# API Folder Structure

# Directories

A description of top-level directories.

Directory	Description
`/env`	For ENV files.
`/src/server`	Only for server related handling.
`/src/server/controller`	Holds all the supported HTTP endpoints.
`/src/app`	This directory has all app-related files.
`/src/app/constants`	For app constants.
`/src/app/contract`	A contract consumers will use for business logic.
`/src/app/decorators`	We use few decorators to enhance a method without modifying its interface.
`src/app/errors`	We have extended `Error` class for more custom handling.
`src/app/models`	These are TypeORM models. Basically a representation of a MySQL table.
`src/app/repositories`	Contains repositories which are used to perform DB operations through TypeORM.
`src/app/services`	For all services.
`src/app/transformers`	Holds methods which transform a data into a contract.
`src/app/utils`	Contains both contextual as well as pure methods.
`/dist`	For build files.

# Core Layers

There are 5 core layers in this project and each layer has a responsibility.

Controller
Service
Repository
Model
Transformer

%%{init: {} }%%
graph LR
    A[Controller] --> B[Service]
    B[Service] --> C[Repository]
    C[Repository] --> D[Model] --> C --> B --> E[Transformer] --> B --> A

Kindly go through this blog.

Handles incoming request and only interacts with service. Can be found in src/server/controller

These are pure methods and don't accept any global or contextual values/params. Their responsibility is to return the required data to any consumer not specifically just the controller. Services interact with

repositories for fetching data
transformers for tranforming data into a contract

Can be found in src/app/services

Their responsibility is to do DB-related operations. Can be found in src/app/repositories

Specifies DB table contract. Can be found in src/app/models

Since each endpoint returns data in form of a contract, it is transformer's responsibility is to prepare that contract. Can be found in src/app/transformers