Mobile app PoC (#281)

Initial checkin of mobile "native" app

plugos/syscalls/fetch.ts

@@ -0,0 +1,38 @@
+import type {
+  SandboxFetchRequest,
+  SandboxFetchResponse,
+} from "../../plug-api/plugos-syscall/fetch.ts";
+import { base64Encode } from "../asset_bundle/base64.ts";
+import { SysCallMapping } from "../system.ts";
+
+export async function sandboxFetch(
+  url: string,
+  req?: SandboxFetchRequest,
+): Promise<SandboxFetchResponse> {
+  const result = await fetch(
+    url,
+    req && {
+      method: req.method,
+      headers: req.headers,
+    },
+  );
+  const body = await (await result.blob()).arrayBuffer();
+  return {
+    ok: result.ok,
+    status: result.status,
+    headers: Object.fromEntries(result.headers.entries()),
+    base64Body: base64Encode(new Uint8Array(body)),
+  };
+}
+
+export function sandboxFetchSyscalls(): SysCallMapping {
+  return {
+    "sandboxFetch.fetch": (
+      _ctx,
+      url: string,
+      options?: SandboxFetchRequest,
+    ): Promise<SandboxFetchResponse> => {
+      return sandboxFetch(url, options);
+    },
+  };
+}