using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[RequireComponent(typeof(CharacterController))]
public class FPSController : MonoBehaviour
{
    public Camera playerCamera;
    public float walkSpeed = 9f;
    public float runSpeed = 18f;
    public float jumpPower = 7f;
    public float gravity = 20f;
    public float lookSpeed = 2f;
    public float lookXLimit = 45f;
    public float airAcceleration = 2f;
    public float groundFriction = 6f;

    Vector3 velocity = Vector3.zero;
    float rotationX = 0;

    public bool canMove = true;

    CharacterController characterController;

    void Start()
    {
        characterController = GetComponent<CharacterController>();
        Cursor.lockState = CursorLockMode.Locked;
        Cursor.visible = false;
    }

    void Update()
    {
        Vector3 forward = playerCamera.transform.TransformDirection(Vector3.forward);
        Vector3 right = playerCamera.transform.TransformDirection(Vector3.right);
        forward.y = 0;
        right.y = 0;
        forward.Normalize();
        right.Normalize();

        bool isRunning = Input.GetKey(KeyCode.LeftShift);
        float speed = isRunning ? runSpeed : walkSpeed;
        Vector3 wishDir = forward * Input.GetAxis("Vertical") + right * Input.GetAxis("Horizontal");

        if (characterController.isGrounded)
        {
            velocity.y = -0.5f;  // Stick to the ground

            if (canMove)
            {
                float drop = velocity.magnitude * groundFriction * Time.deltaTime;
                velocity *= Mathf.Max(velocity.magnitude - drop, 0) / velocity.magnitude;  // Apply friction

                Accelerate(wishDir, speed, groundFriction);  // Ground accelerate

                if (Input.GetButton("Jump"))
                {
                    velocity.y = jumpPower;  // Jump
                }
            }
        }
        else
        {
            velocity.y -= gravity * Time.deltaTime;  // Apply gravity

            if (canMove)
            {
                // Air acceleration is now dependant on how aligned the move direction is with the current velocity direction
                // The closer to straight ahead, the more acceleration, allowing for more maneuverability while keeping strafe speed under control
                float currentSpeed = Vector3.Dot(velocity, wishDir);
                float accel = airAcceleration * Mathf.Max(0, 1 - currentSpeed / speed);
                Accelerate(wishDir, speed, accel);
            }
        }

        // Apply movement
        characterController.Move(velocity * Time.deltaTime);

        // Looking
        if (canMove)
        {
            rotationX += -Input.GetAxis("Mouse Y") * lookSpeed;
            rotationX = Mathf.Clamp(rotationX, -lookXLimit, lookXLimit);
            playerCamera.transform.localRotation = Quaternion.Euler(rotationX, 0, 0);
            transform.rotation *= Quaternion.Euler(0, Input.GetAxis("Mouse X") * lookSpeed, 0);
        }
    }

    // Acceleration function to add force to the velocity in the given direction
    void Accelerate(Vector3 wishDir, float wishSpeed, float accel)
    {
        float currentSpeed = Vector3.Dot(velocity, wishDir);
        float addSpeed = wishSpeed - currentSpeed;
        if (addSpeed <= 0) return;
        float accelerationSpeed = accel * Time.deltaTime * wishSpeed;
        if (accelerationSpeed > addSpeed)
        {
            accelerationSpeed = addSpeed;
        }
        velocity += wishDir.normalized * accelerationSpeed;
    }
}