feat: add MP3 conversion with mirrored folder structure

src/library/convert.ts

@@ -0,0 +1,100 @@
+import path from "node:path";
+import { promises as fs } from "node:fs";
+import { execa } from "execa";
+import { resolvedFfmpegPath } from "../bin/ffmpeg-fetch";
+import type { Track } from "./types";
+
+/**
+ * Mirror a track's library-relative folder structure under `<libraryDir>/mp3/`,
+ * swapping the extension to `.mp3`. A track at
+ *   `<libraryDir>/YouTube/@nasa/My Playlist/song.opus`
+ * converts to
+ *   `<libraryDir>/mp3/YouTube/@nasa/My Playlist/song.mp3`.
+ *
+ * This keeps the per-source / per-owner / per-playlist grouping intact, so
+ * converted files sit beside their originals' layout instead of being
+ * flattened (which collided same-named files from different playlists and
+ * threw away the source/owner hierarchy). Tracks whose `filePath` isn't
+ * actually under `libraryDir` (e.g. adopted local files elsewhere) fall back
+ * to `<libraryDir>/mp3/<basename>.mp3` so we never write outside the library.
+ */
+export function mp3MirroredPath(libraryDir: string, track: Track): string {
+  const rel = path.relative(libraryDir, track.filePath);
+  // `..` segments mean the file lives outside the library: don't mirror a
+  // path that would escape `<libraryDir>/mp3/`. Drop to a flat basename.
+  const safe = rel && !rel.startsWith("..") && !path.isAbsolute(rel)
+    ? rel
+    : path.basename(track.filePath);
+  const withoutExt = safe.replace(/\.[^./\\]+$/, "");
+  return path.join(libraryDir, "mp3", `${withoutExt}.mp3`);
+}
+
+export interface ConvertProgress {
+  /** 1-based index of the track being processed (includes skips). */
+  done: number;
+  /** Total non-mp3 tracks in this batch. */
+  total: number;
+  track: Track;
+}
+
+export interface ConvertResult {
+  /** Newly converted + already-present skips (matches the old UI counter). */
+  converted: number;
+  /** Already present on disk, left as-is. */
+  skipped: number;
+  /** ffmpeg failed for these. */
+  failed: number;
+}
+
+/**
+ * Convert a batch of tracks to MP3 (192k libmp3lame), mirroring each track's
+ * library folder structure under `<libraryDir>/mp3/`. Already-mp3 sources are
+ * skipped up front; existing mp3 outputs are left untouched (counted as
+ * skipped). The caller drives the progress UI through `onProgress`.
+ */
+export async function convertTracksToMp3(
+  libraryDir: string,
+  tracks: Track[],
+  onProgress?: (p: ConvertProgress) => void,
+): Promise<ConvertResult> {
+  const toConvert = tracks.filter((t) => !t.filePath.endsWith(".mp3"));
+  let converted = 0;
+  let skipped = 0;
+  let failed = 0;
+
+  for (const track of toConvert) {
+    const mp3Path = mp3MirroredPath(libraryDir, track);
+
+    // Skip if the mp3 already exists.
+    try {
+      await fs.access(mp3Path);
+      skipped++;
+      converted++;
+      onProgress?.({ done: converted, total: toConvert.length, track });
+      continue;
+    } catch {
+      // not present, proceed
+    }
+
+    onProgress?.({ done: converted + 1, total: toConvert.length, track });
+
+    try {
+      await fs.mkdir(path.dirname(mp3Path), { recursive: true });
+      await execa(resolvedFfmpegPath(), [
+        "-i",
+        track.filePath,
+        "-codec:a",
+        "libmp3lame",
+        "-b:a",
+        "192k",
+        mp3Path,
+      ]);
+      converted++;
+    } catch (e) {
+      failed++;
+      console.error(`Failed to convert ${track.title}:`, e);
+    }
+  }
+
+  return { converted, skipped, failed };
+}

