/**
 * Prepares the ITA ITO brand assets.
 *
 *   npm run brand
 *
 * Downloads the shop logo once and writes two files into `public/brand`, both
 * of which are committed:
 *
 *   logo.png       the original, for the admin interface
 *   logo-eink.png  the wordmark alone, 1-bit and thresholded, for the panel
 *
 * The outputs are committed on purpose. Rendering must not depend on a
 * Shopify CDN being reachable, and the panel image feeds a content hash that
 * decides whether the screen redraws — so the bytes have to be stable.
 *
 * `sharp` is a devDependency used only here. Nothing at runtime needs it.
 */

import { mkdir, writeFile } from 'node:fs/promises';
import path from 'node:path';

import sharp from 'sharp';

import { encodePng, toBitmap } from '../lib/screen/encode';

const LOGO_URL =
  process.env.BRAND_LOGO_URL ?? 'https://ita-ito.com/cdn/shop/files/ITA_ITO_knitwear_logo.png';

/** Wide enough to read from the pavement, short enough for a 76px header. */
const EINK_WIDTH = 260;

async function main(): Promise<void> {
  const directory = path.join(process.cwd(), 'public', 'brand');
  await mkdir(directory, { recursive: true });

  const response = await fetch(LOGO_URL);
  if (!response.ok) {
    throw new Error(`Could not fetch the logo: ${response.status} ${response.statusText}`);
  }
  const original = Buffer.from(await response.arrayBuffer());
  await writeFile(path.join(directory, 'logo.png'), original);

  const band = await findWordmarkBand(original);
  const cropped = await sharp(original)
    .extract({ left: 0, top: band.top, width: band.width, height: band.height })
    .resize({ width: EINK_WIDTH })
    .flatten({ background: '#ffffff' })
    .ensureAlpha()
    .raw()
    .toBuffer({ resolveWithObject: true });

  // Reuse the panel's own encoder, so the logo is thresholded by exactly the
  // rule the rest of the screen is. A line drawing gets no dithering: it would
  // only fuzz the serifs.
  const bitmap = toBitmap(cropped.data, cropped.info.width, cropped.info.height);
  await writeFile(path.join(directory, 'logo-eink.png'), encodePng(bitmap));

  console.log(`logo.png       ${original.length} bytes (original)`);
  console.log(`logo-eink.png  ${cropped.info.width}x${cropped.info.height}, 1-bit`);
  console.log('Both are committed; the CDN is never read at runtime.');
}

/**
 * The logo stacks a wordmark, a two-line tagline and a drawn motif. Only the
 * wordmark survives at panel size, so find its band rather than hard-coding
 * pixel offsets that a future logo revision would silently break.
 */
async function findWordmarkBand(
  source: Buffer,
): Promise<{ top: number; height: number; width: number }> {
  const { data, info } = await sharp(source)
    .flatten({ background: '#ffffff' })
    .greyscale()
    .raw()
    .toBuffer({ resolveWithObject: true });

  const bands: { top: number; bottom: number }[] = [];
  let start: number | null = null;

  for (let y = 0; y < info.height; y += 1) {
    let ink = 0;
    for (let x = 0; x < info.width; x += 1) {
      if ((data[y * info.width + x] ?? 255) < 128) {
        ink += 1;
      }
    }
    if (ink > 0 && start === null) {
      start = y;
    } else if (ink === 0 && start !== null) {
      bands.push({ top: start, bottom: y - 1 });
      start = null;
    }
  }
  if (start !== null) {
    bands.push({ top: start, bottom: info.height - 1 });
  }

  const wordmark = bands[0];
  if (!wordmark) {
    throw new Error('Found no ink in the logo; is the download correct?');
  }

  // A couple of pixels of air, so the thresholding cannot clip a serif.
  const top = Math.max(0, wordmark.top - 2);
  const bottom = Math.min(info.height - 1, wordmark.bottom + 2);
  return { top, height: bottom - top + 1, width: info.width };
}

main().catch((error: unknown) => {
  console.error(error);
  process.exitCode = 1;
});