using System.Diagnostics;
using FinalFactory.Rendezvous.Contracts;

namespace FinalFactory.Rendezvous.Client;

public sealed class RendezvousJoinClient : IRendezvousJoinClient
{
    private const string LeaseTokenHeader = "X-Rendezvous-Lease-Token";
    private const string ClientPunchCapabilityHeader = "X-Rendezvous-Client-Punch-Capability";

    private readonly RendezvousHttpTransport _transport;

    public RendezvousJoinClient(
        HttpClient httpClient,
        RendezvousClientOptions? options = null,
        IRendezvousDelay? delay = null)
    {
        _transport = new(httpClient, options, delay);
    }

    public Task<RendezvousClientResult<CreateJoinAttemptResponse>> CreateAsync(
        CreateJoinAttemptRequest request,
        CancellationToken cancellationToken = default)
    {
        if (request is null)
        {
            throw new ArgumentNullException(nameof(request));
        }
        CreateJoinAttemptRequest body = new()
        {
            ContractVersion = request.ContractVersion,
            IdempotencyKey = request.IdempotencyKey,
            GameId = request.GameId,
            EnvironmentId = request.EnvironmentId,
            ListingId = request.ListingId,
            ProtocolVersion = request.ProtocolVersion,
        };
        return _transport.SendSafeAsync<CreateJoinAttemptResponse>(
            () => RendezvousHttpTransport.JsonRequest(HttpMethod.Post, "v1/join-attempts", body),
            cancellationToken);
    }

    public async Task<RendezvousConnectionStartResult> CreateConnectionAttemptAsync(
        CreateJoinAttemptRequest request,
        NetworkEndpoint? dedicatedFallback = null,
        CancellationToken cancellationToken = default)
    {
        if (dedicatedFallback is not null
            && !ContractValidation.IsNetworkEndpointValid(dedicatedFallback))
        {
            throw new ArgumentException("The dedicated fallback endpoint is invalid.", nameof(dedicatedFallback));
        }

        Stopwatch elapsed = Stopwatch.StartNew();
        try
        {
            RendezvousClientResult<CreateJoinAttemptResponse> result = await CreateAsync(
                request,
                cancellationToken).ConfigureAwait(false);
            elapsed.Stop();
            return result.IsSuccess && result.Value is not null
                ? RendezvousConnectionStartResult.ReadyForTraversal(result.Value)
                : RendezvousConnectionStartResult.Completed(
                    RendezvousConnectionOutcome.FromServiceError(
                        result.Error,
                        elapsed.Elapsed,
                        dedicatedFallback));
        }
        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
        {
            elapsed.Stop();
            return RendezvousConnectionStartResult.Completed(
                RendezvousConnectionOutcome.Create(
                    ConnectionOutcomeKind.Cancelled,
                    RendezvousConnectionOutcomeSource.Caller,
                    RendezvousConnectionFailureCategory.Lifecycle,
                    RendezvousConnectionPhase.Authorization,
                    elapsed.Elapsed,
                    dedicatedFallback));
        }
    }

    public Task<RendezvousClientResult<bool>> CancelAsync(
        CreateJoinAttemptResponse attempt,
        CancellationToken cancellationToken = default)
    {
        if (attempt is null)
        {
            throw new ArgumentNullException(nameof(attempt));
        }
        return _transport.SendSafeAsync<bool>(
            () => HeaderRequest(
                HttpMethod.Delete,
                $"v1/join-attempts/{attempt.AttemptId}",
                ClientPunchCapabilityHeader,
                RequireHeaderValue(attempt.ClientPunchCapability, nameof(attempt))),
            cancellationToken);
    }

    public Task<RendezvousClientResult<BrowseHostJoinAttemptsResponse>> BrowseForHostAsync(
        PublishedSession session,
        int pageSize = ContractLimits.BrowserPageMaxItems,
        string? cursor = null,
        CancellationToken cancellationToken = default)
    {
        if (session is null)
        {
            throw new ArgumentNullException(nameof(session));
        }
        if (pageSize is < 1 or > ContractLimits.BrowserPageMaxItems)
        {
            throw new ArgumentOutOfRangeException(nameof(pageSize));
        }

