using MLAPI;
using UnityEngine;
using UnityEngine.AI;
using UnityEngine.Assertions;

namespace BossRoom.Server
{
    public enum MovementState
    {
        Idle = 0,
        PathFollowing = 1,
    }

    /// <summary>
    /// Component responsible for moving a character on the server side based on inputs.
    /// </summary>
    [RequireComponent(typeof(NetworkCharacterState), typeof(NavMeshAgent), typeof(ServerCharacter)), RequireComponent(typeof(Rigidbody))]
    public class ServerCharacterMovement : NetworkedBehaviour
    {
        private NavMeshAgent m_NavMeshAgent;
        private Rigidbody m_Rigidbody;
        private NetworkCharacterState m_NetworkCharacterState;
        private NavigationSystem m_NavigationSystem;

        private DynamicNavPath m_NavPath;

        private MovementState m_MovementState;
        private ServerCharacter m_CharLogic;

        [SerializeField]
        private float m_MovementSpeed; // TODO [GOMPS-86] this should be assigned based on character definition 

        private void Awake()
        {
            m_NavMeshAgent = GetComponent<NavMeshAgent>();
            m_NetworkCharacterState = GetComponent<NetworkCharacterState>();
            m_CharLogic = GetComponent<ServerCharacter>();
            m_Rigidbody = GetComponent<Rigidbody>();

            m_NavigationSystem = GameObject.FindGameObjectWithTag(NavigationSystem.NavigationSytemTag).GetComponent<NavigationSystem>();
        }

        public override void NetworkStart()
        {
            if (!IsServer)
            {
                // Disable server component on clients
                enabled = false;
                return;
            }

            // On the server enable navMeshAgent and initialize
            m_NavMeshAgent.enabled = true;
            m_NetworkCharacterState.OnReceivedClientInput += OnReceivedClientInput;
            m_NavPath = new DynamicNavPath(m_NavMeshAgent, m_NavigationSystem);
        }

        private void OnReceivedClientInput(Vector3 position)
        {
            m_CharLogic.ClearActions(); //a fresh movement request trumps whatever we were doing before. 
            SetMovementTarget(position);
        }

        /// <summary>
        /// Sets a movement target. We will path to this position, avoiding static obstacles. 
        /// </summary>
        /// <param name="position">Position in world space to path to. </param>
        public void SetMovementTarget(Vector3 position)
        {
            m_MovementState = MovementState.PathFollowing;
            m_NavPath.SetTargetPosition(position);
        }

        /// <summary>
        /// Follow the given transform until it is reached.
        /// </summary>
        /// <param name="followTransform">The transform to follow</param>
        public void FollowTransform(Transform followTransform)
        {
            m_MovementState = MovementState.PathFollowing;
            m_NavPath.FollowTransform(followTransform);
        }

        /// <summary>
        /// Cancels any moves that are currently in progress. 
        /// </summary>
        public void CancelMove()
        {
            m_NavPath.Clear();
            m_MovementState = MovementState.Idle;
        }

        private void FixedUpdate()
        {
            if (m_MovementState == MovementState.PathFollowing)
            {
                Movement();
            }

            // Send new position values to the client
            m_NetworkCharacterState.NetworkPosition.Value = transform.position;
            m_NetworkCharacterState.NetworkRotationY.Value = transform.rotation.eulerAngles.y;
            m_NetworkCharacterState.NetworkMovementSpeed.Value =
                m_MovementState == MovementState.Idle ? 0 : m_MovementSpeed;
        }

        private void OnValidate()
        {
            if (gameObject.scene.rootCount > 1) // Hacky way for checking if this is a scene object or a prefab instance and not a prefab definition.
            {
                Assert.IsTrue(
                    GameObject.FindGameObjectWithTag(NavigationSystem.NavigationSytemTag)?.GetComponent<NavigationSystem>() != null,
                    $"NavigationSystem not found. Is there a NavigationSystem Behaviour in the Scene and does its GameObject have the {NavigationSystem.NavigationSytemTag} tag? {gameObject.scene.name}"
                );
            }
        }

        private void OnDestroy()
        {
            m_NavPath.Dispose();
        }

        private void Movement()
        {
            var desiredMovementAmount = m_MovementSpeed * Time.fixedDeltaTime;

            var movementVector = m_NavPath.MoveAlongPath(desiredMovementAmount);

            // If we didn't move stop moving.
            if (movementVector == Vector3.zero)
            {
                m_MovementState = MovementState.Idle;
                return;
            }

            m_NavMeshAgent.Move(movementVector);
            transform.rotation = Quaternion.LookRotation(movementVector);

            // After moving adjust the position of the dynamic rigidbody.
            m_Rigidbody.position = transform.position;
            m_Rigidbody.rotation = transform.rotation;
        }
    }
}