using System.Text;
using System.Text.Json;
using System.Linq;
using ZB.MOM.NatsNet.Server.Internal;
using ZB.MOM.NatsNet.Server.Internal.DataStructures;

namespace ZB.MOM.NatsNet.Server;

internal sealed partial class NatsStream
{
    internal static (string Ttl, bool Ok) GetMessageScheduleTTL(byte[]? hdr)
    {
        if (hdr == null || hdr.Length == 0)
            return (string.Empty, true);

        var ttl = NatsMessageHeaders.GetHeader(NatsHeaderConstants.JsScheduleTtl, hdr);
        if (ttl == null || ttl.Length == 0)
            return (string.Empty, true);

        var ttlValue = Encoding.ASCII.GetString(ttl);
        var (_, err) = ParseMessageTTL(ttlValue);
        return err == null ? (ttlValue, true) : (string.Empty, false);
    }

    internal static string GetMessageScheduleTarget(byte[]? hdr)
    {
        if (hdr == null || hdr.Length == 0)
            return string.Empty;

        var value = NatsMessageHeaders.GetHeader(NatsHeaderConstants.JsScheduleTarget, hdr);
        return value == null || value.Length == 0 ? string.Empty : Encoding.ASCII.GetString(value);
    }

    internal static string GetMessageScheduleSource(byte[]? hdr)
    {
        if (hdr == null || hdr.Length == 0)
            return string.Empty;

        var value = NatsMessageHeaders.GetHeader(NatsHeaderConstants.JsScheduleSource, hdr);
        return value == null || value.Length == 0 ? string.Empty : Encoding.ASCII.GetString(value);
    }

    internal static string GetBatchId(byte[]? hdr)
    {
        if (hdr == null || hdr.Length == 0)
            return string.Empty;

        var value = NatsMessageHeaders.GetHeader(NatsHeaderConstants.JsBatchId, hdr);
        return value == null || value.Length == 0 ? string.Empty : Encoding.ASCII.GetString(value);
    }

    internal static (ulong Seq, bool Exists) GetBatchSequence(byte[]? hdr)
    {
        if (hdr == null || hdr.Length == 0)
            return (0, false);

        var value = NatsMessageHeaders.SliceHeader(NatsHeaderConstants.JsBatchSeq, hdr);
        if (value is null || value.Value.Length == 0)
            return (0, false);

        var parsed = ServerUtilities.ParseInt64(value.Value.Span);
        return parsed < 0 ? (0, false) : ((ulong)parsed, true);
    }

    public bool IsClustered()
    {
        _mu.EnterReadLock();
        try
        {
            return IsClusteredInternal();
        }
        finally
        {
            _mu.ExitReadLock();
        }
    }

    internal bool IsClusteredInternal() => _node is IRaftNode;

    internal void QueueInbound(IpQueue<InMsg> inbound, string subject, string? reply, byte[]? hdr, byte[]? msg, object? sourceInfo, object? trace)
    {
        _ = sourceInfo;
        _ = trace;

        var inboundMsg = InMsg.Rent();
        inboundMsg.Subject = subject;
        inboundMsg.Reply = reply;
        inboundMsg.Hdr = hdr;
        inboundMsg.Msg = msg;

        var (_, error) = inbound.Push(inboundMsg);
        if (error != null)
            inboundMsg.ReturnToPool();
    }

    internal JsApiMsgGetResponse ProcessDirectGetRequest(string reply, byte[]? hdr, byte[]? msg)
    {
        var response = new JsApiMsgGetResponse();
        if (string.IsNullOrWhiteSpace(reply))
            return response;

        if (JetStreamVersioning.ErrorOnRequiredApiLevel(GetRequiredApiLevelHeader(hdr)))
        {
            response.Error = JsApiErrors.NewJSRequiredApiLevelError();
            return response;
        }

        if (msg == null || msg.Length == 0)
        {
            response.Error = JsApiErrors.NewJSBadRequestError();
            return response;
        }

