using System;
using System.Collections.Generic;
using System.Linq;
using Unity.Collections;
using UnityEngine;
using UnityEngine.Serialization;

namespace Unity.Netcode
{
    /// <summary>
    /// The configuration object used to start server, client and hosts
    /// </summary>
    [Serializable]
    public class NetworkConfig
    {
        /// <summary>
        /// The protocol version. Different versions doesn't talk to each other.
        /// </summary>
        [Tooltip("Use this to make two builds incompatible with each other")]
        public ushort ProtocolVersion = 0;

        /// <summary>
        /// The transport hosts the sever uses
        /// </summary>
        [Tooltip("The NetworkTransport to use")]
        public NetworkTransport NetworkTransport = null;

        /// <summary>
        /// The default player prefab
        /// </summary>
        [Tooltip("When set, NetworkManager will automatically create and spawn the assigned player prefab. This can be overridden by adding it to the NetworkPrefabs list and selecting override.")]
        public GameObject PlayerPrefab;

        [SerializeField]
        public NetworkPrefabs Prefabs = new NetworkPrefabs();


        /// <summary>
        /// The tickrate of network ticks. This value controls how often netcode runs user code and sends out data.
        /// </summary>
        [Tooltip("The tickrate. This value controls how often netcode runs user code and sends out data. The value is in 'ticks per seconds' which means a value of 50 will result in 50 ticks being executed per second or a fixed delta time of 0.02.")]
        public uint TickRate = 30;

        /// <summary>
        /// The amount of seconds for the server to wait for the connection approval handshake to complete before the client is disconnected.
        ///
        /// If the timeout is reached before approval is completed the client will be disconnected.
        /// </summary>
        /// <remarks>
        /// The period begins after the <see cref="NetworkEvent.Connect"/> is received on the server.
        /// The period ends once the server finishes processing a <see cref="ConnectionRequestMessage"/> from the client.
        ///
        /// This setting is independent of any Transport-level timeouts that may be in effect. It covers the time between
        /// the connection being established on the Transport layer, the client sending a
        /// <see cref="ConnectionRequestMessage"/>, and the server processing that message through <see cref="ConnectionApproval"/>.
        ///
        /// This setting is server-side only.
        /// </remarks>
        [Tooltip("The amount of seconds for the server to wait for the connection approval handshake to complete before the client is disconnected")]
        public int ClientConnectionBufferTimeout = 10;

        /// <summary>
        /// Whether or not to use connection approval
        /// </summary>
        [Tooltip("Whether or not to force clients to be approved before they connect")]
        public bool ConnectionApproval = false;

        /// <summary>
        /// The data to send during connection which can be used to decide on if a client should get accepted
        /// </summary>
        [Tooltip("The connection data sent along with connection requests")]
        public byte[] ConnectionData = new byte[0];

        /// <summary>
        /// If your logic uses the NetworkTime, this should probably be turned off. If however it's needed to maximize accuracy, this is recommended to be turned on
        /// </summary>
        [Tooltip("Enable this to re-sync the NetworkTime after the initial sync")]
        public bool EnableTimeResync = false;

        /// <summary>
        /// If time re-sync is turned on, this specifies the interval between syncs in seconds.
        /// </summary>
        [Tooltip("The amount of seconds between re-syncs of NetworkTime, if enabled")]
        public int TimeResyncInterval = 30;

        /// <summary>
        /// Whether or not to ensure that NetworkVariables can be read even if a client accidentally writes where its not allowed to. This costs some CPU and bandwidth.
        /// </summary>
        [Tooltip("Ensures that NetworkVariables can be read even if a client accidental writes where its not allowed to. This will cost some CPU time and bandwidth")]
        public bool EnsureNetworkVariableLengthSafety = false;

        /// <summary>
        /// Enables scene management. This will allow network scene switches and automatic scene difference corrections upon connect.
        /// SoftSynced scene objects wont work with this disabled. That means that disabling SceneManagement also enables PrefabSync.
        /// </summary>
        [Tooltip("Enables scene management. This will allow network scene switches and automatic scene difference corrections upon connect.\n" +
                 "SoftSynced scene objects wont work with this disabled. That means that disabling SceneManagement also enables PrefabSync.")]
        public bool EnableSceneManagement = true;

        /// <summary>
        /// Whether or not the netcode should check for differences in the prefabs at connection.
        /// If you dynamically add prefabs at runtime, turn this OFF
        /// </summary>
        [Tooltip("Whether or not the netcode should check for differences in the prefab lists at connection")]
        public bool ForceSamePrefabs = true;

        /// <summary>
        /// If true, NetworkIds will be reused after the NetworkIdRecycleDelay.
        /// </summary>
        [Tooltip("If true, NetworkIds will be reused after the NetworkIdRecycleDelay")]
        public bool RecycleNetworkIds = true;

        /// <summary>
        /// The amount of seconds a NetworkId has to be unused in order for it to be reused.
        /// </summary>
        [Tooltip("The amount of seconds a NetworkId has to unused in order for it to be reused")]
        public float NetworkIdRecycleDelay = 120f;

