module Elasticsearch
  module API
    module Actions

      # Return documents similar to the specified one.
      #
      # Performs a `more_like_this` query with the specified document as the input.
      #
      # @example Search for similar documents using the `title` property of document `myindex/mytype/1`
      #
      #     client.mlt index: 'myindex', type: 'mytype', id: '1', mlt_fields: 'title'
      #
      # @option arguments [String] :id The document ID (*Required*)
      # @option arguments [String] :index The name of the index (*Required*)
      # @option arguments [String] :type The type of the document (use `_all` to fetch
      #                                  the first document matching the ID across all types) (*Required*)
      # @option arguments [Hash] :body A specific search request definition
      # @option arguments [Number] :boost_terms The boost factor
      # @option arguments [Number] :max_doc_freq The word occurrence frequency as count: words with higher occurrence
      #                                          in the corpus will be ignored
      # @option arguments [Number] :max_query_terms The maximum query terms to be included in the generated query
      # @option arguments [Number] :max_word_len The minimum length of the word: longer words will be ignored
      # @option arguments [Number] :min_doc_freq The word occurrence frequency as count: words with lower occurrence
      #                                          in the corpus will be ignored
      # @option arguments [Number] :min_term_freq The term frequency as percent: terms with lower occurence
      #                                           in the source document will be ignored
      # @option arguments [Number] :min_word_len The minimum length of the word: shorter words will be ignored
      # @option arguments [List] :mlt_fields Specific fields to perform the query against
      # @option arguments [Number] :percent_terms_to_match How many terms have to match in order to consider
      #                                                    the document a match (default: 0.3)
      # @option arguments [String] :routing Specific routing value
      # @option arguments [Number] :search_from The offset from which to return results
      # @option arguments [List] :search_indices A comma-separated list of indices to perform the query against
      #                                          (default: the index containing the document)
      # @option arguments [String] :search_query_hint The search query hint
      # @option arguments [String] :search_scroll A scroll search request definition
      # @option arguments [Number] :search_size The number of documents to return (default: 10)
      # @option arguments [String] :search_source A specific search request definition (instead of using the request body)
      # @option arguments [String] :search_type Specific search type (eg. `dfs_then_fetch`, `count`, etc)
      # @option arguments [List] :search_types A comma-separated list of types to perform the query against
      #                                        (default: the same type as the document)
      # @option arguments [List] :stop_words A list of stop words to be ignored
      #
      # @see http://elasticsearch.org/guide/reference/api/more-like-this/
      #
      def mlt(arguments={})
        raise ArgumentError, "Required argument 'index' missing" unless arguments[:index]
        raise ArgumentError, "Required argument 'type' missing"  unless arguments[:type]
        raise ArgumentError, "Required argument 'id' missing"    unless arguments[:id]
        method = 'GET'
        path   = Utils.__pathify( arguments[:index], arguments[:type], arguments[:id], '_mlt' )
        params = arguments.select do |k,v|
          [ :boost_terms,
            :max_doc_freq,
            :max_query_terms,
            :max_word_len,
            :min_doc_freq,
            :min_term_freq,
            :min_word_len,
            :mlt_fields,
            :percent_terms_to_match,
            :routing,
            :search_from,
            :search_indices,
            :search_query_hint,
            :search_scroll,
            :search_size,
            :search_source,
            :search_type,
            :search_types,
            :stop_words ].include?(k)
        end
        # Normalize Ruby 1.8 and Ruby 1.9 Hash#select behaviour
        params = Hash[params] unless params.is_a?(Hash)

        [:mlt_fields, :search_indices, :search_types, :stop_words].each do |name|
          params[name] = Utils.__listify(params[name]) if params[name]
        end

        body   = arguments[:body]

        perform_request(method, path, params, body).body
      end
    end
  end
end