// How an attachment is drawn, decided in one place for the card and the editor.

/** Whether a file is shown as a picture rather than as a chip to download.
 *
 *  Every `image/` type except SVG. An SVG is a document that can carry its own
 *  script, so neither surface serves one to render: the server sends it as a download
 *  (#1981) and the desktop's blob scheme as opaque bytes, where an `<img>` of it would
 *  only ever show broken. */
export function rendersInline(mime: string): boolean {
  return mime.startsWith("image/") && mime !== "image/svg+xml";
}

/** Whether this browser can put a picture on the clipboard at all.
 *
 *  The async clipboard only exists in a secure context, so a server reached over plain
 *  http has none — the viewer then leaves copying to the browser's own context menu
 *  on the full-size image. */
export function canCopyImages(): boolean {
  return typeof ClipboardItem !== "undefined" && typeof navigator.clipboard?.write === "function";
}

/** Put the image at `url` on the clipboard.
 *
 *  As PNG whatever it was stored as: PNG is the one image type every browser's
 *  clipboard accepts, so a JPEG or WebP is redrawn through a canvas first. The item is
 *  given a promise rather than a blob so the write starts inside the click — Safari
 *  refuses a clipboard write that begins after an await. */
export async function copyImage(url: string): Promise<void> {
  await navigator.clipboard.write([new ClipboardItem({ "image/png": asPng(url) })]);
}

async function asPng(url: string): Promise<Blob> {
  const res = await fetch(url);
  if (!res.ok) throw new Error(`HTTP ${res.status}`);
  const blob = await res.blob();
  if (blob.type === "image/png") return blob;
  const bitmap = await createImageBitmap(blob);
  const canvas = document.createElement("canvas");
  canvas.width = bitmap.width;
  canvas.height = bitmap.height;
  canvas.getContext("2d")?.drawImage(bitmap, 0, 0);
  bitmap.close();
  return new Promise((resolve, reject) =>
    canvas.toBlob((png) => (png ? resolve(png) : reject(new Error("Could not encode the image."))), "image/png"),
  );
}