package server

import (
	"encoding/json"
	"sync"

	"gospeak-live-sfu-demo/gen"
)

// roomHub 维护房间 -> 各后端分发目标（StreamTarget）的内存状态，
// 并向订阅者广播拓扑变化（实现「分流」状态实时可见）。
type roomHub struct {
	mu    sync.RWMutex
	rooms map[string]*roomEntry
}

type roomEntry struct {
	targets map[string]*gen.StreamTarget // key: 后端名（cloudflare / srs）
	subs    map[chan []byte]struct{}
}

func newRoomHub() *roomHub {
	return &roomHub{rooms: map[string]*roomEntry{}}
}

func (h *roomHub) get(name string) *roomEntry {
	e, ok := h.rooms[name]
	if !ok {
		e = &roomEntry{targets: map[string]*gen.StreamTarget{}, subs: map[chan []byte]struct{}{}}
		h.rooms[name] = e
	}
	return e
}

func (h *roomHub) setTarget(room, backend string, t *gen.StreamTarget) {
	h.mu.Lock()
	defer h.mu.Unlock()
	e := h.get(room)
	e.targets[backend] = t
	h.broadcast(room, e)
}

func (h *roomHub) removeTarget(room, backend string) {
	h.mu.Lock()
	defer h.mu.Unlock()
	e, ok := h.rooms[room]
	if !ok {
		return
	}
	delete(e.targets, backend)
	if len(e.targets) == 0 && len(e.subs) == 0 {
		delete(h.rooms, room)
		return
	}
	h.broadcast(room, e)
}

func (h *roomHub) targets(room string) []*gen.StreamTarget {
	h.mu.RLock()
	defer h.mu.RUnlock()
	e, ok := h.rooms[room]
	if !ok {
		return nil
	}
	out := make([]*gen.StreamTarget, 0, len(e.targets))
	for _, t := range e.targets {
		out = append(out, t)
	}
	return out
}

func (h *roomHub) list() []*gen.Room {
	h.mu.RLock()
	defer h.mu.RUnlock()
	out := make([]*gen.Room, 0, len(h.rooms))
	for name, e := range h.rooms {
		room := &gen.Room{Name: name}
		for _, t := range e.targets {
			room.Targets = append(room.Targets, t)
		}
		out = append(out, room)
	}
	return out
}

func (h *roomHub) subscribe(room string) (chan []byte, func()) {
	h.mu.Lock()
	defer h.mu.Unlock()
	e := h.get(room)
	ch := make(chan []byte, 8)
	e.subs[ch] = struct{}{}
	return ch, func() {
		h.mu.Lock()
		defer h.mu.Unlock()
		if e2, ok := h.rooms[room]; ok {
			delete(e2.subs, ch)
		}
	}
}

func (h *roomHub) broadcast(room string, e *roomEntry) {
	payload, _ := json.Marshal(map[string]interface{}{
		"room":    room,
		"targets": e.targets,
	})
	for ch := range e.subs {
		select {
		case ch <- payload:
		default:
		}
	}
}