import { join, resolve } from "node:path";
import { mkdir } from "node:fs/promises";
import type { Role } from "../core/types.ts";
import { parseSmf } from "../align/smf.ts";
import { guessRole } from "../align/roles.ts";

export interface SongEntry {
  id: string; title: string; audio: string; midi: string;
  roles: Record<string, Role | null>; capo: Record<string, number>; tuning?: Record<string, number[]>;
}

const ID_RE = /^[A-Za-z0-9][A-Za-z0-9_-]*$/;

export function songDir(id: string, root = "reference"): string {
  if (!ID_RE.test(id)) throw new Error(`invalid song id: ${JSON.stringify(id)}`);
  return join(root, id);
}

export async function readManifest(root = "reference"): Promise<SongEntry[]> {
  const f = Bun.file(join(root, "songs.json"));
  if (!(await f.exists())) return [];
  return (await f.json()) as SongEntry[];
}

// Role-map key for a track: its name, or "track N" when unnamed; disambiguated on collision.
export function trackKeys(tracks: { index: number; name: string }[]): string[] {
  const used = new Set<string>();
  return tracks.map((t) => {
    let k = t.name || `track ${t.index}`;
    if (used.has(k)) k = `${k} #${t.index}`;
    used.add(k);
    return k;
  });
}

export async function addSong(e: Omit<SongEntry, "roles"> & { roles?: SongEntry["roles"] }, root = "reference"): Promise<SongEntry> {
  const dir = songDir(e.id, root);
  const all = await readManifest(root);
  if (all.some((s) => s.id === e.id)) throw new Error(`duplicate song id: ${e.id}`);
  let roles = e.roles;
  if (!roles) {
    const tracks = parseSmf(new Uint8Array(await Bun.file(e.midi).arrayBuffer())).tracks;
    const keys = trackKeys(tracks);
    roles = Object.fromEntries(tracks.map((t, i) => [keys[i]!, guessRole(t)]));
  }
  const entry: SongEntry = { ...e, audio: resolve(e.audio), midi: resolve(e.midi), roles };
  await mkdir(dir, { recursive: true });
  await Bun.write(join(root, "songs.json"), JSON.stringify([...all, entry], null, 2) + "\n");
  return entry;
}