import { clsx } from "clsx";
import { twMerge } from "tailwind-merge"

export function cn(...inputs) {
  return twMerge(clsx(inputs));
}

/**
 * Compresses and resizes an image file on the client side.
 * If the file is not an image (e.g. PDF), it resolves with the original file.
 * 
 * @param {File} file - The file to compress.
 * @param {number} maxWidth - Max width of compressed image.
 * @param {number} maxHeight - Max height of compressed image.
 * @param {number} quality - Compression quality between 0 and 1.
 * @returns {Promise<File>} - A promise that resolves to the compressed File object.
 */
export function compressImage(file, maxWidth = 1200, maxHeight = 1200, quality = 0.8) {
  return new Promise((resolve) => {
    if (!file || !file.type.startsWith('image/')) {
      resolve(file);
      return;
    }

    const reader = new FileReader();
    reader.onload = (event) => {
      const img = new Image();
      img.onload = () => {
        let width = img.width;
        let height = img.height;

        // Calculate aspect ratio
        if (width > height) {
          if (width > maxWidth) {
            height = Math.round((height * maxWidth) / width);
            width = maxWidth;
          }
        } else {
          if (height > maxHeight) {
            width = Math.round((width * maxHeight) / height);
            height = maxHeight;
          }
        }

        const canvas = document.createElement('canvas');
        canvas.width = width;
        canvas.height = height;
        const ctx = canvas.getContext('2d');
        if (!ctx) {
          resolve(file);
          return;
        }

        // Draw image
        ctx.drawImage(img, 0, 0, width, height);

        // Convert to blob
        if (canvas.toBlob) {
          canvas.toBlob(
            (blob) => {
              if (blob) {
                // Keep original extension or use jpeg, but File constructor needs a name
                const compressedFile = new File([blob], file.name.substring(0, file.name.lastIndexOf('.')) + '.jpg', {
                  type: 'image/jpeg',
                  lastModified: Date.now()
                });
                resolve(compressedFile);
              } else {
                resolve(file);
              }
            },
            'image/jpeg',
            quality
          );
        } else {
          resolve(file);
        }
      };
      img.onerror = () => resolve(file);
      img.src = event.target.result;
    };
    reader.onerror = () => resolve(file);
    reader.readAsDataURL(file);
  });
}