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"));
}