Release Helper Tools 0.1.0

src/helpers/downloads.ts

@@ -0,0 +1,91 @@
+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;
+}