep, &block)
end

def recursively_merge(first_hash, other_hash, deep, &block)
  first_hash.merge(other_hash) do |key, first_val, other_val|
    if first_val.is_a?(Hash) && other_val.is_a?(Hash) && deep
      recursively_merge(first_val, other_val, deep)
    elsif block_given?
      yield key, first_val, other_val
    else
      other_val
    end
  end
end