From 2d54538d8193475b07fcdbd961ca7feb0be3517b Mon Sep 17 00:00:00 2001
From: imfozilbek <fozilbek.samiyev@gmail.com>
Date: Sun, 23 Nov 2025 21:43:38 +0500
Subject: [PATCH] feat(core): add application layer components

Add application layer:
- UseCase base class for use cases
- ResponseDto for standardized responses
- Mapper for domain-DTO conversion
---
 .../core/src/application/dtos/ResponseDto.ts  | 31 +++++++++++++++++++
 packages/core/src/application/index.ts        |  3 ++
 .../core/src/application/interfaces/.gitkeep  |  0
 .../core/src/application/mappers/Mapper.ts    | 20 ++++++++++++
 .../core/src/application/use-cases/UseCase.ts | 13 ++++++++
 5 files changed, 67 insertions(+)
 create mode 100644 packages/core/src/application/dtos/ResponseDto.ts
 create mode 100644 packages/core/src/application/index.ts
 create mode 100644 packages/core/src/application/interfaces/.gitkeep
 create mode 100644 packages/core/src/application/mappers/Mapper.ts
 create mode 100644 packages/core/src/application/use-cases/UseCase.ts

diff --git a/packages/core/src/application/dtos/ResponseDto.ts b/packages/core/src/application/dtos/ResponseDto.ts
new file mode 100644
index 0000000..1a1e587
--- /dev/null
+++ b/packages/core/src/application/dtos/ResponseDto.ts
@@ -0,0 +1,31 @@
+/**
+ * Standard response wrapper for use cases
+ */
+export interface IResponseDto<T> {
+    success: boolean;
+    data?: T;
+    error?: string;
+    timestamp: Date;
+}
+
+export class ResponseDto<T> implements IResponseDto<T> {
+    public readonly success: boolean;
+    public readonly data?: T;
+    public readonly error?: string;
+    public readonly timestamp: Date;
+
+    private constructor(success: boolean, data?: T, error?: string) {
+        this.success = success;
+        this.data = data;
+        this.error = error;
+        this.timestamp = new Date();
+    }
+
+    public static ok<T>(data: T): ResponseDto<T> {
+        return new ResponseDto<T>(true, data);
+    }
+
+    public static fail<T>(error: string): ResponseDto<T> {
+        return new ResponseDto<T>(false, undefined, error);
+    }
+}
\ No newline at end of file
diff --git a/packages/core/src/application/index.ts b/packages/core/src/application/index.ts
new file mode 100644
index 0000000..ea26bfd
--- /dev/null
+++ b/packages/core/src/application/index.ts
@@ -0,0 +1,3 @@
+export * from './use-cases/UseCase';
+export * from './dtos/ResponseDto';
+export * from './mappers/Mapper';
diff --git a/packages/core/src/application/interfaces/.gitkeep b/packages/core/src/application/interfaces/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/packages/core/src/application/mappers/Mapper.ts b/packages/core/src/application/mappers/Mapper.ts
new file mode 100644
index 0000000..40644a9
--- /dev/null
+++ b/packages/core/src/application/mappers/Mapper.ts
@@ -0,0 +1,20 @@
+/**
+ * Generic mapper interface for converting between domain entities and DTOs
+ */
+export interface IMapper<TDomain, TDto> {
+    toDto(domain: TDomain): TDto;
+    toDomain(dto: TDto): TDomain;
+}
+
+export abstract class Mapper<TDomain, TDto> implements IMapper<TDomain, TDto> {
+    public abstract toDto(domain: TDomain): TDto;
+    public abstract toDomain(dto: TDto): TDomain;
+
+    public toDtoList(domains: TDomain[]): TDto[] {
+        return domains.map((domain) => this.toDto(domain));
+    }
+
+    public toDomainList(dtos: TDto[]): TDomain[] {
+        return dtos.map((dto) => this.toDomain(dto));
+    }
+}
diff --git a/packages/core/src/application/use-cases/UseCase.ts b/packages/core/src/application/use-cases/UseCase.ts
new file mode 100644
index 0000000..6301e69
--- /dev/null
+++ b/packages/core/src/application/use-cases/UseCase.ts
@@ -0,0 +1,13 @@
+/**
+ * Base interface for all use cases
+ */
+export interface IUseCase<TRequest, TResponse> {
+    execute(request: TRequest): Promise<TResponse>;
+}
+
+/**
+ * Abstract base class for use cases
+ */
+export abstract class UseCase<TRequest, TResponse> implements IUseCase<TRequest, TResponse> {
+    public abstract execute(request: TRequest): Promise<TResponse>;
+}
\ No newline at end of file