package main

import (
	"encoding/json"
	"net/http"
	"strconv"
	"sync"

	"github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
	CheckOrigin: func(r *http.Request) bool {
		origin := r.Header.Get("Origin")
		if origin == "" {
			// Non-browser client without Origin header — allow.
			return true
		}
		if originAllowed(origin) {
			return true
		}
		return sameOriginRequest(r)
	},
}

type wsMessage struct {
	Type    string `json:"type"`
	Payload any    `json:"payload,omitempty"`
}

type client struct {
	conn          *websocket.Conn
	competitionID int64
	send          chan []byte
}

type Hub struct {
	mu      sync.RWMutex
	clients map[int64]map[*client]struct{}
}

var hub *Hub

func newHub() *Hub {
	return &Hub{clients: map[int64]map[*client]struct{}{}}
}

func (h *Hub) run() {}

func (h *Hub) register(c *client) {
	h.mu.Lock()
	defer h.mu.Unlock()
	set, ok := h.clients[c.competitionID]
	if !ok {
		set = map[*client]struct{}{}
		h.clients[c.competitionID] = set
	}
	set[c] = struct{}{}
}

func (h *Hub) unregister(c *client) {
	h.mu.Lock()
	defer h.mu.Unlock()
	if set, ok := h.clients[c.competitionID]; ok {
		if _, ok := set[c]; ok {
			delete(set, c)
			close(c.send)
		}
		if len(set) == 0 {
			delete(h.clients, c.competitionID)
		}
	}
}

func (h *Hub) broadcast(competitionID int64, kind string, payload any) {
	msg := wsMessage{Type: kind, Payload: payload}
	data, err := json.Marshal(msg)
	if err != nil {
		return
	}
	h.mu.RLock()
	defer h.mu.RUnlock()
	set, ok := h.clients[competitionID]
	if !ok {
		return
	}
	for c := range set {
		select {
		case c.send <- data:
		default:
		}
	}
}

func registerWSRoutes(mux *http.ServeMux) {
	mux.HandleFunc("GET /api/competitions/{id}/ws", requireAuth(handleWS))
}

func handleWS(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid_id")
		return
	}
	u := userFromCtx(r)
	if _, ok := canAccessCompetition(u, id); !ok {
		writeError(w, http.StatusForbidden, "forbidden")
		return
	}
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		return
	}
	c := &client{conn: conn, competitionID: id, send: make(chan []byte, 16)}
	hub.register(c)
	go writePump(c)
	readPump(c)
}

func readPump(c *client) {
	defer func() {
		hub.unregister(c)
		c.conn.Close()
	}()
	c.conn.SetReadLimit(1024)
	for {
		if _, _, err := c.conn.ReadMessage(); err != nil {
			return
		}
	}
}

func writePump(c *client) {
	defer c.conn.Close()
	for msg := range c.send {
		if err := c.conn.WriteMessage(websocket.TextMessage, msg); err != nil {
			return
		}
	}
}