/* 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.
*/
/*
* Modifications Copyright OpenSearch Contributors. See
* GitHub history for details.
*
*  Licensed to Elasticsearch B.V. under one or more contributor
*  license agreements. See the NOTICE file distributed with
*  this work for additional information regarding copyright
*  ownership. Elasticsearch B.V. licenses this file to you under
*  the Apache License, Version 2.0 (the "License"); you may
*  not use this file except in compliance with the License.
*  You may obtain a copy of the License at
*
* 	http://www.apache.org/licenses/LICENSE-2.0
*
*  Unless required by applicable law or agreed to in writing,
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*  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
*  KIND, either express or implied.  See the License for the
*  specific language governing permissions and limitations
*  under the License.
*/

using System;
using System.Linq;
using System.Text;
using OpenSearch.OpenSearch.Xunit.XunitPlumbing;
using OpenSearch.Client;
using Newtonsoft.Json.Linq;
using Tests.Core.Client;
using Tests.Core.ManagedOpenSearch.Clusters;
using Tests.Domain;
using Tests.Framework;
using static Tests.Core.Serialization.SerializationTestHelper;

namespace Tests.Search
{
	// TODO: Additional sections on Paging results (from/size, scroll and search_after), Multisearch and Conditionless queries
	/**=== Writing queries
	 *
	 * Once you have data indexed within OpenSearch, you're going to want to be able to search it. OpenSearch
	 * offers a powerful query DSL to define queries to execute against OpenSearch. This DSL is based on JSON
	 * and is exposed in OSC in the form of both a Fluent API and an Object Initializer syntax
	 *
	 */
	public class WritingQueries : IClusterFixture<ReadOnlyCluster>
	{
		private readonly ReadOnlyCluster _cluster;
		private readonly IOpenSearchClient _client = TestClient.DisabledStreaming;

		public WritingQueries(ReadOnlyCluster cluster) => _cluster = cluster;

		/**==== Match All query
		 *
		 * The simplest of queries is the {ref_current}/query-dsl-match-all-query.html[match_all] query;
		 * this will return all documents, giving them all a `_score` of 1.0
		 *
		 * [NOTE]
		 * --
		 * Not _all_ of the matching documents are returned in the one response; by default, only the first ten documents
		 * are returned. You can use `from` and `size` to paginate results.
		 * --
		 */
		[U]
		public void MatchAllQuery()
		{
			var searchResponse = _client.Search<Project>(s => s
				.Query(q => q
					.MatchAll()
				)
			);

			/**
			 * which serializes to the following JSON
			 */
			//json
			var expected = new
			{
				query = new
				{
					match_all = new {}
				}
			};

			//hide
			Expect(expected).FromRequest(searchResponse);

			/**Since `match_all` queries are common, the previous example also has a shorthand which
			 * serializes to the same query DSL JSON
			 */
			searchResponse = _client.Search<Project>(s => s
				.MatchAll()
			);

			//hide
			Expect(expected).FromRequest(searchResponse);

			/**
			 * The two previous examples both used the Fluent API to express the query. OSC also exposes an
			 * Object Initializer syntax to compose queries
			 */
			var searchRequest = new SearchRequest<Project>
			{
				Query = new MatchAllQuery()
			};

			searchResponse = _client.Search<Project>(searchRequest);

			//hide
			Expect(expected).FromRequest(searchResponse);
		}

		/**==== Search request parameters
		 *
		 * There are several parameters available on a search request; take a look at the reference section
		 * on <<reference-search, search>> for more details.
		 *
		 *[float]
		 * === Common queries
		 *
		 * By default, documents will be returned in `_score` descending order, where the `_score` for each hit
		 * is the relevancy score calculated for how well the document matched the query criteria.
		 *
		 * There are a number of search queries at your disposal, all of which are documented in
		 * the <<query-dsl, Query DSL>> reference section. Here, we want to highlight the three types of query
		 * operations that users typically want to perform
		 *
		 * - <<structured-search, Structured search>>
		 * - <<unstructured-search, Unstructured search>>
		 * - <<combining-queries, Combining queries>>
		 *
		 * [[structured-search]]
		 * ==== Structured search
		 *
		 * Structured search is about querying data that has inherent structure. Dates, times and numbers
		 * are all structured and it is common to want to query against fields of these types to look
		 * for exact matches, values that fall within a range, etc. Text can also be structured, for example,
		 * the keyword tags applied to a blog post.
		 *
		 * With structured search, the answer to a query is *always* yes or no; a document is either a match
		 * for the query or it isn't.
		 *
		 * The <<term-level-queries, term level queries>> are typically used for structured search. Here's an
		 * example that looks for documents whose started on date falls within a specified range
		 */
		[U]
		public void StructuredSearch()
		{
			var searchResponse = _client.Search<Project>(s => s
				.Query(q => q
					.DateRange(r => r
						.Field(f => f.StartedOn)
						.GreaterThanOrEquals(new DateTime(2017, 01, 01))
						.LessThan(new DateTime(2018, 01, 01))// <1> Find all the projects that have been started in 2017
					)
				)
			);

