using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using Google.Protobuf;

namespace MLAgents
{
    /// <summary>
    /// The batcher is an RL specific class that makes sure that the information each object in 
    /// Unity (Academy and Brains) wants to send to External is appropriately batched together 
    /// and sent only when necessary.
    /// 
    /// The Batcher will only send a Message to the Communicator when either :
    ///     1 - The academy is done
    ///     2 - At least one brain has data to send
    /// 
    /// At each step, the batcher will keep track of the brains that queried the batcher for that 
    /// step. The batcher can only send the batched data when all the Brains have queried the
    /// Batcher.
    /// </summary>
    public class Batcher
    {
        /// The default number of agents in the scene
        private const int NumAgents = 32;

        /// Keeps track of which brains have data to send on the current step
        Dictionary<string, bool> m_hasData =
            new Dictionary<string, bool>();

        /// Keeps track of which brains queried the batcher on the current step
        Dictionary<string, bool> m_hasQueried =
            new Dictionary<string, bool>();

        /// Keeps track of the agents of each brain on the current step
        Dictionary<string, List<Agent>> m_currentAgents =
            new Dictionary<string, List<Agent>>();

        /// The Communicator of the batcher, sends a message at most once per step
        Communicator m_communicator;

        /// The current UnityRLOutput to be sent when all the brains queried the batcher
        CommunicatorObjects.UnityRLOutput m_currentUnityRLOutput =
            new CommunicatorObjects.UnityRLOutput();

        /// Keeps track of the done flag of the Academy
        bool m_academyDone;

        /// Keeps track of last CommandProto sent by External
        CommunicatorObjects.CommandProto m_command;

        /// Keeps track of last EnvironmentParametersProto sent by External
        CommunicatorObjects.EnvironmentParametersProto m_environmentParameters;

        /// Keeps track of last training mode sent by External
        bool m_isTraining;

        /// Keeps track of the number of messages received
        private ulong m_messagesReceived;

        /// <summary>
        /// Initializes a new instance of the Batcher class.
        /// </summary>
        /// <param name="communicator">The communicator to be used by the batcher.</param>
        public Batcher(Communicator communicator)
        {
            this.m_communicator = communicator;
        }

        /// <summary>
        /// Sends the academy parameters through the Communicator. 
        /// Is used by the academy to send the AcademyParameters to the communicator.
        /// </summary>
        /// <returns>The External Initialization Parameters received.</returns>
        /// <param name="academyParameters">The Unity Initialization Parameters to be sent.</param>
        public CommunicatorObjects.UnityRLInitializationInput SendAcademyParameters(
            CommunicatorObjects.UnityRLInitializationOutput academyParameters)
        {
            CommunicatorObjects.UnityInput input;
            var initializationInput = new CommunicatorObjects.UnityInput();
            try
            {
                initializationInput = m_communicator.Initialize(
                    new CommunicatorObjects.UnityOutput
                    {
                        RlInitializationOutput = academyParameters
                    },
                    out input);
            }
            catch
            {
                throw new UnityAgentsException(
                    "The Communicator was unable to connect. Please make sure the External " +
                    "process is ready to accept communication with Unity.");
            }

            var firstRlInput = input.RlInput;
            m_command = firstRlInput.Command;
            m_environmentParameters = firstRlInput.EnvironmentParameters;
            m_isTraining = firstRlInput.IsTraining;
            return initializationInput.RlInitializationInput;
        }

        /// <summary>
        /// Registers the done flag of the academy to the next output to be sent
        /// to the communicator.
        /// </summary>
        /// <param name="done">If set to <c>true</c> 
        /// The academy done state will be sent to External at the next Exchange.</param>
        public void RegisterAcademyDoneFlag(bool done)
        {
            m_academyDone = done;
        }

        /// <summary>
        /// Gets the command. Is used by the academy to get reset or quit signals.
        /// </summary>
        /// <returns>The current command.</returns>
        public CommunicatorObjects.CommandProto GetCommand()
        {
            return m_command;
        }

        /// <summary>
        /// Gets the number of messages received so far. Can be used to check for new messages.
        /// </summary>
        /// <returns>The number of messages received since start of the simulation</returns>
        public ulong GetNumberMessageReceived()
        {
            return m_messagesReceived;
        }

        /// <summary>
        /// Gets the environment parameters. Is used by the academy to update
        /// the environment parameters.
        /// </summary>
        /// <returns>The environment parameters.</returns>
        public CommunicatorObjects.EnvironmentParametersProto GetEnvironmentParameters()
        {
            return m_environmentParameters;
        }

