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import type { MakeProm, λ } from "./types.ts";import noop from "./noop.ts";
/** * Creates a `queue` function that accepts a function as it's only parameter. * When `queue` is invoked, the passed in function is executed after the last * function passed to `queue` has finished executing. The `queue` function * returns the result of the passed in function asynchronously. * * Reading `queue.done` is `true` if no functions are currently executing / * scheduled and otherwise a promise that resolves once the last function has * stopped executing and no futher functions are queued. * * @example * ``` * const queue = createQueue() * * queue(async () => { *   console.log('start a') *   await delay() *   return 'end a' * }).then(console.log) * * queue(async () => { *   console.log('start b') *   await delay() *   return 'end b' * }).then(console.log) * * queue(async () => { *   console.log('start c') *   await delay() *   return 'end c' * }).then(console.log) * * await queue.done * * // start a * // end a * // start b * // end b * // start c * // end c * ``` */const createQueue = (): Queue => {  let last: Promise<unknown> | null = null;
  const queued = (fun: λ) =>    last = (last ?? Promise.resolve()).catch(noop).then(fun).finally(      () => {        last = null;      },    );
  return Object.defineProperty(queued, "done", {    get: () => last?.catch(noop).then(noop) ?? true,  }) as Queue;};
export default createQueue;
type Queue = (<T extends λ<[], unknown>>(fun: T) => MakeProm<ReturnType<T>>) & {  done: Promise<void> | true;};