package subscription

//TODO WILDCARD SUBSCRIPTIONS

import (
	"strings"
	"sync"

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

var Subscriptions SubscriptionTreeNode = *newSubscriptionTreeNode()

type SubscriptionChannel chan packets.PublishPacket

type Subscription struct {
	SubscriptionChannel
	packets.TopicFilter
}

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) removeSubscription(subChan SubscriptionChannel) {
	for i, sub := range s.subscriptions {
		if sub.SubscriptionChannel == subChan {
			lst := len(s.subscriptions) - 1
			s.subscriptions[i] = s.subscriptions[lst]
			s.subscriptions = s.subscriptions[:lst]
		}
	}
}

func (s *SubscriptionTreeNode) Subscribe(topicFilter packets.TopicFilter, subChan SubscriptionChannel) {
	sub := Subscription{subChan, topicFilter}

	node := s.findNode(topicFilter.Topic.Fields)
	node.nodeLock.Lock()
	node.subscriptions = append(node.subscriptions, sub)
	node.nodeLock.Unlock()
}

func (s *SubscriptionTreeNode) Unsubscribe(topic packets.Topic, subChan SubscriptionChannel) {
	node := s.findNode(topic.Fields)

	node.nodeLock.Lock()
	node.removeSubscription(subChan)
	node.nodeLock.Unlock()
}

func (s *SubscriptionTreeNode) RemoveSubsForChannel(subChan SubscriptionChannel) {
	for _, node := range s.children {
		node.nodeLock.Lock()
		node.removeSubscription(subChan)
		node.nodeLock.Unlock()

		node.RemoveSubsForChannel(subChan)
	}
}

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

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