package main

//TODO FULLY IMPLEMENT SUBSCRIPTIONS INSTEAD OF JUST THE TOPIC FILTERS

import (
	"strings"
	"sync"

	"badat.dev/maeqtt/v2/mqtt/packets"
)

var Subscriptions SubscriptionTreeNode = *NewSubscriptionTreeNode()

type Subscription chan packets.PublishPacket

type SubscriptionTreeNode struct {
	subscriptions []Subscription
	children      map[string]*SubscriptionTreeNode
	nodeLock      sync.RWMutex
}
func NewSubscriptionTreeNode() *SubscriptionTreeNode {
	s := SubscriptionTreeNode{}
	s.children = make(map[string]*SubscriptionTreeNode)
	return &s
}

func (s *SubscriptionTreeNode) findNode(fields []string) *SubscriptionTreeNode {
	if len(fields) == 0 {
		return s
	}

	field := fields[0]

	s.nodeLock.RLock()
	_, exists := s.children[field]
	// Insert a value into the map if one doesn't exist yet
	if !exists {
		// Can't upgrade a read lock so we need to unlock and
		// check again, this time with a write lock
		s.nodeLock.RUnlock()
		s.nodeLock.Lock()

		_, exists = s.children[field]
		if !exists {
			s.children[field] = NewSubscriptionTreeNode()
		}
		s.nodeLock.Unlock()
		s.nodeLock.RLock()
	}

	child, _ := s.children[field]
	s.nodeLock.RUnlock()
	return child.findNode(fields[1:])
}

func (s *SubscriptionTreeNode) Subscribe(topic packets.Topic, sub Subscription) {
	node := s.findNode(topic.Fields)
	node.nodeLock.Lock()
	node.subscriptions = append(node.subscriptions, sub)
	node.nodeLock.Unlock()
}

func (s *SubscriptionTreeNode) GetSubscriptions(topic string) ([]Subscription, sync.Locker) {
	fields := strings.Split(topic,"/")

	child := s.findNode(fields)
	locker := child.nodeLock.RLocker()
	locker.Lock()
	return child.subscriptions, locker
}

func (s *SubscriptionTreeNode) findMatchingRec(topic []string) ([]Subscription, sync.Locker) {
	locker := s.nodeLock.RLocker()
	s.nodeLock.RLock()
	if len(topic) == 0 {
		return s.subscriptions,locker
	}
	defer s.nodeLock.RUnlock()

	child, exists := s.children[topic[0]]
	if exists {
		return child.findMatchingRec(topic[1:])
	} else {
		return []Subscription{},locker
	}
}