From ba177a89d49da59f9cfe56b96b82c7a2f4040b7e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20Ho=CC=88=C3=9Fl?= <tobias@hoessl.eu>
Date: Mon, 5 Apr 2021 10:00:47 +0200
Subject: [PATCH] Allow formatting-only-changes without breaking the inline
 diff

---
 .../app/core/ui-services/diff.service.spec.ts | 28 ++++++++++++-
 .../src/app/core/ui-services/diff.service.ts  | 42 ++++++++++++++++++-
 2 files changed, 67 insertions(+), 3 deletions(-)

diff --git a/client/src/app/core/ui-services/diff.service.spec.ts b/client/src/app/core/ui-services/diff.service.spec.ts
index 2247ffb0b..24309298d 100644
--- a/client/src/app/core/ui-services/diff.service.spec.ts
+++ b/client/src/app/core/ui-services/diff.service.spec.ts
@@ -936,7 +936,7 @@ describe('DiffService', () => {
             const diff = service.diff(before, after);
 
             expect(diff).toBe(
-                '<P class="delete">...so frißt er Euch alle mit Haut und Haar.</P><P class="insert">...so frißt er <SPAN>Euch alle</SPAN> mit Haut und Haar.</P>'
+                '<p>...so frißt er <del>Euch alle</del><ins><span style="color: #000000;">Euch alle</span></ins> mit Haut und Haar.</p>'
             );
         }));
 
@@ -947,7 +947,7 @@ describe('DiffService', () => {
             const diff = service.diff(before, after);
 
             expect(diff).toBe(
-                '<P class="delete">...so frißt er Euch alle mit Haut und Haar.</P><P class="insert">...so frißt er <SPAN style="font-size: 2em; opacity: 0.5">Euch alle</SPAN> mit Haut und Haar.</P>'
+                '<p>...so frißt er <del>Euch alle</del><ins><span style="font-size: 2em; color: #000000; opacity: 0.5">Euch alle</span></ins> mit Haut und Haar.</p>'
             );
         }));
 
@@ -1001,6 +1001,30 @@ describe('DiffService', () => {
             }
         ));
 
+        it('does not fall back to block level replacement when only a formatting is inserted', inject(
+            [DiffService],
+            (service: DiffService) => {
+                const before = '<p>This is a text with a word that will be formatted</p>',
+                    after = '<p>This is a text with a <span class="testclass">word</span> that will be formatted</p>';
+                const diff = service.diff(before, after);
+                expect(diff).toBe(
+                    '<p>This is a text with a <del>word</del><ins><span class="testclass">word</span></ins> that will be formatted</p>'
+                );
+            }
+        ));
+
+        it('does not fall back to block level replacement when only a formatting is deleted', inject(
+            [DiffService],
+            (service: DiffService) => {
+                const before = '<p>This is a text with a <strong>word</strong> that is formatted</p>',
+                    after = '<p>This is a text with a word that is formatted</p>';
+                const diff = service.diff(before, after);
+                expect(diff).toBe(
+                    '<p>This is a text with a <del><strong>word</strong></del><ins>word</ins> that is formatted</p>'
+                );
+            }
+        ));
+
         it('works with multiple inserted paragraphs', inject([DiffService], (service: DiffService) => {
             const before = '<p>This is the text before</p>',
                 after = '<p>This is the text before</p>\n<p>This is one added line</p>\n<p>Another added line</p>';
diff --git a/client/src/app/core/ui-services/diff.service.ts b/client/src/app/core/ui-services/diff.service.ts
index 33bb4d247..480af42b4 100644
--- a/client/src/app/core/ui-services/diff.service.ts
+++ b/client/src/app/core/ui-services/diff.service.ts
@@ -965,7 +965,7 @@ export class DiffService {
         let found, inner;
         while (!!(found = findDel.exec(html))) {
             inner = found[1].replace(/<br[^>]*>/gi, '');
-            if (inner.match(/<[^>]*>/)) {
+            if (!this.isValidInlineHtml(inner)) {
                 return true;
             }
         }
@@ -2081,6 +2081,46 @@ export class DiffService {
             }
         );
 
+        // <ins><STRONG></ins>formatted<ins></STRONG></ins> => <del>formatted</del><ins><STRONG>formatted</STRONG></ins>
+        diffUnnormalized = diffUnnormalized.replace(
+            /<ins><(span|strong|em|b|i|u|s|a|small|big|sup|sub)( [^>]*)?><\/ins>([^<]*)<ins><\/\1><\/ins>/gi,
+            (whole: string, inlineTag: string, tagAttributes: string, content: string): string => {
+                return (
+                    '<del>' +
+                    content +
+                    '</del>' +
+                    '<ins><' +
+                    inlineTag +
+                    (tagAttributes ? tagAttributes : '') +
+                    '>' +
+                    content +
+                    '</' +
+                    inlineTag +
+                    '></ins>'
+                );
+            }
+        );
+
+        // <del><STRONG></del>formatted<del></STRONG></del> => <del><STRONG>formatted</STRONG></del><ins>formatted</ins>
+        diffUnnormalized = diffUnnormalized.replace(
+            /<del><(span|strong|em|b|i|u|s|a|small|big|sup|sub)( [^>]*)?><\/del>([^<]*)<del><\/\1><\/del>/gi,
+            (whole: string, inlineTag: string, tagAttributes: string, content: string): string => {
+                return (
+                    '<del><' +
+                    inlineTag +
+                    (tagAttributes ? tagAttributes : '') +
+                    '>' +
+                    content +
+                    '</' +
+                    inlineTag +
+                    '></del>' +
+                    '<ins>' +
+                    content +
+                    '</ins>'
+                );
+            }
+        );
+
         // </p> </ins> -> </ins></p>
         diffUnnormalized = diffUnnormalized.replace(
             /(<\/(p|div|blockquote|li)>)(\s*)<\/(ins|del)>/gi,