'use strict';
const crypto = require('node:crypto');

// Short-lived transfers/jobs/challenges. Identity/history live in accounts.js.
module.exports = function ({ session, now = Date.now } = {}) {
  const transfers = new Map(), challenges = new Map(), rates = new Map(), jobs = new Map();
  const lifetime = 5 * 60000, maxChunk = 64 * 1024, maxPhoto = 4 * 1024 * 1024;
  let bytes = 0;
  function clearPhotos(row) {
    for (const photo of Object.values(row.photos)) bytes -= photo.bytes;
    row.photos = {};
  }
  function sweep() {
    for (const [id, row] of transfers) if (row.expires <= now() && !row.active) { clearPhotos(row); transfers.delete(id); }
    for (const [id, until] of challenges) if (until <= now()) challenges.delete(id);
    for (const [id, row] of rates) if (row.until <= now()) rates.delete(id);
    for (const [id, job] of jobs) if (job.expires <= now() && job.status !== 'running') jobs.delete(id);
  }
  function challenge(address) {
    sweep();
    const rate = rates.get(address) || { count: 0, until: now() + 60000 };
    if (rates.size >= 10000 && !rates.has(address)) return null;
    rates.set(address, rate);
    if (++rate.count > 30 || challenges.size >= 1000) return null;
    const id = crypto.randomBytes(24).toString('hex');
    challenges.set(id, now() + 60000);
    return id;
  }
  function consume(id) {
    sweep();
    if (!challenges.has(id)) return false;
    challenges.delete(id); return true;
  }
  function row(req, create = false) {
    sweep();
    const owner = session(req);
    if (!owner) return null;
    if (!transfers.has(owner.id) && create && transfers.size < 1000) transfers.set(owner.id, { photos: {}, active: false, expires: now() + lifetime });
    return transfers.get(owner.id) || null;
  }
  function upload(req, body) {
    const current = row(req, true);
    if (!current) return { status: 401, message: '检测会话已失效，请重新开始' };
    if (current.active) return { status: 409, message: '检测进行中，请稍候' };
    const { view, upload_id: id, index, total, data } = body || {};
    if (!['front', 'left', 'right'].includes(view) || !/^[a-z0-9-]{8,64}$/.test(id || '') ||
        !Number.isInteger(total) || total < 1 || total > 64 || !Number.isInteger(index) || index < 0 || index >= total ||
        typeof data !== 'string' || !data.length || data.length > maxChunk || !/^[A-Za-z0-9+/]+={0,2}$/.test(data)) {
      return { status: 400, message: '照片分片数据异常，请重新拍摄' };
    }
    let photo = current.photos[view];
    if (!photo || photo.id !== id) {
      if (index !== 0) return { status: 409, message: '照片上传已失效，请重试' };
      if (photo) bytes -= photo.bytes;
      photo = current.photos[view] = { id, total, chunks: [], bytes: 0 };
    }
    if (photo.total !== total || index > photo.chunks.length || (index < photo.chunks.length && photo.chunks[index] !== data)) {
      return { status: 409, message: '照片上传顺序异常，请重试' };
    }
    if (index === photo.chunks.length) {
      if (photo.bytes + data.length > maxPhoto || bytes + data.length > 64 * 1024 * 1024) return { status: 413, message: '照片过大或服务繁忙，请稍后重试' };
      photo.chunks.push(data); photo.bytes += data.length; bytes += data.length;
    }
    current.expires = now() + lifetime;
    return { status: 200, complete: photo.chunks.length === total, photo_ref: id };
  }
  function takePhotos(req, refs) {
    const current = row(req);
    if (!current || current.active) return null;
    if (!refs || !['front', 'left', 'right'].every(view => {
      const photo = current.photos[view];
      return photo && photo.id === refs[view] && photo.chunks.length === photo.total;
    })) return null;
    const photos = Object.fromEntries(['front', 'left', 'right'].map(view => [view + '_image', current.photos[view].chunks.join('')]));
    clearPhotos(current); current.active = true;
    return photos;
  }
  function finish(req, ownerId) { const current = ownerId ? transfers.get(ownerId) : row(req); if (current) { current.active = false; current.expires = now() + lifetime; } }
  function revoke(req) { const current = row(req); if (current) { clearPhotos(current); current.expires = 0; sweep(); } }
  function start(req, run, releasePhotos = false) {
    sweep();
    const owner = session(req);
    if (!owner || jobs.size >= 1000) return null;
    const id = crypto.randomBytes(24).toString('hex');
    const job = { owner: owner.id, status: 'running', expires: now() + lifetime, result: null };
    jobs.set(id, job);
    Promise.resolve().then(run).then(result => { job.result = result; }, () => { job.result = { ok: false, message: '检测服务暂不可用，请重试' }; })
      .finally(() => { job.status = 'complete'; job.expires = now() + lifetime; if (releasePhotos) finish(req, owner.id); });
    return id;
  }
  function result(req, id) {
    sweep();
    const job = jobs.get(id), owner = session(req);
    return job && owner && job.owner === owner.id ? { status: job.status, payload: job.result } : null;
  }
  const timer = setInterval(sweep, 60000); timer.unref();
  return { challenge, consume, upload, takePhotos, finish, revoke, start, result };
};