using System;
using UnityEngine;
using Unity.MLAgents;
using Unity.Barracuda;
using Unity.MLAgents.Actuators;
using Unity.MLAgentsExamples;
using Unity.MLAgents.Sensors;
using Random = UnityEngine.Random;

[RequireComponent(typeof(JointDriveController))] // Required to set joint forces
public class CrawlerAgent : Agent
{
    public enum CrawlerAgentBehaviorType
    {
        CrawlerDynamic, CrawlerDynamicVariableSpeed, CrawlerStatic, CrawlerStaticVariableSpeed
    }

    public CrawlerAgentBehaviorType typeOfCrawler;

    //Crawler Brains
    //A different brain will be used depending on the CrawlerAgentBehaviorType selected
    [Header("NN Models")]
    public NNModel crawlerDyBrain;
    public NNModel crawlerDyVSBrain;
    public NNModel crawlerStBrain;
    public NNModel crawlerStVSBrain;

    [Header("Walk Speed")]
    [Range(0.1f, 10)]
    [SerializeField]
    //The walking speed to try and achieve
    private float m_TargetWalkingSpeed = 10;


    public float TargetWalkingSpeed // property
    {
        get { return m_TargetWalkingSpeed; }
        set { m_TargetWalkingSpeed = Mathf.Clamp(value, .1f, m_maxWalkingSpeed); }
    }

    const float m_maxWalkingSpeed = 10; //The max walking speed

    //Should the agent sample a new goal velocity each episode?
    //If true, walkSpeed will be randomly set between zero and m_maxWalkingSpeed in OnEpisodeBegin()
    //If false, the goal velocity will be walkingSpeed
    public bool randomizeWalkSpeedEachEpisode;

    //The direction an agent will walk during training.
    private Vector3 m_WorldDirToWalk = Vector3.right;
    [Header("Target To Walk Towards")]
    public Transform targetPrefab; //Target prefab
    public Transform target; //Target the agent will walk towards during training.

    [Header("Body Parts")] [Space(10)] public Transform body;
    public Transform leg0Upper;
    public Transform leg0Lower;
    public Transform leg1Upper;
    public Transform leg1Lower;
    public Transform leg2Upper;
    public Transform leg2Lower;
    public Transform leg3Upper;
    public Transform leg3Lower;


    //This will be used as a stabilized model space reference point for observations
    //Because ragdolls can move erratically during training, using a stabilized reference transform improves learning
    OrientationCubeController m_OrientationCube;

    //The indicator graphic gameobject that points towards the target
    DirectionIndicator m_DirectionIndicator;
    JointDriveController m_JdController;

    [Header("Foot Grounded Visualization")] [Space(10)]
    public bool useFootGroundedVisualization;

    public MeshRenderer foot0;
    public MeshRenderer foot1;
    public MeshRenderer foot2;
    public MeshRenderer foot3;
    public Material groundedMaterial;
    public Material unGroundedMaterial;
    private Unity.MLAgents.Policies.BehaviorParameters m_BehaviorParams;


    public override void Initialize()
    {

        m_BehaviorParams = GetComponent<Unity.MLAgents.Policies.BehaviorParameters>();
        switch (typeOfCrawler)
        {
            case CrawlerAgentBehaviorType.CrawlerDynamic :
            {
                m_BehaviorParams.BehaviorName = "CrawlerDynamic";
                if(crawlerDyBrain)
                    m_BehaviorParams.Model = crawlerDyBrain;
                randomizeWalkSpeedEachEpisode = false;
                target = Instantiate(targetPrefab, transform.position, Quaternion.identity, transform);
                break;
            }
            case CrawlerAgentBehaviorType.CrawlerDynamicVariableSpeed :
            {
                m_BehaviorParams.BehaviorName = "CrawlerDynamicVariableSpeed";
                if(crawlerDyVSBrain)
                    m_BehaviorParams.Model = crawlerDyVSBrain;
//                    SetModel("CrawlerDynamicVariableSpeed", crawlerDyVSBrain);
                target = Instantiate(targetPrefab, transform.position, Quaternion.identity, transform);
                randomizeWalkSpeedEachEpisode = true;
                break;
            }
            case CrawlerAgentBehaviorType.CrawlerStatic :
            {
                m_BehaviorParams.BehaviorName = "CrawlerStatic";
                if(crawlerStBrain)
                    m_BehaviorParams.Model = crawlerStBrain;
                var targetSpawnPos = transform.TransformPoint(new Vector3(0, 0, 1000));
                target = Instantiate(targetPrefab, targetSpawnPos, Quaternion.identity, transform);
                randomizeWalkSpeedEachEpisode = false;
                break;
            }
            case CrawlerAgentBehaviorType.CrawlerStaticVariableSpeed :
            {
                m_BehaviorParams.BehaviorName = "CrawlerStaticVariableSpeed";
                if(crawlerStVSBrain)
                    m_BehaviorParams.Model = crawlerStVSBrain;
                var targetSpawnPos = transform.TransformPoint(new Vector3(0, 0, 1000));
                target = Instantiate(targetPrefab, targetSpawnPos, Quaternion.identity, transform);
                randomizeWalkSpeedEachEpisode = true;
                break;
            }
        }

        m_OrientationCube = GetComponentInChildren<OrientationCubeController>();
        m_DirectionIndicator = GetComponentInChildren<DirectionIndicator>();
        m_JdController = GetComponent<JointDriveController>();

