feat(plugins): stream cancellable downloads to atomic local files

Refs: t8y2/dbx-plugin-s3#22

apps/desktop/src/components/plugins/PluginWorkbenchHost.vue

@@ -6,6 +6,7 @@ import { isTauriRuntime } from "@/lib/backend/tauriRuntime";
 import { copyToClipboard } from "@/lib/common/clipboard";
 import { PluginHostBridge, pluginSandboxDocument, type PluginBridgeTheme, type PluginSaveFileRequest, type PluginSaveFileResult, type PluginWorkbenchContext } from "@/lib/plugins/pluginHostBridge";
 import { buildPluginEditorAppearance } from "@/lib/plugins/pluginAppearance";
+import { downloadPluginFile, cancelPluginDownload } from "@/lib/plugins/pluginFileDownload";
 import type { InstalledPlugin, PluginUiContribution } from "@/types/database";
 import { useI18n } from "vue-i18n";
 import { useTheme } from "@/composables/useTheme";
@@ -68,6 +69,7 @@ function currentBridgeTheme(): PluginBridgeTheme {
 }
 
 function createBridge() {
+  bridge?.dispose();
   bridge = new PluginHostBridge(
     props.plugin,
     props.contribution,
@@ -83,6 +85,8 @@ function createBridge() {
       reopenConnection: (pluginId, connectionId) => useConnectionStore().reopenPluginConnection(connectionId, pluginId),
       closeTab: () => emit("closeTab"),
       saveFile: (_pluginId, request, data) => savePluginFile(request, data),
+      downloadFile: isTauriRuntime() ? downloadPluginFile : undefined,
+      cancelDownload: isTauriRuntime() ? cancelPluginDownload : undefined,
       copyText: (_pluginId, text) => copyToClipboard(text),
     },
     appLocale.value,

apps/desktop/src/lib/plugins/pluginFileDownload.ts

@@ -0,0 +1,19 @@
+import { Channel, invoke } from "@tauri-apps/api/core";
+import type { PluginDownloadRequest, PluginSaveFileResult } from "./pluginHostBridge";
+
+export async function downloadPluginFile(pluginId: string, request: PluginDownloadRequest, onProgress: (progress: unknown) => void): Promise<PluginSaveFileResult | null> {
+  const channel = new Channel<unknown>();
+  channel.onmessage = onProgress;
+  const path = await invoke<string | null>("download_plugin_file", {
+    pluginId,
+    downloadId: request.downloadId,
+    fileName: request.fileName || "download.bin",
+    params: request.params,
+    onProgress: channel,
+  });
+  return path === null ? null : { path };
+}
+
+export async function cancelPluginDownload(pluginId: string, downloadId: string): Promise<void> {
+  await invoke("cancel_plugin_download", { pluginId, downloadId });
+}

apps/desktop/src/lib/plugins/pluginHostBridge.spec.ts

@@ -14,6 +14,65 @@ const workbench: PluginWorkbenchContribution = { type: "workbench", id: "sample.
 const resultView: PluginResultViewContribution = { type: "result-view", id: "sample.graph", label: "Graph" };
 
