workaround non latin character db bug

src/library/tagEncoding.ts

@@ -0,0 +1,40 @@
+// Repairs mojibake produced by MediaMetadataRetriever mis-decoding legacy ID3v2
+// text frames — the classic case being Japanese MP3s with Shift-JIS bytes in an
+// ISO-8859-1-flagged frame. MMR decodes each raw byte to a Latin-1 char, so the
+// original bytes survive in the low byte of every code unit and can be recovered
+// and re-decoded here. Desktop avoids this entirely via music-metadata, which
+// honours the frame's encoding byte.
+
+import * as Encoding from 'encoding-japanese';
+
+// Characters that prove a recovered string is real Japanese/CJK text (kana, CJK
+// unified ideographs, hangul, full/half-width forms). Used as the final gate so a
+// mis-detection of accented Latin-1 (e.g. "Beyoncé") can never corrupt good text.
+const CJK = /[\u3040-\u30FF\u3400-\u9FFF\uAC00-\uD7AF\uF900-\uFAFF\uFF00-\uFFEF]/;
+
+/**
+ * Returns `value` re-decoded from a Japanese multibyte encoding when it is
+ * recoverable mojibake; otherwise returns `value` unchanged. Safe to call on any
+ * tag string — it is a no-op for ASCII, accented Latin, and already-correct
+ * Unicode.
+ */
+export function repairMojibakeTag(value: string): string {
+  let hasHighByte = false;
+  const bytes = new Array<number>(value.length);
+  for (let i = 0; i < value.length; i++) {
+    const code = value.charCodeAt(i);
+    // A code unit above 0xFF means the string already holds real Unicode (e.g.
+    // MMR decoded a UTF-16 frame correctly) — there is nothing to recover.
+    if (code > 0xff) return value;
+    if (code >= 0x80) hasHighByte = true;
+    bytes[i] = code;
+  }
+  if (!hasHighByte) return value; // pure ASCII/Latin — nothing to recover
+
+  const detected = Encoding.detect(bytes);
+  if (detected !== 'SJIS' && detected !== 'EUCJP') return value;
+
+  const repaired = Encoding.convert(bytes, { to: 'UNICODE', from: detected, type: 'string' });
+  // Only accept the conversion when it actually produced CJK text.
+  return CJK.test(repaired) ? repaired : value;
+}