From cfb4decf676223fb6d6e593e2af5e9ce459254ef Mon Sep 17 00:00:00 2001
From: dgtlmoon <dgtlmoon@gmail.com>
Date: Fri, 11 Apr 2025 17:36:29 +0200
Subject: [PATCH] UI Edit/Stats - Add levenshtein distance info, explains how
 "different" the last two snapshot are (#3109)

---
 changedetectionio/blueprint/ui/edit.py  | 19 +++++++++++++++++--
 changedetectionio/templates/edit.html   |  4 ++++
 changedetectionio/tests/test_backend.py |  5 +++++
 requirements.txt                        |  2 ++
 4 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/changedetectionio/blueprint/ui/edit.py b/changedetectionio/blueprint/ui/edit.py
index d4bd51ab..0f6ac006 100644
--- a/changedetectionio/blueprint/ui/edit.py
+++ b/changedetectionio/blueprint/ui/edit.py
@@ -19,6 +19,20 @@ def construct_blueprint(datastore: ChangeDetectionStore, update_q, queuedWatchMe
             if tag_uuid in watch.get('tags', []) and (tag.get('include_filters') or tag.get('subtractive_selectors')):
                 return True
 
+    def levenshtein_ratio_recent_history(watch):
+        try:
+            from Levenshtein import ratio, distance
+            k = list(watch.history.keys())
+            if len(k) >= 2:
+                a = watch.get_history_snapshot(timestamp=k[0])
+                b = watch.get_history_snapshot(timestamp=k[1])
+                distance = distance(a, b)
+                return distance
+        except Exception as e:
+            logger.warning("Unable to calc similarity", e)
+            return "Unable to calc similarity"
+        return ''
+
     @edit_blueprint.route("/edit/<string:uuid>", methods=['GET', 'POST'])
     @login_optionally_required
     # https://stackoverflow.com/questions/42984453/wtforms-populate-form-with-data-if-data-exists
@@ -247,14 +261,15 @@ def construct_blueprint(datastore: ChangeDetectionStore, update_q, queuedWatchMe
                 'has_default_notification_urls': True if len(datastore.data['settings']['application']['notification_urls']) else False,
                 'has_extra_headers_file': len(datastore.get_all_headers_in_textfile_for_watch(uuid=uuid)) > 0,
                 'has_special_tag_options': _watch_has_tag_options_set(watch=watch),
-                'watch_uses_webdriver': watch_uses_webdriver,
                 'jq_support': jq_support,
+                'lev_info': levenshtein_ratio_recent_history(watch),
                 'playwright_enabled': os.getenv('PLAYWRIGHT_DRIVER_URL', False),
                 'settings_application': datastore.data['settings']['application'],
                 'timezone_default_config': datastore.data['settings']['application'].get('timezone'),
                 'using_global_webdriver_wait': not default['webdriver_delay'],
                 'uuid': uuid,
-                'watch': watch
+                'watch': watch,
+                'watch_uses_webdriver': watch_uses_webdriver,
             }
 
             included_content = None
diff --git a/changedetectionio/templates/edit.html b/changedetectionio/templates/edit.html
index 47f4d8af..925af81d 100644
--- a/changedetectionio/templates/edit.html
+++ b/changedetectionio/templates/edit.html
@@ -443,6 +443,10 @@ Math: {{ 1 + 1 }}") }}
                         </tr>
                         </tbody>
                     </table>
+
+                    <h4>Text similarity</h4>
+                    <p><strong>Levenshtein Distance</strong> - Last 2 snapshots: {{ lev_info }}</p>
+                    <p style="max-width: 80%; font-size: 80%"><strong>Levenshtein Distance</strong> Calculates the minimum number of insertions, deletions, and substitutions required to change one text into the other.</p>
                     {% if watch.history_n %}
                         <p>
                              <a href="{{url_for('ui.ui_edit.watch_get_latest_html', uuid=uuid)}}" class="pure-button button-small">Download latest HTML snapshot</a>
diff --git a/changedetectionio/tests/test_backend.py b/changedetectionio/tests/test_backend.py
index b67bd179..aac59be1 100644
--- a/changedetectionio/tests/test_backend.py
+++ b/changedetectionio/tests/test_backend.py
@@ -74,6 +74,11 @@ def test_check_basic_change_detection_functionality(client, live_server, measure
     res = client.get(url_for("ui.ui_edit.watch_get_latest_html", uuid=uuid))
     assert b'which has this one new line' in res.data
 
+    # Check the 'levenshtein' distance calc showed something useful
+    res = client.get(url_for("ui.ui_edit.edit_page", uuid=uuid))
+    assert b'Last 2 snapshots: 17' in res.data
+
+
     # Now something should be ready, indicated by having a 'unviewed' class
     res = client.get(url_for("watchlist.index"))
     assert b'unviewed' in res.data
diff --git a/requirements.txt b/requirements.txt
index 745503f5..68ae6ede 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -68,6 +68,8 @@ openpyxl
 jq~=1.3; python_version >= "3.8" and sys_platform == "darwin"
 jq~=1.3; python_version >= "3.8" and sys_platform == "linux"
 
+levenshtein
+
 # playwright is installed at Dockerfile build time because it's not available on all platforms
 
 pyppeteer-ng==2.0.0rc9