 describe("PluginHostBridge", () => {
+  it("streams downloads under the owning plugin, scopes cancellation and reports native capability", async () => {
+    const messages: any[] = [];
+    const target = { postMessage: (message: unknown) => messages.push(message) } as unknown as Window;
+    let finish!: (value: null) => void;
+    const downloadFile = vi.fn((_pluginId, _request, onProgress) => {
+      onProgress({ downloadId: "download-1", sent: 300 * 1024 * 1024 });
+      return new Promise<null>((resolve) => {
+        finish = resolve;
+      });
+    });
+    const cancelDownload = vi.fn().mockResolvedValue(undefined);
+    const bridge = new PluginHostBridge(plugin(), workbench, {}, () => target, {
+      invoke: vi.fn(),
+      notify: vi.fn(),
+      sendBinary: vi.fn(),
+      readAsset: vi.fn(),
+      downloadFile,
+      cancelDownload,
+    });
+    const send = (id: string, method: string, params: unknown) => bridge.handleWindowMessage({ source: target, data: { source: "dbx-plugin", version: 1, type: "request", id, method, params } } as MessageEvent);
+    bridge.sendInit();
+    expect(messages[0].capabilities.downloadFile).toBe(true);
+    send("open", "host.downloadFile", { downloadId: "download-1", fileName: "report.bin", params: { uri: "s3://bucket/report.bin" }, pluginId: "other" });
+    await vi.waitFor(() => expect(downloadFile).toHaveBeenCalledOnce());
+    expect(downloadFile.mock.calls[0][0]).toBe("sample");
+    expect(messages.some((message) => message.method === "host.download.progress" && message.params.sent === 300 * 1024 * 1024)).toBe(true);
+    send("other", "host.cancelDownload", { downloadId: "someone-else" });
+    expect(cancelDownload).not.toHaveBeenCalled();
+    send("cancel", "host.cancelDownload", { downloadId: "download-1" });
+    await vi.waitFor(() => expect(cancelDownload).toHaveBeenCalledWith("sample", "download-1"));
+    finish(null);
+    await vi.waitFor(() => expect(messages.some((message) => message.id === "open" && message.result === null)).toBe(true));
+  });
+
+  it("cancels unfinished native downloads when the workbench is disposed", async () => {
+    const target = { postMessage: vi.fn() } as unknown as Window;
+    const cancelDownload = vi.fn().mockResolvedValue(undefined);
+    const bridge = new PluginHostBridge(plugin(), workbench, {}, () => target, {
+      invoke: vi.fn(),
+      notify: vi.fn(),
+      sendBinary: vi.fn(),
+      readAsset: vi.fn(),
+      downloadFile: vi.fn(() => new Promise<null>(() => {})),
+      cancelDownload,
+    });
+    bridge.handleWindowMessage({ source: target, data: { source: "dbx-plugin", version: 1, type: "request", id: "open", method: "host.downloadFile", params: { downloadId: "owned", params: {} } } } as MessageEvent);
+    bridge.dispose();
+    expect(cancelDownload).toHaveBeenCalledWith("sample", "owned");
+  });
+
+  it("does not advertise native downloads on legacy or web hosts", async () => {
+    const messages: any[] = [];
+    const target = { postMessage: (message: unknown) => messages.push(message) } as unknown as Window;
+    const bridge = new PluginHostBridge(plugin(), workbench, {}, () => target, { invoke: vi.fn(), notify: vi.fn(), sendBinary: vi.fn(), readAsset: vi.fn() });
+    bridge.sendInit();
+    expect(messages[0].capabilities.downloadFile).toBe(false);
+    bridge.handleWindowMessage({ source: target, data: { source: "dbx-plugin", version: 1, type: "request", id: "open", method: "host.downloadFile", params: {} } } as MessageEvent);
+    await vi.waitFor(() => expect(messages[1].error).toContain("desktop host"));
+  });
   it("binds backend calls to the owning plugin identity", async () => {
     const messages: unknown[] = [];
     const target = { postMessage: (message: unknown) => messages.push(message) } as unknown as Window;

apps/desktop/src/lib/plugins/pluginHostBridge.ts

@@ -44,6 +44,11 @@ export interface PluginSaveFileResult {
   path: string;
 }
 
+export interface PluginDownloadRequest extends PluginSaveFileRequest {
+  downloadId: string;
+  params: Record<string, unknown>;
+}
+
 export interface PluginHostBridgeApi {
   invoke<T = unknown>(pluginId: string, method: string, params?: unknown, timeoutMs?: number): Promise<T>;
   notify(pluginId: string, method: string, params?: unknown): Promise<void>;
@@ -56,6 +61,8 @@ export interface PluginHostBridgeApi {
   closeTab?(): Promise<void> | void;
   /** Persist plugin bytes through the host's native save dialog. Resolves null when the user cancels. */
   saveFile?(pluginId: string, request: PluginSaveFileRequest, data: Uint8Array): Promise<PluginSaveFileResult | null>;
+  downloadFile?(pluginId: string, request: PluginDownloadRequest, onProgress: (progress: unknown) => void): Promise<PluginSaveFileResult | null>;
+  cancelDownload?(pluginId: string, downloadId: string): Promise<void>;
   /** Write text to the system clipboard on behalf of the sandboxed plugin iframe. */
   copyText?(pluginId: string, text: string): Promise<void>;
 }
@@ -72,6 +79,7 @@ interface PluginRequestMessage {
 }
 