			/**which yields the following query JSON
			 *
			 */
			// json
			var expected = new
			{
				query = new
				{
					range = new
					{
						startedOn = new {
							lt = "2018-01-01T00:00:00",
							gte = "2017-01-01T00:00:00"
						}
					}
				}
			};

			//hide
			Expect(expected).FromRequest(searchResponse);

			/**
			 * Since the answer to this query is always yes or no, we don't want to _score_ the query. To do this,
			 * we can get the query to be __executed in a filter context__ by wrapping it in a `bool` query `filter`
			 * clause
			 */
			searchResponse = _client.Search<Project>(s => s
			   .Query(q => q
				   .Bool(b => b
					   .Filter(bf => bf
						   .DateRange(r => r
							   .Field(f => f.StartedOn)
							   .GreaterThanOrEquals(new DateTime(2017, 01, 01))
							   .LessThan(new DateTime(2018, 01, 01))
						   )
					   )
				   )

			   )
			);

			//json
			var expected2 = new
			{
				query = new
				{
					@bool = new
					{
						filter = new object[]
						{
							new
							{
								range = new
								{
									startedOn = new
									{
										lt = "2018-01-01T00:00:00",
										gte = "2017-01-01T00:00:00"
									}
								}
							}
						}
					}

				}
			};

			//hide
			Expect(expected2).FromRequest(searchResponse);
		}

		 /**
		 * The benefit of executing a query in a filter context is that OpenSearch is able to
		 * forgo calculating a relevancy score, as well as cache filters for faster subsequent performance.
		 *
		 * [IMPORTANT]
		 * --
		 * <<term-level-queries, term level queries>> have no analysis phase, that is, the query input
		 * is not analyzed, and an *exact match* to the input is looked for in the inverted index. This can
		 * trip many new users up when using a term level query against a field that is analyzed at index
		 * time.
		 *
		 * When a field is _only_ to be used for exact matching, you should consider indexing it as a
		 * {ref_current}/keyword.html[keyword] datatype. If a field is used for both exact matches and
		 * full text search, you should consider indexing it with <<multi-fields, multi fields>>.
		 * --
		 *
		 * [[unstructured-search]]
		 * ==== Unstructured search
		 *
		 * Another common use case is to search within full text fields in order to find the most relevant documents.
		 *
		 * <<full-text-queries, Full text queries>> are used for unstructured search; here we use the `match` query
		 * to find all documents that contain `"Russ"` in the lead developer first name field
		 */
		[U]
		public void UnstructuredSearch()
		{
			var searchResponse = _client.Search<Project>(s => s
				.Query(q => q
					.Match(m => m
						.Field(f => f.LeadDeveloper.FirstName)
						.Query("Russ")
					)
				)
			);

			/**which yields the following query JSON
			 *
			 */
			// json
			var expected = new
			{
				query = new
				{
					match = new JObject
					{
						{
							"leadDeveloper.firstName", new JObject
							{
								{ "query", "Russ" }
							}
						}
					}
				}
			};

