package events

import (
	"sync"

	"go.neonxp.dev/djson/internal/model"
)

type subscriberNode struct {
	parent   *subscriberNode
	children map[string]*subscriberNode
	channels map[string]chan model.Mutation
	mu       sync.RWMutex
}

func (sn *subscriberNode) subscribe(path []string, id string, ch chan model.Mutation) {
	sn.mu.Lock()
	defer sn.mu.Unlock()
	if len(path) == 0 {
		sn.channels[id] = ch
		return
	}
	head, rest := path[0], path[1:]
	child, ok := sn.children[head]
	if !ok {
		child = &subscriberNode{
			parent:   sn,
			children: make(map[string]*subscriberNode),
			channels: make(map[string]chan model.Mutation),
		}
		sn.children[head] = child
	}
	if len(rest) == 0 {
		child.channels[id] = ch
		return
	}
	child.subscribe(rest, id, ch)
}

func (sn *subscriberNode) unsubscribe(path []string, id string) {
	sn.mu.Lock()
	defer sn.mu.Unlock()
	if len(path) == 0 {
		close(sn.channels[id])
		delete(sn.channels, id)
		return
	}
	head, rest := path[0], path[1:]
	if child, ok := sn.children[head]; ok {
		child.unsubscribe(rest, id)
	}
}

func (sn *subscriberNode) notify(path []string, event *model.Mutation) {
	sn.mu.RLock()
	defer sn.mu.RUnlock()
	for _, ch := range sn.channels {
		go func(ch chan model.Mutation) {
			ch <- *event
		}(ch)
	}
	if len(path) == 0 {
		return
	}
	head, rest := path[0], path[1:]
	if child, ok := sn.children[head]; ok {
		child.notify(rest, event)
	}
}