let indent: string = '';
const logs: string[] = [];

let logging: boolean = false;
export function log(): void {
  logging = true;
}

export function withLog<T>(before: string, f: () => T, after: (v: T) => string): T {
  if (!logging) {
    return f();
  }

  logs.push(`${indent}${before}`);
  const l = logs.length;
  indent += '  ';
  const result = f();
  indent = indent.slice(2);
  if (logs.length === l) {
    logs[logs.length - 1] += ` ${after(result)}`;
  } else {
    logs.push(`${indent}${after(result)}`);
  }
  return result;
}

export function dump() {
  console.log('\n\nExecution log:');
  console.log(logs.join('\n'));
}