﻿/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace DotPulsar.Internal;

using Abstractions;
using DotPulsar.Abstractions;
using DotPulsar.Exceptions;
using DotPulsar.Extensions;
using DotPulsar.Internal.Extensions;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;

public sealed class Producer<TMessage> : IProducer<TMessage>, IRegisterEvent
{
    private readonly string _operationName;
    private readonly KeyValuePair<string, object?>[] _activityTags;
    private readonly KeyValuePair<string, object?>[] _meterTags;
    private readonly SequenceId _sequenceId;
    private readonly StateManager<ProducerState> _state;
    private readonly IConnectionPool _connectionPool;
    private readonly IHandleException _exceptionHandler;
    private readonly ICompressorFactory? _compressorFactory;
    private readonly ProducerOptions<TMessage> _options;
    private readonly ProcessManager _processManager;
    private readonly ConcurrentDictionary<int, SubProducer<TMessage>> _producers;
    private readonly IMessageRouter _messageRouter;
    private readonly CancellationTokenSource _cts;
    private readonly IExecute _executor;
    private int _isDisposed;
    private int _producerCount;
    private Exception? _throw;

    public Uri ServiceUrl { get; }
    public string Topic { get; }

    public Producer(
        Uri serviceUrl,
        ProducerOptions<TMessage> options,
        ProcessManager processManager,
        IHandleException exceptionHandler,
        IConnectionPool connectionPool,
        ICompressorFactory? compressorFactory)
    {
        _operationName = $"{options.Topic} send";
        _activityTags = new KeyValuePair<string, object?>[]
        {
                new KeyValuePair<string, object?>("messaging.destination", options.Topic),
                new KeyValuePair<string, object?>("messaging.destination_kind", "topic"),
                new KeyValuePair<string, object?>("messaging.system", "pulsar"),
                new KeyValuePair<string, object?>("messaging.url", serviceUrl),
        };
        _meterTags = new KeyValuePair<string, object?>[]
        {
                new KeyValuePair<string, object?>("topic", options.Topic)
        };
        _sequenceId = new SequenceId(options.InitialSequenceId);
        _state = new StateManager<ProducerState>(ProducerState.Disconnected, ProducerState.Closed, ProducerState.Faulted);
        ServiceUrl = serviceUrl;
        Topic = options.Topic;
        _isDisposed = 0;
        _options = options;
        _exceptionHandler = exceptionHandler;
        _connectionPool = connectionPool;
        _compressorFactory = compressorFactory;
        _processManager = processManager;
        _messageRouter = options.MessageRouter;
        _cts = new CancellationTokenSource();
        _executor = new Executor(Guid.Empty, this, _exceptionHandler);
        _producers = new ConcurrentDictionary<int, SubProducer<TMessage>>();
        _ = Setup();
    }

    private async Task Setup()
    {
        await Task.Yield();

        try
        {
            await _executor.Execute(Monitor, _cts.Token).ConfigureAwait(false);
        }
        catch (Exception exception)
        {
            if (_cts.IsCancellationRequested)
                return;

            _throw = exception;
            _state.SetState(ProducerState.Faulted);
        }
    }

    private async Task Monitor()
    {
        var numberOfPartitions = await GetNumberOfPartitions(Topic, _cts.Token).ConfigureAwait(false);
        var isPartitionedTopic = numberOfPartitions != 0;
        var monitoringTasks = new Task<ProducerStateChanged>[isPartitionedTopic ? numberOfPartitions : 1];

        var topic = Topic;

        for (var partition = 0; partition < monitoringTasks.Length; ++partition)
        {
            if (isPartitionedTopic)
                topic = $"{Topic}-partition-{partition}";

            var producer = CreateSubProducer(topic);
            _ = _producers.TryAdd(partition, producer);
            monitoringTasks[partition] = producer.StateChangedFrom(ProducerState.Disconnected, _cts.Token).AsTask();
        }

        Interlocked.Exchange(ref _producerCount, monitoringTasks.Length);

        var connectedProducers = 0;

        while (true)
        {
            await Task.WhenAny(monitoringTasks).ConfigureAwait(false);

            for (var i = 0; i < monitoringTasks.Length; ++i)
            {
                var task = monitoringTasks[i];
                if (!task.IsCompleted)
                    continue;

                var state = task.Result.ProducerState;
                switch (state)
                {
                    case ProducerState.Connected:
                        ++connectedProducers;
                        break;
                    case ProducerState.Disconnected:
                        --connectedProducers;
                        break;
                    case ProducerState.Faulted:
                        _state.SetState(ProducerState.Faulted);
                        return;
                }

                monitoringTasks[i] = task.Result.Producer.StateChangedFrom(state, _cts.Token).AsTask();
            }

            if (connectedProducers == 0)
                _state.SetState(ProducerState.Disconnected);
            else if (connectedProducers == monitoringTasks.Length)
                _state.SetState(ProducerState.Connected);
            else
                _state.SetState(ProducerState.PartiallyConnected);
        }
    }

