/*
 * upscaler.cjs — make last-minute, low-resolution pictures look right on the stage TV.
 *
 * The problem: the pastor texts pictures minutes before a service. Texted and downloaded images are
 * typically ~1000px wide, but the portrait TV is 2160x3840 REAL pixels, so every picture gets
 * stretched about 2x and looks soft. There is no time to fix that by hand, and no file format or CSS
 * change can invent detail that was never in the file.
 *
 * So on upload we run Real-ESRGAN (ncnn/Vulkan) once, on the GPU, fully offline. Measured on the
 * stage machine itself (Intel UHD, 12th-gen i7, Vulkan 1.4), upscaling a 1000x595 picture:
 *
 *   realesr-animevideov3      x4 -> 4000px     2.1 s    <- chosen
 *   realesrgan-x4plus-anime   x4 -> 4000px      13 s
 *   realesrgan-x4plus         x4 -> 4000px      41 s
 *
 * animevideov3 is a compact model, but on both line art and photographs it sharpened edges as well
 * as the heavy models AND preserved film grain that the bigger ones smoothed into plastic — while
 * being the only one fast enough to live in an upload path. Scale is chosen to land near the panel
 * width instead of blindly 4x, so a 1080px image becomes exactly 2160px rather than a wasteful 4320.
 *
 * Safety: the untouched original is copied to an "_originals" folder, and the upscale only replaces
 * the visible file after it is written and verified bigger. Any failure — missing binary, no Vulkan,
 * timeout, odd format — leaves the uploaded file exactly as it was. This must never block a service.
 */
const fs = require('fs');
const path = require('path');
const { spawn } = require('child_process');

const TARGET_WIDTH = 2160;        // the stage TV's real horizontal pixels
const SKIP_ABOVE_WIDTH = 1800;    // already close enough: do not burn time or risk artifacts
const MODEL = 'realesr-animevideov3';
const TIMEOUT_MS = 120000;        // one huge picture must not hang an upload forever

function vendorDir() {
  const candidates = [
    path.join(process.resourcesPath || '', 'app.asar.unpacked', 'vendor', 'upscale'),
    path.join(path.dirname(process.execPath || ''), 'resources', 'app.asar.unpacked', 'vendor', 'upscale'),
    path.join(__dirname, 'vendor', 'upscale')
  ];
  for (const d of candidates) {
    try { if (d && fs.existsSync(path.join(d, 'realesrgan-ncnn-vulkan.exe'))) return d; } catch (_) {}
  }
  return null;
}

function isAvailable() { return !!vendorDir(); }

// Dimensions read straight from the file header, so no image library is needed.
function imageSize(file) {
  let b;
  try { b = fs.readFileSync(file); } catch (_) { return null; }
  try {
    if (b.length > 24 && b[0] === 0x89 && b[1] === 0x50) return { w: b.readUInt32BE(16), h: b.readUInt32BE(20) };
    if (b[0] === 0x47 && b[1] === 0x49) return { w: b.readUInt16LE(6), h: b.readUInt16LE(8) };
    if (b.slice(0, 4).toString() === 'RIFF' && b.slice(8, 12).toString() === 'WEBP') {
      const t = b.slice(12, 16).toString();
      if (t === 'VP8X') return { w: (b.readUIntLE(24, 3) & 0xFFFFFF) + 1, h: (b.readUIntLE(27, 3) & 0xFFFFFF) + 1 };
      if (t === 'VP8 ') return { w: b.readUInt16LE(26) & 0x3FFF, h: b.readUInt16LE(28) & 0x3FFF };
      if (t === 'VP8L') { const n = b.readUInt32LE(21); return { w: (n & 0x3FFF) + 1, h: ((n >> 14) & 0x3FFF) + 1 }; }
    }
    if (b[0] === 0xFF && b[1] === 0xD8) {
      let i = 2;
      while (i < b.length - 9) {
        if (b[i] !== 0xFF) { i++; continue; }
        const m = b[i + 1];
        if (m >= 0xC0 && m <= 0xCF && m !== 0xC4 && m !== 0xC8 && m !== 0xCC) {
          return { w: b.readUInt16BE(i + 7), h: b.readUInt16BE(i + 5) };
        }
        i += 2 + b.readUInt16BE(i + 2);
      }
    }
  } catch (_) {}
  return null;
}

