Address response bodies by response id instead of a filesystem path (#550)

packages/platform/src/registry.ts

@@ -49,6 +49,9 @@ export const platform: Platform = {
   get files() {
     return host().files;
   },
+  get blobs() {
+    return host().blobs;
+  },
   rpc: (cmd, payload) => host().rpc(cmd, payload),
   rpcStream: (cmd, payload, onMessage) => host().rpcStream(cmd, payload, onMessage),
   listen: (event, callback) => host().listen(event, callback),

packages/platform/src/tauri/index.ts

@@ -104,6 +104,18 @@ async function rpc<T>(cmd: string, payload?: RpcPayload): Promise<T> {
   }
 }
 
+/**
+ * Where this host keeps the bytes stored under an id, or null if it has none.
+ *
+ * The desktop stores them as files the engine wrote, so answering means asking
+ * the backend. Callers hold ids and nothing else; the path exists for exactly
+ * as long as it takes to open the file, which is the one thing a desktop host
+ * can do that a tab cannot.
+ */
+function storedBodyPath(id: string): Promise<string | null> {
+  return rpc<string | null>("cmd_http_response_body_path", { responseId: id });
+}
+
 export function createTauriPlatform(): Platform {
   const window = createWindow();
 
@@ -124,13 +136,24 @@ export function createTauriPlatform(): Platform {
     },
 
     files: {
-      readFile: (path) => readFile(path),
       readDir: (path) => readDir(path),
       url: (path) => convertFileSrc(path),
       basename: (path) => basename(path),
       resolveResource: (path) => resolveResource(path),
     },
 
+    blobs: {
+      async read(id) {
+        const path = await storedBodyPath(id);
+        return path == null ? null : readFile(path);
+      },
+
+      async url(id) {
+        const path = await storedBodyPath(id);
+        return path == null ? null : convertFileSrc(path);
+      },
+    },
+
     rpc,
 
     async rpcStream<T, M>(

packages/platform/src/types.ts

@@ -135,11 +135,10 @@ export interface PlatformDialog {
  * File-ish operations, keyed by paths the backend handed us.
  *
  * A path here is an opaque handle, not something to parse or construct: the UI
- * only ever passes one back to `readFile` or `url`. A host without a filesystem
+ * only ever passes one back to `url` or `readDir`. A host without a filesystem
  * can mint handles of its own (a blob id, a URL) and stay compatible.
  */
 export interface PlatformFiles {
-  readFile(path: string): Promise<Uint8Array<ArrayBuffer>>;
   readDir(path: string): Promise<DirEntry[]>;
 
   /** A URL the page can load a file from, for `<img>`, `<video>`, and friends. */
@@ -151,12 +150,38 @@ export interface PlatformFiles {
   resolveResource(path: string): Promise<string>;
 }
 
+/**
+ * Content the backend stored, addressed by the id it stored it under.
+ *
+ * Where those bytes actually live is the one thing every host answers
+ * differently — a file the engine wrote, a row in a database, a URL on the
+ * other end of a socket — so finding them is the host's job and nobody else's.
+ * The caller passes an id and never a location, which is also what keeps a page
+ * from naming something the backend never wrote.
+ *
+ * What the content *means* is the app's business, not this package's.
+ */
+export interface PlatformBlobs {
+  /** The bytes, or null if the host has nothing stored under that id. */
+  read(id: string): Promise<Uint8Array<ArrayBuffer> | null>;
+
+  /**
+   * A URL an element can load the content from, for `<img>`, `<video>` and
+   * friends, or null if the host has nothing stored under that id.
+   *
+   * Asynchronous because the host may have to ask its backend where the bytes
+   * are, and it only does that the moment before it reads them.
+   */
+  url(id: string): Promise<string | null>;
+}
+
 export interface Platform {
   readonly capabilities: PlatformCapabilities;
   readonly window: PlatformWindow;
   readonly clipboard: PlatformClipboard;
   readonly dialog: PlatformDialog;
   readonly files: PlatformFiles;
+  readonly blobs: PlatformBlobs;
 
   /** Call a backend command and await its result. */
   rpc<T>(cmd: string, payload?: RpcPayload): Promise<T>;