    private SubProducer<TMessage> CreateSubProducer(string topic)
    {
        var correlationId = Guid.NewGuid();
        var producerName = _options.ProducerName;
        var schema = _options.Schema;
        var factory = new ProducerChannelFactory(correlationId, _processManager, _connectionPool, topic, producerName, schema.SchemaInfo, _compressorFactory);
        var stateManager = new StateManager<ProducerState>(ProducerState.Disconnected, ProducerState.Closed, ProducerState.Faulted);
        var initialChannel = new NotReadyChannel<TMessage>();
        var executor = new Executor(correlationId, _processManager, _exceptionHandler);
        var producer = new SubProducer<TMessage>(correlationId, ServiceUrl, topic, _processManager, initialChannel, executor, stateManager, factory, schema);
        var process = new ProducerProcess(correlationId, stateManager, producer);
        _processManager.Add(process);
        process.Start();
        return producer;
    }

    private async Task<uint> GetNumberOfPartitions(string topic, CancellationToken cancellationToken)
    {
        var connection = await _connectionPool.FindConnectionForTopic(topic, cancellationToken).ConfigureAwait(false);
        var commandPartitionedMetadata = new PulsarApi.CommandPartitionedTopicMetadata { Topic = topic };
        var response = await connection.Send(commandPartitionedMetadata, cancellationToken).ConfigureAwait(false);

        response.Expect(PulsarApi.BaseCommand.Type.PartitionedMetadataResponse);

        if (response.PartitionMetadataResponse.Response == PulsarApi.CommandPartitionedTopicMetadataResponse.LookupType.Failed)
            response.PartitionMetadataResponse.Throw();

        return response.PartitionMetadataResponse.Partitions;
    }

    public bool IsFinalState()
        => _state.IsFinalState();

    public bool IsFinalState(ProducerState state)
        => _state.IsFinalState(state);

    public async ValueTask<ProducerState> OnStateChangeTo(ProducerState state, CancellationToken cancellationToken)
        => await _state.StateChangedTo(state, cancellationToken).ConfigureAwait(false);

    public async ValueTask<ProducerState> OnStateChangeFrom(ProducerState state, CancellationToken cancellationToken)
        => await _state.StateChangedFrom(state, cancellationToken).ConfigureAwait(false);

    public async ValueTask DisposeAsync()
    {
        if (Interlocked.Exchange(ref _isDisposed, 1) != 0)
            return;

        _cts.Cancel();
        _cts.Dispose();

        _state.SetState(ProducerState.Closed);

        foreach (var producer in _producers.Values)
        {
            await producer.DisposeAsync().ConfigureAwait(false);
        }
    }

    private async ValueTask<int> ChoosePartitions(MessageMetadata metadata, CancellationToken cancellationToken)
    {
        if (_producerCount == 0)
        {
            _ = await _state.StateChangedFrom(ProducerState.Disconnected, cancellationToken).ConfigureAwait(false);
            if (_throw is not null)
                throw _throw;
        }

        if (_producerCount == 1)
            return 0;

        return _messageRouter.ChoosePartition(metadata, _producerCount);
    }

    public async ValueTask<MessageId> Send(MessageMetadata metadata, TMessage message, CancellationToken cancellationToken)
    {
        ThrowIfDisposed();

        var autoAssignSequenceId = metadata.SequenceId == 0;
        if (autoAssignSequenceId)
            metadata.SequenceId = _sequenceId.FetchNext();

        var activity = DotPulsarActivitySource.StartProducerActivity(metadata, _operationName, _activityTags);
        var startTimestamp = DotPulsarMeter.MessageSentEnabled ? Stopwatch.GetTimestamp() : 0;

        try
        {
            var partition = await ChoosePartitions(metadata, cancellationToken).ConfigureAwait(false);
            var producer = _producers[partition];
            var data = _options.Schema.Encode(message);

            var messageId = await producer.Send(metadata.Metadata, data, cancellationToken).ConfigureAwait(false);

            if (startTimestamp != 0)
                DotPulsarMeter.MessageSent(startTimestamp, _meterTags);

            if (activity is not null && activity.IsAllDataRequested)
            {
                activity.SetMessageId(messageId);
                activity.SetPayloadSize(data.Length);
                activity.SetStatus(ActivityStatusCode.Ok);
            }

            return messageId;
        }
        catch (Exception exception)
        {
            if (activity is not null && activity.IsAllDataRequested)
                activity.AddException(exception);

            throw;
        }
        finally
        {
            activity?.Dispose();

            if (autoAssignSequenceId)
                metadata.SequenceId = 0;
        }
    }

    private void ThrowIfDisposed()
    {
        if (_isDisposed != 0)
            throw new ProducerDisposedException(GetType().FullName!);
    }

    public void Register(IEvent @event) { }
}