        /// <summary>
        /// Gets the last training_mode flag External sent
        /// </summary>
        /// <returns><c>true</c>, if training mode is requested, <c>false</c> otherwise.</returns>
        public bool GetIsTraining()
        {
            return m_isTraining;
        }

        /// <summary>
        /// Adds the brain to the list of brains which will be sending information to External.
        /// </summary>
        /// <param name="brainKey">Brain key.</param>
        public void SubscribeBrain(string brainKey)
        {
            m_hasQueried[brainKey] = false;
            m_hasData[brainKey] = false;
            m_currentAgents[brainKey] = new List<Agent>(NumAgents);
            m_currentUnityRLOutput.AgentInfos.Add(
                brainKey,
                new CommunicatorObjects.UnityRLOutput.Types.ListAgentInfoProto());
        }

        /// <summary>
        /// Sends the brain info. If at least one brain has an agent in need of
        /// a decision or if the academy is done, the data is sent via 
        /// Communicator. Else, a new step is realized. The data can only be
        /// sent once all the brains that subscribed to the batcher have tried
        /// to send information.
        /// </summary>
        /// <param name="brainKey">Brain key.</param>
        /// <param name="agentInfo">Agent info.</param>
        public void SendBrainInfo(
            string brainKey, Dictionary<Agent, AgentInfo> agentInfo)
        {
            // If no communicator is initialized, the Batcher will not transmit
            // BrainInfo
            if (m_communicator == null)
            {
                return;
            }

            // The brain tried called GiveBrainInfo, update m_hasQueried
            m_hasQueried[brainKey] = true;
            // Populate the currentAgents dictionary
            m_currentAgents[brainKey].Clear();
            foreach (Agent agent in agentInfo.Keys)
            {
                m_currentAgents[brainKey].Add(agent);
            }

            // If at least one agent has data to send, then append data to
            // the message and update hasSentState
            if (m_currentAgents[brainKey].Count > 0)
            {
                foreach (Agent agent in m_currentAgents[brainKey])
                {
                    CommunicatorObjects.AgentInfoProto agentInfoProto = agentInfo[agent].ToProto();
                    m_currentUnityRLOutput.AgentInfos[brainKey].Value.Add(agentInfoProto);
                }

                m_hasData[brainKey] = true;
            }

            // If any agent needs to send data, then the whole message
            // must be sent
            if (m_hasQueried.Values.All(x => x))
            {
                if (m_hasData.Values.Any(x => x) || m_academyDone)
                {
                    m_currentUnityRLOutput.GlobalDone = m_academyDone;
                    SendBatchedMessageHelper();
                }

                // The message was just sent so we must reset hasSentState and
                // triedSendState
                foreach (string k in m_currentAgents.Keys)
                {
                    m_hasData[k] = false;
                    m_hasQueried[k] = false;
                }
            }
        }

        /// <summary>
        /// Helper method that sends the curent UnityRLOutput, receives the next UnityInput and
        /// Applies the appropriate AgentAction to the agents.
        /// </summary>
        void SendBatchedMessageHelper()
        {
            var input = m_communicator.Exchange(
                new CommunicatorObjects.UnityOutput
                {
                    RlOutput = m_currentUnityRLOutput
                });
            m_messagesReceived += 1;

            foreach (string k in m_currentUnityRLOutput.AgentInfos.Keys)
            {
                m_currentUnityRLOutput.AgentInfos[k].Value.Clear();
            }

            if (input == null)
            {
                m_command = CommunicatorObjects.CommandProto.Quit;
                return;
            }

            CommunicatorObjects.UnityRLInput rlInput = input.RlInput;

            if (rlInput == null)
            {
                m_command = CommunicatorObjects.CommandProto.Quit;
                return;
            }

            m_command = rlInput.Command;
            m_environmentParameters = rlInput.EnvironmentParameters;
            m_isTraining = rlInput.IsTraining;

            if (rlInput.AgentActions == null)
            {
                return;
            }

            foreach (var brainName in rlInput.AgentActions.Keys)
            {
                if (!m_currentAgents[brainName].Any())
                {
                    continue;
                }

                if (!rlInput.AgentActions[brainName].Value.Any())
                {
                    continue;
                }

                for (var i = 0; i < m_currentAgents[brainName].Count; i++)
                {
                    var agent = m_currentAgents[brainName][i];
                    var action = rlInput.AgentActions[brainName].Value[i];
                    agent.UpdateVectorAction(action.VectorActions.ToArray());
                    agent.UpdateMemoriesAction(action.Memories.ToList());
                    agent.UpdateTextAction(action.TextActions);
                    agent.UpdateValueAction(action.Value);
                }
            }
        }
    }
}
