update README.md for describing the project

README.md

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-# nestled
+# Nestled
+
+**A family expense tracking backend service** for managing household finances, tracking expenses, and setting budget alerts on expense categories.
+
+> ⚠️ **Status**: Implementation in progress
+
+## Overview
+
+Nestled is the backend service that enables families to:
+
+- Track income and expenses
+- Organize transactions by categories
+- Define and monitor budgets for each category
+- Receive alerts when spending approaches or exceeds budget limits
+- View financial reports and spending insights
+
+## Tech Stack
+
+- **Language**: Go 1.26.0
+- **Framework**: [Gin Web Framework](https://github.com/gin-gonic/gin)
+- **Database**: PostgreSQL 17
+- **Migrations**: [golang-migrate](https://github.com/golang-migrate/migrate)
+- **Testing**: Go's built-in testing + [testify](https://github.com/stretchr/testify) + [testcontainers](https://github.com/testcontainers/testcontainers-go)
+- **ORM**: [sqlx](https://github.com/jmoiron/sqlx)
+
+## Prerequisites
+
+Before you begin, ensure you have installed:
+
+- **Go**: 1.26.0 or later ([download](https://golang.org/dl/))
+- **PostgreSQL**: 17 or later (for local development)
+  - OR **Docker & Docker Compose** (for containerized setup)
+- **migrate CLI**: For running database migrations locally ([installation](https://github.com/golang-migrate/migrate#cli-usage))
+
+## Getting Started
+
+### 1. Clone the repository
+
+```bash
+git clone <repo-url>
+cd nestled
+```
+
+### 2. Set up environment variables
+
+Copy the default configuration:
+
+```bash
+cp config.yml .env
+```
+
+Or create a `.env` file with your database credentials:
+
+```env
+DB_HOST=localhost
+DB_PORT=5432
+DB_USER=postgres
+DB_PASSWORD=password
+DB_NAME=nestled_db
+GIN_MODE=debug
+```
+
+### 3. Install dependencies
+
+```bash
+go mod download
+go mod tidy
+```
+
+## Building the Application
+
+### Build with Make
+
+```bash
+make build
+```
+
+This compiles the application and outputs a binary to `bin/nestled`.
+
+### Build with Go directly
+
+```bash
+go build -o bin/nestled cmd/main/main.go
+```
+
+## Running the Application
+
+### Option 1: Local Development (with local PostgreSQL)
+
+#### Start PostgreSQL (if not running)
+
+```bash
+# Using Homebrew on macOS
+brew services start postgresql
+
+# Or using Docker
+docker run -d \
+  --name nestled-db \
+  -e POSTGRES_USER=postgres \
+  -e POSTGRES_PASSWORD=password \
+  -e POSTGRES_DB=nestled_db \
+  -p 5432:5432 \
+  postgres:17
+```
+
+#### Run migrations
+
+```bash
+make migrate-up
+```
+
+#### Start the application
+
+```bash
+make run
+```
+
+The API will be available at `http://localhost:8080`
+
+### Option 2: Docker Compose (Recommended)
+
+Start all services (PostgreSQL, migrations, and the app) with one command:
+
+```bash
+docker-compose up --build
+```
+
+This will:
+1. Start PostgreSQL database
+2. Run all pending migrations
+3. Start the application on port 8080
+
+Stop all services:
+
+```bash
+docker-compose down
+```
+
+View logs:
+
+```bash
+docker-compose logs -f app
+```
+
+## Running Tests
+
+### Run all tests
+
+```bash
+make test
+```
+
+### Run specific package tests
+
+```bash
+go test ./internal/handlers -v
+```
+
+### Run tests with coverage
+
+```bash
+go test ./... -cover
+```
+
+Integration tests use [testcontainers](https://www.testcontainers.org/) to automatically spin up a PostgreSQL container, run migrations, and tear down after completion.
+
+## Database Migrations
+
+Migrations are SQL scripts stored in the `migrations/` directory and are automatically versioned.
+
+### Run pending migrations
+
+```bash
+make migrate-up
+```
+
+Or with environment variables manually:
+
+```bash
+migrate -path migrations/ -database "postgres://postgres:password@localhost:5432/nestled_db?sslmode=disable" up
+```
+
+### Rollback last migration
+
+```bash
+make migrate-down
+```
+
+### Create a new migration
+
+```bash
+make migrate-create name=add_user_preferences
+```
+
+This creates two files:
+- `migrations/000003_add_user_preferences.up.sql` (applies the change)
+- `migrations/000003_add_user_preferences.down.sql` (reverts the change)
+
+## Project Structure
+
+```
+nestled/
+├── cmd/
+│   └── main/
+│       └── main.go                 # Application entry point
+├── internal/
+│   ├── config/                     # Configuration management
+│   ├── crypto/                     # Cryptography utilities
+│   ├── database/                   # Database setup
+│   ├── dto/                        # Data transfer objects
+│   ├── errors/                     # Error definitions
+│   ├── handlers/                   # HTTP route handlers
+│   ├── model/                      # Domain models
+│   ├── repositories/               # Data access layer
+│   ├── routes/                     # Route definitions
+│   ├── services/                   # Business logic
+│   └── testhelpers/                # Testing utilities
+├── migrations/                     # SQL migrations
+├── bin/                            # Build outputs
+├── config.yml                      # Configuration template
+├── docker-compose.yml              # Docker Compose setup
+├── Dockerfile                      # Application Docker image
+├── Makefile                        # Build and run targets
+├── go.mod                          # Go module definition
+└── README.md                       # This file
+```
+
+## Common Tasks
+
+### Lint the codebase
+
+```bash
+make lint
+```
+
+Requires [golangci-lint](https://golangci-lint.run/).
+
+### Clean build artifacts
+
+```bash
+make clean
+```
+
+### Update dependencies
+
+```bash
+make tidy
+```
+
+## API Endpoints
+
+The API is built with Gin and provides RESTful endpoints for:
+
+- **Health Check**: `GET /health`
+- **User Management**: Registration, authentication (in development)
+- **Expense Tracking**: CRUD operations for expenses
+- **Budget Management**: Set and monitor budgets per category
+- **Reports**: Financial summaries and insights (planned)
+
+See the handlers in `internal/handlers/` for detailed endpoint implementations.
+
+## Development
+
+### Git Workflow
+
+```bash
+# Create a feature branch
+git checkout -b feature/your-feature-name
+
+# Make changes, commit, and push
+git add .
+git commit -m "feat: add your feature"
+git push origin feature/your-feature-name
+
+# Create a pull request
+```
+
+### Code Style
+
+This project follows Go conventions:
+- Format code with `go fmt`
+- Follow [Effective Go](https://golang.org/doc/effective_go)
+- Write clear, idiomatic Go
+
+## Troubleshooting
+
+### Migration failures in tests
+
+If you see `"unknown driver file"` errors during tests, ensure the test helpers use the correct import path for golang-migrate (v4-compatible).
+
+### PostgreSQL connection refused
+
+- Verify PostgreSQL is running: `psql -U postgres`
+- Check environment variables match your database setup
+- Ensure the database exists: `createdb nestled_db`
+
+## Contributing
+
+1. Create a feature branch
+2. Make your changes and write/update tests
+3. Run `make test` and `make lint` to verify
+4. Submit a pull request
+
+## License
+
+See [LICENSE](LICENSE) for details.
+
+## Support
+
+For issues or questions, please open an issue on the repository.