feat: get transformer from TransformerService

Author: sgomez

src/errors/index.ts

@@ -1 +1,2 @@
 export * from './key-not-found.error';
+export * from './transformer-not-found.error';

src/errors/transformer-not-found.error.ts

@@ -0,0 +1,5 @@
+export class TransformerNotFoundError extends Error {
+  public static withType(type: string) {
+    return new TransformerNotFoundError(`Missed ${type} event map transformer`);
+  }
+}

src/services/transformer.service.ts

@@ -1,13 +1,15 @@
+import { ResolvedEvent } from '@eventstore/db-client';
 import { Injectable } from '@nestjs/common';
 import { ModulesContainer } from '@nestjs/core';
 
-import { TransformerRepo } from '../interfaces/transformer.type';
+import { TransformerNotFoundError } from '../errors';
+import { Transformer, TransformerRepo } from '../interfaces';
 
 export const EVENT_STORE_TRANSFORMERS_TOKEN = 'EVENT_STORE_TRANSFORMERS_TOKEN';
 
 @Injectable()
 export class TransformerService {
-  public readonly repo: TransformerRepo;
+  private readonly repo: TransformerRepo;
 
   constructor(private readonly modules: ModulesContainer) {
     const transformers = [...this.modules.values()]
@@ -17,4 +19,17 @@ export class TransformerService {
 
     this.repo = Object.fromEntries(transformers);
   }
+
+  public getTransformerToEvent(
+    resolvedEvent: ResolvedEvent,
+  ): Transformer | null {
+    const type = resolvedEvent.event.type;
+
+    const transformer = this.repo[type];
+    if (!transformer) {
+      throw TransformerNotFoundError.withType(type);
+    }
+
+    return transformer;
+  }
 }