Fixes Completion, Phrase, and Term suggesters

Signed-off-by: Harsha Vamsi Kalluri <harshavamsi096@gmail.com>

CHANGELOG.md

@@ -23,6 +23,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ### Fixed
 - Fix version and build ([#254](https://github.com/opensearch-project/opensearch-java/pull/254))
+- Fixed Suggesters for Completion, Term, and Phrase and refactored the Suggestion class ([#477](https://github.com/opensearch-project/opensearch-java/pull/477))
 
 ### Security
 

USER_GUIDE.md

@@ -11,6 +11,11 @@
  - [Search for the documents](#search-for-the-documents)
  - [Get raw JSON results](#get-raw-json-results)
  - [Search documents using a match query](#search-documents-using-a-match-query)
+ - [Search documents using suggesters](#search-documents-using-suggesters)
+ - [App Data class](#app-data-class)
+ - [Using completion suggester](#using-completion-suggester)
+ - [Using term suggester](#using-term-suggester)
+ - [Using phrase suggester](#using-phrase-suggester)
  - [Bulk requests](#bulk-requests)
  - [Aggregations](#aggregations)
  - [Delete the document](#delete-the-document)
@@ -169,6 +174,236 @@ for (int i = 0; i < searchResponse.hits().hits().size(); i++) {
 }
 ```
 
+## Search documents using suggesters
+
+### App Data class
+
+```java
+public static class AppData {
+
+ private int intValue;
+ private String msg;
+
+ public int getIntValue() {
+ return intValue;
+ }
+
+ public void setIntValue(int intValue) {
+ this.intValue = intValue;
+ }
+
+ public String getMsg() {
+ return msg;
+ }
+
+ public void setMsg(String msg) {
+ this.msg = msg;
+ }
+}
+```
+
+### Using completion suggester
+
+```java
+String index = "completion-suggester";
+
+Property intValueProp = new Property.Builder()
+ .long_(v -> v)
+ .build();
+Property msgCompletionProp = new Property.Builder()
+ .completion(c -> c)
+ .build();
+client.indices().create(c -> c
+ .index(index)
+ .mappings(m -> m
+ .properties("intValue", intValueProp)
+ .properties("msg", msgCompletionProp)));
+
+AppData appData = new AppData();
+appData.setIntValue(1337);
+appData.setMsg("foo");
+
+client.index(b -> b
+ .index(index)
+ .id("1")
+ .document(appData)
+ .refresh(Refresh.True));
+
+appData.setIntValue(1338);
+appData.setMsg("foobar");
+
+client.index(b -> b
+ .index(index)
+ .id("2")
+ .document(appData)
+ .refresh(Refresh.True));
+
+String suggesterName = "msgSuggester";
+
+CompletionSuggester completionSuggester = FieldSuggesterBuilders.completion()
+ .field("msg")
+ .size(1)
+ .build();
+FieldSuggester fieldSuggester = new FieldSuggester.Builder().prefix("foo")
+ .completion(completionSuggester)
+ .build();
+Suggester suggester = new Suggester.Builder()
+ .suggesters(Collections.singletonMap(suggesterName, fieldSuggester))
+ .build();
+SearchRequest searchRequest = new SearchRequest.Builder()
+ .index(index)
+ .suggest(suggester)
+ .build();
+
+SearchResponse<AppData> response = client.search(searchRequest, AppData.class);
+```
+
+### Using term suggester
+
+```java
+ String index = "term-suggester";
+
+// term suggester does not require a special mapping
+client.indices().create(c -> c
+ .index(index));
+
+AppData appData = new AppData();
+appData.setIntValue(1337);
+appData.setMsg("foo");
+
+client.index(b -> b
