track-gopher/web/server.go

package web

import (
	"embed"
	"fmt"
	"html/template"
	"io/fs"
	"net/http"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"

	"track-gopher/derby"
)

//go:embed templates static
var content embed.FS

// Server represents the web server for the derby clock
type Server struct {
	router     *chi.Mux
	clock      *derby.DerbyClock
	templates  *template.Template
	raceEvents chan derby.Event
	clients    map[chan string]bool
	port       int
}

// NewServer creates a new web server
func NewServer(clock *derby.DerbyClock, port int) (*Server, error) {
	// Parse templates
	templates, err := template.ParseFS(content, "templates/*.html", "templates/**/*.html")
	if err != nil {
		return nil, fmt.Errorf("failed to parse templates: %w", err)
	}

	// Create server
	s := &Server{
		router:     chi.NewRouter(),
		clock:      clock,
		templates:  templates,
		raceEvents: make(chan derby.Event, 10),
		clients:    make(map[chan string]bool),
		port:       port,
	}

	// Set up routes
	s.routes()

	// Start event forwarder
	go s.forwardEvents()

	return s, nil
}

// routes sets up the HTTP routes
func (s *Server) routes() {
	// Middleware
	s.router.Use(middleware.Logger)
	s.router.Use(middleware.Recoverer)
	s.router.Use(middleware.Timeout(10 * time.Second))

	// Static files
	staticFS, _ := fs.Sub(content, "static")
	s.router.Handle("/static/*", http.StripPrefix("/static/", http.FileServer(http.FS(staticFS))))

	// Pages
	s.router.Get("/", s.handleIndex())

	// API endpoints
	s.router.Post("/api/reset", s.handleReset())
	s.router.Post("/api/force-end", s.handleForceEnd())
	s.router.Get("/api/status", s.handleStatus())
	s.router.Get("/api/events", s.handleEvents())
}

// Start starts the web server
func (s *Server) Start() error {
	fmt.Printf("Starting web server on port %d...\n", s.port)
	return http.ListenAndServe(fmt.Sprintf(":%d", s.port), s.router)
}

// forwardEvents forwards derby clock events to the web clients
func (s *Server) forwardEvents() {
	for event := range s.clock.Events() {
		// Store the event for new clients
		s.raceEvents <- event

		// Create the SSE message based on the event type
		var message string
		switch event.Type {
		case derby.EventRaceStart:
			message = "event: race-start\ndata: {\"status\": \"running\"}\n\n"

		case derby.EventLaneFinish:
			result := event.Result
			message = fmt.Sprintf("event: lane-finish\ndata: {\"lane\": %d, \"place\": %d, \"time\": %.4f}\n\n",
				result.Lane, result.FinishPlace, result.Time)

		case derby.EventRaceComplete:
			message = "event: race-complete\ndata: {\"status\": \"finished\"}\n\n"
		}

		// Send to all connected clients
		for clientChan := range s.clients {
			select {
			case clientChan <- message:
				// Message sent successfully
			default:
				// Client is not receiving, remove it
				delete(s.clients, clientChan)
				close(clientChan)
			}
		}
	}
}

// handleIndex handles the index page
func (s *Server) handleIndex() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		s.templates.ExecuteTemplate(w, "index.html", nil)
	}
}

// handleReset handles the reset API endpoint
func (s *Server) handleReset() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if err := s.clock.Reset(); err != nil {
			http.Error(w, fmt.Sprintf("Failed to reset clock: %v", err), http.StatusInternalServerError)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.Write([]byte(`{"status": "reset"}`))
	}
}

// handleForceEnd handles the force end API endpoint
func (s *Server) handleForceEnd() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if err := s.clock.ForceEnd(); err != nil {
			http.Error(w, fmt.Sprintf("Failed to force end race: %v", err), http.StatusInternalServerError)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.Write([]byte(`{"status": "forced"}`))
	}
}

// handleStatus handles the status API endpoint
func (s *Server) handleStatus() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		status := s.clock.Status()

		var statusStr string
		switch status {
		case derby.StatusIdle:
			statusStr = "idle"
		case derby.StatusRunning:
			statusStr = "running"
		case derby.StatusFinished:
			statusStr = "finished"
		}

		w.Header().Set("Content-Type", "application/json")
		w.Write([]byte(fmt.Sprintf(`{"status": "%s"}`, statusStr)))
	}
}

// handleEvents handles the SSE events endpoint
func (s *Server) handleEvents() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// Set headers for SSE
		w.Header().Set("Content-Type", "text/event-stream")
		w.Header().Set("Cache-Control", "no-cache")
		w.Header().Set("Connection", "keep-alive")
		w.Header().Set("Access-Control-Allow-Origin", "*")

		// Create a channel for this client
		clientChan := make(chan string, 10)
		s.clients[clientChan] = true

		// Clean up when the client disconnects
		defer func() {
			delete(s.clients, clientChan)
			close(clientChan)
		}()

		// Send initial status
		status := s.clock.Status()
		var statusStr string
		switch status {
		case derby.StatusIdle:
			statusStr = "idle"
		case derby.StatusRunning:
			statusStr = "running"
		case derby.StatusFinished:
			statusStr = "finished"
		}

		fmt.Fprintf(w, "event: status\ndata: {\"status\": \"%s\"}\n\n", statusStr)
		w.(http.Flusher).Flush()

		// Keep the connection open
		for {
			select {
			case message, ok := <-clientChan:
				if !ok {
					return
				}

				// Send the message to the client
				fmt.Fprint(w, message)
				w.(http.Flusher).Flush()

			case <-r.Context().Done():
				// Client disconnected
				return
			}
		}
	}
}