ui/src/base/utils.ts

// Copyright (C) 2023 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Return true if value is not nullish - i.e. not null or undefined
// Allows doing the following
//   exists(val) && m('div', val)
// Even if val is a non-nullish falsey value like 0 or ''
export function exists<T>(value: T): value is NonNullable<T> {
  return value !== undefined && value !== null;
}

// Generic result type - similar to Rust's Result<T, E>
export type Result<T, E = {}> =
  | {success: true; result: T}
  | {success: false; error: E};

// Escape characters that are not allowed inside a css selector
export function escapeCSSSelector(selector: string): string {
  return selector.replace(/([!"#$%&'()*+,.\/:;<=>?@[\\\]^`{|}~])/g, '\\$1');
}

// Make field K required in T
export type RequiredField<T, K extends keyof T> = Omit<T, K> &
  Required<Pick<T, K>>;

// The lowest common denoninator between Map<> and WeakMap<>.
// This is just to avoid duplication of the getOrCreate below.
interface MapLike<K, V> {
  get(key: K): V | undefined;
  set(key: K, value: V): this;
}

export function getOrCreate<K, V>(
  map: MapLike<K, V>,
  key: K,
  factory: () => V,
): V {
  let value = map.get(key);
  if (value !== undefined) return value;
  value = factory();
  map.set(key, value);
  return value;
}