1 files changed, 59 insertions, 0 deletions
diff --git a/app/Issue/Filter.hs b/app/Issue/Filter.hs
new file mode 100644
index 0000000..0ce945d
--- /dev/null
+++ b/app/Issue/Filter.hs
@@ -0,0 +1,59 @@
+{-# LANGUAGE OverloadedRecordDot #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ViewPatterns #-}
+
+module Issue.Filter
+  ( Filter,
+    filterOption,
+    applyFilter,
+  )
+where
+
+import Control.Arrow (second)
+import Data.Text (Text)
+import Data.Text qualified as T
+import Issue (Issue (..))
+import Issue.Tag (Tag (..))
+import Options.Applicative qualified as O
+
+data Filter
+  = ExcludeByTag Text (Maybe Text)
+  | IncludeByTag Text (Maybe Text)
+  deriving (Show)
+
+filterOption :: O.Parser [Filter]
+filterOption =
+  O.many
+    ( O.option
+        (O.maybeReader (parse . T.pack))
+        ( O.long "filter"
+            <> O.short 'f'
+            <> O.metavar "FILTER"
+            <> O.help "Filters selected issues. Examples: @assigned, !@assigned joe"
+        )
+    )
+  where
+    parse s
+      | "@" `T.isPrefixOf` s =
+          Just (uncurry IncludeByTag (splitValue (T.drop 1 s)))
+      | "!@" `T.isPrefixOf` s =
+          Just (uncurry ExcludeByTag (splitValue (T.drop 2 s)))
+      | otherwise = Nothing
+
+    splitValue :: Text -> (Text, Maybe Text)
+    splitValue s = case second T.strip (T.breakOn " " s) of
+      (k, "") -> (k, Nothing)
+      (k, v) -> (k, Just v)
+
+applyFilter :: [Filter] -> Issue -> Bool
+applyFilter [] _ = True
+applyFilter (IncludeByTag k v : fs) i =
+  applyByTag k v i && applyFilter fs i
+applyFilter (ExcludeByTag k v : fs) i =
+  not (applyByTag k v i) && applyFilter fs i
+
+applyByTag :: Text -> Maybe Text -> Issue -> Bool
+applyByTag k v i = any ((&&) <$> matchKey <*> matchValue) i.tags
+  where
+    matchKey (Tag k' _) = k' == k
+    matchValue (Tag _ v') = maybe True ((==) v') v