using System.Collections;
using System.Collections.Generic;
using UnityEditor;
using UnityEngine;
using UnityEngine.InputSystem;

public class PlayerMovement : MonoBehaviour, PlayerInput.IMovementActions
{
    //          TYPES
    public enum State
    {
        INVALID     = 0,

        GROUNDED    = 1,
        SLIDING     = 2,
        AIRBORNE    = 3
    }


    //          REFERENCES
    public CapsuleCollider playerNavCollider;
    public Rigidbody rgdBdy;
    public PlayerCameraController camCntlr;


    //          PARAMETERS
    public float smoothing;

    public string[] groundingLayers;
    public float moveForce = 30f;
    public float maxSpeed = 10f;
    public AnimationCurve brakingForceCurve = null;
    public float slidingAngle = 45f;

    public float jumpHeight = 3f;
    public float jumpCooldown = 0.15f;
    public float coyoteTime = 0.1f;

    public float turnRate = 270f;


    //          PROPERTIES
    public State CurState
    {
        get { return this._curState; }
        set
        {
            // Guard; same state
            if (value == this._curState)
                return;

            // TODO: Teardown

            // Swap
            this._curState = value;

            // TODO: Setup
        }
    }


    //          INTERNALS
    private int _groundingMask = -1;
    private PlayerInput _inpt = null;

    private State _curState = State.AIRBORNE;

    private Vector2 _curMvInpt = Vector2.zero;
    private Vector2 _smoothMvInpt = Vector2.zero;

    private bool _strafeToggleHeld = false;

    private float _jumpHoldStartTime = -1f;
    private float _lastJumpTime = -1f;

    // Record the results of the grounding check
    // as instance variables
    private float _groundedTime = -1f;
    private Vector3 _groundNormal = Vector3.up;


    //          LIFECYCLE
    private void Awake()
    {
        this._groundingMask = LayerMask.GetMask(this.groundingLayers);
    }

    private void OnEnable()
    {
        if (this._inpt == null)
        {
            this._inpt = new PlayerInput();
            this._inpt.Movement.SetCallbacks(this);
        }

        this._inpt.Enable();
    }

    private void OnDisable()
    {
        if (this._inpt != null)
        {
            this._inpt.Disable();
        }
    }

    private void FixedUpdate()
    {
        this.HandleInput();
        this.GroundCheck();

        switch(this._curState)
        {
            case State.GROUNDED:
                this.HandleGrounded();
                break;
            case State.SLIDING:
                this.HandleSliding();
                break;
            case State.AIRBORNE:
                this.HandleAirborne();
                break;
            default:
                break;
        }
    }


    //          BEHAVIORS
    private void HandleInput()
    {
        // Smooth input
        this._smoothMvInpt = MathExtras.LerpSmooth2(this._smoothMvInpt, Vector2.ClampMagnitude(this._curMvInpt, 1f), Time.fixedDeltaTime, this.smoothing);

        // Clip Input
        if (this._curMvInpt.sqrMagnitude < 1e-3f && this._smoothMvInpt.sqrMagnitude < 1e-3f)
            this._smoothMvInpt = Vector2.zero;
    }

    // This gets run once per FixedUpdate
    private void GroundCheck()
    {
        // Spherecast parameters determined from player's capsule collider
        Vector3 start = (((this.playerNavCollider.height * 0.5f) - this.playerNavCollider.radius - 0.1f) * Vector3.down) + this.rgdBdy.position;
        float dist = (Physics.gravity * Time.fixedDeltaTime * 3f).magnitude;

        Ray ry = new Ray(start, Physics.gravity);
        RaycastHit ht;

        // _groundingMask determines which layers are checked for ground
        // See LayerMask.GetMask(string[] layers) for more info. Can leave as -1 to check all layers.
        if (Physics.SphereCast(ry, this.playerNavCollider.radius, out ht, dist, this._groundingMask))   
        {
            // Hit ground, record
            this._groundedTime = Time.time;
            this._groundNormal = ht.normal;
        }
        else
        {
            // Timeout ground normal
            if (this._groundedTime > 0f && (Time.time - this._groundedTime) > this.coyoteTime)
            {
                this._groundedTime = -1f;
                this._groundNormal = Vector3.up;
            }
        }
    }

    private void ApplyGroundForces()
    {
        // Convert input direction to camera local
        Vector3 input = this.camCntlr.cam.transform.TransformVector(new Vector3(this._smoothMvInpt.x, 0f, this._smoothMvInpt.y));

        // Rotate to horizontal, then to match ground orientation
        input = Quaternion.FromToRotation(Vector3.up, this._groundNormal) * Quaternion.FromToRotation(this.camCntlr.transform.up, Vector3.up) * input;

        // Apply input force
        this.rgdBdy.AddForce(input * this.moveForce, ForceMode.Force);

        Debug.DrawLine(this.rgdBdy.position, this.rgdBdy.position + (input * this.moveForce), Color.white);