        JsApiMsgGetRequest? request;
        try
        {
            request = JsonSerializer.Deserialize<JsApiMsgGetRequest>(msg);
        }
        catch (JsonException)
        {
            response.Error = JsApiErrors.NewJSBadRequestError();
            return response;
        }

        if (request == null)
        {
            response.Error = JsApiErrors.NewJSBadRequestError();
            return response;
        }

        return GetDirectRequest(request, reply);
    }

    internal JsApiMsgGetResponse ProcessDirectGetLastBySubjectRequest(string subject, string reply, byte[]? hdr, byte[]? msg)
    {
        var response = new JsApiMsgGetResponse();
        if (string.IsNullOrWhiteSpace(reply))
            return response;

        if (JetStreamVersioning.ErrorOnRequiredApiLevel(GetRequiredApiLevelHeader(hdr)))
        {
            response.Error = JsApiErrors.NewJSRequiredApiLevelError();
            return response;
        }

        var request = msg == null || msg.Length == 0
            ? new JsApiMsgGetRequest()
            : JsonSerializer.Deserialize<JsApiMsgGetRequest>(msg) ?? new JsApiMsgGetRequest();

        var key = ExtractDirectGetLastBySubjectKey(subject);
        if (string.IsNullOrEmpty(key))
        {
            response.Error = JsApiErrors.NewJSBadRequestError();
            return response;
        }

        request.LastFor = key;
        return GetDirectRequest(request, reply);
    }

    internal JsApiMsgGetResponse GetDirectMulti(JsApiMsgGetRequest request, string reply)
    {
        _ = reply;

        if (Store == null)
            return new JsApiMsgGetResponse { Error = JsApiErrors.NewJSNoMessageFoundError() };

        var filters = request.MultiLastFor ?? [];
        if (filters.Length == 0)
            return new JsApiMsgGetResponse { Error = JsApiErrors.NewJSNoMessageFoundError() };

        var (seqs, error) = Store.MultiLastSeqs(filters, request.UpToSeq, 1024);
        if (error != null || seqs.Length == 0)
            return new JsApiMsgGetResponse { Error = JsApiErrors.NewJSNoMessageFoundError() };

        var firstSeq = seqs[0];
        var loaded = Store.LoadMsg(firstSeq, new StoreMsg());
        if (loaded == null)
            return new JsApiMsgGetResponse { Error = JsApiErrors.NewJSNoMessageFoundError() };

        return new JsApiMsgGetResponse { Message = ToStoredMsg(loaded) };
    }

    internal JsApiMsgGetResponse GetDirectRequest(JsApiMsgGetRequest request, string reply)
    {
        _ = reply;
        if (request.MultiLastFor is { Length: > 0 })
            return GetDirectMulti(request, reply);

        if (Store == null)
            return new JsApiMsgGetResponse { Error = JsApiErrors.NewJSNoMessageFoundError() };

        StoreMsg? loaded = null;
        if (request.Seq > 0)
        {
            loaded = Store.LoadMsg(request.Seq, new StoreMsg());
        }
        else if (!string.IsNullOrWhiteSpace(request.LastFor))
        {
            loaded = Store.LoadLastMsg(request.LastFor!, new StoreMsg());
        }
        else if (!string.IsNullOrWhiteSpace(request.NextFor))
        {
            var (sm, _) = Store.LoadNextMsg(request.NextFor!, SubscriptionIndex.SubjectHasWildcard(request.NextFor!), request.Seq, new StoreMsg());
            loaded = sm;
        }
        else if (request.StartTime.HasValue)
        {
            var seq = Store.GetSeqFromTime(request.StartTime.Value);
            if (seq > 0)
                loaded = Store.LoadMsg(seq, new StoreMsg());
        }

        if (loaded == null)
            return new JsApiMsgGetResponse { Error = JsApiErrors.NewJSNoMessageFoundError() };

        return new JsApiMsgGetResponse { Message = ToStoredMsg(loaded) };
    }

    private static StoredMsg ToStoredMsg(StoreMsg loaded) => new()
    {
        Subject = loaded.Subject,
        Sequence = loaded.Seq,
        Header = loaded.Hdr,
        Data = loaded.Msg,
        Time = DateTimeOffset.FromUnixTimeMilliseconds(loaded.Ts / 1_000_000L).UtcDateTime,
    };

    private static string? GetRequiredApiLevelHeader(byte[]? hdr)
    {
        if (hdr == null || hdr.Length == 0)
            return null;

        var value = NatsMessageHeaders.GetHeader(JsApiSubjects.JsRequiredApiLevel, hdr);
        return value == null || value.Length == 0 ? null : Encoding.ASCII.GetString(value);
    }

    private static string ExtractDirectGetLastBySubjectKey(string subject)
    {
        if (string.IsNullOrWhiteSpace(subject))
            return string.Empty;

        var parts = subject.Split('.');
        return parts.Length <= 5 ? string.Empty : string.Join('.', parts.Skip(5));
    }
}