using System;
using System.Collections.Generic;
using System.Text;

namespace MQTTnet.TestApp
{
    public class TopicGenerator
    {
        public void Generate(
           int numPublishers, int numTopicsPerPublisher,
           out Dictionary<string, List<string>> topicsByPublisher,
           out Dictionary<string, List<string>> singleWildcardTopicsByPublisher,
           out Dictionary<string, List<string>> multiWildcardTopicsByPublisher
           )
        {
            topicsByPublisher = new Dictionary<string, List<string>>();
            singleWildcardTopicsByPublisher = new Dictionary<string, List<string>>();
            multiWildcardTopicsByPublisher = new Dictionary<string, List<string>>();

            // Find some reasonable distribution across three topic levels
            var topicsPerLevel = (int)Math.Pow(numTopicsPerPublisher, (1.0 / 3.0));

            int numLevel1Topics = topicsPerLevel;
            if (numLevel1Topics <= 0)
            {
                numLevel1Topics = 1;
            }
            int numLevel2Topics = topicsPerLevel;
            if (numLevel2Topics <= 0)
            {
                numLevel2Topics = 1;
            }
            var maxNumLevel3Topics = 1 + (int)((double)numTopicsPerPublisher / numLevel1Topics / numLevel2Topics);
            if (maxNumLevel3Topics <= 0)
            {
                maxNumLevel3Topics = 1;
            }
            for (var p = 0; p < numPublishers; ++p)
            {
                int publisherTopicCount = 0;

                var publisherName = "pub" + p;
                for (var l1 = 0; l1 < numLevel1Topics; ++l1)
                {
                    for (var l2 = 0; l2 < numLevel2Topics; ++l2)
                    {
                        for (var l3 = 0; l3 < maxNumLevel3Topics; ++l3)
                        {
                            if (publisherTopicCount >= numTopicsPerPublisher)
                                break;

                            var topic = string.Format("{0}/building{1}/level{2}/sensor{3}", publisherName, l1 + 1, l2 + 1, l3 + 1);
                            AddPublisherTopic(publisherName, topic, topicsByPublisher);

                            if (l2 == 0)
                            {
                                var singleWildcardTopic = string.Format("{0}/building{1}/+/sensor{2}", publisherName, l1 + 1, l3 + 1);
                                AddPublisherTopic(publisherName, singleWildcardTopic, singleWildcardTopicsByPublisher);
                                if (l1 == 0)
                                {
                                    var multiWildcardTopic = string.Format("{0}/+/level{1}/+", publisherName, l3 + 1);
                                    AddPublisherTopic(publisherName, multiWildcardTopic, multiWildcardTopicsByPublisher);
                                }
                            }

                            ++publisherTopicCount;
                        }
                    }
                }
            }
        }

        void AddPublisherTopic(string publisherName, string topic, Dictionary<string, List<string>> topicsByPublisher)
        {
            List<string> topicList;
            if (!topicsByPublisher.TryGetValue(publisherName, out topicList))
            {
                topicList = new List<string>();
                topicsByPublisher.Add(publisherName, topicList);
            }
            topicList.Add(topic);
        }
    }
}