villa/src/chainable.ts

Promise utilities for async/await-ready environment.

import {
  EachHandler,
  EveryHandler,
  FilterHandler,
  FindHandler,
  MapTransformer,
  ParallelHandler,
  RaceTransformer,
  ReduceTransformer,
  Resolvable,
  SomeHandler,
  each,
  every,
  filter,
  find,
  findIndex,
  map,
  reduce,
  reduceRight,
  some,
} from '.';

export class Chainable<T> extends Promise<T[]> {
  each(handler: EachHandler<T>): Promise<boolean> {
    let chainable = this.then(values => each(values, handler));
    return Promise.resolve(chainable);
  }

  every(handler: EveryHandler<T>): Promise<boolean> {
    let chainable = this.then(values => every(values, handler));
    return Promise.resolve(chainable);
  }

  filter(handler: FilterHandler<T>): Chainable<T> {
    return this.then(values => filter(values, handler)) as Chainable<T>;
  }

  find(handler: FindHandler<T>): Promise<T | undefined> {
    let chainable = this.then(values => find(values, handler));
    return Promise.resolve(chainable);
  }

  findIndex(handler: FindHandler<T>): Promise<number> {
    let chainable = this.then(values => findIndex(values, handler));
    return Promise.resolve(chainable);
  }

  map<TResult>(
    transformer: MapTransformer<T, TResult>,
    concurrency?: number,
  ): Chainable<TResult> {
    return this.then(values =>
      map(values, transformer, concurrency),
    ) as Chainable<TResult>;
  }

  parallel(handler: ParallelHandler<T>, concurrency?: number): Promise<void> {
    let chainable = this.then(values => map(values, handler, concurrency));
    return Promise.resolve(chainable).then(() => undefined);
  }

  race<TResult>(transformer: RaceTransformer<T, TResult>): Promise<TResult> {
    let chainable = this.then(values => Promise.race(values.map(transformer)));
    return Promise.resolve(chainable);
  }

  reduce<TResult>(
    transformer: ReduceTransformer<T, TResult[]>,
    initial: TResult[],
  ): Chainable<TResult>;
  reduce<TResult>(
    transformer: ReduceTransformer<T, TResult>,
    initial: TResult,
  ): Promise<TResult>;
  reduce(transformer: ReduceTransformer<T, T>): Promise<T>;
  reduce(
    transformer: ReduceTransformer<any, any>,
    ...args: any[]
  ): Chainable<any> | Promise<any> {
    let chainable = this.then(values =>
      (reduce as Function)(values, transformer, ...args),
    );
    return Array.isArray(args[0])
      ? (chainable as Chainable<any>)
      : Promise.resolve(chainable);
  }

  reduceRight<TResult>(
    transformer: ReduceTransformer<T, TResult[]>,
    initial: TResult[],
  ): Chainable<TResult>;
  reduceRight<TResult>(
    transformer: ReduceTransformer<T, TResult>,
    initial: TResult,
  ): Promise<TResult>;
  reduceRight(transformer: ReduceTransformer<T, T>): Promise<T>;
  reduceRight(
    transformer: ReduceTransformer<any, any>,
    ...args: any[]
  ): Chainable<any> | Promise<any> {
    let chainable = this.then(values =>
      (reduceRight as Function)(values, transformer, ...args),
    );
    return Array.isArray(args[0])
      ? (chainable as Chainable<any>)
      : Promise.resolve(chainable);
  }

  some(handler: SomeHandler<T>): Promise<boolean> {
    let chainable = this.then(values => some(values, handler));
    return Promise.resolve(chainable);
  }

  static resolve(): Promise<any>;
  static resolve<T>(resolvable: Resolvable<T[]>): Chainable<T>;
  static resolve<T>(resolvable?: Resolvable<T[]>): Chainable<T> {
    return new Chainable<T>(resolve => resolve(resolvable));
  }
}

/**
 * Wrap given resolvable with a chainable derived of built-in promise.
 */
export function chainable<T>(resolvable: Resolvable<T[]>): Chainable<T> {
  return Chainable.resolve(resolvable);
}