From dd7b5236805cdf16431b3a9fadc9f39cfb2f6a8e Mon Sep 17 00:00:00 2001
From: Sephyi <me@sephy.io>
Date: Sun, 19 Apr 2026 19:02:12 +0200
Subject: [PATCH] fix(history): round float-to-int percentage conversion
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The commit-type percentage shown in the project-style prompt section
was computed by truncating a float cast (`as u32`), which discards the
fractional part — 66.666% became 66% instead of 67%. Replace the
truncating cast with `.round() as u32` so percentages round to the
nearest integer, matching what users reading the prompt would expect.

Add a unit test covering the round-up case (2/3 → 67%) alongside the
exact-percentage case (1/3 → 33%) to guard against accidental
regression to truncation.

Closes audit entry F-027 from #3.
---
 src/services/history.rs | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/services/history.rs b/src/services/history.rs
index e562b8f..68c4684 100644
--- a/src/services/history.rs
+++ b/src/services/history.rs
@@ -46,7 +46,7 @@ impl HistoryContext {
                 .iter()
                 .map(|(t, c)| {
                     let pct = if total > 0 {
-                        (*c as f32 / total as f32 * 100.0) as u32
+                        (*c as f32 / total as f32 * 100.0).round() as u32
                     } else {
                         0
                     };
@@ -427,6 +427,33 @@ mod tests {
         assert!(!ctx.uses_lowercase); // Below 80% threshold
     }
 
+    #[test]
+    fn to_prompt_section_rounds_percentages() {
+        // 2/3 = 66.666...% — truncation yields 66, rounding yields 67.
+        // 1/3 = 33.333...% — both rounding and truncation yield 33.
+        let ctx = HistoryContext {
+            type_distribution: vec![("feat".to_string(), 2), ("fix".to_string(), 1)],
+            scope_patterns: vec![],
+            avg_subject_length: 40,
+            uses_lowercase: true,
+            conventional_ratio: 1.0,
+            sample_subjects: vec![],
+        };
+
+        let section = ctx.to_prompt_section(10);
+
+        assert!(
+            section.contains("feat (67%)"),
+            "expected rounded percentage 67% for 2/3, got: {}",
+            section
+        );
+        assert!(
+            section.contains("fix (33%)"),
+            "expected 33% for 1/3, got: {}",
+            section
+        );
+    }
+
     #[test]
     fn to_prompt_section_format() {
         let ctx = HistoryContext {