package mqttingest

import "strings"

// TopicMatches reports whether a topic filter (with + or # wildcards) matches a topic name.
// It follows the MQTT v3.1.1 wildcard rules and supports shared subscriptions ($share).
func TopicMatches(filter, topic string) bool {
	return matchTopic(routeSplit(filter), strings.Split(topic, "/"))
}

func matchTopic(route []string, topic []string) bool {
	if len(route) == 0 {
		return len(topic) == 0
	}
	if len(topic) == 0 {
		return route[0] == "#"
	}
	if route[0] == "#" {
		return true
	}
	if route[0] == "+" || route[0] == topic[0] {
		return matchTopic(route[1:], topic[1:])
	}
	return false
}

// routeSplit removes $share/group/ when matching shared subscription filters.
func routeSplit(route string) []string {
	if strings.HasPrefix(route, "$share/") {
		parts := strings.Split(route, "/")
		if len(parts) > 2 {
			return parts[2:]
		}
	}
	return strings.Split(route, "/")
}