refactor(gateway): share server-method param validation

src/gateway/server-methods/validation.ts

@@ -0,0 +1,27 @@
+import type { ErrorObject } from "ajv";
+import type { RespondFn } from "./types.js";
+import { ErrorCodes, errorShape, formatValidationErrors } from "../protocol/index.js";
+
+export type Validator<T> = ((params: unknown) => params is T) & {
+  errors?: ErrorObject[] | null;
+};
+
+export function assertValidParams<T>(
+  params: unknown,
+  validate: Validator<T>,
+  method: string,
+  respond: RespondFn,
+): params is T {
+  if (validate(params)) {
+    return true;
+  }
+  respond(
+    false,
+    undefined,
+    errorShape(
+      ErrorCodes.INVALID_REQUEST,
+      `invalid ${method} params: ${formatValidationErrors(validate.errors)}`,
+    ),
+  );
+  return false;
+}