const fs = require("fs");
const path = require("path");
const sharp = require("sharp");

const { loadMeals, repoRoot } = require("./lib/meals");

const fullsDir = path.join(repoRoot, "images", "fulls");
const thumbsDir = path.join(repoRoot, "images", "thumbs");

const THUMB_WIDTH = 240;
const THUMB_HEIGHT = 320;
const JPEG_QUALITY = 82;

function clamp(value, min, max) {
  return Math.min(Math.max(value, min), max);
}

function getThumbnailPaths(meal) {
  return {
    fullPath: path.join(fullsDir, `${meal.id}.jpg`),
    thumbPath: path.join(thumbsDir, `${meal.id}.jpg`),
  };
}

function getCropArea(width, height, focus) {
  const targetRatio = THUMB_WIDTH / THUMB_HEIGHT;
  const sourceRatio = width / height;

  let cropWidth = width;
  let cropHeight = height;

  if (sourceRatio > targetRatio) {
    cropWidth = Math.round(height * targetRatio);
  } else if (sourceRatio < targetRatio) {
    cropHeight = Math.round(width / targetRatio);
  }

  const centerX = (focus?.x ?? 0.5) * width;
  const centerY = (focus?.y ?? 0.5) * height;
  const left = Math.round(centerX - cropWidth / 2);
  const top = Math.round(centerY - cropHeight / 2);

  return {
    left: clamp(left, 0, width - cropWidth),
    top: clamp(top, 0, height - cropHeight),
    width: cropWidth,
    height: cropHeight,
  };
}

async function generateThumbnail(meal) {
  const { fullPath, thumbPath } = getThumbnailPaths(meal);

  if (!fs.existsSync(fullPath)) {
    throw new Error(`Missing full-size image for meal ${meal.id}: ${fullPath}`);
  }

  const image = sharp(fullPath);
  const metadata = await image.metadata();

  if (!metadata.width || !metadata.height) {
    throw new Error(`Could not read image dimensions for ${fullPath}`);
  }

  const cropArea = getCropArea(
    metadata.width,
    metadata.height,
    meal.thumbnail?.focus
  );

  await image
    .extract(cropArea)
    .resize(THUMB_WIDTH, THUMB_HEIGHT)
    .jpeg({ quality: JPEG_QUALITY, mozjpeg: true })
    .toFile(thumbPath);
}

async function main() {
  const meals = loadMeals();

  await fs.promises.mkdir(thumbsDir, { recursive: true });

  for (const meal of meals) {
    await generateThumbnail(meal);
  }

  console.log(`Generated ${meals.length} thumbnails in images/thumbs`);
}

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