Clamp custom skill values to official ranges, migrate pre-fix chart groupings

src/router/custom_song/migrate.rs

@@ -0,0 +1,80 @@
+use std::fs;
+
+use super::{chart, database, song_path, asset_meta, LEVEL_COUNT};
+use crate::runtime::get_data_path;
+
+// One-time, idempotent startup migration for charts transcoded before the spawn-group pairing
+// rule (chart.rs header): the old transcoder gave every note of an equal-time cluster ONE
+// shared num, and the client creates no head markers for a group of 3+ notes
+// (LiveMarkerControl.CreateMarkerUI plain-returns on count > 2), so 3+ simultaneous notes
+// were judged but never rendered. Stored transcoded charts are derived data with everything
+// the regroup needs (time + line per note), so they are rewritten in place — no original
+// upload required, which also covers songs from before export support.
+//
+// For each song directory with a catalog row, every chart with an over-shared num is
+// regrouped (chart::regroup), rewritten to disk, and its level's md5/size in the catalog
+// blob updated — the changed md5 re-keys the client's content-addressed cache, so clients
+// re-download the fixed chart on their next catalog sync. The revision is bumped ONCE if
+// anything changed. Charts the current transcoder produced (and official-shaped encodings)
+// are left byte-identical, so re-running every boot is free.
+pub fn run() {
+    if super::disabled() {
+        return;
+    }
+    let Ok(entries) = fs::read_dir(get_data_path("custom_songs")) else {
+        // No custom_songs directory yet - nothing was ever uploaded
+        return;
+    };
+
+    let mut music_ids: Vec<i64> = entries.flatten()
+        .filter_map(|entry| entry.file_name().to_string_lossy().parse::<i64>().ok())
+        .collect();
+    music_ids.sort();
+
+    let mut songs_changed = 0;
+    let mut charts_changed = 0;
+    for music_id in music_ids {
+        // A song directory without a catalog row is never served; leave it alone
+        let Some(mut song) = database::get_song(music_id) else { continue; };
+
+        let mut changed = false;
+        for level in 1..=LEVEL_COUNT {
+            let path = song_path(music_id, &format!("chart_{}.json", level));
+            let Ok(bytes) = fs::read(&path) else { continue; };
+            let Ok(mut chart_data) = jzon::parse(&String::from_utf8_lossy(&bytes)) else {
+                println!("Custom song {} chart {}: not valid JSON, migration skipped", music_id, level);
+                continue;
+            };
+            if !chart::regroup(&mut chart_data) {
+                continue;
+            }
+            let new_bytes = jzon::stringify(chart_data);
+            if let Err(e) = fs::write(&path, &new_bytes) {
+                println!("Custom song {} chart {}: rewrite failed ({}), migration skipped", music_id, level, e);
+                continue;
+            }
+            // The catalog md5/size must follow the served bytes or the client's
+            // download-and-verify loop would never accept the asset
+            let (md5, size) = asset_meta(new_bytes.as_bytes());
+            for entry in song["levels"].members_mut() {
+                if entry["level"] == level {
+                    entry["md5"] = md5.clone().into();
+                    entry["size"] = size.into();
+                }
+            }
+            changed = true;
+            charts_changed += 1;
+            println!("Custom song {}: regrouped chart level {} (pre-pairing spawn groups)", music_id, level);
+        }
+
+        if changed {
+            database::update_song(music_id, &song);
+            songs_changed += 1;
+        }
+    }
+
+    if songs_changed > 0 {
+        database::bump_revision();
+        println!("Custom song spawn-group migration: rewrote {} chart(s) in {} song(s), catalog revision bumped", charts_changed, songs_changed);
+    }
+}