        string query = $"v1/sessions/{session.ListingId}/join-attempts"
            + $"?contractVersion={ContractLimits.ContractVersion}"
            + $"&pageSize={pageSize}"
            + (cursor is null ? string.Empty : $"&cursor={Uri.EscapeDataString(cursor)}");
        return _transport.SendSafeAsync<BrowseHostJoinAttemptsResponse>(
            () => HeaderRequest(
                HttpMethod.Get,
                query,
                LeaseTokenHeader,
                RequireHeaderValue(session.LeaseToken, nameof(session))),
            cancellationToken);
    }

    public async Task<RendezvousClientResult<IReadOnlyList<HostJoinAttempt>>> BrowseAllForHostAsync(
        PublishedSession session,
        int maximumPages = 100,
        CancellationToken cancellationToken = default)
    {
        if (session is null)
        {
            throw new ArgumentNullException(nameof(session));
        }
        if (maximumPages is < 1 or > 1_000)
        {
            throw new ArgumentOutOfRangeException(nameof(maximumPages));
        }

        List<HostJoinAttempt> attempts = [];
        string? cursor = null;
        for (int page = 0; page < maximumPages; page++)
        {
            RendezvousClientResult<BrowseHostJoinAttemptsResponse> result =
                await BrowseForHostAsync(
                    session,
                    ContractLimits.BrowserPageMaxItems,
                    cursor,
                    cancellationToken).ConfigureAwait(false);
            if (!result.IsSuccess || result.Value is null)
            {
                return RendezvousClientResult.Failure<IReadOnlyList<HostJoinAttempt>>(
                    result.Error,
                    result.Message,
                    result.RetryAfterSeconds);
            }

            attempts.AddRange(result.Value.Items);
            cursor = result.Value.NextCursor;
            if (string.IsNullOrEmpty(cursor))
            {
                return RendezvousClientResult.Success<IReadOnlyList<HostJoinAttempt>>(
                    attempts.AsReadOnly());
            }
        }

        return RendezvousClientResult.Failure<IReadOnlyList<HostJoinAttempt>>(
            RendezvousErrorCode.CapacityExceeded,
            $"Host invitation polling exceeded the configured {maximumPages}-page limit.");
    }

    public Task<RendezvousClientResult<ReportConnectionOutcomeResponse>> ReportOutcomeAsync(
        CreateJoinAttemptResponse attempt,
        RendezvousConnectionOutcome outcome,
        CancellationToken cancellationToken = default)
    {
        if (attempt is null)
        {
            throw new ArgumentNullException(nameof(attempt));
        }
        if (outcome is null)
        {
            throw new ArgumentNullException(nameof(outcome));
        }
        if (!ContractValidation.IsReportableConnectionOutcome(outcome.Kind))
        {
            throw new ArgumentException(
                "This outcome cannot be reported for an issued join attempt.",
                nameof(outcome));
        }

        ReportConnectionOutcomeRequest body = new()
        {
            Outcome = outcome.Kind,
            ElapsedBucket = RendezvousConnectionOutcome.BucketElapsed(outcome.Elapsed),
        };
        return _transport.SendSafeAsync<ReportConnectionOutcomeResponse>(
            () => HeaderJsonRequest(
                HttpMethod.Post,
                $"v1/join-attempts/{attempt.AttemptId}/outcome",
                ClientPunchCapabilityHeader,
                RequireHeaderValue(attempt.ClientPunchCapability, nameof(attempt)),
                body),
            cancellationToken);
    }

    private static HttpRequestMessage HeaderRequest(
        HttpMethod method,
        string uri,
        string header,
        string value)
    {
        HttpRequestMessage request = new(method, uri);
        request.Headers.TryAddWithoutValidation(header, value);
        return request;
    }

    private static HttpRequestMessage HeaderJsonRequest<T>(
        HttpMethod method,
        string uri,
        string header,
        string value,
        T body)
    {
        HttpRequestMessage request = RendezvousHttpTransport.JsonRequest(method, uri, body);
        request.Headers.TryAddWithoutValidation(header, value);
        return request;
    }

    private static string RequireHeaderValue(string value, string parameterName) =>
        !string.IsNullOrWhiteSpace(value)
            ? value
            : throw new ArgumentException("The required capability is missing.", parameterName);
}