frontend/src/util.ts

// Like Object.values but with a stronger return type.
export function values<T extends {[key: string]: any}, K extends keyof T>(
  o: T
): Required<T>[K][] {
  return Object.values(o);
}

// Like Object.entries but with a stronger return type.
export function entries<T extends {[key: string]: any}, K extends keyof T>(
  o: T
): [keyof T, Required<T>[K]][] {
  return Object.entries(o);
}

// Wraps text to the given maximum width, preserving existing newlines.
export function wordWrap(text: string, width: number): string {
  function wrap(line: string): string {
    const words = line.split(' ');
    let lineLength = 0;
    const withNewlines = words.map(w => {
      lineLength += w.length + 1;
      if (lineLength > width) {
        lineLength = w.length;
        return '\n' + w;
      }
      return w;
    });
    return withNewlines.join(' ');
  }
  const lines = text.split('\n');
  return lines.map(wrap).join('\n');
}

// A type for timeout IDs.
export type Timeout = ReturnType<typeof setTimeout>;

// Wraps a promise with a timeout, in milliseconds.
export function withTimeout<T>(
  ms: number,
  errMsg: string,
  promise: Promise<T>
): Promise<T> {
  return new Promise((resolve, reject) => {
    const timeout = setTimeout(() => {
      reject(new Error(errMsg));
    }, ms);
    promise.then(
      (res: T) => {
        clearTimeout(timeout);
        resolve(res);
      },
      err => {
        clearTimeout(timeout);
        reject(err);
      }
    );
  });
}