src/ui/App.tsx

@@ -44,6 +44,7 @@ import { Library as LibrarySection } from "./sections/Library";
 import { Playlists } from "./sections/Playlists";
 import { History } from "./sections/History";
 import { Download } from "./sections/Download";
+import { Mp3 } from "./sections/Mp3";
 import { Settings } from "./sections/Settings";
 import { Welcome } from "./views/Welcome";
 import { useMouseWheel } from "./hooks/useMouseWheel";
@@ -66,6 +67,8 @@ function Content({ section }: { section: Section }) {
       return <History />;
     case "download":
       return <Download />;
+    case "mp3":
+      return <Mp3 />;
     case "settings":
       return <Settings />;
   }

src/ui/components/Sidebar.tsx

@@ -13,6 +13,7 @@ const NAV: NavItem[] = [
   { key: "playlists", label: "Playlists" },
   { key: "history", label: "History" },
   { key: "download", label: "Download" },
+  { key: "mp3", label: "MP3" },
   { key: "settings", label: "Settings" },
 ];
 

src/ui/keymap.ts

@@ -21,12 +21,13 @@ const SECTION_ORDER: Section[] = [
   "playlists",
   "history",
   "download",
+  "mp3",
   "settings",
 ];
 
-/** Map "1".."5" to its section (the sidebar's display order); null otherwise. */
+/** Map "1".."6" to its section (the sidebar's display order); null otherwise. */
 export function sectionForDigit(input: string): Section | null {
-  if (!/^[1-5]$/.test(input)) return null;
+  if (!/^[1-6]$/.test(input)) return null;
   return SECTION_ORDER[Number(input) - 1] ?? null;
 }
 
@@ -38,7 +39,7 @@ export const HELP_GROUPS: HelpGroup[] = [
       { keys: "↑ ↓", label: "Move" },
       { keys: "PgUp PgDn", label: "Jump a page" },
       { keys: "↵", label: "Open / play" },
-      { keys: "1-5", label: "Jump section" },
+      { keys: "1-6", label: "Jump section" },
       { keys: "/", label: "Search" },
       { keys: "d", label: "Delete" },
       { keys: "t", label: "Rename" },
@@ -151,5 +152,13 @@ export function footerHints(
         PANE,
         ALWAYS,
       ];
+    case "mp3":
+      return [
+        { keys: "↵", label: "Play" },
+        { keys: "d", label: "Delete" },
+        { keys: "o", label: "Open folder" },
+        PANE,
+        ALWAYS,
+      ];
   }
 }

src/ui/sections/Library.tsx

@@ -16,6 +16,7 @@ import { cleanText, formatDuration } from "../../util/format";
 import { deleteTracks } from "../../library/delete";
 import { displaySource } from "../../library/drift";
 import { renameTrack } from "../../library/rename";
+import { convertTracksToMp3 } from "../../library/convert";
 import { SOURCE_LABELS, type SourceId, type Track } from "../../library/types";
 
 const SOURCE_ORDER: SourceId[] = [
@@ -71,6 +72,10 @@ export function Library() {
   // Pending track rename.
   const [renamingTrackId, setRenamingTrackId] = useState<string | null>(null);
   const [newTrackTitle, setNewTrackTitle] = useState("");
+  // Pending MP3 conversion.
+  const [convertConfirm, setConvertConfirm] = useState<{ count: number } | null>(null);
+  const [converting, setConverting] = useState(false);
+  const [convertProgress, setConvertProgress] = useState<string | null>(null);
 
   const songs = useMemo(
     // library.all() is already newest-first (addedAt desc); recompute on new
@@ -178,18 +183,19 @@ export function Library() {
   // Take over the keyboard only while typing in the search box; a pending
   // delete confirm owns esc so the global one doesn't bounce to the sidebar.
   const renaming = focused && renamingTrackId !== null;
+  const convertingConfirm = focused && convertConfirm !== null;
   useEffect(() => {
     setCaptureMode(
       focused && editing
         ? "text"
-        : focused && confirm
+        : focused && (confirm !== null || convertingConfirm)
           ? "esc"
           : renaming
             ? "text"
             : "none",
     );
     return () => setCaptureMode("none");
-  }, [focused, editing, confirm, renaming, setCaptureMode]);
+  }, [focused, editing, confirm, convertingConfirm, renaming, setCaptureMode]);
 
