feat: add 3 new plugin hooks : onBeforeBlobUpload, onBeforeDraftAutoSave, onBeforeEditDraft (#586)

Co-authored-by: Linus Rath <minipixxelinfo@gmail.com>

lib/plugin-sandbox/host-api.ts

@@ -9,6 +9,8 @@ import { useAuthStore } from '@/stores/auth-store';
 import { useEmailStore } from '@/stores/email-store';
 import { apiFetch } from '../browser-navigation';
 import { awaitDialog } from './host-dialog';
+import { fileStorage} from '../plugin-storage'
+import { generateUUID } from '../utils';
 
 /**
  * Methods only callable from the privileged (same-origin) tier. These expose
@@ -19,6 +21,8 @@ import { awaitDialog } from './host-dialog';
 const PRIVILEGED_ONLY_METHODS = new Set<string>([
   'jmap.fetchBlob',
   'jmap.sendRaw',
+  'upfiles.get',
+  'upfiles.set',
 ]);
 
 const PERM_PER_METHOD: Record<string, Permission | null> = {
@@ -38,6 +42,11 @@ const PERM_PER_METHOD: Record<string, Permission | null> = {
   // jmap (privileged-tier only; see PRIVILEGED_ONLY_METHODS)
   'jmap.fetchBlob': 'email:blob-read',
   'jmap.sendRaw': 'email:raw-send',
+  // uploaded files (privileged-tier only) : 
+  // Used only to get a file before it is uploaded to alterate it. 
+  // To just read, use jmap.fetchBlob.
+  'upfiles.get' : 'email:blob-write',
+  'upfiles.save' : 'email:blob-write',
   // admin
   'admin.getConfig': 'admin:config',
   'admin.getAllConfig': 'admin:config',
@@ -263,6 +272,19 @@ async function doJmapSendRaw(
   );
 }
 
+// ─── Uploaded files in IndexedDB (privileged tier) ──────────────────────────
+
+async function getFile(fileID:string): Promise<File | null> {
+  return await fileStorage.getFile(fileID)
+}
+
+async function saveFile(formerFileID:string, file: File): Promise<string> {
+  const fileId = generateUUID();
+  await fileStorage.saveFile(fileId, file);
+  await fileStorage.deleteFile(formerFileID);
+  return fileId;
+}
+
 // ─── admin config (same as before) ────────────────────────────
 
 async function adminGetAll(pluginId: string): Promise<Record<string, unknown>> {
@@ -335,6 +357,8 @@ export async function dispatchApiCall(
       args[1] as string,
       args[2] as { delayedUntil?: string; envelopeRecipients?: string[] } | undefined,
     );
+    case 'upfiles.get' : return getFile(args[0] as string);
+    case 'upfiles.save' : return saveFile(args[0] as string, args[1] as File);
 
     case 'admin.getConfig':    return adminGet(plugin.id, args[0] as string);
     case 'admin.getAllConfig': return adminGetAll(plugin.id);