import fs from 'node:fs/promises';
import path from 'node:path';
import { SESSION_DIR } from './config.js';

// id -> meta. Backed by data/sessions/<id>/meta.json so restarts keep decks.
const sessions = new Map();

export async function initSessions() {
  await fs.mkdir(SESSION_DIR, { recursive: true });
  const entries = await fs.readdir(SESSION_DIR, { withFileTypes: true });
  for (const entry of entries) {
    if (!entry.isDirectory()) continue;
    try {
      const raw = await fs.readFile(path.join(SESSION_DIR, entry.name, 'meta.json'), 'utf8');
      const meta = JSON.parse(raw);
      // A deck still "processing" when the server died can never finish; mark it.
      if (meta.status === 'processing') {
        meta.status = 'error';
        meta.error = 'Processing was interrupted by a restart. Please re-upload.';
      }
      sessions.set(meta.id, meta);
    } catch {
      // Skip unreadable session folders rather than crash on boot.
    }
  }
}

export function getSession(id) {
  return sessions.get(id);
}

export function listSessions() {
  return [...sessions.values()].sort((a, b) => b.createdAt - a.createdAt);
}

export function sessionDir(id) {
  return path.join(SESSION_DIR, id);
}

export function outDir(id) {
  return path.join(SESSION_DIR, id, 'out');
}

export async function saveSession(meta) {
  sessions.set(meta.id, meta);
  const dir = sessionDir(meta.id);
  await fs.mkdir(dir, { recursive: true });
  await fs.writeFile(path.join(dir, 'meta.json'), JSON.stringify(meta, null, 2));
  return meta;
}

export async function deleteSession(id) {
  sessions.delete(id);
  await fs.rm(sessionDir(id), { recursive: true, force: true });
}

// Fields safe to expose to an audience member (no presenter token).
export function publicMeta(meta) {
  if (!meta) return null;
  return {
    id: meta.id,
    title: meta.title,
    kind: meta.kind,
    status: meta.status,
    error: meta.error || null,
    viewerFile: meta.viewerFile || null,
    createdAt: meta.createdAt
  };
}