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diff --git a/src/FSD/ChangeLog.hs b/src/FSD/ChangeLog.hs
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+{-
+Copyright (C) 2022 Yuchen Pei.
+
+This file is part of fsd.
+
+fsd is free software: you can redistribute it and/or modify it under
+the terms of the GNU Affero General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+fsd is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General
+Public License for more details.
+
+You should have received a copy of the GNU Affero General Public
+License along with fsd.  If not, see <https://www.gnu.org/licenses/>.
+
+-}
+
+{-# LANGUAGE ImportQualifiedPost #-}
+module FSD.ChangeLog where
+
+import Data.Generics
+import Data.Time
+import Data.Text qualified as T
+import Debian.Changes
+import Debian.Version
+import Text.Regex.TDFA
+import FSD.Types
+
+readChangeLog :: String -> Maybe ChangeLogEntry
+readChangeLog raw = case parseEntry raw of
+  Left _ -> Nothing
+  Right (entry, _) -> Just entry
+
+-- Debian version is an abstract type with no constructor, hence the ugly hack.
+getVersion :: DebianVersion -> Maybe String
+getVersion v =
+  let match = show v =~ ("\".*\"" :: String)
+   in if null match then Nothing else Just $ init $ tail match
+
+convertChangeLogEntry :: ChangeLogEntry -> Maybe FSDChangeLogEntry
+convertChangeLogEntry entry = do
+  version <- getVersion $ logVersion entry
+  time <- parseTime' $ logDate entry
+  return $
+    FSDChangeLogEntry
+      (T.pack $ logPackage entry)
+      (T.pack version)
+      (T.pack $ logWho entry)
+      time
+  where
+    parseTime' raw =
+      orElse
+        (parseTimeM False defaultTimeLocale "%a, %d %b %Y %T %Z" raw)
+        (parseTimeM False defaultTimeLocale "%a, %e %b %Y %T %Z" raw)
+
+getChangeLogEntry :: String -> Maybe FSDChangeLogEntry
+getChangeLogEntry raw = readChangeLog raw >>= convertChangeLogEntry