const MAX_DIMENSION = 384;

/**
 * Resize an image to fit within MAX_DIMENSION while preserving aspect ratio.
 * Returns a base64 data URL.
 */
export function resizeImage(file: File): Promise<string> {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onload = () => {
      const img = new Image();
      img.onload = () => {
        let { width, height } = img;

        if (width > MAX_DIMENSION || height > MAX_DIMENSION) {
          const scale = MAX_DIMENSION / Math.max(width, height);
          width = Math.round(width * scale);
          height = Math.round(height * scale);
        }

        const canvas = document.createElement("canvas");
        canvas.width = width;
        canvas.height = height;
        const ctx = canvas.getContext("2d")!;
        ctx.drawImage(img, 0, 0, width, height);
        resolve(canvas.toDataURL("image/jpeg", 0.9));
      };
      img.onerror = reject;
      img.src = reader.result as string;
    };
    reader.onerror = reject;
    reader.readAsDataURL(file);
  });
}

/**
 * Load an image URL, resize to MAX_DIMENSION, return as base64 data URL.
 */
export async function urlToDataUrl(url: string): Promise<string> {
  const response = await fetch(url);
  if (!response.ok) throw new Error(`HTTP ${response.status} for ${url}`);
  const blob = await response.blob();
  const file = new File([blob], "image.jpg", { type: blob.type });
  return resizeImage(file);
}

/**
 * Get image dimensions from a data URL.
 */
export function getImageDimensions(
  dataUrl: string,
): Promise<{ width: number; height: number }> {
  return new Promise((resolve, reject) => {
    const img = new Image();
    img.onload = () => resolve({ width: img.width, height: img.height });
    img.onerror = reject;
    img.src = dataUrl;
  });
}