Improve GitHub PR comment formatting

src/handlers/github.rs

@@ -1,4 +1,4 @@
-use std::{cmp::Ordering, fmt::Display};
+use std::{cmp::Ordering, fmt::Display, mem::take};
 
 use anyhow::{Context, Result};
 use axum::{
@@ -469,6 +469,46 @@ fn process_new_items(items: &[ReportItem]) -> Vec<ChangeItem> {
         .collect()
 }
 
+fn measure_line_matched(
+    name: &str,
+    from: u64,
+    from_percent: f32,
+    to: u64,
+    to_percent: f32,
+) -> String {
+    let emoji = if to > from { "📈" } else { "📉" };
+    let percent_diff = to_percent - from_percent;
+    let percent_str = if percent_diff < 0.0 {
+        format!("{percent_diff:.2}%")
+    } else {
+        format!("+{percent_diff:.2}%")
+    };
+    let bytes_diff = to as i64 - from as i64;
+    let bytes_str = match bytes_diff.cmp(&0) {
+        Ordering::Less => bytes_diff.to_string(),
+        Ordering::Equal | Ordering::Greater => format!("+{bytes_diff}"),
+    };
+    format!("{emoji} **{name}**: {to_percent:.2}% ({percent_str}, {bytes_str} bytes)\n")
+}
+
+fn measure_line_bytes(name: &str, from: u64, to: u64) -> String {
+    let diff = to as i64 - from as i64;
+    let diff_str = match diff.cmp(&0) {
+        Ordering::Less => diff.to_string(),
+        Ordering::Equal | Ordering::Greater => format!("+{diff}"),
+    };
+    format!("**{name}**: {to} bytes ({diff_str} bytes)\n")
+}
+
+fn measure_line_simple(name: &str, from: u64, to: u64) -> String {
+    let diff = to as i64 - from as i64;
+    let diff_str = match diff.cmp(&0) {
+        Ordering::Less => diff.to_string(),
+        Ordering::Equal | Ordering::Greater => format!("+{diff}"),
+    };
+    format!("**{name}**: {to} ({diff_str})\n")
+}
+
 fn generate_comment(
     from: &FullReportFile,
     to: &ProcessArtifactResult,
@@ -476,15 +516,60 @@ fn generate_comment(
     changes: Changes,
 ) -> String {
     let mut comment = format!(
-        "## Report for {} ({} - {})\n\n",
+        "### Report for {} ({} - {})\n\n",
         to.version,
         &from.commit.sha[..7],
         &to_commit.sha[..7]
     );
-    comment.push_str("### Changes\n");
-    for unit in changes.units {
-        for function in unit.functions {
-            let (from, to) = match (function.from, function.to) {
+    let mut measure_written = false;
+    let from_measures = from.report.measures;
+    let to_measures = to.report.measures.unwrap_or_default();
+    if from_measures.total_code != to_measures.total_code {
+        comment.push_str(&measure_line_bytes(
+            "Total code",
+            from_measures.total_code,
+            to_measures.total_code,
+        ));
+        measure_written = true;
+    }
+    if from_measures.total_functions != to_measures.total_functions {
+        comment.push_str(&measure_line_simple(
+            "Total functions",
+            from_measures.total_functions as u64,
+            to_measures.total_functions as u64,
+        ));
+        measure_written = true;
+    }
+    if from_measures.matched_code != to_measures.matched_code {
+        comment.push_str(&measure_line_matched(
+            "Matched code",
+            from_measures.matched_code,
+            from_measures.matched_code_percent,
+            to_measures.matched_code,
+            to_measures.matched_code_percent,
+        ));
+        measure_written = true;
+    }
+    if from_measures.complete_code != to_measures.complete_code {
+        comment.push_str(&measure_line_matched(
+            "Linked code",
+            from_measures.complete_code,
+            from_measures.complete_code_percent,
+            to_measures.complete_code,
+            to_measures.complete_code_percent,
+        ));
+        measure_written = true;
+    }
+    if measure_written {
+        comment.push('\n');
+    }
+    let mut total_changes = 0;
+    let mut iter = changes.units.into_iter().flat_map(|mut unit| {
+        let functions = take(&mut unit.functions);
+        functions.into_iter().map(move |f| (unit.clone(), f))
+    });
+    for (unit, item) in iter.by_ref() {
+        let (from, to) = match (item.from, item.to) {
             (Some(from), Some(to)) => (from, to),
             (None, Some(to)) => (ChangeItemInfo::default(), to),
             (Some(from), None) => (from, ChangeItemInfo::default()),
@@ -505,17 +590,23 @@ fn generate_comment(
             Ordering::Equal => "0".to_string(),
             Ordering::Greater => format!("+{}", bytes_diff),
         };
-            let name = function
-                .metadata
-                .as_ref()
-                .and_then(|m| m.demangled_name.as_deref())
-                .unwrap_or(&function.name);
+        let name =
+            item.metadata.as_ref().and_then(|m| m.demangled_name.as_deref()).unwrap_or(&item.name);
         comment.push_str(&format!(
-                "- {} `{} | {}` {} bytes -> {:.2}%\n",
-                emoji, unit.name, name, bytes_str, to.fuzzy_match_percent
+            "{emoji} `{} | {}` {} bytes -> {:.2}%\n",
+            unit.name, name, bytes_str, to.fuzzy_match_percent
         ));
+        total_changes += 1;
+        if total_changes >= 30 {
+            break;
         }
     }
+    let remaining = iter.count();
+    if remaining > 0 {
+        comment.push_str(&format!("...and {} more items\n", remaining));
+    } else if total_changes == 0 {
+        comment.push_str("No changes\n");
+    }
     comment
 }