			//hide
			Expect(expected).FromRequest(searchResponse);
		}


		/**
		 *
		 * [IMPORTANT]
		 * --
		 * <<full-text-queries, full text queries>> have an analysis phase, that is, the query input
		 * is analyzed, and the resulting terms from query analysis are compared to the terms in the inverted
		 * index.
		 *
		 * You have full control over the analysis that is applied at both search time and index time, by applying
		 * <<writing-analyzers, analyzers>> to {ref_current}/text.html[text] datatype fields through
		 * <<mapping, mapping>>.
		 * --
		 *
		 * [[combining-queries]]
		* ==== Combining queries
		*
		* An extremely common scenario is to combine separate queries together to form a
		* <<compound-queries, compound query>>, the most common of which is the `bool` query
		*/
		[U]
		public void BoolQuery()
		{
			var searchResponse = _client.Search<Project>(s => s
				.Query(q => q
					.Bool(b => b
						.Must(mu => mu
							.Match(m => m // <1> match documents where lead developer first name contains Russ
								.Field(f => f.LeadDeveloper.FirstName)
								.Query("Russ")
							), mu => mu
							.Match(m => m // <2> ...and where the lead developer last name contains Cam
								.Field(f => f.LeadDeveloper.LastName)
								.Query("Cam")
							)
						)
						.Filter(fi => fi
							 .DateRange(r => r
								.Field(f => f.StartedOn)
								.GreaterThanOrEquals(new DateTime(2017, 01, 01))
								.LessThan(new DateTime(2018, 01, 01)) // <3> ...and where the project started in 2017
							)
						)
					)
				)
			);

			/**which yields the following query JSON
			 *
			 */
			// json
			var expected = new
			{
				query = new
				{
					@bool = new
					{
						must = new object[]
						{
							new
							{
								match = new JObject
								{
									{
										"leadDeveloper.firstName", new JObject
										{
											{ "query", "Russ" }
										}
									}
								}
							},
							new
							{
								match = new JObject
								{
									{
										"leadDeveloper.lastName", new JObject
										{
											{ "query", "Cam" }
										}
									}
								}
							},
						},
						filter = new object[]
						{
							new
							{
								range = new
								{
									startedOn = new
									{
										lt = "2018-01-01T00:00:00",
										gte = "2017-01-01T00:00:00"
									}
								}
							}
						}
					}
				}
			};

			//hide
			Expect(expected).FromRequest(searchResponse);

			/**
			 * A document must
			 * satisfy all three queries in this example to be a match
			 *
			 * . the `match` queries on both first name and last name will contribute to
			 * the relevancy score calculated, since both queries are running in a query context
			 *
			 * . the `range` query against the started on date is running in a filter context,
			 * so no score is calculated for matching documents (all documents have the same score
			 * of 1.0 for this query).
			 *
			 * Because `bool` queries are so common, OSC overloads operators on queries to make forming
			 * `bool` queries much more succinct. The previous `bool` query can be more concisely
			 * expressed as
			 */
			searchResponse = _client.Search<Project>(s => s
				.Query(q => q
					.Match(m => m
						.Field(f => f.LeadDeveloper.FirstName)
						.Query("Russ")
					) && q // <1> combine queries using the binary `&&` operator
					.Match(m => m
						.Field(f => f.LeadDeveloper.LastName)
						.Query("Cam")
					) && +q // <2> wrap a query in a `bool` query filter clause using the unary `+` operator and combine using the binary `&&` operator
					.DateRange(r => r
						.Field(f => f.StartedOn)
						.GreaterThanOrEquals(new DateTime(2017, 01, 01))
						.LessThan(new DateTime(2018, 01, 01))
					)
				)
			);

			/**
			 * Take a look at the dedicated section on <<bool-queries, writing `bool` queries>> for more detail
			 * and further examples.
			 */
			//hide
			Expect(expected).FromRequest(searchResponse);
		}

		/**
		* ==== Search response
		*
		* The response returned from a search query is an `SearchResponse<T>`, where `T` is the
		* generic parameter type defined in the search method call. There are a fair few properties
		* on the response, but the most common you're likely to work with is `.Documents`,
		* which we'll demonstrate below.
		*
		* ==== Matching documents
		*
		* To get the documents in the response that match the search query is easy enough
		*/
		[I]
		public void GettingDocuments()
		{
			// hide
			var client = _cluster.Client;

			var searchResponse = client.Search<Project>(s => s
				.Query(q => q
					.MatchAll()
				)
			);

			var projects = searchResponse.Documents;

			/**
			 * `.Documents` is a convenient shorthand for retrieving the `_source`
			 * for each hit
			 */
			var sources = searchResponse.HitsMetadata.Hits.Select(h => h.Source);

			/**
			 * and it's possible to retrieve other metadata about each hit from the hits collection. Here's
			 * an example that retrieves the highlights for a hit, when using <<highlighting-usage, highlighting>>
			 */
			var highlights = searchResponse.HitsMetadata.Hits.Select(h => h
				.Highlight // <1> Get the highlights for the hit, when using highlighting
			);
		}
	}
}