From aed478153db1c2fa0c2e659a36dcc8dd9eb454ba Mon Sep 17 00:00:00 2001
From: Julian Ospald <hasufell@posteo.de>
Date: Sun, 14 May 2023 21:34:50 +0800
Subject: [PATCH] Print alternative day if day not found

---
 app/ghcup/GHCup/OptParse/Common.hs |  4 +++-
 lib/GHCup/Errors.hs                |  7 +++++--
 lib/GHCup/Utils.hs                 | 16 +++++++++++++---
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/app/ghcup/GHCup/OptParse/Common.hs b/app/ghcup/GHCup/OptParse/Common.hs
index 28a23fd..ad05c34 100644
--- a/app/ghcup/GHCup/OptParse/Common.hs
+++ b/app/ghcup/GHCup/OptParse/Common.hs
@@ -724,7 +724,9 @@ fromVersion' (SetToolTag Latest) tool = do
   bimap mkTVer Just <$> getLatest dls tool ?? TagNotFound Latest tool
 fromVersion' (SetToolDay day) tool = do
   GHCupInfo { _ghcupDownloads = dls } <- lift getGHCupInfo
-  bimap mkTVer Just <$> getByReleaseDay dls tool day ?? DayNotFound day tool
+  bimap mkTVer Just <$> case getByReleaseDay dls tool day of
+                          Left ad -> throwE $ DayNotFound day tool ad
+                          Right v -> pure v
 fromVersion' (SetToolTag LatestPrerelease) tool = do
   GHCupInfo { _ghcupDownloads = dls } <- lift getGHCupInfo
   bimap mkTVer Just <$> getLatestPrerelease dls tool ?? TagNotFound LatestPrerelease tool
diff --git a/lib/GHCup/Errors.hs b/lib/GHCup/Errors.hs
index afb4436..4fb29b2 100644
--- a/lib/GHCup/Errors.hs
+++ b/lib/GHCup/Errors.hs
@@ -314,12 +314,15 @@ instance HFErrorProject TagNotFound where
   eDesc _ = "Unable to find a tag of a tool"
 
 -- | Unable to find a release day of a tool
-data DayNotFound = DayNotFound Day Tool
+data DayNotFound = DayNotFound Day Tool (Maybe Day)
   deriving Show
 
 instance Pretty DayNotFound where
-  pPrint (DayNotFound day tool) =
+  pPrint (DayNotFound day tool Nothing) =
     text "Unable to find release date" <+> text (show day) <+> text "of tool" <+> pPrint tool
+  pPrint (DayNotFound day tool (Just alternateDay)) =
+    text "Unable to find release date" <+> text (show day) <+> text "of tool" <+> pPrint tool <+>
+      text "but found an alternative date" <+> text (show alternateDay)
 
 instance HFErrorProject DayNotFound where
   eBase _ = 95
diff --git a/lib/GHCup/Utils.hs b/lib/GHCup/Utils.hs
index 147a95b..275d403 100644
--- a/lib/GHCup/Utils.hs
+++ b/lib/GHCup/Utils.hs
@@ -94,7 +94,8 @@ import qualified Streamly.Prelude              as S
 import Control.DeepSeq (force)
 import GHC.IO (evaluate)
 import System.Environment (getEnvironment, setEnv)
-import Data.Time (Day)
+import Data.Time (Day(..), diffDays, addDays)
+import Debug.Trace
 
 
 -- $setup
@@ -890,8 +891,17 @@ getTagged tag =
   to (Map.toDescList . Map.filter (\VersionInfo {..} -> tag `elem` _viTags))
   % folding id
 
-getByReleaseDay :: GHCupDownloads -> Tool -> Day -> Maybe (Version, VersionInfo)
-getByReleaseDay av tool day = headOf (ix tool % getByReleaseDayFold day) av
+getByReleaseDay :: GHCupDownloads -> Tool -> Day -> Either (Maybe Day) (Version, VersionInfo)
+getByReleaseDay av tool day = let mvv = fromMaybe mempty $ headOf (ix tool) av
+                                  mdv = Map.foldrWithKey (\k vi@VersionInfo{..} m ->
+                                            maybe m (\d -> let diff = diffDays d day
+                                                           in Map.insert (abs diff) (diff, (k, vi)) m) _viReleaseDay)
+                                          Map.empty mvv
+                              in case headMay (Map.toAscList mdv) of
+                                   Nothing -> Left Nothing
+                                   Just (absDiff, (diff, (k, vi)))
+                                     | absDiff == 0 -> Right (k, vi)
+                                     | otherwise -> Left (Just (addDays diff day))
 
 getByReleaseDayFold :: Day -> Fold (Map.Map Version VersionInfo) (Version, VersionInfo)
 getByReleaseDayFold day = to (Map.toDescList . Map.filter (\VersionInfo {..} -> Just day == _viReleaseDay)) % folding id