feat: first pass at native plugins (#3372)

cli/js/plugins.ts

@@ -0,0 +1,66 @@
+import { sendSync } from "./dispatch_json.ts";
+import { OP_OPEN_PLUGIN, setPluginAsyncHandler } from "./dispatch.ts";
+import { core } from "./core.ts";
+
+export interface AsyncHandler {
+  (msg: Uint8Array): void;
+}
+
+interface PluginOp {
+  dispatch(
+    control: Uint8Array,
+    zeroCopy?: ArrayBufferView | null
+  ): Uint8Array | null;
+  setAsyncHandler(handler: AsyncHandler): void;
+}
+
+class PluginOpImpl implements PluginOp {
+  constructor(private readonly opId: number) {}
+
+  dispatch(
+    control: Uint8Array,
+    zeroCopy?: ArrayBufferView | null
+  ): Uint8Array | null {
+    return core.dispatch(this.opId, control, zeroCopy);
+  }
+
+  setAsyncHandler(handler: AsyncHandler): void {
+    setPluginAsyncHandler(this.opId, handler);
+  }
+}
+
+// TODO(afinch7): add close method.
+
+interface Plugin {
+  ops: {
+    [name: string]: PluginOp;
+  };
+}
+
+class PluginImpl implements Plugin {
+  private _ops: { [name: string]: PluginOp } = {};
+
+  constructor(private readonly rid: number, ops: { [name: string]: number }) {
+    for (const op in ops) {
+      this._ops[op] = new PluginOpImpl(ops[op]);
+    }
+  }
+
+  get ops(): { [name: string]: PluginOp } {
+    return Object.assign({}, this._ops);
+  }
+}
+
+interface OpenPluginResponse {
+  rid: number;
+  ops: {
+    [name: string]: number;
+  };
+}
+
+export function openPlugin(filename: string): Plugin {
+  const response: OpenPluginResponse = sendSync(OP_OPEN_PLUGIN, {
+    filename
+  });
+  return new PluginImpl(response.rid, response.ops);
+}