        //Setup each body part
        m_JdController.SetupBodyPart(body);
        m_JdController.SetupBodyPart(leg0Upper);
        m_JdController.SetupBodyPart(leg0Lower);
        m_JdController.SetupBodyPart(leg1Upper);
        m_JdController.SetupBodyPart(leg1Lower);
        m_JdController.SetupBodyPart(leg2Upper);
        m_JdController.SetupBodyPart(leg2Lower);
        m_JdController.SetupBodyPart(leg3Upper);
        m_JdController.SetupBodyPart(leg3Lower);
    }

    /// <summary>
    /// Loop over body parts and reset them to initial conditions.
    /// </summary>
    public override void OnEpisodeBegin()
    {
        foreach (var bodyPart in m_JdController.bodyPartsDict.Values)
        {
            bodyPart.Reset(bodyPart);
        }

        //Random start rotation to help generalize
        body.rotation = Quaternion.Euler(0, Random.Range(0.0f, 360.0f), 0);

        UpdateOrientationObjects();

        //Set our goal walking speed
        TargetWalkingSpeed =
            randomizeWalkSpeedEachEpisode ? Random.Range(0.1f, m_maxWalkingSpeed) : TargetWalkingSpeed;

    }

    /// <summary>
    /// Add relevant information on each body part to observations.
    /// </summary>
    public void CollectObservationBodyPart(BodyPart bp, VectorSensor sensor)
    {
        //GROUND CHECK
        sensor.AddObservation(bp.groundContact.touchingGround); // Is this bp touching the ground

        if (bp.rb.transform != body)
        {
            sensor.AddObservation(bp.currentStrength / m_JdController.maxJointForceLimit);
        }
    }

    /// <summary>
    /// Loop over body parts to add them to observation.
    /// </summary>
    public override void CollectObservations(VectorSensor sensor)
    {
        var cubeForward = m_OrientationCube.transform.forward;

        //velocity we want to match
        var velGoal = cubeForward * TargetWalkingSpeed;
        //ragdoll's avg vel
        var avgVel = GetAvgVelocity();

        //current ragdoll velocity. normalized
        sensor.AddObservation(Vector3.Distance(velGoal, avgVel));
        //avg body vel relative to cube
        sensor.AddObservation(m_OrientationCube.transform.InverseTransformDirection(avgVel));
        //vel goal relative to cube
        sensor.AddObservation(m_OrientationCube.transform.InverseTransformDirection(velGoal));
        //rotation delta
        sensor.AddObservation(Quaternion.FromToRotation(body.forward, cubeForward));

        //Add pos of target relative to orientation cube
        sensor.AddObservation(m_OrientationCube.transform.InverseTransformPoint(target.transform.position));

        RaycastHit hit;
        float maxRaycastDist = 10;
        if (Physics.Raycast(body.position, Vector3.down, out hit, maxRaycastDist))
        {
            sensor.AddObservation(hit.distance / maxRaycastDist);
        }
        else
            sensor.AddObservation(1);

        foreach (var bodyPart in m_JdController.bodyPartsList)
        {
            CollectObservationBodyPart(bodyPart, sensor);
        }
    }


//    /// <summary>
//    /// Loop over body parts to add them to observation.
//    /// </summary>
//    public override void CollectObservations(VectorSensor sensor)
//    {
//        //Add pos of target relative to orientation cube
//        sensor.AddObservation(m_OrientationCube.transform.InverseTransformPoint(target.transform.position));
//
//        RaycastHit hit;
//        float maxRaycastDist = 10;
//        if (Physics.Raycast(body.position, Vector3.down, out hit, maxRaycastDist))
//        {
//            sensor.AddObservation(hit.distance / maxRaycastDist);
//        }
//        else
//            sensor.AddObservation(1);
//
//        foreach (var bodyPart in m_JdController.bodyPartsList)
//        {
//            CollectObservationBodyPart(bodyPart, sensor);
//        }
//    }

    public override void OnActionReceived(ActionBuffers actionBuffers)
    {
        // The dictionary with all the body parts in it are in the jdController
        var bpDict = m_JdController.bodyPartsDict;

        var continuousActions = actionBuffers.ContinuousActions;
        var i = -1;
        // Pick a new target joint rotation
        bpDict[leg0Upper].SetJointTargetRotation(continuousActions[++i], continuousActions[++i], 0);
        bpDict[leg1Upper].SetJointTargetRotation(continuousActions[++i], continuousActions[++i], 0);
        bpDict[leg2Upper].SetJointTargetRotation(continuousActions[++i], continuousActions[++i], 0);
        bpDict[leg3Upper].SetJointTargetRotation(continuousActions[++i], continuousActions[++i], 0);
        bpDict[leg0Lower].SetJointTargetRotation(continuousActions[++i], 0, 0);
        bpDict[leg1Lower].SetJointTargetRotation(continuousActions[++i], 0, 0);
        bpDict[leg2Lower].SetJointTargetRotation(continuousActions[++i], 0, 0);
        bpDict[leg3Lower].SetJointTargetRotation(continuousActions[++i], 0, 0);