+ .index(index)
+ .id("1")
+ .document(appData)
+ .refresh(Refresh.True));
+
+appData.setIntValue(1338);
+appData.setMsg("foobar");
+
+client.index(b -> b
+ .index(index)
+ .id("2")
+ .document(appData)
+ .refresh(Refresh.True));
+
+String suggesterName = "msgSuggester";
+
+TermSuggester termSuggester = FieldSuggesterBuilders.term()
+ .field("msg")
+ .size(1)
+ .build();
+FieldSuggester fieldSuggester = new FieldSuggester.Builder().text("fool")
+ .term(termSuggester)
+ .build();
+Suggester suggester = new Suggester.Builder()
+ .suggesters(Collections.singletonMap(suggesterName, fieldSuggester))
+ .build();
+SearchRequest searchRequest = new SearchRequest.Builder()
+ .index(index)
+ .suggest(suggester)
+ .build();
+
+SearchResponse<AppData> response = client.search(searchRequest, AppData.class);
+```
+
+### Using phrase suggester
+
+```java
+String index = "phrase-suggester";
+
+String settingsJson = "{\n" +
+ "\"index\": {\n" +
+ "\"analysis\": {\n" +
+ "\"analyzer\": {\n" +
+ "\"trigram\": {\n" +
+ "\"type\": \"custom\",\n" +
+ "\"tokenizer\": \"standard\",\n" +
+ "\"filter\": [\n" +
+ "\"lowercase\",\n" +
+ "\"shingle\"\n" +
+ "]\n" +
+ "}\n" +
+ "},\n" +
+ "\"filter\": {\n" +
+ "\"shingle\": {\n" +
+ "\"type\": \"shingle\",\n" +
+ "\"min_shingle_size\": 2,\n" +
+ "\"max_shingle_size\": 3\n" +
+ "}\n" +
+ "}\n" +
+ "}\n" +
+ "}\n" +
+ "}";
+
+String mappingJson = "{\n" +
+ "\"properties\": {\n" +
+ "\"msg\": {\n" +
+ "\"type\": \"text\",\n" +
+ "\"fields\": {\n" +
+ "\"trigram\": {\n" +
+ "\"type\": \"text\",\n" +
+ "\"analyzer\": \"trigram\"\n" +
+ "}\n" +
+ "}\n" +
+ "}\n" +
+ "}\n" +
+ "}";
+
+ ObjectMapper mapper = new JsonMapper();
+JsonpMapper jsonpMapper = new JacksonJsonpMapper(mapper);
+IndexSettings settings;
+try (JsonParser settingsParser = new JacksonJsonpParser(mapper.createParser(settingsJson))) {
+settings = IndexSettings._DESERIALIZER.deserialize(settingsParser, jsonpMapper);
+}
+
+TypeMapping mapping;
+try (JsonParser mappingParser = new JacksonJsonpParser(mapper.createParser(mappingJson))) {
+mapping = TypeMapping._DESERIALIZER.deserialize(mappingParser, jsonpMapper);
+}
+
+client.indices().create(c -> c
+ .index(index)
+ .settings(settings)
+ .mappings(mapping));
+
+AppData appData = new AppData();
+appData.setIntValue(1337);
+appData.setMsg("Design Patterns");
+
+client.index(b -> b
+ .index(index)
+ .id("1")
+ .document(appData)
+ .refresh(Refresh.True));
+
+appData.setIntValue(1338);
+appData.setMsg("Software Architecture Patterns Explained");
+
+client.index(b -> b
+ .index(index)
+ .id("2")
+ .document(appData)
+ .refresh(Refresh.True));
+
+String suggesterName = "msgSuggester";
+
+PhraseSuggester phraseSuggester = FieldSuggesterBuilders.phrase()
+ .field("msg.trigram")
+ .build();
+FieldSuggester fieldSuggester = new FieldSuggester.Builder().text("design paterns")
+ .phrase(phraseSuggester)
+ .build();
+Suggester suggester = new Suggester.Builder()
+ .suggesters(Collections.singletonMap(suggesterName, fieldSuggester))
+ .build();
+SearchRequest searchRequest = new SearchRequest.Builder()
+ .index(index)
+ .suggest(suggester)
+ .build();
+
+SearchResponse<AppData> response = client.search(searchRequest, AppData.class);
+```
+
 ## Bulk requests
 
 ```java