1 files changed, 51 insertions, 0 deletions
diff --git a/pysite/views/wiki/history/compare.py b/pysite/views/wiki/history/compare.py
new file mode 100644
index 00000000..46dad8e9
--- /dev/null
+++ b/pysite/views/wiki/history/compare.py
@@ -0,0 +1,51 @@
+# coding=utf-8
+import difflib
+
+from pygments import highlight
+from pygments.formatters import HtmlFormatter
+from pygments.lexers import DiffLexer
+from werkzeug.exceptions import BadRequest, NotFound
+
+from pysite.base_route import RouteView
+from pysite.mixins import DBMixin
+
+
+class CompareView(RouteView, DBMixin):
+    path = "/history/compare/<string:first_rev>/<string:second_rev>"
+    name = "history.compare"
+
+    table_name = "wiki_revisions"
+    table_primary_key = "id"
+
+    def get(self, first_rev, second_rev):
+        before = self.db.get(self.table_name, first_rev)
+        after = self.db.get(self.table_name, second_rev)
+
+        if not (before and after):
+            raise NotFound()
+
+        if before["date"] > after["date"]:  # Check whether the before was created after the after
+            raise BadRequest()
+
+        if before["id"] == after["id"]:  # The same revision has been requested
+            raise BadRequest()
+
+        before_text = before["post"]["rst"]
+        after_text = after["post"]["rst"]
+
+        if not before_text.endswith("\n"):
+            before_text += "\n"
+
+        if not after_text.endswith("\n"):
+            after_text += "\n"
+
+        before_text = before_text.splitlines(keepends=True)
+        after_text = after_text.splitlines(keepends=True)
+
+        if not before["slug"] == after["slug"]:
+            raise BadRequest()  # The revisions are not from the same post
+
+        diff = difflib.unified_diff(before_text, after_text, fromfile=f"{first_rev}.rst", tofile=f"{second_rev}.rst")
+        diff = "".join(diff)
+        diff = highlight(diff, DiffLexer(), HtmlFormatter())
+        return self.render("wiki/compare_revision.html", title=after["post"]["title"], diff=diff)