service.ts

/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.dev/license
 */

import {AbstractType, Type} from '../interface/type';
import {makeDecorator, TypeDecorator} from '../util/decorators';
import {compileService} from './jit/service';

/**
 * Type of the Service decorator / constructor function.
 *
 * @publicApi
 */
export interface ServiceDecorator {
  /**
   * Decorator that marks a class as a service and makes it automatically available
   * in the dependency injection system.
   *
   * @see [Introduction to Services and DI](guide/di)
   * @see [Creating and using services](guide/di/creating-and-using-services)
   * @see [Defining dependency providers](guide/di/defining-dependency-providers)
   */
  (): TypeDecorator;

  /**
   * When `autoProvided` is set to `false`, the service won't be exposed to the dependency
   * injection system automatically. It is up to the user to expose it in a providers list.
   */
  (options: {autoProvided: false}): TypeDecorator;

  /**
   * Creates a service that is automatically provided and uses
   * the value returned from the `factory` function.
   */
  <T>(options: {
    autoProvided?: true;
    factory: () => T;
  }): <C extends Type<unknown> | AbstractType<unknown>>(
    target: C,
  ) => C extends Type<unknown> ? Type<T> : abstract new (...args: any[]) => T;

  /**
   * Creates a service that is automatically provided.
   */
  (options?: {autoProvided?: true}): TypeDecorator;
}

/**
 * Type of the Service metadata.
 *
 * @publicApi
 */
export interface Service {
  /**
   * Determines whether the service should be provided automatically or by the user.
   * Defaults to `true`.
   */
  autoProvided?: boolean;

  /**
   * A function to invoke to create a value for this service.
   */
  factory?: () => unknown;
}

/**
 * Service decorator and metadata.
 *
 * @Annotation
 * @publicApi
 */
export const Service: ServiceDecorator = makeDecorator(
  'Service',
  undefined,
  undefined,
  undefined,
  (type: Type<unknown>, meta: Service | undefined) => compileService(type, meta),
);