feat(spotify): implement milestone M4 importers

skills/spotify/src/importers/m3u.ts

@@ -0,0 +1,38 @@
+import { readFile } from "node:fs/promises";
+import { basename } from "node:path";
+
+import type { ParsedTrackRef } from "../types.js";
+import { dedupeTrackRefs, parseArtistTitle } from "./importer-utils.js";
+
+function parseExtInf(line: string): string | undefined {
+  const comma = line.indexOf(",");
+  if (comma === -1 || comma === line.length - 1) {
+    return undefined;
+  }
+  return line.slice(comma + 1).trim();
+}
+
+export function parseM3u(content: string): ParsedTrackRef[] {
+  const refs: ParsedTrackRef[] = [];
+  let pendingExtInf: string | undefined;
+  for (const rawLine of content.split(/\r?\n/u)) {
+    const line = rawLine.trim();
+    if (!line) {
+      continue;
+    }
+    if (line.startsWith("#EXTINF:")) {
+      pendingExtInf = parseExtInf(line);
+      continue;
+    }
+    if (line.startsWith("#")) {
+      continue;
+    }
+    refs.push(...parseArtistTitle(pendingExtInf ?? basename(line)));
+    pendingExtInf = undefined;
+  }
+  return dedupeTrackRefs(refs);
+}
+
+export async function readM3u(path: string): Promise<ParsedTrackRef[]> {
+  return parseM3u(await readFile(path, "utf8"));
+}