        // Update joint strength
        bpDict[leg0Upper].SetJointStrength(continuousActions[++i]);
        bpDict[leg1Upper].SetJointStrength(continuousActions[++i]);
        bpDict[leg2Upper].SetJointStrength(continuousActions[++i]);
        bpDict[leg3Upper].SetJointStrength(continuousActions[++i]);
        bpDict[leg0Lower].SetJointStrength(continuousActions[++i]);
        bpDict[leg1Lower].SetJointStrength(continuousActions[++i]);
        bpDict[leg2Lower].SetJointStrength(continuousActions[++i]);
        bpDict[leg3Lower].SetJointStrength(continuousActions[++i]);
    }

    void FixedUpdate()
    {
        UpdateOrientationObjects();

        // If enabled the feet will light up green when the foot is grounded.
        // This is just a visualization and isn't necessary for function
        if (useFootGroundedVisualization)
        {
            foot0.material = m_JdController.bodyPartsDict[leg0Lower].groundContact.touchingGround
                ? groundedMaterial
                : unGroundedMaterial;
            foot1.material = m_JdController.bodyPartsDict[leg1Lower].groundContact.touchingGround
                ? groundedMaterial
                : unGroundedMaterial;
            foot2.material = m_JdController.bodyPartsDict[leg2Lower].groundContact.touchingGround
                ? groundedMaterial
                : unGroundedMaterial;
            foot3.material = m_JdController.bodyPartsDict[leg3Lower].groundContact.touchingGround
                ? groundedMaterial
                : unGroundedMaterial;
        }

        var cubeForward = m_OrientationCube.transform.forward;

        // Set reward for this step according to mixture of the following elements.
        // a. Match target speed
        //This reward will approach 1 if it matches perfectly and approach zero as it deviates
        var matchSpeedReward = GetMatchingVelocityReward(cubeForward * TargetWalkingSpeed, GetAvgVelocity());

        //Check for NaNs
        if (float.IsNaN(matchSpeedReward))
        {
            throw new ArgumentException(
                "NaN in moveTowardsTargetReward.\n" +
                $" cubeForward: {cubeForward}\n" +
                $" hips.velocity: {m_JdController.bodyPartsDict[body].rb.velocity}\n" +
                $" maximumWalkingSpeed: {m_maxWalkingSpeed}"
            );
        }

        // b. Rotation alignment with target direction.
        //This reward will approach 1 if it faces the target direction perfectly and approach zero as it deviates
        var lookAtTargetReward = (Vector3.Dot(cubeForward, body.forward) + 1) * .5F;

        //Check for NaNs
        if (float.IsNaN(lookAtTargetReward))
        {
            throw new ArgumentException(
                "NaN in lookAtTargetReward.\n" +
                $" cubeForward: {cubeForward}\n" +
                $" body.forward: {body.forward}"
            );
        }

        AddReward(matchSpeedReward * lookAtTargetReward);

    }

    //Update OrientationCube and DirectionIndicator
    void UpdateOrientationObjects()
    {
        m_WorldDirToWalk = target.position - body.position;
        m_OrientationCube.UpdateOrientation(body, target);
        if (m_DirectionIndicator)
        {
            m_DirectionIndicator.MatchOrientation(m_OrientationCube.transform);
        }
    }

    //Returns the average velocity of all of the body parts
    //Using the velocity of the hips only has shown to result in more erratic movement from the limbs, so...
    //...using the average helps prevent this erratic movement
    Vector3 GetAvgVelocity()
    {
        Vector3 velSum = Vector3.zero;
        Vector3 avgVel = Vector3.zero;

        //ALL RBS
        int numOfRB = 0;
        foreach (var item in m_JdController.bodyPartsList)
        {
            numOfRB++;
            velSum += item.rb.velocity;
        }

        avgVel = velSum / numOfRB;
        return avgVel;
    }

    //normalized value of the difference in avg speed vs goal walking speed.
    public float GetMatchingVelocityReward(Vector3 velocityGoal, Vector3 actualVelocity)
    {
        //distance between our actual velocity and goal velocity
        var velDeltaMagnitude = Mathf.Clamp(Vector3.Distance(actualVelocity, velocityGoal), 0, TargetWalkingSpeed);

        //return the value on a declining sigmoid shaped curve that decays from 1 to 0
        //This reward will approach 1 if it matches perfectly and approach zero as it deviates
        return Mathf.Pow(1 - Mathf.Pow(velDeltaMagnitude / TargetWalkingSpeed, 2), 2);
    }

    /// <summary>
    /// Agent touched the target
    /// </summary>
    public void TouchedTarget()
    {
        AddReward(1f);
    }
}