using System;
using System.Collections.Generic;

namespace MQTTnet.Benchmarks;

public class TopicGenerator
{
    public static 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);
        if (topicsPerLevel <= 0)
        {
            topicsPerLevel = 1;
        }

        var numLevel1Topics = topicsPerLevel;
        var numLevel2Topics = topicsPerLevel;

        var maxNumLevel3Topics = 1 + (int)((double)numTopicsPerPublisher / numLevel1Topics / numLevel2Topics);
        if (maxNumLevel3Topics <= 0)
        {
            maxNumLevel3Topics = 1;
        }

        for (var p = 0; p < numPublishers; ++p)
        {
            var 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 = $"{publisherName}/building{l1 + 1}/level{l2 + 1}/sensor{l3 + 1}";
                        AddPublisherTopic(publisherName, topic, topicsByPublisher);

                        if (l2 == 0)
                        {
                            var singleWildcardTopic = $"{publisherName}/building{l1 + 1}/+/sensor{l3 + 1}";
                            AddPublisherTopic(publisherName, singleWildcardTopic, singleWildcardTopicsByPublisher);
                        }

                        if (l1 == 0 && l3 == 0)
                        {
                            var multiWildcardTopic = $"{publisherName}/+/level{l2 + 1}/+";
                            AddPublisherTopic(publisherName, multiWildcardTopic, multiWildcardTopicsByPublisher);
                        }

                        ++publisherTopicCount;
                    }
                }
            }
        }
    }

    static 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);
    }
}