track-gopher/web/server.go

package web

import (
	"context"
	"embed"
	"encoding/json"
	"fmt"
	"io/fs"
	"net/http"
	"sync"
	"time"

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

	"track-gopher/derby"
	"track-gopher/web/templates"
)

//go:embed static
var content embed.FS

// Server represents the web server for the derby clock
type Server struct {
	router     *chi.Mux
	clock      *derby.DerbyClock
	events     <-chan derby.Event
	clients    map[chan string]bool
	clientsMux sync.Mutex
	port       int
	server     *http.Server
	shutdown   chan struct{}
}

// NewServer creates a new web server
func NewServer(clock *derby.DerbyClock, events <-chan derby.Event, port int) (*Server, error) {
	// Create server
	s := &Server{
		router:     chi.NewRouter(),
		clock:      clock,
		events:     events,
		clients:    make(map[chan string]bool),
		clientsMux: sync.Mutex{},
		port:       port,
		shutdown:   make(chan struct{}),
	}

	// 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 {
	addr := fmt.Sprintf(":%d", s.port)
	s.server = &http.Server{
		Addr:    addr,
		Handler: s.router,
	}

	// Start server in a goroutine
	go func() {
		if err := s.server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			fmt.Printf("HTTP server error: %v\n", err)
		}
	}()

	return nil
}

// Stop gracefully shuts down the server
func (s *Server) Stop() error {
	// Signal event forwarder to stop
	close(s.shutdown)

	// Close all client connections
	s.clientsMux.Lock()
	for clientChan := range s.clients {
		delete(s.clients, clientChan)
		close(clientChan)
	}
	s.clientsMux.Unlock()

	// Create a context with timeout for shutdown
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	// Shutdown the HTTP server
	if s.server != nil {
		return s.server.Shutdown(ctx)
	}

	return nil
}

// forwardEvents forwards derby events to SSE clients
func (s *Server) forwardEvents() {
	for {
		select {
		case event, ok := <-s.events:
			if !ok {
				return
			}
			// Process the event and send to clients
			s.broadcastEvent(event)
		case <-s.shutdown:
			return
		}
	}
}

// broadcastEvent sends an event to all connected clients
func (s *Server) broadcastEvent(event derby.Event) {
	var message string

	switch event.Type {
	case derby.EventRaceStart:
		statusMsg := struct {
			Status string `json:"status"`
		}{
			Status: "running",
		}
		statusJSON, _ := json.Marshal(statusMsg)
		message = fmt.Sprintf("event: status\ndata: %s", statusJSON)

	case derby.EventLaneFinish:
		// Create a message for lane finish
		laneData := struct {
			Lane  int     `json:"lane"`
			Time  float64 `json:"time"`
			Place int     `json:"place"`
		}{
			Lane:  event.Result.Lane,
			Time:  event.Result.Time,
			Place: event.Result.FinishPlace,
		}
		laneJSON, _ := json.Marshal(laneData)
		message = fmt.Sprintf("event: lane-finish\ndata: %s", laneJSON)

	case derby.EventRaceComplete:
		statusMsg := struct {
			Status string `json:"status"`
		}{
			Status: "finished",
		}
		statusJSON, _ := json.Marshal(statusMsg)
		message = fmt.Sprintf("event: status\ndata: %s", statusJSON)
	}

	if message == "" {
		return
	}

	// Send to all clients
	s.clientsMux.Lock()
	for clientChan := range s.clients {
		select {
		case clientChan <- message:
		default:
			// Client channel is full, could log this
		}
	}
	s.clientsMux.Unlock()
}

// handleIndex handles the index page
func (s *Server) handleIndex() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		templates.Index().Render(r.Context(), w)
	}
}

// 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 SSE events
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)

		// Add client to map with mutex protection
		s.clientsMux.Lock()
		s.clients[clientChan] = true
		s.clientsMux.Unlock()

		// Remove client when connection is closed
		defer func() {
			s.clientsMux.Lock()
			delete(s.clients, clientChan)
			s.clientsMux.Unlock()
			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
			}
		}
	}
}