using System.Collections.Concurrent;
using NATS.Server.Auth;
using NATS.Server.JetStream.Api;
using NATS.Server.JetStream.Cluster;
using NATS.Server.JetStream.MirrorSource;
using NATS.Server.JetStream.Models;
using NATS.Server.JetStream.Publish;
using NATS.Server.JetStream.Storage;
using NATS.Server.Subscriptions;

namespace NATS.Server.JetStream;

public sealed class StreamManager
{
    private readonly Account? _account;
    private readonly JetStreamMetaGroup? _metaGroup;
    private readonly ConcurrentDictionary<string, StreamHandle> _streams =
        new(StringComparer.Ordinal);
    private readonly ConcurrentDictionary<string, StreamReplicaGroup> _replicaGroups =
        new(StringComparer.Ordinal);
    private readonly ConcurrentDictionary<string, List<MirrorCoordinator>> _mirrorsByOrigin =
        new(StringComparer.Ordinal);
    private readonly ConcurrentDictionary<string, List<SourceCoordinator>> _sourcesByOrigin =
        new(StringComparer.Ordinal);

    public StreamManager(JetStreamMetaGroup? metaGroup = null, Account? account = null)
    {
        _metaGroup = metaGroup;
        _account = account;
    }

    public IReadOnlyCollection<string> StreamNames => _streams.Keys.ToArray();

    public JetStreamApiResponse CreateOrUpdate(StreamConfig config)
    {
        if (string.IsNullOrWhiteSpace(config.Name))
            return JetStreamApiResponse.ErrorResponse(400, "stream name required");

        var normalized = NormalizeConfig(config);
        var isCreate = !_streams.ContainsKey(normalized.Name);
        if (isCreate && _account is not null && !_account.TryReserveStream())
            return JetStreamApiResponse.ErrorResponse(10027, "maximum streams exceeded");

        var handle = _streams.AddOrUpdate(
            normalized.Name,
            _ => new StreamHandle(normalized, new MemStore()),
            (_, existing) => existing with { Config = normalized });
        _replicaGroups.AddOrUpdate(
            normalized.Name,
            _ => new StreamReplicaGroup(normalized.Name, normalized.Replicas),
            (_, existing) => existing.Nodes.Count == Math.Max(normalized.Replicas, 1)
                ? existing
                : new StreamReplicaGroup(normalized.Name, normalized.Replicas));
        RebuildReplicationCoordinators();
        _metaGroup?.ProposeCreateStreamAsync(normalized, default).GetAwaiter().GetResult();

        return BuildStreamInfoResponse(handle);
    }

    public JetStreamApiResponse GetInfo(string name)
    {
        if (_streams.TryGetValue(name, out var stream))
            return BuildStreamInfoResponse(stream);

        return JetStreamApiResponse.NotFound($"$JS.API.STREAM.INFO.{name}");
    }

    public bool TryGet(string name, out StreamHandle handle) => _streams.TryGetValue(name, out handle!);

    public ValueTask<StreamState> GetStateAsync(string name, CancellationToken ct)
    {
        if (_streams.TryGetValue(name, out var stream))
            return stream.Store.GetStateAsync(ct);

        return ValueTask.FromResult(new StreamState());
    }

    public StreamHandle? FindBySubject(string subject)
    {
        foreach (var stream in _streams.Values)
        {
            if (stream.Config.Subjects.Any(p => SubjectMatch.MatchLiteral(subject, p)))
                return stream;
        }

        return null;
    }

    public PubAck? Capture(string subject, ReadOnlyMemory<byte> payload)
    {
        var stream = FindBySubject(subject);
        if (stream == null)
            return null;

        if (_replicaGroups.TryGetValue(stream.Config.Name, out var replicaGroup))
            _ = replicaGroup.ProposeAsync($"PUB {subject}", default).GetAwaiter().GetResult();

        var seq = stream.Store.AppendAsync(subject, payload, default).GetAwaiter().GetResult();
        EnforceLimits(stream);
        var stored = stream.Store.LoadAsync(seq, default).GetAwaiter().GetResult();
        if (stored != null)
            ReplicateIfConfigured(stream.Config.Name, stored);

        return new PubAck
        {
            Stream = stream.Config.Name,
            Seq = seq,
        };
    }

    public Task StepDownStreamLeaderAsync(string stream, CancellationToken ct)
    {
        if (_replicaGroups.TryGetValue(stream, out var replicaGroup))
            return replicaGroup.StepDownAsync(ct);

        return Task.CompletedTask;
    }

    private static StreamConfig NormalizeConfig(StreamConfig config)
    {
        var copy = new StreamConfig
        {
            Name = config.Name,
            Subjects = config.Subjects.Count == 0 ? [] : [.. config.Subjects],
            MaxMsgs = config.MaxMsgs,
            Replicas = config.Replicas,
            Mirror = config.Mirror,
            Source = config.Source,
        };

        return copy;
    }

    private static JetStreamApiResponse BuildStreamInfoResponse(StreamHandle handle)
    {
        var state = handle.Store.GetStateAsync(default).GetAwaiter().GetResult();
        return new JetStreamApiResponse
        {
            StreamInfo = new JetStreamStreamInfo
            {
                Config = handle.Config,
                State = state,
            },
        };
    }

    private static void EnforceLimits(StreamHandle stream)
    {
        if (stream.Config.MaxMsgs <= 0)
            return;

        var maxMessages = (ulong)stream.Config.MaxMsgs;
        if (stream.Store is MemStore memStore)
        {
            memStore.TrimToMaxMessages(maxMessages);
            return;
        }

        if (stream.Store is FileStore fileStore)
            fileStore.TrimToMaxMessages(maxMessages);
    }

    private void RebuildReplicationCoordinators()
    {
        _mirrorsByOrigin.Clear();
        _sourcesByOrigin.Clear();

        foreach (var stream in _streams.Values)
        {
            if (!string.IsNullOrWhiteSpace(stream.Config.Mirror)
                && _streams.TryGetValue(stream.Config.Mirror, out _))
            {
                var list = _mirrorsByOrigin.GetOrAdd(stream.Config.Mirror, _ => []);
                list.Add(new MirrorCoordinator(stream.Store));
            }

            if (!string.IsNullOrWhiteSpace(stream.Config.Source)
                && _streams.TryGetValue(stream.Config.Source, out _))
            {
                var list = _sourcesByOrigin.GetOrAdd(stream.Config.Source, _ => []);
                list.Add(new SourceCoordinator(stream.Store));
            }
        }
    }

    private void ReplicateIfConfigured(string originStream, StoredMessage stored)
    {
        if (_mirrorsByOrigin.TryGetValue(originStream, out var mirrors))
        {
            foreach (var mirror in mirrors)
                mirror.OnOriginAppendAsync(stored, default).GetAwaiter().GetResult();
        }

        if (_sourcesByOrigin.TryGetValue(originStream, out var sources))
        {
            foreach (var source in sources)
                source.OnOriginAppendAsync(stored, default).GetAwaiter().GetResult();
        }
    }
}

public sealed record StreamHandle(StreamConfig Config, IStreamStore Store);