prisma-eventify/src/handlers/bus.handler.ts

Prisma-Eventify is a crucial module designed to facilitate seamless communication between the ORM (Prisma) and the HTTP server (GraphQL | Rest) by employing event-driven development principles.

import path from 'path'
import { EventBus } from 'ts-bus'
import { EventService } from '../services/eventify.service'
import { PrismaService } from './../services/prisma.service'
import { PrismaAPI } from '../types'
import { Prisma, type PrismaClient } from '@prisma/client'
import { ConfigService } from '../services/config.service'
import { DMMF } from '@prisma/generator-helper'
import { EventifyConfig } from '../types/config'

/**
 * @description ** BusHandler **
 * Wrapper class of ts-bus EventBus to allow Eventify automation.
 * */
export class BusHandler {
  private events = {}
  private config: Record<string, () => {}>
  constructor(
    config: EventifyConfig,
    schema = Prisma.dmmf as DMMF.Document,
    private prismaService = new PrismaService(schema),
    private configService = new ConfigService(config),
    private eventService = new EventService(),
    public bus = new EventBus()
  ) {}

  /**
   * @description Imports and subscribes Eventify autogenerated events.
   * @returns {Promise<boolean>} subscription status.
   */
  public async subscribeConfigEvents(): Promise<boolean> {
    try {
      /* Dont do this at home :D */
      this.events = await import(process.cwd() + '/eventify/events')
      this.config = (await import(process.cwd() + '/eventify.config'))?.config

      if (!Object.keys(this.events).length)
        throw new Error('An error occurred while trying to retrieve generated events.')
      if (!Object.keys(this.config).length)
        throw new Error('An error occurred while trying to retrieve eventify.config.ts.')

      Object.entries(this.config).forEach(([event, callback]) => this.bus.subscribe(this.events[event], callback))

      return true
    } catch (err) {
      console.error(err)
      return false
    }
  }

  /**
   * @description Given an event name:
   * - retrieves that event within auto generated event declarations.
   * - retrieves all sub-events (ex. user.email) of the given event (ex. user).
   * - publishes every retrieved event.
   * @param {string} event target event name.
   * @param meta Event metadata injected into the event handler.
   * @returns { boolean } publishment status.
   */
  public publishEvent(event: string, meta: { prisma: PrismaClient; [x: string]: any }): boolean {
    try {
      if (!this.events?.[event]?.eventType) return false
      const { model, field, hook, method } = this.eventService.destructureEventIdentifiers({
        dotCase: this.events[event].eventType,
      })
      if (!this.configService.modelAllowed(model)) return false
      if (model && !field && method && [PrismaAPI.create, PrismaAPI.update, PrismaAPI.delete].includes(method)) {
        /* publish also model fields events */
        const fields = this.prismaService.getModelFields(model)
        fields.forEach(({ name: field }) => {
          if (!this.configService.fieldAllowed(model, field)) return
          const fieldEvent = this.eventService.composeEventIdentifiers({
            model,
            field,
            hook,
            method,
          }).camelCase

          if (this.events[fieldEvent]) this.bus.publish(this.events[fieldEvent](), meta)
        })
      }

      this.bus.publish(this.events[event](), meta)
      return true
    } catch (err) {
      console.error(err)
      return false
    }
  }
}