From b80e4566f6bf37a78a715dd04ede018c04b9a093 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20Barrag=C3=A1n=20Merino?=
 <david.barragan@kaleidos.net>
Date: Wed, 22 Jun 2016 16:52:56 +0200
Subject: [PATCH] Compress diffs to show only the changes and some context

---
 CHANGELOG.md              |  1 +
 taiga/mdrender/service.py | 38 ++++++++++++++++++++++++++++++++------
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 76ed1d66..293cb3d0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 - Add gravatar url to Users API endpoint.
 - ProjectTemplates now are sorted by the attribute 'order'.
 - Create enpty wiki pages (if not exist) when a new link is created.
+- Diff messages in history entries now show only the relevant changes (with some context).
 - Comments:
     - Now comment owners and project admins can edit existing comments with the history Entry endpoint.
     - Add a new permissions to allow add comments instead of use the existent modify permission for this purpose.
diff --git a/taiga/mdrender/service.py b/taiga/mdrender/service.py
index cc87e25b..701ed0d4 100644
--- a/taiga/mdrender/service.py
+++ b/taiga/mdrender/service.py
@@ -126,16 +126,42 @@ def render_and_extract(project, text):
 
 class DiffMatchPatch(diff_match_patch.diff_match_patch):
     def diff_pretty_html(self, diffs):
+        def _sanitize_text(text):
+            return (text.replace("&", "&amp;").replace("<", "&lt;")
+                        .replace(">", "&gt;").replace("\n", "<br />"))
+
+        def _split_long_text(text, idx, size):
+            splited_text = text.split()
+
+            if len(splited_text) > 25:
+                if idx == 0:
+                    # The first is (...)text
+                    first = ""
+                else:
+                    first = " ".join(splited_text[:10])
+
+                if idx != 0 and idx == size - 1:
+                    # The last is text(...)
+                    last = ""
+                else:
+                    last = " ".join(splited_text[-10:])
+
+                return "{}(...){}".format(first, last)
+            return text
+
+        size = len(diffs)
         html = []
-        for (op, data) in diffs:
-            text = (data.replace("&", "&amp;").replace("<", "&lt;")
-                    .replace(">", "&gt;").replace("\n", "<br />"))
+        for idx, (op, data) in enumerate(diffs):
             if op == self.DIFF_INSERT:
-                html.append("<ins style=\"background:#e6ffe6;\">%s</ins>" % text)
+                text = _sanitize_text(data)
+                html.append("<ins style=\"background:#e6ffe6;\">{}</ins>".format(text))
             elif op == self.DIFF_DELETE:
-                html.append("<del style=\"background:#ffe6e6;\">%s</del>" % text)
+                text = _sanitize_text(data)
+                html.append("<del style=\"background:#ffe6e6;\">{}</del>".format(text))
             elif op == self.DIFF_EQUAL:
-                html.append("<span>%s</span>" % text)
+                text = _split_long_text(_sanitize_text(data), idx, size)
+                html.append("<span>{}</span>".format(text))
+
         return "".join(html)