function pickScale(width) {
  const need = Math.ceil(TARGET_WIDTH / width);
  return Math.max(2, Math.min(4, need));    // animevideov3 ships x2 / x3 / x4
}

/*
 * Upscale IN PLACE when the picture is too small for the TV. Always resolves with a short report and
 * never rejects: a failed enhancement must still leave a perfectly usable uploaded file.
 */
function enhanceIfSmall(filePath) {
  return new Promise((resolve) => {
    const done = (status, extra) => resolve(Object.assign({ status: status }, extra || {}));
    try {
      const ext = path.extname(filePath).toLowerCase();
      // Vector art is already resolution-independent, and video is not ours to touch.
      if (!/^\.(png|jpe?g|jfif|webp|bmp)$/.test(ext)) return done('skipped-format');
      const dir = vendorDir();
      if (!dir) return done('unavailable');
      const size = imageSize(filePath);
      if (!size || !size.w) return done('unreadable');
      if (size.w >= SKIP_ABOVE_WIDTH) return done('already-sharp', { width: size.w });

      const scale = pickScale(size.w);
      // Write to a temp file and swap it in only on success, so a crash mid-run can never leave a
      // half-written image where the operator expects their picture.
      const outExt = (ext === '.jpeg' || ext === '.jfif') ? '.jpg' : ext;
      const tmp = filePath + '.upscaling' + outExt;
      const exe = path.join(dir, 'realesrgan-ncnn-vulkan.exe');
      const args = ['-i', filePath, '-o', tmp, '-n', MODEL, '-s', String(scale), '-f', outExt.replace('.', '')];
      const t0 = Date.now();
      let finished = false;
      const child = spawn(exe, args, { cwd: dir, windowsHide: true });
      const killTimer = setTimeout(() => { try { child.kill(); } catch (_) {} }, TIMEOUT_MS);

      child.on('error', () => {
        if (finished) return;
        finished = true;
        clearTimeout(killTimer);
        try { fs.unlinkSync(tmp); } catch (_) {}
        done('spawn-failed');
      });
      child.on('close', () => {
        if (finished) return;
        finished = true;
        clearTimeout(killTimer);
        const ms = Date.now() - t0;
        let out = null;
        try { out = fs.existsSync(tmp) ? imageSize(tmp) : null; } catch (_) {}
        if (!out || !out.w || out.w <= size.w) {
          try { fs.unlinkSync(tmp); } catch (_) {}
          return done('failed', { ms: ms });
        }
        try {
          // Keep the untouched original beside the content, in case it is ever wanted back or the
          // enhancement made an odd call on some picture.
          const backupDir = path.join(path.dirname(filePath), '_originals');
          fs.mkdirSync(backupDir, { recursive: true });
          const backup = path.join(backupDir, path.basename(filePath));
          if (!fs.existsSync(backup)) fs.copyFileSync(filePath, backup);
          fs.renameSync(tmp, filePath);
        } catch (e) {
          try { fs.unlinkSync(tmp); } catch (_) {}
          return done('replace-failed', { ms: ms, error: e.message });
        }
        done('enhanced', {
          from: size.w + 'x' + size.h,
          to: out.w + 'x' + out.h,
          scale: scale,
          ms: ms
        });
      });
    } catch (e) {
      done('error', { error: e.message });
    }
  });
}

module.exports = { isAvailable, imageSize, enhanceIfSmall, TARGET_WIDTH, SKIP_ABOVE_WIDTH, MODEL };