 export class PluginHostBridge {
+  private downloads = new Set<string>();
   private context: PluginWorkbenchContext;
   private locale: string;
   private theme?: PluginBridgeTheme;
@@ -120,6 +128,8 @@ export class PluginHostBridge {
 
   private requestInit(signal: "load" | "ready"): void {
     if ((this.initSignals.load && this.initSignals.ready) || (signal === "load" && this.initSignals.load)) {
+      for (const downloadId of this.downloads) void this.api.cancelDownload?.(this.plugin.manifest.id, downloadId).catch(() => undefined);
+      this.downloads.clear();
       this.initGeneration += 1;
       this.initSignals = { load: false, ready: false };
       this.initStarted = false;
@@ -148,6 +158,8 @@ export class PluginHostBridge {
   /** Stop future posts (queued inits after an async reinit) for a torn-down bridge. */
   dispose(): void {
     this.disposed = true;
+    for (const downloadId of this.downloads) void this.api.cancelDownload?.(this.plugin.manifest.id, downloadId).catch(() => undefined);
+    this.downloads.clear();
   }
 
   private disposed = false;
@@ -165,6 +177,7 @@ export class PluginHostBridge {
       locale: this.locale,
       theme: this.theme ? clonePluginData(this.theme) : undefined,
       permissions: [...(this.plugin.manifest.permissions || [])],
+      capabilities: { downloadFile: !!this.api.downloadFile },
       context: snapshotPluginWorkbenchContext(this.context),
     });
   }
@@ -215,6 +228,27 @@ export class PluginHostBridge {
   }
 
   private async dispatch(method: string, params: unknown, binary?: ArrayBuffer): Promise<unknown> {
+    if (method === "host.downloadFile") {
+      if (!this.api.downloadFile) throw new Error("Streaming file downloads require the desktop host");
+      const input = requireRecord(params, "download params");
+      const downloadId = requireProtocolName(input.downloadId, "download ID");
+      if (this.downloads.size >= 2 || this.downloads.has(downloadId)) throw new Error("Too many active downloads or duplicate download ID");
+      const request = { downloadId, fileName: optionalTrimmedString(input.fileName), params: requireRecord(input.params, "download source") };
+      this.downloads.add(downloadId);
+      try {
+        return await this.api.downloadFile(this.plugin.manifest.id, request, (progress) => {
+          this.post({ source: HOST_MESSAGE_SOURCE, version: BRIDGE_VERSION, type: "event", method: "host.download.progress", params: progress });
+        });
+      } finally {
+        this.downloads.delete(downloadId);
+      }
+    }
+    if (method === "host.cancelDownload") {
+      const input = requireRecord(params, "cancel download params");
+      const downloadId = requireProtocolName(input.downloadId, "download ID");
+      if (this.downloads.has(downloadId)) await this.api.cancelDownload?.(this.plugin.manifest.id, downloadId);
+      return null;
+    }
     if (method === "host.getContext") return snapshotPluginWorkbenchContext(this.context);
     if (method === "backend.invoke") {
       const input = requireRecord(params, "backend.invoke params");
@@ -451,6 +485,7 @@ export function pluginSdkSource(initialTheme?: PluginBridgeTheme): string {
     let context;
     let locale = 'en';
     let theme;
+    let capabilities = {};
     let resolveReady;
     const initialTheme = ${serializedInitialTheme};
     const applyTheme = (value) => {
@@ -551,6 +586,9 @@ export function pluginSdkSource(initialTheme?: PluginBridgeTheme): string {
       get context() { return context; },
       get locale() { return locale; },
       get theme() { return theme; },
+      get capabilities() { return capabilities; },
+      downloadFile: (options) => request('host.downloadFile', options),
+      cancelDownload: (downloadId) => request('host.cancelDownload', { downloadId }),
       request,
       invoke: (method, params, options = {}) => request('backend.invoke', { method, params, timeoutMs: options.timeoutMs }),
       stream,
@@ -591,6 +629,7 @@ export function pluginSdkSource(initialTheme?: PluginBridgeTheme): string {
         pending.delete(message.id);
         if (message.error) handler.reject(new Error(message.error)); else handler.resolve(message.result);
       } else if (message.type === 'init') {
+        capabilities = message.capabilities || {};
         context = message.context;
         locale = typeof message.locale === 'string' ? message.locale : 'en';
         applyTheme(message.theme);