Add script_score to query DSL (#254)

* Add script_score to query DSL

Signed-off-by: Kim Quang Cap <kimquangcap@gmail.com>

* Fix example for script_score

Signed-off-by: Kim Quang Cap <kimquangcap@gmail.com>

* Fixed example description and added changelog

Signed-off-by: Kim Quang Cap <kimquangcap@gmail.com>

* Remove ES header

Signed-off-by: Kim Quang Cap <kimquangcap@gmail.com>

* Add license header for OS.

Signed-off-by: Kim Quang Cap <kimquangcap@gmail.com>

---------

Signed-off-by: Kim Quang Cap <kimquangcap@gmail.com>
Co-authored-by: Kim Quang Cap <kimquangcap@gmail.com>

CHANGELOG.md

@@ -3,6 +3,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## [Unreleased]
 ### Added
+- Added `script_score` to Query DSL ([#254](https://github.com/opensearch-project/opensearch-ruby/pull/254))
 ### Changed
 ### Deprecated
 ### Removed

lib/opensearch/dsl/search/queries/script_score.rb

@@ -0,0 +1,62 @@
+# SPDX-License-Identifier: Apache-2.0
+#
+# The OpenSearch Contributors require contributions made to
+# this file be licensed under the Apache-2.0 license or a
+# compatible open source license.
+
+module OpenSearch
+  module DSL
+    module Search
+      module Queries
+        # A query which wraps another query and returns a customized score for matching documents
+        #
+        # @example
+        #
+        #     search do
+        #       query do
+        #         script_score do
+        #           query do
+        #             match content: 'Twitter'
+        #           end
+        #
+        #           script source: "_score * params['multiplier']",
+        #                  params: { multiplier: 2.0 }
+        #         end
+        #       end
+        #     end
+        #
+        # @see https://opensearch.org/docs/latest/query-dsl/specialized/script-score/
+        #
+        class ScriptScore
+          include BaseComponent
+
+          option_method :script
+          option_method :min_score
+          option_method :boost
+
+          # DSL method for building the `query` part of the query definition
+          #
+          # @return [self]
+          #
+          def query(*args, &block)
+            @query = block ? @query = Query.new(*args, &block) : args.first
+            self
+          end
+
+          # Converts the query definition to a Hash
+          #
+          # @return [Hash]
+          #
+          def to_hash
+            hash = super
+            if @query
+              _query = @query.respond_to?(:to_hash) ? @query.to_hash : @query
+              hash[name].update(query: _query)
+            end
+            hash
+          end
+        end
+      end
+    end
+  end
+end

spec/opensearch/dsl/search/queries/script_score_spec.rb

@@ -0,0 +1,90 @@
+# SPDX-License-Identifier: Apache-2.0
+#
+# The OpenSearch Contributors require contributions made to
+# this file be licensed under the Apache-2.0 license or a
+# compatible open source license.
+
+require_relative '../../../../spec_helper'
+
+describe OpenSearch::DSL::Search::Queries::ScriptScore do
+  describe '#to_hash' do
+    let(:search) do
+      described_class.new
+    end
+
+    it 'can be converted to a hash' do
+      expect(search.to_hash).to eq(script_score: {})
+    end
+  end
+
+  context 'when options methods are called' do
+    let(:search) do
+      described_class.new
+    end
+
+    describe '#query' do
+      before do
+        search.query('bar')
+      end
+
+      it 'applies the option' do
+        expect(search.to_hash[:script_score][:query]).to eq('bar')
+      end
+    end
+
+    describe '#boost' do
+      before do
+        search.boost('bar')
+      end
+
+      it 'applies the option' do
+        expect(search.to_hash[:script_score][:boost]).to eq('bar')
+      end
+    end
+
+    describe '#script' do
+      before do
+        search.script('bar')
+      end
+
+      it 'applies the option' do
+        expect(search.to_hash[:script_score][:script]).to eq('bar')
+      end
+    end
+
+    describe '#min_score' do
+      before do
+        search.min_score('bar')
+      end
+
+      it 'applies the option' do
+        expect(search.to_hash[:script_score][:min_score]).to eq('bar')
+      end
+    end
+  end
+
+  describe '#initialize' do
+    context 'when a block is provided' do
+      let(:search) do
+        described_class.new do
+          query do
+            term foo: 'bar'
+          end
+
+          script source: 'foo',
+                 params: { foo: 'bar' }
+          boost 'bar'
+          min_score 'bar'
+        end
+      end
+
+      it 'executes the block' do
+        expect(search.to_hash[:script_score][:query][:term][:foo]).to eq('bar')
+        expect(search.to_hash[:script_score][:script][:source]).to eq('foo')
+        expect(search.to_hash[:script_score][:script][:params]).to eq(foo: 'bar')
+        expect(search.to_hash[:script_score][:boost]).to eq('bar')
+        expect(search.to_hash[:script_score][:min_score]).to eq('bar')
+      end
+    end
+  end
+end