callback-to-observable.ts

callback-to-observable.ts

import { Inject, Injectable } from '@nestjs/common';
import { from, Observable } from 'rxjs';

/**
 * Костыль который превращает функции сервиса с калбак аргументом в обзервабл,
 * для поддержки типизации в тестах
 *
 * @param service сервис созданный через загрузку прото файла (GRPC.loadPackageDefinition)
 */
// tslint:disable-next-line: typedef
export function callbackToObservable<T = Observable<any>>(service: T, showErrors = true) {
    return new Proxy(
        {},
        {
            // tslint:disable-next-line: typedef
            get(target, name) {
                // tslint:disable-next-line: typedef
                return function() {
                    if (arguments.length === 0) {
                        return from(
                            new Promise((resolve, reject) => {
                                try {
                                    service[name](callback(name, reject, resolve, showErrors));
                                } catch (error) {
                                    callback(name, reject, resolve, showErrors)(error, null);
                                }
                            })
                        );
                    }
                    if (arguments.length === 1) {
                        return from(
                            new Promise((resolve, reject) => {
                                try {
                                    service[name](arguments[0], callback(name, reject, resolve, showErrors));
                                } catch (error) {
                                    callback(name, reject, resolve, showErrors)(error, null);
                                }
                            })
                        );
                    }
                    if (arguments.length === 2) {
                        return from(
                            new Promise((resolve, reject) => {
                                try {
                                    service[name](arguments[0], arguments[1], callback(name, reject, resolve, showErrors));
                                } catch (error) {
                                    callback(name, reject, resolve, showErrors)(error, null);
                                }
                            })
                        );
                    }
                    if (arguments.length === 3) {
                        return from(
                            new Promise((resolve, reject) => {
                                try {
                                    service[name](arguments[0], arguments[1], arguments[2], callback(name, reject, resolve, showErrors));
                                } catch (error) {
                                    callback(name, reject, resolve, showErrors)(error, null);
                                }
                            })
                        );
                    }
                    if (arguments.length === 4) {
                        return from(
                            new Promise((resolve, reject) => {
                                try {
                                    service[name](arguments[0], arguments[1], arguments[2], arguments[3], callback(name, reject, resolve, showErrors));
                                } catch (error) {
                                    callback(name, reject, resolve, showErrors)(error, null);
                                }
                            })
                        );
                    }

                    // эта штука не работает, пришлось вызывать явно - выше ифы
                    return from(
                        new Promise((resolve, reject) => {
                            try {
                                service[name].apply(null, [...Array.from(arguments), callback(name, reject, resolve, showErrors)]);
                            } catch (error) {
                                callback(name, reject, resolve, showErrors)(error, null);
                            }
                        })
                    );
                };
            }
        }
    ) as T;

    function callback(name: string | number | symbol, reject: (reason?: any) => void, resolve: (value?: unknown) => void, showCallbackErrors: boolean): any {
        return (err, res) => {
            setTimeout(() => {
                if (err) {
                    if (showCallbackErrors) {
                        console.error(`Error in run method "${String(name)}"`);
                    }
                    reject(err);
                } else {
                    resolve(res);
                }
            }, 1000);
        };
    }
}