# Architecture

## Two-Server Design

The application runs two separate HTTP servers from a single binary:

- **Public server** (default `:8080`) — Customer-facing UI: registration, login, ticket management, OAuth callbacks, Forgejo webhooks.
- **Admin server** (default `:8081`) — Internal admin panel: dashboard, user/ticket/repo management. Protected by Tailscale authentication.

Both servers are started as goroutines in `cmd/server/main.go` and share the same database connection, template renderer, and service instances. Graceful shutdown handles SIGINT/SIGTERM with a 30-second timeout.

## Directory Structure

```
cmd/
  server/
    main.go              # Entry point — wires dependencies, starts both servers

internal/
  config/
    config.go            # Loads env vars into Config struct
  database/
    database.go          # PostgreSQL connection (GORM) and migration runner
  models/
    models.go            # GORM models: User, OAuthAccount, Session, Repo, Ticket, TicketComment, EmailToken
  auth/
    auth.go              # Service: register, login, password hashing, session create/destroy
    session.go           # Session middleware, RequireAuth, CurrentUser helpers
    store.go             # PGStore — PostgreSQL-backed gorilla/sessions store
    tokens.go            # Email verification and password reset token generation/redemption
    oauth.go             # Google and Microsoft OAuth provider setup, FindOrCreateOAuthUser
    apple.go             # Apple Sign In provider (JWT client secret, ID token parsing)
  middleware/
    middleware.go        # RequestID, Logging, Recovery middleware
    csrf.go              # CSRF protection via gorilla/csrf adapted for Gin
  handlers/
    public/
      routes.go          # Public router setup and route registration
      home.go            # Landing page
      auth.go            # Login, register, logout, email verification, password reset
      oauth.go           # OAuth login/callback for Google, Microsoft, Apple
      tickets.go         # Ticket list, create, detail, add comment
      webhook.go         # Forgejo webhook receiver (issue close -> ticket close)
    admin/
      routes.go          # Admin router setup and route registration
      auth.go            # Tailscale whois-based authentication middleware
      dashboard.go       # Dashboard with aggregate counts
      users.go           # User list, detail, create
      tickets.go         # Ticket list (with status filter), detail, status update
      repos.go           # Repo list, create, edit
  templates/
    render.go            # Template renderer: parses layouts + partials + pages, injects PageData
    funcs.go             # Template helper functions
  email/
    email.go             # Postmark email client: verification, password reset, ticket closed, welcome
    templates.go         # HTML email templates
  forgejo/
    client.go            # Forgejo API client: create issue, create comment
    webhook.go           # Webhook signature verification (HMAC-SHA256) and payload parsing

web/
  templates/
    layouts/
      base.html          # Public page layout
      admin.html         # Admin page layout
    pages/               # Page templates (mapped by path: "login", "tickets/list", "admin/dashboard", etc.)
    partials/            # Shared partials (nav, flash messages)
  static/
    css/
      input.css          # Tailwind CSS source
      output.css         # Compiled CSS (generated by build)
```

## Package Responsibilities

| Package | Role |
|---------|------|
| `config` | Reads all configuration from environment variables; validates required fields |
| `database` | Opens the GORM PostgreSQL connection; runs auto-migrations including enum types and custom indexes |
| `models` | Defines all database models and the `AutoMigrate` function |
| `auth` | User registration/login with bcrypt, session management via PostgreSQL-backed gorilla/sessions, email token generation/redemption, OAuth user linking |
| `middleware` | Request ID generation, structured logging, panic recovery, CSRF protection |
| `handlers/public` | All customer-facing HTTP handlers and route wiring |
| `handlers/admin` | All admin HTTP handlers, Tailscale auth middleware, and route wiring |
| `templates` | Parses Go HTML templates with layout/partial/page inheritance; injects current user, CSRF token, and flash messages into every render |
| `email` | Sends transactional emails via Postmark: verification, password reset, ticket closed notification, welcome/account creation |
| `forgejo` | Forgejo API client for creating issues and comments; webhook signature verification and payload parsing |

## Request Lifecycle

### Public Server

```
Request
  -> RequestID middleware (generates X-Request-ID header)
  -> Logging middleware (logs method, path, status, duration)
  -> Recovery middleware (catches panics)
  -> Session middleware (loads user from session cookie into context)
  -> CSRF middleware (gorilla/csrf — on routes that need it)
  -> Handler (processes request)
  -> Template render (injects User, CSRFToken, Flash into PageData)
```

The webhook endpoint (`POST /webhooks/forgejo/:repoSlug`) sits outside the CSRF group since it authenticates via HMAC signature.

### Admin Server

```
Request
  -> RequestID middleware
  -> Logging middleware
  -> Recovery middleware
  -> Tailscale auth middleware (whois lookup to verify allowed user)
  -> Handler
  -> Template render
```

The admin server has no session/CSRF middleware — authentication is handled entirely by Tailscale identity.

## Gin + Gorilla Interop

The application uses [Gin](https://github.com/gin-gonic/gin) as the HTTP framework but relies on [gorilla/sessions](https://github.com/gorilla/sessions) for session management and [gorilla/csrf](https://github.com/gorilla/csrf) for CSRF protection.

Gorilla middleware expects `http.ResponseWriter` and `*http.Request`, while Gin provides `*gin.Context`. The CSRF middleware bridges this by wrapping Gin's handler chain as an `http.Handler` and passing `c.Writer` / `c.Request` through. After gorilla/csrf processes the request (potentially adding context values), the modified `*http.Request` is written back to `c.Request` so downstream handlers can access the CSRF token via `csrf.Token(req)`.

See [Configuration](./configuration.md) for environment variable details and [Deployment](./deployment.md) for running the application.