const fs = require('fs');
const path = require('path');
const { v4: uuidv4 } = require('uuid');

const DATA_DIR = path.join(__dirname, '..', '..', 'data');
const QUEUE_PATH = path.join(DATA_DIR, 'scheduled-emails.json');

function ensureStore() {
  try {
    if (!fs.existsSync(DATA_DIR)) fs.mkdirSync(DATA_DIR, { recursive: true });
    if (!fs.existsSync(QUEUE_PATH)) fs.writeFileSync(QUEUE_PATH, JSON.stringify({ jobs: [] }, null, 2), 'utf-8');
  } catch (e) {
    // Best-effort; throws will surface to caller
  }
}

function loadAll() {
  ensureStore();
  try {
    const raw = fs.readFileSync(QUEUE_PATH, 'utf-8');
    const data = JSON.parse(raw);
    const jobs = Array.isArray(data?.jobs) ? data.jobs : [];
    return jobs;
  } catch (e) {
    return [];
  }
}

function saveAll(jobs) {
  ensureStore();
  const payload = { jobs: Array.isArray(jobs) ? jobs : [] };
  // Simple atomic-ish write
  const tmp = QUEUE_PATH + '.tmp';
  fs.writeFileSync(tmp, JSON.stringify(payload, null, 2), 'utf-8');
  fs.renameSync(tmp, QUEUE_PATH);
}

/**
 * Add a scheduled job
 * @param {object} job { id?, eventId, createdById, scheduledAt: ISO string, payload: body for emailEventAttendees }
 */
function addJob(job) {
  const now = new Date();
  const id = job.id || uuidv4();
  const rec = {
    id,
    eventId: job.eventId || null,
    broadcast: !!job.broadcast,
    channel: job.channel || 'email',
    recipientSummary: job.recipientSummary || null,
    createdById: job.createdById || null,
    scheduledAt: job.scheduledAt,
    createdAt: now.toISOString(),
    status: 'queued', // queued | sending | sent | error
    attempts: 0,
    lastError: null,
    payload: job.payload || {},
  };
  const jobs = loadAll();
  jobs.push(rec);
  saveAll(jobs);
  return rec;
}

function listJobs(filter = {}) {
  const jobs = loadAll();
  // Basic filter support
  return jobs.filter(j => {
    if (filter.status && j.status !== filter.status) return false;
    if (filter.eventId && j.eventId !== filter.eventId) return false;
    if (filter.channel && (j.channel || 'email') !== filter.channel) return false;
    return true;
  });
}

/**
 * Permanently remove jobs that finished sending more than maxAgeMs ago.
 * Only touches 'sent' jobs - queued/sending/error jobs are left for admins to review.
 */
function purgeSentJobs(maxAgeMs = 24 * 60 * 60 * 1000) {
  const jobs = loadAll();
  const now = Date.now();
  const kept = jobs.filter(j => {
    if (j.status !== 'sent' || !j.sentAt) return true;
    return (now - new Date(j.sentAt).getTime()) <= maxAgeMs;
  });
  if (kept.length !== jobs.length) saveAll(kept);
  return jobs.length - kept.length;
}

function getDueJobs(now = new Date()) {
  const jobs = loadAll();
  const t = now instanceof Date ? now : new Date(now);
  return jobs.filter(j => j.status === 'queued' && new Date(j.scheduledAt).getTime() <= t.getTime());
}

function updateJob(id, patch) {
  const jobs = loadAll();
  const idx = jobs.findIndex(j => j.id === id);
  if (idx === -1) return null;
  jobs[idx] = { ...jobs[idx], ...patch };
  saveAll(jobs);
  return jobs[idx];
}

function getJob(id) {
  const jobs = loadAll();
  return jobs.find(j => j.id === id) || null;
}

function deleteJob(id) {
  const jobs = loadAll();
  const filtered = jobs.filter(j => j.id !== id);
  if (filtered.length === jobs.length) return false;
  saveAll(filtered);
  return true;
}

module.exports = {
  addJob,
  listJobs,
  getDueJobs,
  updateJob,
  getJob,
  deleteJob,
  purgeSentJobs,
};