import type { ExportFormat } from "../types";

export interface LoadedImage {
  file: File;
  /** Object URL for display in the cropper. Revoke when replaced. */
  url: string;
  width: number;
  height: number;
}

const ACCEPTED = /^image\/(jpeg|png|webp|avif|gif|bmp|x-icon|svg\+xml)$/;

export function isImageFile(file: File): boolean {
  return file.type ? ACCEPTED.test(file.type) : /\.(jpe?g|png|webp|avif|gif|bmp|ico|svg)$/i.test(file.name);
}

function readSize(url: string): Promise<{ width: number; height: number }> {
  return new Promise((resolve, reject) => {
    const img = new Image();
    img.onload = () => resolve({ width: img.naturalWidth, height: img.naturalHeight });
    img.onerror = () => reject(new Error("Could not decode this image."));
    img.src = url;
  });
}

export async function loadImage(file: File): Promise<LoadedImage> {
  const url = URL.createObjectURL(file);
  try {
    const { width, height } = await readSize(url);
    return { file, url, width, height };
  } catch (err) {
    URL.revokeObjectURL(url);
    throw err;
  }
}

const EXT: Record<ExportFormat, string> = {
  jpeg: "jpg",
  webp: "webp",
  png: "png",
  avif: "avif",
};

export function buildFilename(sourceName: string, templateId: string, format: ExportFormat): string {
  const base = sourceName.replace(/\.[^./\\]+$/, "") || "image";
  const suffix = templateId === "original" ? "edited" : templateId;
  return `${base}-${suffix}.${EXT[format]}`;
}

export function triggerDownload(blob: Blob, filename: string): void {
  const url = URL.createObjectURL(blob);
  const a = document.createElement("a");
  a.href = url;
  a.download = filename;
  document.body.appendChild(a);
  a.click();
  a.remove();
  // Defer revocation so the download has time to start.
  setTimeout(() => URL.revokeObjectURL(url), 10_000);
}

export function formatBytes(bytes: number): string {
  if (bytes < 1024) return `${bytes} B`;
  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
  return `${(bytes / (1024 * 1024)).toFixed(2)} MB`;
}

export function megapixels(width: number, height: number): string {
  const mp = (width * height) / 1_000_000;
  return mp >= 1 ? `${mp.toFixed(1)} MP` : `${(mp * 1000).toFixed(0)} KP`;
}