From 1a811e528fdab2648aa43841ee23661ea9a9c17f Mon Sep 17 00:00:00 2001
From: Chau Tran <nartc7789@gmail.com>
Date: Mon, 11 Jan 2021 11:11:31 -0600
Subject: [PATCH] feat(nestjs): add MapInterceptor

---
 packages/nestjs/src/index.ts                  |  1 +
 packages/nestjs/src/lib/interceptors/index.ts |  1 +
 .../src/lib/interceptors/map.interceptor.ts   | 71 +++++++++++++++++++
 .../src/lib/interceptors/memoize.util.ts      | 21 ++++++
 4 files changed, 94 insertions(+)

diff --git a/packages/nestjs/src/index.ts b/packages/nestjs/src/index.ts
index 20833a4e4..6dea53ce2 100644
--- a/packages/nestjs/src/index.ts
+++ b/packages/nestjs/src/index.ts
@@ -2,3 +2,4 @@ export * from './lib/automapper.module';
 export * from './lib/interfaces';
 export * from './lib/di';
 export * from './lib/abstracts';
+export * from './lib/interceptors';
diff --git a/packages/nestjs/src/lib/interceptors/index.ts b/packages/nestjs/src/lib/interceptors/index.ts
index e69de29bb..e852578c9 100644
--- a/packages/nestjs/src/lib/interceptors/index.ts
+++ b/packages/nestjs/src/lib/interceptors/index.ts
@@ -0,0 +1 @@
+export * from './map.interceptor';
diff --git a/packages/nestjs/src/lib/interceptors/map.interceptor.ts b/packages/nestjs/src/lib/interceptors/map.interceptor.ts
index e69de29bb..b934077ef 100644
--- a/packages/nestjs/src/lib/interceptors/map.interceptor.ts
+++ b/packages/nestjs/src/lib/interceptors/map.interceptor.ts
@@ -0,0 +1,71 @@
+import type { MapOptions, Mapper } from '@automapper/types';
+import type {
+  CallHandler,
+  ExecutionContext,
+  NestInterceptor,
+} from '@nestjs/common';
+import { mixin, Optional } from '@nestjs/common';
+import type { Observable } from 'rxjs';
+import { map } from 'rxjs/operators';
+import { InjectMapper } from '../di';
+import { memoize } from './memoize.util';
+
+export const MapInterceptor: (
+  to: unknown,
+  from: unknown,
+  options?: { isArray?: boolean; mapperName?: string } & MapOptions
+) => NestInterceptor = memoize(createMapInterceptor);
+
+function createMapInterceptor(
+  to: unknown,
+  from: unknown,
+  options?: { isArray?: boolean; mapperName?: string }
+): new (...args) => NestInterceptor {
+  const { isArray = false, mapperName, ...mapOptions } = options || {};
+
+  class MixinMapInterceptor implements NestInterceptor {
+    constructor(
+      @Optional() @InjectMapper(mapperName) private readonly mapper: Mapper
+    ) {}
+
+    async intercept(
+      context: ExecutionContext,
+      next: CallHandler
+    ): Promise<Observable<unknown>> {
+      if (!this.mapper || !to || !from) {
+        return next.handle();
+      }
+
+      try {
+        return next.handle().pipe(
+          map((response) => {
+            if (isArray) {
+              if (!Array.isArray(response)) return response;
+              return this.mapper.mapArray(
+                response,
+                // eslint-disable-next-line @typescript-eslint/no-explicit-any
+                to as any,
+                // eslint-disable-next-line @typescript-eslint/no-explicit-any
+                from as any,
+                mapOptions
+              );
+            }
+
+            return this.mapper.map(
+              response,
+              // eslint-disable-next-line @typescript-eslint/no-explicit-any
+              to as any,
+              // eslint-disable-next-line @typescript-eslint/no-explicit-any
+              from as any,
+              mapOptions
+            );
+          })
+        );
+      } catch {
+        return next.handle();
+      }
+    }
+  }
+
+  return mixin(MixinMapInterceptor);
+}
diff --git a/packages/nestjs/src/lib/interceptors/memoize.util.ts b/packages/nestjs/src/lib/interceptors/memoize.util.ts
index e69de29bb..52042be85 100644
--- a/packages/nestjs/src/lib/interceptors/memoize.util.ts
+++ b/packages/nestjs/src/lib/interceptors/memoize.util.ts
@@ -0,0 +1,21 @@
+const defaultKey = 'default';
+
+// eslint-disable-next-line @typescript-eslint/ban-types
+export function memoize(fn: Function) {
+  const cache = {};
+  return (...args) => {
+    const n =
+      args.reduce(
+        (key, arg) =>
+          key.concat('|', typeof arg === 'string' ? arg : arg.toString()),
+        ''
+      ) || defaultKey;
+    if (n in cache) {
+      return cache[n];
+    }
+
+    const result = n === defaultKey ? fn() : fn(...args);
+    cache[n] = result;
+    return result;
+  };
+}