const express = require('express');
const sharp = require('sharp');
const crypto = require('crypto');
const fs = require('fs');
const path = require('path');
const { Readable } = require('stream');
const { pipeline } = require('stream/promises');
const { createCanvas, loadImage, ImageData, GlobalFonts } = require('@napi-rs/canvas');
/* Works with a public/ folder or with all files uploaded flat into the repo root */
const PUB = fs.existsSync(path.join(__dirname, 'public', 'render.js')) ? path.join(__dirname, 'public') : __dirname;
const R = require(path.join(PUB, 'render.js'));

const PORT = process.env.PORT || 7860;
const ROOT = process.env.DATA_DIR || '/tmp/mr';
const PREVIEW_EDGE = 1600;
const SESSION_TTL = 3 * 3600 * 1000;
fs.mkdirSync(ROOT, { recursive: true });
sharp.cache(false);

/* Windows font names used by the app -> Linux look-alikes (best effort) */
for (const [real, alias] of [
  ['Liberation Sans', 'Arial'],
  ['Liberation Mono', 'Courier New'],
  ['DejaVu Serif', 'Georgia'],
  ['DejaVu Sans', 'Impact'],
  ['Noto Sans Sinhala', 'Iskoola Pota'],
]) {
  try { GlobalFonts.setAlias(real, alias); } catch {}
}

/* ---------- sessions (one per browser tab, id is random and unguessable) ---------- */
const sessions = new Map();
function getSess(sid) {
  if (!/^[a-f0-9]{32}$/.test(sid || '')) throw Object.assign(new Error('bad session'), { code: 400 });
  let s = sessions.get(sid);
  if (!s) {
    const dir = path.join(ROOT, sid);
    fs.mkdirSync(dir, { recursive: true });
    s = { dir, items: new Map(), layers: [], t: Date.now() };
    sessions.set(sid, s);
  }
  s.t = Date.now();
  return s;
}
setInterval(() => {
  const now = Date.now();
  for (const [sid, s] of sessions) {
    if (now - s.t > SESSION_TTL) {
      sessions.delete(sid);
      fs.rm(s.dir, { recursive: true, force: true }, () => {});
    }
  }
}, 10 * 60 * 1000).unref();

/* ---------- helpers ---------- */
const bearer = req => (req.headers.authorization || '').replace(/^Bearer\s+/i, '');
async function pool(list, n, fn) {
  let i = 0;
  await Promise.all(Array.from({ length: Math.min(n, list.length) }, async () => {
    while (i < list.length) await fn(list[i++]);
  }));
}
function ndjson(res) {
  res.setHeader('Content-Type', 'application/x-ndjson; charset=utf-8');
  res.setHeader('Cache-Control', 'no-store');
  res.setHeader('X-Accel-Buffering', 'no');
  res.flushHeaders();
  return o => { if (!res.writableEnded && !res.destroyed) res.write(JSON.stringify(o) + '\n'); };
}
const fail = (res, e) => res.status(e.code && e.code < 600 ? e.code : 500).send(e.message || 'error');

async function driveUpload(tok, folderId, name, mime, buf) {
  let last;
  for (let attempt = 0; attempt < 3; attempt++) {
    try {
      const init = await fetch('https://www.googleapis.com/upload/drive/v3/files?uploadType=resumable&fields=id', {
        method: 'POST',
        headers: {
          Authorization: 'Bearer ' + tok,
          'Content-Type': 'application/json; charset=UTF-8',
          'X-Upload-Content-Type': mime,
          'X-Upload-Content-Length': String(buf.length),
        },
        body: JSON.stringify({ name, parents: [folderId] }),
      });
      if (init.status === 401) throw new Error('Google session expired');
      if (!init.ok) throw new Error('Drive ' + init.status);
      const put = await fetch(init.headers.get('location'), {
        method: 'PUT',
        headers: { 'Content-Type': mime, 'Content-Length': String(buf.length) },
        body: buf,
      });
      if (!put.ok) throw new Error('Drive upload ' + put.status);
      return;
    } catch (e) {
      last = e;
      if (/expired/.test(e.message)) break;
      await new Promise(r => setTimeout(r, 800 * (attempt + 1)));
    }
  }
  throw last;
}

/* Same drawing code as the browser preview (public/render.js), at full resolution. */
async function renderBuf(sess, rid, ov, o) {
  const it = sess.items.get(rid);
  if (!it) throw Object.assign(new Error('unknown photo'), { code: 404 });
  const k = o.max ? Math.min(1, o.max / Math.max(it.w, it.h)) : 1;
  const w = Math.round(it.w * k), h = Math.round(it.h * k);
  let pipe = sharp(it.file).rotate();
  if (k < 1) pipe = pipe.resize(w, h, { fit: 'fill' });
  const { data, info } = await pipe.ensureAlpha().raw().toBuffer({ resolveWithObject: true });
  const c = createCanvas(info.width, info.height);
  const ctx = c.getContext('2d');
  ctx.putImageData(new ImageData(new Uint8ClampedArray(data.buffer, data.byteOffset, data.length), info.width, info.height), 0, 0);
  R.drawAll(ctx, info.width, info.height, sess.layers, { ov: ov || {} });
  const png = o.fmt === 'png';
  const q = Math.round(Math.min(1, Math.max(0.5, +o.q || 0.92)) * 100);
  return { buf: await c.encode(png ? 'png' : 'jpeg', q), mime: png ? 'image/png' : 'image/jpeg' };
}

