From b30746cafc8ac21225652d7bfc45ca13db3ab761 Mon Sep 17 00:00:00 2001
From: Ben Sima <ben@bsima.me>
Date: Sun, 27 Dec 2020 21:01:37 -0500
Subject: devalloc: calculate staleness and score

---
 Biz/Devalloc.hs | 72 +++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 57 insertions(+), 15 deletions(-)

diff --git a/Biz/Devalloc.hs b/Biz/Devalloc.hs
index d1172ee..7dbc4a5 100644
--- a/Biz/Devalloc.hs
+++ b/Biz/Devalloc.hs
@@ -45,6 +45,8 @@ import qualified Data.List as List
 import qualified Data.String as String
 import qualified Data.Text as Text
 import qualified Data.Text.Encoding as Encoding
+import qualified Data.Time.Clock as Clock
+import qualified Data.Time.Format as Time
 import Data.Vector (Vector)
 import qualified Data.Vector as Vector
 import qualified GitHub
@@ -151,7 +153,6 @@ instance Lucid.ToHtml a => Lucid.ToHtml (HtmlApp a) where
 data Paths path = Paths
   { home :: path :- Get '[HTML] (HtmlApp Home),
     githubAuth ::
-      --    auth/github/callback?code=...
       path :- "auth" :> "github" :> "callback"
         :> QueryParam "code" Text
         :> Get '[HTML] (HtmlApp SelectRepo),
@@ -311,7 +312,7 @@ data Analysis = Analysis
     -- | A path with < 3 active contributors
     liabilities :: [Text],
     -- | Files that have not been touched in 6 months
-    stale :: [Text],
+    stale :: [(FilePath, Int)],
     -- | Total score for the repo
     score :: Int,
     -- | List of all the active users we care about
@@ -327,9 +328,15 @@ instance Lucid.ToHtml Analysis where
       render Analysis {..} =
         Lucid.div_ <| do
           Lucid.h1_ "Analysis Results"
+          Lucid.h3_ "score:"
+          Lucid.p_ <| Lucid.toHtml <| Text.pack <| show score
           Lucid.h3_ "blackholes:"
           Lucid.ul_ <| do
             mapM_ (Lucid.toHtml .> Lucid.li_) blackholes
+          Lucid.h3_ "stale files:"
+          Lucid.ul_ <| do
+            forM_ stale <| \(path, days) ->
+              Lucid.li_ <| Lucid.toHtml <| path <> " (" <> show days <> " days)"
 
 -- | Takes a list of active authors and a path to a bare git repo and runs a
 -- regular analysis
@@ -357,27 +364,62 @@ analyze activeAuthors bareRepo = do
           tree
           authors ::
           [(FilePath, [(Text, Text, Text)])]
-
+  stalenessMap <- mapM (lastTouched bareRepo) tree
+  let blackholes =
+        [ Text.pack path
+          | (path, authors_) <- authorMap,
+            null (map third authors_ `List.intersect` activeAuthors)
+        ]
+  let liabilities =
+        [ Text.pack path
+          | (path, authors_) <- authorMap,
+            length (map third authors_ `List.intersect` activeAuthors) < 3
+        ]
+  let numBlackholes = frac <| length blackholes
+  let numLiabilities = frac <| length liabilities
+  let numTotal = length tree
   return
     Analysis
-      { blackholes =
-          [ Text.pack path
-            | (path, authors_) <- authorMap,
-              null (map third authors_ `List.intersect` activeAuthors)
-          ],
-        liabilities =
-          [ Text.pack path
-            | (path, authors_) <- authorMap,
-              length (map third authors_ `List.intersect` activeAuthors) < 3
+      { stale =
+          [ (path, days)
+            | (path, days) <- stalenessMap,
+              days > 180
           ],
-        stale = [], -- actually a map of path->staleness
-        score = 10,
+        score =
+          maxScore
+            * ( (numBlackholes * frac (5 // 10)) * (numLiabilities * frac (7 // 10))
+                  * (numTotal - numBlackholes - numLiabilities)
+              )
+            `div` numTotal,
         ..
       }
   where
+    (//) = div
+    frac = fromIntegral :: Num a => Int -> a
+    maxScore = 10
     third :: (a, b, c) -> c
     third (_, _, a) = a
 
+lastTouched :: FilePath -> FilePath -> IO (FilePath, Int)
+lastTouched bareRepo path = do
+  now <- Clock.getCurrentTime
+  timestamp <-
+    Process.readProcess
+      "git"
+      [ "--git-dir",
+        bareRepo,
+        "log",
+        "-n1",
+        "--pretty=%aI",
+        "--",
+        path
+      ]
+      ""
+      /> filter (/= '\n')
+      /> Time.parseTimeOrError True Time.defaultTimeLocale "%Y-%m-%dT%H:%M:%S%z"
+  let days = round <| Clock.diffUTCTime now timestamp / Clock.nominalDay
+  return (path, days)
+
 -- | Given a git dir and a path inside the git repo, return a list of tuples
 -- with number of commits and author.
 authorsFor ::
@@ -385,7 +427,7 @@ authorsFor ::
   FilePath ->
   -- | Returns (number of commits, author name, author email)
   IO [(Text, Text, Text)]
-authorsFor gitDir path = do
+authorsFor gitDir path =
   -- git shortlog writes to stderr for some reason, so we can't just use
   -- Process.readProcess
   Process.readProcess
-- 
cgit v1.2.3