Add button and custom modal flow implemented

lib/server/uploads/uploadConstants.ts

@@ -0,0 +1,62 @@
+import type { CreateFlowUploadPurpose } from "../../create/createFlowUploadPurpose";
+
+export type { CreateFlowUploadPurpose };
+export { CREATE_FLOW_UPLOAD_PURPOSES } from "../../create/createFlowUploadPurpose";
+
+/** Max body size for multipart upload (bytes). */
+export const CREATE_FLOW_UPLOAD_MAX_BYTES = 12 * 1024 * 1024;
+
+const COMMUNITY_MAX = 5 * 1024 * 1024;
+const CUSTOM_MAX = 10 * 1024 * 1024;
+
+const IMAGE_MIMES = new Set([
+  "image/jpeg",
+  "image/png",
+  "image/webp",
+  "image/gif",
+]);
+
+const CUSTOM_EXTRA_MIMES = new Set(["application/pdf"]);
+
+export function maxBytesForPurpose(purpose: CreateFlowUploadPurpose): number {
+  return purpose === "communityAvatar" ? COMMUNITY_MAX : CUSTOM_MAX;
+}
+
+export function isAllowedMime(
+  purpose: CreateFlowUploadPurpose,
+  mime: string,
+): boolean {
+  const m = mime.toLowerCase().split(";")[0]?.trim() ?? "";
+  if (IMAGE_MIMES.has(m)) return true;
+  if (purpose === "customMethodAttachment" && CUSTOM_EXTRA_MIMES.has(m)) {
+    return true;
+  }
+  return false;
+}
+
+/** Extension including dot, from normalized mime (lowercase). */
+export function extensionForMime(mime: string): string {
+  const m = mime.toLowerCase().split(";")[0]?.trim() ?? "";
+  switch (m) {
+    case "image/jpeg":
+      return ".jpg";
+    case "image/png":
+      return ".png";
+    case "image/webp":
+      return ".webp";
+    case "image/gif":
+      return ".gif";
+    case "application/pdf":
+      return ".pdf";
+    default:
+      return ".bin";
+  }
+}
+
+/** Strict id: uuid v4 filename stem (no extension in id param for GET). */
+const UPLOAD_ID_RE =
+  /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
+
+export function isValidUploadFileId(id: string): boolean {
+  return UPLOAD_ID_RE.test(id);
+}