   // Consume the global "/" intent: arrive with the search box already open.
   useEffect(() => {
@@ -202,19 +208,27 @@ export function Library() {
   // Browsing keys:
   //   "/" opens search
   //   "[" / "]" step the source tabs
+  //   "c" converts visible tracks to MP3
   useInput(
     (input) => {
       if (input === "/") {
         setEditing(true);
         return;
       }
+      if (input === "c" && !converting) {
+        const tracksToConvert = visible.filter((t) => !t.filePath.endsWith(".mp3"));
+        if (tracksToConvert.length > 0) {
+          setConvertConfirm({ count: tracksToConvert.length });
+        }
+        return;
+      }
       if (input === "[" || input === "]") {
         const dir = input === "]" ? 1 : -1;
         const i = tabs.indexOf(filter);
         setFilter(tabs[(i + dir + tabs.length) % tabs.length]!);
       }
     },
-    { isActive: focused && !editing && !confirm && !renaming },
+    { isActive: focused && !editing && !confirm && !renaming && !convertConfirm },
   );
 
   // esc closes the search box (back to browsing), without leaving the section.
@@ -248,6 +262,47 @@ export function Library() {
     setNewTrackTitle("");
   };
 
+  const convertVisibleToMp3 = async () => {
+    setConverting(true);
+    setConvertProgress("Starting conversion…");
+
+    try {
+      const tracksToConvert = visible.filter((t) => !t.filePath.endsWith(".mp3"));
+      const { converted } = await convertTracksToMp3(
+        config.libraryDir,
+        tracksToConvert,
+        (p) =>
+          setConvertProgress(
+            `Converting ${p.done}/${p.total}: ${p.track.title}`,
+          ),
+      );
+
+      setConvertProgress(
+        `Conversion complete: ${converted}/${tracksToConvert.length} songs converted`
+      );
+      setTimeout(() => setConvertProgress(null), 3000);
+    } catch (e) {
+      setConvertProgress("Conversion failed");
+      console.error("Conversion error:", e);
+      setTimeout(() => setConvertProgress(null), 3000);
+    } finally {
+      setConverting(false);
+    }
+  };
+
+  // esc cancels convert confirm, y confirms it.
+  useInput(
+    (input, key) => {
+      if (key.escape) {
+        setConvertConfirm(null);
+      } else if (input === "y" && convertConfirm) {
+        setConvertConfirm(null);
+        void convertVisibleToMp3();
+      }
+    },
+    { isActive: convertingConfirm },
+  );
+
   // y commits the pending delete, esc keeps the song. Playback stops first
   // when it's the one playing: the player holds the file handle open and
   // Windows refuses to unlink it.
@@ -321,7 +376,14 @@ export function Library() {
   // delete, or showing an active query; when compact and idle, drop it so the
   // list gets the row back.
   const showSearchRow =
-    !compact || editing || confirm !== null || searching || renaming;
+    !compact ||
+    editing ||
+    confirm !== null ||
+    convertConfirm !== null ||
+    converting ||
+    convertProgress !== null ||
+    searching ||
+    renaming;
   // Rows above the list beyond the standard header (which listRows already
   // accounts for): tabs (1) + the search row when shown (2 normally, 1 compact
   // since its margin goes too).
@@ -335,7 +397,15 @@ export function Library() {
           the list's height budget never moves. Hidden when compact + idle. */}
       {showSearchRow ? (
         <Box marginBottom={compact ? 0 : 1}>
-          {confirm ? (
+          {convertProgress ? (
+            <Text color={COLOR.accent} wrap="truncate-end">
+              {convertProgress}
+            </Text>
+          ) : convertConfirm ? (
+            <Text color={COLOR.warn} wrap="truncate-end">
+              {`Convert ${convertConfirm.count} song${convertConfirm.count === 1 ? "" : "s"} to MP3?  y Convert  ${ICON.dot}  esc Cancel`}
+            </Text>
+          ) : confirm ? (
             <Text color={COLOR.warn} wrap="truncate-end">
               {`Delete '${cleanText(confirm.title)}'?  y Delete  ${ICON.dot}  esc Keep`}
             </Text>
@@ -373,7 +443,7 @@ export function Library() {
           groups={groups}
           action={action}
           playingId={playingId}
-          focused={focused && !editing && !confirm && !renaming}
+          focused={focused && !editing && !confirm && !renaming && !convertConfirm && !converting}
           reserveRows={reserveRows}
           deleteTargetsPlaying
           onDelete={handleDelete}