import { closeSync, constants, fstatSync, openSync, readFileSync } from "node:fs";
import { tmpdir } from "node:os";
import { basename, dirname } from "node:path";
import { detectImageMimeType, type SupportedImageMimeType } from "./attachments.ts";

const PI_CLIPBOARD_FILE =
  /^pi-clipboard-[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}\.(png|jpe?g|gif|webp)$/i;

export const MAX_CLIPBOARD_IMAGE_BYTES = 20 * 1024 * 1024;

export interface LoadedClipboardImage {
  path: string;
  bytes: Uint8Array;
  mimeType: SupportedImageMimeType;
}

export function isPiClipboardImagePath(value: string): boolean {
  return dirname(value) === tmpdir() && PI_CLIPBOARD_FILE.test(basename(value));
}

export function loadPiClipboardImage(value: string): LoadedClipboardImage | undefined {
  if (!isPiClipboardImagePath(value)) return undefined;

  let fileDescriptor: number | undefined;
  try {
    const noFollow = "O_NOFOLLOW" in constants ? constants.O_NOFOLLOW : 0;
    fileDescriptor = openSync(value, constants.O_RDONLY | noFollow);
    const stat = fstatSync(fileDescriptor);
    if (!stat.isFile() || stat.size <= 0 || stat.size > MAX_CLIPBOARD_IMAGE_BYTES) {
      return undefined;
    }

    const bytes = new Uint8Array(readFileSync(fileDescriptor));
    const mimeType = detectImageMimeType(bytes);
    if (!mimeType) return undefined;
    return { path: value, bytes, mimeType };
  } catch {
    return undefined;
  } finally {
    if (fileDescriptor !== undefined) closeSync(fileDescriptor);
  }
}