Add reverse token filter docs #8274 (#8395)

* adding reverse token filter docs #8274

Signed-off-by: Anton Rubin <anton.rubin@eliatra.com>

* Doc review

Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>

* Apply suggestions from code review

Co-authored-by: Nathan Bower <nbower@amazon.com>
Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>

---------

Signed-off-by: Anton Rubin <anton.rubin@eliatra.com>
Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>
Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Co-authored-by: Fanit Kolchina <kolchfa@amazon.com>
Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Co-authored-by: Nathan Bower <nbower@amazon.com>

_analyzers/token-filters/index.md

@@ -51,7 +51,7 @@ Token filter | Underlying Lucene token filter|  Description
 [`porter_stem`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/porter-stem/) | [PorterStemFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/en/PorterStemFilter.html) | Uses the [Porter stemming algorithm](https://tartarus.org/martin/PorterStemmer/) to perform algorithmic stemming for the English language.
 [`predicate_token_filter`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/predicate-token-filter/) | N/A | Removes tokens that do not match the specified predicate script. Supports only inline Painless scripts.
 [`remove_duplicates`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/remove-duplicates/) | [RemoveDuplicatesTokenFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/miscellaneous/RemoveDuplicatesTokenFilter.html) | Removes duplicate tokens that are in the same position.
-`reverse` | [ReverseStringFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/reverse/ReverseStringFilter.html) | Reverses the string corresponding to each token in the token stream. For example, the token `dog` becomes `god`.
+[`reverse`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/reverse/) | [ReverseStringFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/reverse/ReverseStringFilter.html) | Reverses the string corresponding to each token in the token stream. For example, the token `dog` becomes `god`.
 `shingle` | [ShingleFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/shingle/ShingleFilter.html) | Generates shingles of lengths between `min_shingle_size` and `max_shingle_size` for tokens in the token stream. Shingles are similar to n-grams but apply to words instead of letters. For example, two-word shingles added to the list of unigrams [`contribute`, `to`, `opensearch`] are [`contribute to`, `to opensearch`].
 `snowball` | N/A | Stems words using a [Snowball-generated stemmer](https://snowballstem.org/). You can use the `snowball` token filter with the following languages in the `language` field: `Arabic`, `Armenian`, `Basque`, `Catalan`, `Danish`, `Dutch`, `English`, `Estonian`, `Finnish`, `French`, `German`, `German2`, `Hungarian`, `Irish`, `Italian`, `Kp`, `Lithuanian`, `Lovins`, `Norwegian`, `Porter`, `Portuguese`, `Romanian`, `Russian`, `Spanish`, `Swedish`, `Turkish`.
 `stemmer` | N/A | Provides algorithmic stemming for the following languages in the `language` field: `arabic`, `armenian`, `basque`, `bengali`, `brazilian`, `bulgarian`, `catalan`, `czech`, `danish`, `dutch`, `dutch_kp`, `english`, `light_english`, `lovins`, `minimal_english`, `porter2`, `possessive_english`, `estonian`, `finnish`, `light_finnish`, `french`, `light_french`, `minimal_french`, `galician`, `minimal_galician`, `german`, `german2`, `light_german`, `minimal_german`, `greek`, `hindi`, `hungarian`, `light_hungarian`, `indonesian`, `irish`, `italian`, `light_italian`, `latvian`, `Lithuanian`, `norwegian`, `light_norwegian`, `minimal_norwegian`, `light_nynorsk`, `minimal_nynorsk`, `portuguese`, `light_portuguese`, `minimal_portuguese`, `portuguese_rslp`, `romanian`, `russian`, `light_russian`, `sorani`, `spanish`, `light_spanish`, `swedish`, `light_swedish`, `turkish`.

_analyzers/token-filters/reverse.md

@@ -0,0 +1,86 @@
+---
+layout: default
+title: Reverse
+parent: Token filters
+nav_order: 360
+---
+
+# Reverse token filter
+
+The `reverse` token filter reverses the order of the characters in each token, making suffix information accessible at the beginning of the reversed tokens during analysis. 
+
+This is useful for suffix-based searches:
+
+The `reverse` token filter is useful when you need to perform suffix-based searches, such as in the following scenarios:  
+
+- **Suffix matching**: Searching for words based on their suffixes, such as identifying words with a specific ending (for example, `-tion` or `-ing`).
+- **File extension searches**: Searching for files by their extensions, such as `.txt` or `.jpg`.
+- **Custom sorting or ranking**: By reversing tokens, you can implement unique sorting or ranking logic based on suffixes.  
+- **Autocomplete for suffixes**: Implementing autocomplete suggestions that use suffixes rather than prefixes.  
+
+
+## Example
+
+The following example request creates a new index named `my-reverse-index` and configures an analyzer with a `reverse` filter:
+
+```json
+PUT /my-reverse-index
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "reverse_filter": {
+          "type": "reverse"
+        }
+      },
+      "analyzer": {
+        "my_reverse_analyzer": {
+          "type": "custom",
+          "tokenizer": "standard",
+          "filter": [
+            "lowercase",
+            "reverse_filter"
+          ]
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+GET /my-reverse-index/_analyze
+{
+  "analyzer": "my_reverse_analyzer",
+  "text": "hello world"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "olleh",
+      "start_offset": 0,
+      "end_offset": 5,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "dlrow",
+      "start_offset": 6,
+      "end_offset": 11,
+      "type": "<ALPHANUM>",
+      "position": 1
+    }
+  ]
+}
+```