using LightlessSync.LightlessConfiguration;
using LightlessSync.Services.Mediator;
using LightlessSync.WebAPI.Files.Models;
using LightlessSync.WebAPI.SignalR;
using Microsoft.Extensions.Logging;
using System.Collections.Concurrent;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Net.Http.Json;
using System.Net.Sockets;
using System.Reflection;

namespace LightlessSync.WebAPI.Files;

public class FileTransferOrchestrator : DisposableMediatorSubscriberBase
{
    private readonly ConcurrentDictionary<Guid, bool> _downloadReady = new();
    private readonly HttpClient _httpClient;
    private readonly LightlessConfigService _lightlessConfig;
    private readonly object _semaphoreModificationLock = new();
    private readonly TokenProvider _tokenProvider;
    private int _availableDownloadSlots;
    private SemaphoreSlim _downloadSemaphore;
    private int CurrentlyUsedDownloadSlots => _availableDownloadSlots - _downloadSemaphore.CurrentCount;

    public FileTransferOrchestrator(ILogger<FileTransferOrchestrator> logger, LightlessConfigService lightlessConfig,
        LightlessMediator mediator, TokenProvider tokenProvider, HttpClient httpClient) : base(logger, mediator)
    {
        _lightlessConfig = lightlessConfig;
        _tokenProvider = tokenProvider;
        _httpClient = httpClient;
        var ver = Assembly.GetExecutingAssembly().GetName().Version;
        _httpClient.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("LightlessSync", ver!.Major + "." + ver!.Minor + "." + ver!.Build));

        _availableDownloadSlots = lightlessConfig.Current.ParallelDownloads;
        _downloadSemaphore = new(_availableDownloadSlots, _availableDownloadSlots);

        Mediator.Subscribe<ConnectedMessage>(this, (msg) =>
        {
            FilesCdnUri = msg.Connection.ServerInfo.FileServerAddress;
        });

        Mediator.Subscribe<DisconnectedMessage>(this, (msg) =>
        {
            FilesCdnUri = null;
        });
        Mediator.Subscribe<DownloadReadyMessage>(this, (msg) =>
        {
            _downloadReady[msg.RequestId] = true;
        });
    }

    public Uri? FilesCdnUri { private set; get; }
    public List<FileTransfer> ForbiddenTransfers { get; } = [];
    public bool IsInitialized => FilesCdnUri != null;

    public void ClearDownloadRequest(Guid guid)
    {
        _downloadReady.Remove(guid, out _);
    }

    public bool IsDownloadReady(Guid guid)
    {
        if (_downloadReady.TryGetValue(guid, out bool isReady) && isReady)
        {
            return true;
        }

        return false;
    }

    public void ReleaseDownloadSlot()
    {
        try
        {
            _downloadSemaphore.Release();
            Mediator.Publish(new DownloadLimitChangedMessage());
        }
        catch (SemaphoreFullException)
        {
            // ignore
        }
    }

    public async Task<HttpResponseMessage> SendRequestAsync(HttpMethod method, Uri uri,
        CancellationToken? ct = null, HttpCompletionOption httpCompletionOption = HttpCompletionOption.ResponseContentRead,
        bool withToken = true)
    {
        return await SendRequestInternalAsync(() => new HttpRequestMessage(method, uri),
            ct, httpCompletionOption, withToken, allowRetry: true).ConfigureAwait(false);
    }

    public async Task<HttpResponseMessage> SendRequestAsync<T>(HttpMethod method, Uri uri, T content, CancellationToken ct,
        bool withToken = true) where T : class
    {
        return await SendRequestInternalAsync(() =>
        {
            var requestMessage = new HttpRequestMessage(method, uri);
            if (content is not ByteArrayContent byteArrayContent)
            {
                requestMessage.Content = JsonContent.Create(content);
            }
            else
            {
                var clonedContent = new ByteArrayContent(byteArrayContent.ReadAsByteArrayAsync().GetAwaiter().GetResult());
                foreach (var header in byteArrayContent.Headers)
                {
                    clonedContent.Headers.TryAddWithoutValidation(header.Key, header.Value);
                }
                requestMessage.Content = clonedContent;
            }

            return requestMessage;
        }, ct, HttpCompletionOption.ResponseContentRead, withToken,
            allowRetry: content is not HttpContent || content is ByteArrayContent).ConfigureAwait(false);
    }

    public async Task<HttpResponseMessage> SendRequestStreamAsync(HttpMethod method, Uri uri, ProgressableStreamContent content,
        CancellationToken ct, bool withToken = true)
    {
        return await SendRequestInternalAsync(() =>
        {
            var requestMessage = new HttpRequestMessage(method, uri)
            {
                Content = content
            };
            return requestMessage;
        }, ct, HttpCompletionOption.ResponseContentRead, withToken, allowRetry: false).ConfigureAwait(false);
    }

