// Crop the configurator shell renders down to the product band for the model
// chooser (src/site/partials/model-chooser.html). The source renders are
// 2160-square with large transparent margins; cropping once at build-asset
// time lets the chooser scale them with object-fit: contain (no CSS cropping,
// nothing cut off at any card size).
//
// One shared crop box (union of the four shells' alpha bounds + margin) keeps
// the four renders pixel-aligned so the color crossfade doesn't jump.
//
//   node scripts/crop-chooser-renders.mjs
//
// Input:  public/images/home/Dynamic Configurator/DYN_bs2--<shell>-softstrap-customcushion.webp
// Output: public/images/home/model-chooser/chooser-shell-<shell>.webp
import fs from "node:fs";
import sharp from "sharp";

const SRC = (c) => `public/images/home/Dynamic Configurator/DYN_bs2--${c}-softstrap-customcushion.webp`;
const OUT_DIR = "public/images/home/model-chooser";
const OUT = (c) => `${OUT_DIR}/chooser-shell-${c}.webp`;
const SHELLS = ["clear", "orange", "black", "purple"];
const MARGIN = 24; // px of breathing room around the union bounds
const ALPHA_FLOOR = 8; // ignore near-invisible antialiasing haze

async function bounds(file) {
  const { data, info } = await sharp(file).ensureAlpha().raw().toBuffer({ resolveWithObject: true });
  let minX = info.width, minY = info.height, maxX = 0, maxY = 0;
  for (let y = 0; y < info.height; y++) {
    for (let x = 0; x < info.width; x++) {
      if (data[(y * info.width + x) * 4 + 3] > ALPHA_FLOOR) {
        if (x < minX) minX = x;
        if (x > maxX) maxX = x;
        if (y < minY) minY = y;
        if (y > maxY) maxY = y;
      }
    }
  }
  return { minX, minY, maxX, maxY, width: info.width, height: info.height };
}

const all = await Promise.all(SHELLS.map((c) => bounds(SRC(c))));
const union = all.reduce((u, b) => ({
  minX: Math.min(u.minX, b.minX), minY: Math.min(u.minY, b.minY),
  maxX: Math.max(u.maxX, b.maxX), maxY: Math.max(u.maxY, b.maxY),
  width: b.width, height: b.height,
}));

const left = Math.max(0, union.minX - MARGIN);
const top = Math.max(0, union.minY - MARGIN);
const width = Math.min(union.width, union.maxX + MARGIN + 1) - left;
const height = Math.min(union.height, union.maxY + MARGIN + 1) - top;
console.log(`union crop: ${width}x${height} at ${left},${top} (ratio ${(width / height).toFixed(2)})`);

fs.mkdirSync(OUT_DIR, { recursive: true });
const OUT_WIDTH = 1600; // cards render ~900px max; 1600 covers retina comfortably
for (const c of SHELLS) {
  await sharp(SRC(c)).extract({ left, top, width, height })
    .resize({ width: OUT_WIDTH }).webp({ quality: 82 }).toFile(OUT(c));
  const kb = (fs.statSync(OUT(c)).size / 1024).toFixed(0);
  console.log(`wrote ${OUT(c)} (${kb} KB)`);
}