module Buff
  module Extensions::Hash
    # Borrowd and modified from
    # {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/hash/slice.rb}
    module Slice
      # Slice a hash to include only the given keys. This is useful for
      # limiting an options hash to valid keys before passing to a method:
      #
      #   def search(criteria = {})
      #     criteria.assert_valid_keys(:mass, :velocity, :time)
      #   end
      #
      #   search(options.slice(:mass, :velocity, :time))
      #
      # If you have an array of keys you want to limit to, you should splat them:
      #
      #   valid_keys = [:mass, :velocity, :time]
      #   search(options.slice(*valid_keys))
      def slice(*keys)
        keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
        keys.each_with_object(self.class.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
      end

      # Replaces the hash with only the given keys.
      # Returns a hash containing the removed key/value pairs.
      #
      #   { a: 1, b: 2, c: 3, d: 4 }.slice!(:a, :b)
      #   # => {:c=>3, :d=>4}
      def slice!(*keys)
        keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
        omit = slice(*self.keys - keys)
        hash = slice(*keys)
        replace(hash)
        omit
      end

      # Removes and returns the key/value pairs matching the given keys.
      #
      #   { a: 1, b: 2, c: 3, d: 4 }.extract!(:a, :b) # => {:a=>1, :b=>2}
      #   { a: 1, b: 2 }.extract!(:a, :x)             # => {:a=>1}
      def extract!(*keys)
        keys.each_with_object(self.class.new) { |key, result| result[key] = delete(key) if has_key?(key) }
      end
    end
  end
end

class Hash
  include Buff::Extensions::Hash::Slice
end