        // Apply braking
        Vector3 groundSpeed = Vector3.ProjectOnPlane(this.rgdBdy.velocity, this._groundNormal);
        float brakingForce = this.brakingForceCurve.Evaluate(groundSpeed.magnitude / this.maxSpeed) * this.moveForce;
        this.rgdBdy.AddForce(groundSpeed.normalized * -1f * brakingForce, ForceMode.Force);

        Debug.DrawLine(this.rgdBdy.position, this.rgdBdy.position + (groundSpeed.normalized * -1f * brakingForce), Color.blue);

        // Counteract gravity while grounded on slope
        this.rgdBdy.AddForce(Vector3.ProjectOnPlane(Physics.gravity, this._groundNormal) * -1f);

        // Stopping force (only when no input, only when grounded)
        if (this._groundedTime == Time.time && this._smoothMvInpt == Vector2.zero)
            this.rgdBdy.AddForce(MathExtras.ClipVec3(groundSpeed, 1f) * -1f * this.moveForce, ForceMode.Force);
    }

    private bool ApplyJumpForces()
    {
        // Guard; Jumped to recently
        if ((Time.time - this._lastJumpTime) < this.jumpCooldown)
            return false;

        // Record
        this._lastJumpTime = Time.time;

        // Calculate jump height from gravity
        Vector3 jumpFrc = Physics.gravity.normalized * -1f * Mathf.Sqrt(2f * Physics.gravity.magnitude * this.jumpHeight);
        this.rgdBdy.AddForce(jumpFrc, ForceMode.VelocityChange);

        return true;
    }

    private void HandleFacing()
    {
        // Get desired facing direction
        Vector3 facingDir = this.transform.forward;

        if (this._strafeToggleHeld)
        {
            // Face camera direction
            facingDir = this.camCntlr.cam.transform.forward;
            facingDir.y = 0f;
            facingDir.Normalize();
        }
        else
        {
            // Face direction of travel
            Vector3 groundVel = Vector3.ProjectOnPlane(this.rgdBdy.velocity, this._groundNormal);
            if (groundVel.sqrMagnitude > 1e-2f)
                facingDir = groundVel.normalized;
        }

        // Get target rotation
        Quaternion facingRot = Quaternion.FromToRotation(this.transform.forward, facingDir);
        facingRot = Quaternion.Euler(Vector3.Scale(facingRot.eulerAngles, new Vector3(0f, 1f, 0f))) * this.rgdBdy.rotation;

        // Yaw player towards facing direction
        this.rgdBdy.rotation = Quaternion.RotateTowards(this.rgdBdy.rotation, facingRot, this.turnRate * Time.fixedDeltaTime);
    }

    //          FSM
    private void HandleGrounded()
    {
        // Watch for state change
        if (Time.time != this._groundedTime)
        {
            this.CurState = State.AIRBORNE;
            return;
        }
        else if (Vector3.Angle(Vector3.up, this._groundNormal) > this.slidingAngle)
        {
            this.CurState = State.SLIDING;
            return;
        }

        // Check and execute jump
        // The '&&' operator 'short-circuits', so ApplyJumpForces will only be run if the previous operands are true
        if (this._jumpHoldStartTime > 0f && (Time.time - this._jumpHoldStartTime) < this.coyoteTime && this.ApplyJumpForces())
            return;

        this.ApplyGroundForces();
        this.HandleFacing();
    }

    private void HandleSliding()
    {
        // Watch for state change
        if (Time.time != this._groundedTime)
        {
            this.CurState = State.AIRBORNE;
            return;
        }
        else if (Vector3.Angle(Vector3.up, this._groundNormal) < this.slidingAngle)
        {
            this.CurState = State.GROUNDED;
            return;
        }

        // TODO: Any behavior here? Braking force?
    }

    private void HandleAirborne()
    {
        // Watch for state change
        if (Time.time == this._groundedTime)
        {
            if (Vector3.Angle(Vector3.up, this._groundNormal) > this.slidingAngle)
                this.CurState = State.SLIDING;
            else
                this.CurState = State.GROUNDED;

            return;
        }

        // TODO: Any behavior here? Air control?
    }

    
    //          DEBUG

#if UNITY_EDITOR
    private void OnDrawGizmos()
    {
        Handles.Label(this.transform.position + Vector3.up * 2f, $"State: {this._curState}\r\nSpeed: {this.rgdBdy.velocity.magnitude}\r\nAngle: {Vector3.Angle(Vector3.up, this._groundNormal)}");
    }
#endif

    //          INPUT
    public void OnMoveInput(InputAction.CallbackContext context)
    {
        this._curMvInpt = context.ReadValue<Vector2>();
    }

    public void OnStrafeToggle(InputAction.CallbackContext context)
    {
        if (context.phase == InputActionPhase.Started)
            this._strafeToggleHeld = true;
        else if (context.phase == InputActionPhase.Canceled)
            this._strafeToggleHeld = false;
    }

    public void OnJump(InputAction.CallbackContext context)
    {
        if (context.phase == InputActionPhase.Started)
            this._jumpHoldStartTime = Time.time;
        else if (context.phase == InputActionPhase.Canceled)
            this._jumpHoldStartTime = -1f;
    }
}