        /// <summary>
        /// Decides how many bytes to use for Rpc messaging. Leave this to 2 bytes unless you are facing hash collisions
        /// </summary>
        [Tooltip("The maximum amount of bytes to use for RPC messages.")]
        public HashSize RpcHashSize = HashSize.VarIntFourBytes;

        /// <summary>
        /// The amount of seconds to wait for all clients to load or unload a requested scene
        /// </summary>
        [Tooltip("The amount of seconds to wait for all clients to load or unload a requested scene (only when EnableSceneManagement is enabled)")]
        public int LoadSceneTimeOut = 120;

        /// <summary>
        /// The amount of time a message will be held (deferred) if the destination NetworkObject needed to process the message doesn't exist yet. If the NetworkObject is not spawned within this time period, all deferred messages for that NetworkObject will be dropped.
        /// </summary>
        [Tooltip("The amount of time a message will be held (deferred) if the destination NetworkObject needed to process the message doesn't exist yet. If the NetworkObject is not spawned within this time period, all deferred messages for that NetworkObject will be dropped.")]
        public float SpawnTimeout = 10f;

        /// <summary>
        /// Whether or not to enable network logs.
        /// </summary>
        public bool EnableNetworkLogs = true;

        /// <summary>
        /// The number of RTT samples that is kept as an average for calculations
        /// </summary>
        public const int RttAverageSamples = 5; // number of RTT to keep an average of (plus one)

        /// <summary>
        /// The number of slots used for RTT calculations. This is the maximum amount of in-flight messages
        /// </summary>
        public const int RttWindowSize = 64; // number of slots to use for RTT computations (max number of in-flight packets)

        [Tooltip("Determines whether to use the client-server or distributed authority network topology.")]
        public NetworkTopologyTypes NetworkTopology;

        [HideInInspector]
        public bool UseCMBService;

        [Tooltip("When enabled (default), the player prefab will automatically be spawned (client-side) upon the client being approved and synchronized.")]
        public bool AutoSpawnPlayerPrefabClientSide = true;

#if MULTIPLAYER_TOOLS
        /// <summary>
        /// Controls whether network messaging metrics will be gathered. (defaults to true)
        /// There is a slight performance cost to having this enabled, and can increase in processing time based on network message traffic.
        /// </summary>
        /// <remarks>
        /// The Realtime Network Stats Monitoring tool requires this to be enabled.
        /// </remarks>
        [Tooltip("Enable (default) if you want to gather messaging metrics. Realtime Network Stats Monitor requires this to be enabled. Disabling this can improve performance in release builds.")]
        public bool NetworkMessageMetrics = true;
#endif
        /// <summary>
        /// When enabled (default, this enables network profiling information. This does come with a per message processing cost.
        /// Network profiling information is automatically disabled in release builds.
        /// </summary>
        [Tooltip("Enable (default) if you want to profile network messages with development builds and defaults to being disabled in release builds. When disabled, network messaging profiling will be disabled in development builds.")]
        public bool NetworkProfilingMetrics = true;

        /// <summary>
        /// Returns a base64 encoded version of the configuration
        /// </summary>
        /// <returns></returns>
        public string ToBase64()
        {
            NetworkConfig config = this;
            var writer = new FastBufferWriter(1024, Allocator.Temp);
            using (writer)
            {
                writer.WriteValueSafe(config.ProtocolVersion);
                writer.WriteValueSafe(config.TickRate);
                writer.WriteValueSafe(config.ClientConnectionBufferTimeout);
                writer.WriteValueSafe(config.ConnectionApproval);
                writer.WriteValueSafe(config.LoadSceneTimeOut);
                writer.WriteValueSafe(config.EnableTimeResync);
                writer.WriteValueSafe(config.EnsureNetworkVariableLengthSafety);
                writer.WriteValueSafe(config.RpcHashSize);
                writer.WriteValueSafe(ForceSamePrefabs);
                writer.WriteValueSafe(EnableSceneManagement);
                writer.WriteValueSafe(RecycleNetworkIds);
                writer.WriteValueSafe(NetworkIdRecycleDelay);
                writer.WriteValueSafe(EnableNetworkLogs);

                // Allocates
                return Convert.ToBase64String(writer.ToArray());
            }
        }

        /// <summary>
        /// Sets the NetworkConfig data with that from a base64 encoded version
        /// </summary>
        /// <param name="base64">The base64 encoded version</param>
        public void FromBase64(string base64)
        {
            NetworkConfig config = this;
            byte[] binary = Convert.FromBase64String(base64);
            using var reader = new FastBufferReader(binary, Allocator.Temp);
            using (reader)
            {
                reader.ReadValueSafe(out config.ProtocolVersion);
                reader.ReadValueSafe(out config.TickRate);
                reader.ReadValueSafe(out config.ClientConnectionBufferTimeout);
                reader.ReadValueSafe(out config.ConnectionApproval);
                reader.ReadValueSafe(out config.LoadSceneTimeOut);
                reader.ReadValueSafe(out config.EnableTimeResync);
                reader.ReadValueSafe(out config.EnsureNetworkVariableLengthSafety);
                reader.ReadValueSafe(out config.RpcHashSize);
                reader.ReadValueSafe(out config.ForceSamePrefabs);
                reader.ReadValueSafe(out config.EnableSceneManagement);
                reader.ReadValueSafe(out config.RecycleNetworkIds);
                reader.ReadValueSafe(out config.NetworkIdRecycleDelay);
                reader.ReadValueSafe(out config.EnableNetworkLogs);
            }
        }


        private ulong? m_ConfigHash = null;

