package main

import (
	"encoding/json"
	"log"
	"net/http"
	"time"

	"github.com/gorilla/websocket"
)

const (
	workDuration       = 15 * 60
	shortBreakDuration = 5 * 60
	longBreakDuration  = 10 * 60
	sessions           = 4
)

type BroadcastMessage struct {
	Mode       string `json:"mode"`
	Session    int    `json:"session"`
	MaxSession int    `json:"max_session"`
	TimeLeft   int    `json:"time_left"`
}

var clients = make(map[*websocket.Conn]bool)

// broadcastMessage sends the remaining time to all connected clients.
func broadcastMessage(message BroadcastMessage) {
	jsonMessage, _ := json.Marshal(message)
	for client := range clients {
		err := client.WriteMessage(websocket.TextMessage, jsonMessage)
		if err != nil {
			log.Printf("Error broadcasting to client: %v", err)
			client.Close()
			delete(clients, client)
		}
	}
}

// start a countdown and broadcast ever second
func startTimer(remaining_seconds int, mode string, session int) {
	for remaining_seconds > 0 {
		broadcastMessage(BroadcastMessage{
			Mode:       mode,
			Session:    session,
			MaxSession: sessions,
			TimeLeft:   remaining_seconds,
		})
		time.Sleep(time.Second)
		remaining_seconds--
	}
	// send final 0 timer
	broadcastMessage(BroadcastMessage{
		Mode:       mode,
		Session:    1,
		MaxSession: 4,
		TimeLeft:   0,
	})
}

// iterate the Pomodoro work/break sessions
func runPomodoroTimer() {
	for session := 1; session <= sessions; session++ {
		startTimer(workDuration, "Work", session)
		if session == sessions {
			startTimer(longBreakDuration, "LongBreak", session)
		} else {
			startTimer(shortBreakDuration, "ShortBreak", session)
		}
	}
}

// upgrade HTTP requests to WebSocket connections.
var upgrader = websocket.Upgrader{
	CheckOrigin: func(r *http.Request) bool { return true },
}

func handleConnections(w http.ResponseWriter, r *http.Request) {
	// Upgrade initial GET request to a WebSocket
	ws, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Printf("WebSocket upgrade error: %v", err)
		return
	}
	defer ws.Close()

	// Register the new client
	clients[ws] = true

	// Clean up when the client disconnects
	for {
		_, _, err := ws.ReadMessage()
		if err != nil {
			log.Printf("Client disconnected: %v", err)
			delete(clients, ws)
			break
		}
	}
}

func main() {
	http.HandleFunc("/ws", handleConnections)

	// Start a goroutine that runs the Pomodoro timer and broadcasts updates.
	go runPomodoroTimer()

	log.Println("Pomodoro WebSocket server started on :8080")
	err := http.ListenAndServe(":8080", nil)
	if err != nil {
		log.Fatalf("Error starting server: %v", err)
	}
}