const sharp = require('sharp');

/**
 * Resizes an image from a given buffer based on the specified resolution.
 *
 * @param {Buffer} inputBuffer - The buffer of the image to be resized.
 * @param {'low' | 'high'} resolution - The resolution to resize the image to.
 *                                      'low' for a maximum of 512x512 resolution,
 *                                      'high' for a maximum of 768x2000 resolution.
 * @returns {Promise<{buffer: Buffer, width: number, height: number}>} An object containing the resized image buffer and its dimensions.
 * @throws Will throw an error if the resolution parameter is invalid.
 */
async function resizeImageBuffer(inputBuffer, resolution) {
  const maxLowRes = 512;
  const maxShortSideHighRes = 768;
  const maxLongSideHighRes = 2000;

  let newWidth, newHeight;
  let resizeOptions = { fit: 'inside', withoutEnlargement: true };

  if (resolution === 'low') {
    resizeOptions.width = maxLowRes;
    resizeOptions.height = maxLowRes;
  } else if (resolution === 'high') {
    const metadata = await sharp(inputBuffer).metadata();
    const isWidthShorter = metadata.width < metadata.height;

    if (isWidthShorter) {
      // Width is the shorter side
      newWidth = Math.min(metadata.width, maxShortSideHighRes);
      // Calculate new height to maintain aspect ratio
      newHeight = Math.round((metadata.height / metadata.width) * newWidth);
      // Ensure the long side does not exceed the maximum allowed
      if (newHeight > maxLongSideHighRes) {
        newHeight = maxLongSideHighRes;
        newWidth = Math.round((metadata.width / metadata.height) * newHeight);
      }
    } else {
      // Height is the shorter side
      newHeight = Math.min(metadata.height, maxShortSideHighRes);
      // Calculate new width to maintain aspect ratio
      newWidth = Math.round((metadata.width / metadata.height) * newHeight);
      // Ensure the long side does not exceed the maximum allowed
      if (newWidth > maxLongSideHighRes) {
        newWidth = maxLongSideHighRes;
        newHeight = Math.round((metadata.height / metadata.width) * newWidth);
      }
    }

    resizeOptions.width = newWidth;
    resizeOptions.height = newHeight;
  } else {
    throw new Error('Invalid resolution parameter');
  }

  const resizedBuffer = await sharp(inputBuffer).rotate().resize(resizeOptions).toBuffer();

  const resizedMetadata = await sharp(resizedBuffer).metadata();
  return { buffer: resizedBuffer, width: resizedMetadata.width, height: resizedMetadata.height };
}

/**
 * Resizes an image buffer to webp format as well as reduces 150 px width.
 *
 * @param {Buffer} inputBuffer - The buffer of the image to be resized.
 * @returns {Promise<{ buffer: Buffer, width: number, height: number, bytes: number }>} An object containing the resized image buffer, its size and dimensions.
 * @throws Will throw an error if the resolution parameter is invalid.
 */
async function resizeAndConvert(inputBuffer) {
  const resizedBuffer = await sharp(inputBuffer).resize({ width: 150 }).toFormat('webp').toBuffer();
  const resizedMetadata = await sharp(resizedBuffer).metadata();
  return {
    buffer: resizedBuffer,
    width: resizedMetadata.width,
    height: resizedMetadata.height,
    bytes: Buffer.byteLength(resizedBuffer),
  };
}

module.exports = { resizeImageBuffer, resizeAndConvert };