        /// <summary>
        /// Clears out the configuration hash value generated for a specific network session
        /// </summary>
        internal void ClearConfigHash()
        {
            m_ConfigHash = null;
        }

        /// <summary>
        /// Gets a SHA256 hash of parts of the NetworkConfig instance
        /// </summary>
        /// <param name="cache"></param>
        /// <returns></returns>
        public ulong GetConfig(bool cache = true)
        {
            if (m_ConfigHash != null && cache)
            {
                return m_ConfigHash.Value;
            }

            var writer = new FastBufferWriter(1024, Allocator.Temp, int.MaxValue);
            using (writer)
            {
                writer.WriteValueSafe(ProtocolVersion);
                writer.WriteValueSafe(NetworkConstants.PROTOCOL_VERSION);

                if (ForceSamePrefabs)
                {
                    var sortedDictionary = Prefabs.NetworkPrefabOverrideLinks.OrderBy(x => x.Key);
                    foreach (var sortedEntry in sortedDictionary)

                    {
                        writer.WriteValueSafe(sortedEntry.Key);
                    }
                }

                writer.WriteValueSafe(TickRate);
                writer.WriteValueSafe(ConnectionApproval);
                writer.WriteValueSafe(ForceSamePrefabs);
                writer.WriteValueSafe(EnableSceneManagement);
                writer.WriteValueSafe(EnsureNetworkVariableLengthSafety);
                writer.WriteValueSafe(RpcHashSize);

                if (cache)
                {
                    m_ConfigHash = XXHash.Hash64(writer.ToArray());
                    return m_ConfigHash.Value;
                }

                return XXHash.Hash64(writer.ToArray());
            }
        }

        /// <summary>
        /// Compares a SHA256 hash with the current NetworkConfig instances hash
        /// </summary>
        /// <param name="hash"></param>
        /// <returns></returns>
        public bool CompareConfig(ulong hash)
        {
            return hash == GetConfig();
        }

        internal void InitializePrefabs()
        {
            if (HasOldPrefabList())
            {
                MigrateOldNetworkPrefabsToNetworkPrefabsList();
            }

            Prefabs.Initialize();
        }

        [NonSerialized]
        private bool m_DidWarnOldPrefabList = false;

        private void WarnOldPrefabList()
        {
            if (!m_DidWarnOldPrefabList)
            {
                Debug.LogWarning("Using Legacy Network Prefab List. Consider Migrating.");
                m_DidWarnOldPrefabList = true;
            }
        }

        /// <summary>
        /// Returns true if the old List&lt;NetworkPrefab&gt; serialized data is present.
        /// </summary>
        /// <remarks>
        /// Internal use only to help migrate projects. <seealso cref="MigrateOldNetworkPrefabsToNetworkPrefabsList"/></remarks>
        internal bool HasOldPrefabList()
        {
            return OldPrefabList?.Count > 0;
        }

        /// <summary>
        /// Migrate the old format List&lt;NetworkPrefab&gt; prefab registration to the new NetworkPrefabsList ScriptableObject.
        /// </summary>
        /// <remarks>
        /// OnAfterDeserialize cannot instantiate new objects (e.g. NetworkPrefabsList SO) since it executes in a thread, so we have to do it later.
        /// Since NetworkConfig isn't a Unity.Object it doesn't get an Awake callback, so we have to do this in NetworkManager and expose this API.
        /// </remarks>
        internal NetworkPrefabsList MigrateOldNetworkPrefabsToNetworkPrefabsList()
        {
            if (OldPrefabList == null || OldPrefabList.Count == 0)
            {
                return null;
            }

            if (Prefabs == null)
            {
                throw new Exception("Prefabs field is null.");
            }

            Prefabs.NetworkPrefabsLists.Add(ScriptableObject.CreateInstance<NetworkPrefabsList>());

            if (OldPrefabList?.Count > 0)
            {
                // Migrate legacy types/fields
                foreach (var networkPrefab in OldPrefabList)
                {
                    Prefabs.NetworkPrefabsLists[Prefabs.NetworkPrefabsLists.Count - 1].Add(networkPrefab);
                }
            }

            OldPrefabList = null;
            return Prefabs.NetworkPrefabsLists[Prefabs.NetworkPrefabsLists.Count - 1];
        }

        [FormerlySerializedAs("NetworkPrefabs")]
        [SerializeField]
        internal List<NetworkPrefab> OldPrefabList;
    }
}
