Tutorial
Step-by-step guide of building back-end services for car washing web application using @imqueue.
For those who prefer to learn by example.
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Chapter 4. Other Services
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Chapter 4. Other Services
At this point it should be already clear, that building @imqueue
services is an easy process. To make our app fully functional we need
to develop two more services: Car
and TimeTable
.
Building them does not differ too much of what have been done for two
previous services - User
and Auth
, so it is suggested to work on
them as your homework. Or you can simply refer to their
source
code at GitHub.
Here are the requirements.
Car Service Requirements
- It should utilize data about cars from any available data source, for example, this one publicly available vehicle database
- It should implement in-memory data storage with data update each 24 hours from a selected remote vehicle database.
- It should Provide access to the list of car object containing the
following data (
CarObject
):- Unique car identifier (
id: string
) - Car manufacturer name (
make: string
) - Car model name (
model: string
) - Car years of manufacturing (
years: number[]
) - Car type (
type: 'mini' | 'midsize' | 'large'
)
- Unique car identifier (
Here is the interface of the service which is expected to be implemented:
/**
* Returns a list of car manufacturers (car brands)
*
* @return {string[]} - list of known brands
*/
public brands(): string[];
/**
* Returns car object by its identifier or if multiple identifiers given
* as array of identifiers - returns a list of car objects.
*
* @param {string | string[]} id - car identifier
* @param {string[]} [selectedFields] - fields to return
* @return {Partial<CarObject> | Partial<CarObject|null>[] | null} - found object or null otherwise
*/
public fetch(
id: string | string[],
selectedFields?: string[]
): Partial<CarObject> | Partial<CarObject|null>[] | null;
/**
* Returns list of known cars for a given brand
*
* @param {string} brand - car manufacturer (brand) name
* @param {string[]} [selectedFields] - fields to return
* @param {string} [sort] - sort field, by default is 'model'
* @param {'asc' | 'desc'} [dir] - sort direction, by default is 'asc' - ascending
* @return {Partial<CarObject>[]} - list of found car objects
*/
public list(
brand: string,
selectedFields?: string[],
sort: string = 'model', dir: 'asc' | 'desc' = 'asc'
): Partial<CarObject>[];
For any details and help about implementation, please, refer to corresponding source code.
What to think about: In-memory data synchronization when running multiple instance of services.
TimeTable Service Requirements
That should be a central service. Let’s consider using relational database as a data storage engine, for example, PostgreSQL or any other at your choice with Sequelize ORM library on top.
Here is the interface expected to be built for this service:
/**
* Returns a list of reservations starting from a given time (or from
* current time if omitted)
*
* @param {string} [date] - date to select reservations for, if not passed
* current date is used
* @param {string[]} [fields] - fields to select for reservations data list
* @return {Promise<Reservation[]>} - list of found reservations
*/
public async list(date?: string, fields?: string[]): Promise<Reservation[]>;
/**
* Fetches and returns single reservation record by its identifier
*
* @param {string} id - reservation identifier to fetch
* @param {string[]} [fields] - fields to select for reservation data object
* @return {Promise<Reservation|null>} - reservation data object or null if not found
*/
public async fetch(id: string, fields?: string[]): Promise<Partial<Reservation>|null>;
/**
* Makes a given reservation or throws a proper error
* if action is not possible
*
* @param {Reservation} reservation - reservation data structure
* @param {string[]} [fields] - fields to select for updated reservations list
* @return {Promise<Reservation[]>} - updated reservations list
*/
public async reserve(reservation: Reservation, fields?: string[]): Promise<Reservation[]>;
/**
* Cancels reservation at a given time
*
* @param {string} id - reservation identifier
* @param {string[]} [fields] - fields to select for updated reservations list
* @return {Promise<Reservation[]>} - updated reservations list
*/
public async cancel(id: string, fields?: string[]): Promise<Reservation[]>;
/**
* Returns reservation time-table configuration settings
*
* @return {Promise<TimeTableOptions>} - reservations time-table options
*/
public async config(): Promise<TimeTableOptions>;
Where the following complex types exposed as well:
Reservation
:
- id - reservation record identifier
- carId - user car identifier
- userId - user identifier
- type - washing type selected for this reservation, one of
'fast'|'std'|'full'
- duration - is a range of start time/end time
TimeTableOptions
:
- start - washing station start working time in format HH:MM
- end - washing station end working time in format HH:MM
- baseTime - duration options for different types of washing, should be a list of
{ key: 'fast'|'std'|'full', /* or whatever else... */ title: string, /* human-readable definition title for washing type */ duration: number, /* in minutes */ }
What to think about: a) consider exposing sequelize model as a complex-type of @imqueue service; b) consider options as a configurable database records as well.
Any way, the complete source code is available on GitHub
Go to the next chapter - API Service. Integration