    public async Task WaitForDownloadSlotAsync(CancellationToken token)
    {
        lock (_semaphoreModificationLock)
        {
            if (_availableDownloadSlots != _lightlessConfig.Current.ParallelDownloads && _availableDownloadSlots == _downloadSemaphore.CurrentCount)
            {
                _availableDownloadSlots = _lightlessConfig.Current.ParallelDownloads;
                _downloadSemaphore = new(_availableDownloadSlots, _availableDownloadSlots);
            }
        }

        await _downloadSemaphore.WaitAsync(token).ConfigureAwait(false);
        Mediator.Publish(new DownloadLimitChangedMessage());
    }

    public long DownloadLimitPerSlot()
    {
        var limit = _lightlessConfig.Current.DownloadSpeedLimitInBytes;
        if (limit <= 0) return 0;
        limit = _lightlessConfig.Current.DownloadSpeedType switch
        {
            LightlessConfiguration.Models.DownloadSpeeds.Bps => limit,
            LightlessConfiguration.Models.DownloadSpeeds.KBps => limit * 1024,
            LightlessConfiguration.Models.DownloadSpeeds.MBps => limit * 1024 * 1024,
            _ => limit,
        };
        var currentUsedDlSlots = CurrentlyUsedDownloadSlots;
        var avaialble = _availableDownloadSlots;
        var currentCount = _downloadSemaphore.CurrentCount;
        var dividedLimit = limit / (currentUsedDlSlots == 0 ? 1 : currentUsedDlSlots);
        if (dividedLimit < 0)
        {
            Logger.LogWarning("Calculated Bandwidth Limit is negative, returning Infinity: {value}, CurrentlyUsedDownloadSlots is {currentSlots}, " +
                "DownloadSpeedLimit is {limit}, available slots: {avail}, current count: {count}", dividedLimit, currentUsedDlSlots, limit, avaialble, currentCount);
            return long.MaxValue;
        }
        return Math.Clamp(dividedLimit, 1, long.MaxValue);
    }

    private async Task<HttpResponseMessage> SendRequestInternalAsync(Func<HttpRequestMessage> requestFactory,
        CancellationToken? ct = null, HttpCompletionOption httpCompletionOption = HttpCompletionOption.ResponseContentRead,
        bool withToken = true, bool allowRetry = true)
    {
        const int maxAttempts = 2;
        var attempt = 0;

        while (true)
        {
            attempt++;
            using var requestMessage = requestFactory();

            if (withToken)
            {
                var token = await _tokenProvider.GetToken().ConfigureAwait(false);
                requestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
            }

            if (requestMessage.Content != null && requestMessage.Content is not StreamContent && requestMessage.Content is not ByteArrayContent)
            {
                var content = await ((JsonContent)requestMessage.Content).ReadAsStringAsync().ConfigureAwait(false);
                Logger.LogDebug("Sending {method} to {uri} (Content: {content})", requestMessage.Method, requestMessage.RequestUri, content);
            }
            else
            {
                Logger.LogDebug("Sending {method} to {uri}", requestMessage.Method, requestMessage.RequestUri);
            }

            try
            {
                if (ct != null)
                    return await _httpClient.SendAsync(requestMessage, httpCompletionOption, ct.Value).ConfigureAwait(false);
                return await _httpClient.SendAsync(requestMessage, httpCompletionOption).ConfigureAwait(false);
            }
            catch (TaskCanceledException)
            {
                throw;
            }
            catch (Exception ex) when (allowRetry && attempt < maxAttempts && IsTransientNetworkException(ex))
            {
                Logger.LogWarning(ex, "Transient error during SendRequestInternal for {uri}, retrying attempt {attempt}/{maxAttempts}",
                    requestMessage.RequestUri, attempt, maxAttempts);
                if (ct.HasValue)
                {
                    await Task.Delay(TimeSpan.FromMilliseconds(200), ct.Value).ConfigureAwait(false);
                }
                else
                {
                    await Task.Delay(TimeSpan.FromMilliseconds(200)).ConfigureAwait(false);
                }
            }
            catch (Exception ex)
            {
                Logger.LogWarning(ex, "Error during SendRequestInternal for {uri}", requestMessage.RequestUri);
                throw;
            }
        }
    }

    private static bool IsTransientNetworkException(Exception ex)
    {
        var current = ex;
        while (current != null)
        {
            if (current is SocketException socketEx)
            {
                return socketEx.SocketErrorCode is SocketError.ConnectionReset or SocketError.ConnectionAborted or SocketError.TimedOut;
            }

            current = current.InnerException;
        }

        return false;
    }
}