/* ---------- app ---------- */
const app = express();
app.disable('x-powered-by');
if (PUB === __dirname) {
  app.get('/', (q, r) => r.sendFile(path.join(PUB, 'index.html')));
  app.get('/render.js', (q, r) => r.sendFile(path.join(PUB, 'render.js')));
} else {
  app.use(express.static(PUB));
}

app.get('/api/config', (req, res) => res.json({ clientId: process.env.GOOGLE_CLIENT_ID || '' }));

/* Download picked Drive files on the server (parallel), stream progress back */
app.post('/api/import', express.json({ limit: '2mb' }), async (req, res) => {
  let sess;
  try { sess = getSess(req.body.sid); } catch (e) { return fail(res, e); }
  const tok = bearer(req);
  const files = Array.isArray(req.body.files) ? req.body.files.slice(0, 2000) : [];
  if (!tok) return res.status(401).send('missing token');
  const send = ndjson(res);
  send({ t: 'start', n: files.length });
  await pool(files, 6, async f => {
    try {
      const rid = crypto.randomBytes(6).toString('hex');
      const file = path.join(sess.dir, rid + '.orig');
      const r = await fetch(`https://www.googleapis.com/drive/v3/files/${encodeURIComponent(f.id)}?alt=media&supportsAllDrives=true`, {
        headers: { Authorization: 'Bearer ' + tok },
      });
      if (r.status === 401) throw new Error('Google session expired, reconnect Drive');
      if (!r.ok) throw new Error('Drive returned ' + r.status);
      await pipeline(Readable.fromWeb(r.body), fs.createWriteStream(file));
      const meta = await sharp(file).metadata();
      const swap = (meta.orientation || 1) >= 5;
      const w = swap ? meta.height : meta.width, h = swap ? meta.width : meta.height;
      await sharp(file).rotate()
        .resize({ width: PREVIEW_EDGE, height: PREVIEW_EDGE, fit: 'inside', withoutEnlargement: true })
        .jpeg({ quality: 86 }).toFile(path.join(sess.dir, rid + '.prev.jpg'));
      sess.items.set(rid, { name: String(f.name || rid), w, h, file });
      send({ t: 'item', rid, name: String(f.name || rid), w, h });
    } catch (e) {
      send({ t: 'err', name: f.name, msg: e.message });
    }
  });
  send({ t: 'done' });
  res.end();
});

app.get('/api/preview/:sid/:rid', (req, res) => {
  try {
    const s = getSess(req.params.sid);
    if (!s.items.has(req.params.rid)) return res.sendStatus(404);
    res.setHeader('Cache-Control', 'private, max-age=3600');
    res.sendFile(path.join(s.dir, req.params.rid + '.prev.jpg'));
  } catch (e) { fail(res, e); }
});

/* Watermark layers (image layers arrive as PNG data URLs) */
app.post('/api/settings/:sid', express.json({ limit: '80mb' }), async (req, res) => {
  try {
    const s = getSess(req.params.sid);
    const layers = Array.isArray(req.body.layers) ? req.body.layers : [];
    s.layers = await Promise.all(layers.map(async l => {
      const L = { ...l };
      if (l.type === 'image') {
        L.cv = await loadImage(Buffer.from(String(l.png).split(',')[1] || '', 'base64'));
        delete L.png;
      }
      return L;
    }));
    res.json({ ok: true });
  } catch (e) { fail(res, e); }
});

/* Render one photo at full size and send it back (for ZIP / separate downloads) */
app.post('/api/render/:sid/:rid', express.json({ limit: '1mb' }), async (req, res) => {
  try {
    const s = getSess(req.params.sid);
    const { buf, mime } = await renderBuf(s, req.params.rid, req.body.ov, req.body);
    res.type(mime).send(buf);
  } catch (e) { fail(res, e); }
});

/* Render + upload straight into a Drive folder (created by the browser in the chosen account) */
app.post('/api/export-drive', express.json({ limit: '5mb' }), async (req, res) => {
  let sess;
  try { sess = getSess(req.body.sid); } catch (e) { return fail(res, e); }
  const tok = bearer(req);
  const { folderId, items } = req.body;
  if (!tok || !folderId || !Array.isArray(items)) return res.status(400).send('bad request');
  const send = ndjson(res);
  await pool(items, 3, async it => {
    try {
      const { buf, mime } = await renderBuf(sess, it.rid, it.ov, req.body);
      await driveUpload(tok, folderId, String(it.name), mime, buf);
      send({ t: 'ok', name: it.name });
    } catch (e) {
      send({ t: 'err', name: it.name, msg: e.message });
    }
  });
  send({ t: 'done' });
  res.end();
});

app.listen(PORT, '0.0.0.0', () => console.log('markroom listening on ' + PORT));