App Config API

A simple REST API built with Go (Gin) and PostgreSQL to manage mobile app pages and widgets.

Acts as a configuration backend that lets apps render UI dynamically.

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Tech Stack

• Go (Gin) - lightweight, high-performance HTTP server
• PostgreSQL - reliable relational database
• UUID - globally unique identifiers for entities
• JSONB - flexible storage for dynamic widget configuration
• Raw SQL - clear, explicit queries with minimal abstraction

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Features

Pages

• Create page
• List all pages
• Get single page (with widgets)
• Update page
• Delete page (home page protected)

Widgets

• Add widget to a page
• Update widget
• Delete widget
• Reorder widgets on a page

Validations

• Page name required
• Route must be unique
• Only one home page allowed
• Home page cannot be deleted
• Widget types allowed:
  • banner
  • product_grid
  • text
• Widget config stored as JSONB
• Consistent error response format

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Architecture

This service stores:

• Pages (app screens)
• Widgets (UI components)
• Widget layout order

Mobile apps fetch this configuration and render UI dynamically.

Below is a high-level view of how pages, widgets, and layout configuration flow through the system.

Full Design Overview

The original Excalidraw file is included for reference and can be edited if needed:

You can open it by:

1. Visiting https://excalidraw.com
2. Clicking "Open"
3. Uploading the .excalidraw

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Project Structure

app-config-api/
├── design/
├── images/
├── postman/
├── main.go
├── db.go
├── models.go
├── handlers.go
├── routes.go
├── middleware.go
├── schema.sql
└── README.md

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Run Locally

1) Clone repo

git clone https://github.com/manasa-bhagwat/app-config-api.git
cd app-config-api

2) Create database

Using CLI:

createdb configapp
psql -d configapp -f schema.sql

Or using pgAdmin:

• Create DB: configapp
• Open Query tool.
• Run schema.sql

3) Update DB connection

In db.go:

postgres://username:password@localhost:5432/configapp?sslmode=disable

4) Run server

go run .

Server runs at:

http://localhost:8080

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API Endpoints

Pages

• POST /pages
• GET /pages
• GET /pages/:id
• PUT /pages/:id
• DELETE /pages/:id

Widgets

• POST /pages/:id/widgets
• PUT /widgets/:id
• DELETE /widgets/:id
• POST /pages/:id/widgets/reorder

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Postman Test Flow

Base URL

http://localhost:8080

1) Create Home Page

POST /pages

{
  "name": "Home",
  "route": "/home",
  "is_home": true
}

Save: HOME_PAGE_ID

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2) Create Products Page

POST /pages

{
  "name": "Products",
  "route": "/products",
  "is_home": false
}

Save: PRODUCTS_PAGE_ID

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3) Add Widgets to Home Page

POST /pages/HOME_PAGE_ID/widgets

Banner:

{
  "type": "banner",
  "position": 1,
  "config": {
    "image_url": "https://store.com/sale.jpg",
    "title": "Mega Sale",
    "cta": "Shop Now"
  }
}

Product Grid:

{
  "type": "product_grid",
  "position": 2,
  "config": {
    "collection": "featured",
    "columns": 2
  }
}

Text:

{
  "type": "text",
  "position": 3,
  "config": {
    "content": "Welcome to our store!"
  }
}

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4) Fetch Full Page Config

GET /pages/HOME_PAGE_ID

Returns:

• Page details
• All widgets
• Ordered by position

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5) Reorder Widgets

POST /pages/HOME_PAGE_ID/widgets/reorder

{
  "widget_ids": [
    "TEXT_WIDGET_ID",
    "BANNER_WIDGET_ID",
    "GRID_WIDGET_ID"
  ]
}

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6) Update Widget

PUT /widgets/WIDGET_ID

{
  "type": "banner",
  "position": 1,
  "config": {
    "title": "BIGGEST SALE"
  }
}

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7) Delete Widget

DELETE /widgets/WIDGET_ID

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Postman Collection

A ready-to-use Postman collection export is included in the repository for quick testing of all API endpoints.

File location:

postman/app-config-api.postman_collection.json

To use it:

1. Open Postman
2. Click Import
3. Select the JSON file from the postman/ folder
4. Set the base URL if needed:

http://localhost:8080

This collection contains pre-configured requests for:

• Pages (Create, List, Get, Update, Delete)
• Widgets (Add, Update, Delete)
• Reorder widgets

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Request Logging

Each request logs:

• Method
• Path
• Status
• Response time

Example:

POST /pages | 201 | 2ms
GET /pages | 200 | 1ms