﻿/*
 * 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.Internal.Extensions;
    using Events;
    using Microsoft.Extensions.ObjectPool;
    using PulsarApi;
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Threading;
    using System.Threading.Tasks;

    public sealed class Consumer<TMessage> : IEstablishNewChannel, IConsumer<TMessage>
    {
        private readonly Guid _correlationId;
        private readonly IRegisterEvent _eventRegister;
        private IConsumerChannel<TMessage> _channel;
        private readonly ObjectPool<CommandAck> _commandAckPool;
        private readonly IExecute _executor;
        private readonly IStateChanged<ConsumerState> _state;
        private readonly IConsumerChannelFactory<TMessage> _factory;
        private int _isDisposed;

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

        public Consumer(
            Guid correlationId,
            Uri serviceUrl,
            string subscriptionName,
            string topic,
            IRegisterEvent eventRegister,
            IConsumerChannel<TMessage> initialChannel,
            IExecute executor,
            IStateChanged<ConsumerState> state,
            IConsumerChannelFactory<TMessage> factory)
        {
            _correlationId = correlationId;
            ServiceUrl = serviceUrl;
            SubscriptionName = subscriptionName;
            Topic = topic;
            _eventRegister = eventRegister;
            _channel = initialChannel;
            _executor = executor;
            _state = state;
            _factory = factory;
            _commandAckPool = new DefaultObjectPool<CommandAck>(new DefaultPooledObjectPolicy<CommandAck>());
            _isDisposed = 0;

            _eventRegister.Register(new ConsumerCreated(_correlationId));
        }

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

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

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

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

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

            _eventRegister.Register(new ConsumerDisposed(_correlationId));
            await _channel.ClosedByClient(CancellationToken.None).ConfigureAwait(false);
            await _channel.DisposeAsync().ConfigureAwait(false);
        }

        public async ValueTask<IMessage<TMessage>> Receive(CancellationToken cancellationToken)
        {
            ThrowIfDisposed();

            return await _executor.Execute(() => ReceiveMessage(cancellationToken), cancellationToken).ConfigureAwait(false);
        }

        private async ValueTask<IMessage<TMessage>> ReceiveMessage(CancellationToken cancellationToken)
            => await _channel.Receive(cancellationToken).ConfigureAwait(false);

        public async ValueTask Acknowledge(MessageId messageId, CancellationToken cancellationToken)
            => await Acknowledge(messageId, CommandAck.AckType.Individual, cancellationToken).ConfigureAwait(false);

        public async ValueTask AcknowledgeCumulative(MessageId messageId, CancellationToken cancellationToken)
            => await Acknowledge(messageId, CommandAck.AckType.Cumulative, cancellationToken).ConfigureAwait(false);

        public async ValueTask RedeliverUnacknowledgedMessages(IEnumerable<MessageId> messageIds, CancellationToken cancellationToken)
        {
            ThrowIfDisposed();

            var command = new CommandRedeliverUnacknowledgedMessages();
            command.MessageIds.AddRange(messageIds.Select(messageId => messageId.ToMessageIdData()));
            await _executor.Execute(() => RedeliverUnacknowledgedMessages(command, cancellationToken), cancellationToken).ConfigureAwait(false);
        }

        public async ValueTask RedeliverUnacknowledgedMessages(CancellationToken cancellationToken)
            => await RedeliverUnacknowledgedMessages(Enumerable.Empty<MessageId>(), cancellationToken).ConfigureAwait(false);

        public async ValueTask Unsubscribe(CancellationToken cancellationToken)
        {
            ThrowIfDisposed();

            var unsubscribe = new CommandUnsubscribe();
            await _executor.Execute(() => Unsubscribe(unsubscribe, cancellationToken), cancellationToken).ConfigureAwait(false);
        }

        private async ValueTask Unsubscribe(CommandUnsubscribe command, CancellationToken cancellationToken)
            => await _channel.Send(command, cancellationToken).ConfigureAwait(false);

        public async ValueTask Seek(MessageId messageId, CancellationToken cancellationToken)
        {
            ThrowIfDisposed();

            var seek = new CommandSeek { MessageId = messageId.ToMessageIdData() };
            await _executor.Execute(() => Seek(seek, cancellationToken), cancellationToken).ConfigureAwait(false);
        }

        public async ValueTask Seek(ulong publishTime, CancellationToken cancellationToken)
        {
            ThrowIfDisposed();

            var seek = new CommandSeek { MessagePublishTime = publishTime };
            await _executor.Execute(() => Seek(seek, cancellationToken), cancellationToken).ConfigureAwait(false);
        }

        public async ValueTask<MessageId> GetLastMessageId(CancellationToken cancellationToken)
        {
            ThrowIfDisposed();

            var getLastMessageId = new CommandGetLastMessageId();
            return await _executor.Execute(() => GetLastMessageId(getLastMessageId, cancellationToken), cancellationToken).ConfigureAwait(false);
        }

        private async ValueTask<MessageId> GetLastMessageId(CommandGetLastMessageId command, CancellationToken cancellationToken)
            => await _channel.Send(command, cancellationToken).ConfigureAwait(false);

        private async Task Seek(CommandSeek command, CancellationToken cancellationToken)
            => await _channel.Send(command, cancellationToken).ConfigureAwait(false);

        private async ValueTask Acknowledge(MessageId messageId, CommandAck.AckType ackType, CancellationToken cancellationToken)
        {
            ThrowIfDisposed();

            var commandAck = _commandAckPool.Get();
            commandAck.Type = ackType;
            if (commandAck.MessageIds.Count == 0)
                commandAck.MessageIds.Add(messageId.ToMessageIdData());
            else
                commandAck.MessageIds[0].MapFrom(messageId);

            try
            {
                await _executor.Execute(() => Acknowledge(commandAck, cancellationToken), cancellationToken).ConfigureAwait(false);
            }
            finally
            {
                _commandAckPool.Return(commandAck);
            }
        }

        private async ValueTask Acknowledge(CommandAck command, CancellationToken cancellationToken)
            => await _channel.Send(command, cancellationToken).ConfigureAwait(false);

        private async ValueTask RedeliverUnacknowledgedMessages(CommandRedeliverUnacknowledgedMessages command, CancellationToken cancellationToken)
            => await _channel.Send(command, cancellationToken).ConfigureAwait(false);

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

        public async Task EstablishNewChannel(CancellationToken cancellationToken)
        {
            var channel = await _executor.Execute(() => _factory.Create(cancellationToken), cancellationToken).ConfigureAwait(false);

            var oldChannel = _channel;
            _channel = channel;

            if (oldChannel is not null)
                await oldChannel.DisposeAsync().ConfigureAwait(false);
        }
    }
}