import { assertBoundedText, assertPositiveSafeInteger } from "./limits";

export interface ObjectUrlLease {
  readonly url: string;
  readonly revoked: boolean;
  revoke(): void;
}

export function sanitizeDownloadFilename(
  input: string,
  fallback = "download.bin",
  maximumLength = 180,
): string {
  assertPositiveSafeInteger(maximumLength, "Maximum filename length");
  const cleaned = cleanFilename(input);
  const fallbackName = cleanFilename(fallback) || "download.bin";
  const safe = cleaned || fallbackName;
  if (safe.length <= maximumLength) return safe;
  const dot = safe.lastIndexOf(".");
  const extension = dot > 0 && safe.length - dot <= 16 ? safe.slice(dot) : "";
  let stem = safe.slice(0, Math.max(1, maximumLength - extension.length));
  const finalCodeUnit = stem.charCodeAt(stem.length - 1);
  if (finalCodeUnit >= 0xd800 && finalCodeUnit <= 0xdbff)
    stem = stem.slice(0, -1);
  return `${stem || "_"}${extension}`;
}

function cleanFilename(input: string): string {
  const normalized = assertBoundedText(
    input,
    4096,
    "Filename length",
  ).normalize("NFC");
  const cleaned = Array.from(normalized, (character) => {
    const codePoint = character.codePointAt(0) ?? 0;
    return codePoint <= 31 ||
      (codePoint >= 127 && codePoint <= 159) ||
      (codePoint >= 0x202a && codePoint <= 0x202e) ||
      (codePoint >= 0x2066 && codePoint <= 0x2069) ||
      '/\\:*?"<>|'.includes(character)
      ? "_"
      : character;
  })
    .join("")
    .replace(/\s+/gu, " ")
    .replace(/^\.+|[. ]+$/gu, "")
    .trim();
  return /^(?:con|prn|aux|nul|com[1-9]|lpt[1-9])(?:\.|$)/iu.test(cleaned)
    ? `_${cleaned}`
    : cleaned;
}

export function createObjectUrlLease(
  blob: Blob,
  urlApi: Pick<typeof URL, "createObjectURL" | "revokeObjectURL"> = URL,
): ObjectUrlLease {
  const url = urlApi.createObjectURL(blob);
  let revoked = false;
  return {
    url,
    get revoked() {
      return revoked;
    },
    revoke() {
      if (revoked) return;
      revoked = true;
      urlApi.revokeObjectURL(url);
    },
  };
}

export function triggerBlobDownload(
  blob: Blob,
  filename: string,
  ownerDocument: Document = document,
): ObjectUrlLease {
  const lease = createObjectUrlLease(blob);
  const anchor = ownerDocument.createElement("a");
  anchor.href = lease.url;
  anchor.download = sanitizeDownloadFilename(filename);
  anchor.rel = "noopener";
  anchor.hidden = true;
  ownerDocument.body.append(anchor);
  try {
    anchor.click();
  } finally {
    anchor.remove();
    globalThis.setTimeout(() => lease.revoke(), 0);
  }
  return lease;
}