# ERP System Agent Guidelines

This document provides instructions for coding agents working on the ERP System repository.

## 1. Build, Lint, and Test

### Build
To build the application:
```bash
go build -o erp_system main.go
```
To run the application locally:
```bash
go run main.go
```
The server defaults to port `1337`.

### Test
Run all tests:
```bash
go test ./...
```
Run a specific test package:
```bash
go test ./internal/handlers/...
```
Run a single specific test function:
```bash
# Pattern: go test -v <package_path> -run <TestNameRegex>
go test -v ./internal/handlers -run TestLoginSubmit
```

### Lint / Verify
Run standard Go vetting:
```bash
go vet ./...
```
Format code (always run before committing):
```bash
go fmt ./...
```

## 2. Code Style & Conventions

### General
- **Language:** Go 1.25.6+
- **Formatting:** Strictly adhere to `gofmt` standards.
- **Naming:** 
  - Use `PascalCase` for exported structs, fields, and functions.
  - Use `camelCase` for unexported (private) identifiers.
  - Keep variable names short but descriptive (e.g., `req` vs `r` is fine if context is clear, but `userRequest` is better for complex scopes).

### Project Structure
- `main.go`: Application entry point, router setup, dependency injection.
- `internal/`: Private application code.
  - `database/`: DB initialization and helpers.
  - `handlers/`: HTTP handlers.
  - `models/`: Data structs and business logic/DB queries.
  - `middleware/`: HTTP middleware (Auth, etc.).
- `templates/`: HTML templates (server-side rendered).

### Imports
Group imports into three blocks separated by a newline:
1. Standard library (e.g., `"net/http"`, `"os"`)
2. Third-party packages (e.g., `"github.com/gorilla/sessions"`)
3. Internal project packages (e.g., `"erp_system/internal/models"`)

Example:
```go
import (
	"log"
	"net/http"

	"github.com/gorilla/sessions"

	"erp_system/internal/models"
)
```

### Error Handling
- **Explicit Checks:** Always check errors. `if err != nil { ... }`.
- **Handlers:** Use `http.Error(w, err.Error(), http.Status...)` to return errors to the client.
- **Logging:** Log critical errors on the server side using `log.Printf` or similar before returning HTTP 500.

### HTTP & Routing
- Use Go's standard `net/http` `ServeMux` with Go 1.22+ routing patterns (e.g., `mux.Handle("GET /path/{id}", ...)`).
- **HTMX:** The application uses HTMX.
  - Check for `HX-Request` header to differentiate full page loads vs partials.
  - Use `HX-Redirect` header for client-side redirection when handling HTMX requests.
  - Render partial templates when appropriate.

### Database
- Use `internal/models` for all database interactions.
- Pass the database connection (`*sql.DB`) or a wrapping struct to handlers via dependency injection (see `Handler` struct in `main.go`).

## 3. Cursor / Copilot Rules
(No specific Cursor or Copilot rules found in the repository yet. Adhere to the conventions above.)