fix: compute issueEvents correctly

1 files changed, 10 insertions, 5 deletions

diff --git a/app/History/CommitInfo.hs b/app/History/CommitInfo.hs
index bea0cd3..e260ce6 100644
--- a/app/History/CommitInfo.hs
+++ b/app/History/CommitInfo.hs
@@ -68,13 +68,15 @@ fromPartialCommitInfos (partialCommitInfo : partialCommitInfos) =
 
     eq = (==) `on` id
 
+-- | We assume that [CommitInfo] is sorted starting with the oldest
+-- commits.
 issueEvents :: [CommitInfo] -> [(CommitHash, [IssueEvent])]
-issueEvents xs = zip (map (.hash) xs') (zipWith diffCommitInfos xs xs')
+issueEvents xs = zip (map (.hash) xs) (zipWith diffCommitInfos predecessors xs)
   where
-    xs' = tail xs
+    predecessors = Nothing : map Just xs
 
-diffCommitInfos :: CommitInfo -> CommitInfo -> [IssueEvent]
-diffCommitInfos oldInfo newInfo =
+diffCommitInfos :: Maybe CommitInfo -> CommitInfo -> [IssueEvent]
+diffCommitInfos maybeOldInfo newInfo =
   concat
     [ [IssueCreated newHash issue | issue <- deleteFirstsBy eq newIssues oldIssues],
       [ IssueChanged newHash (last issues)
@@ -86,7 +88,10 @@ diffCommitInfos oldInfo newInfo =
   where
     newHash = newInfo.hash
     newIssues = newInfo.issues
-    oldIssues = oldInfo.issues
+    oldIssues =
+      case maybeOldInfo of
+        Nothing -> []
+        Just oldInfo -> oldInfo.issues
 
     eq = (==) `on` id