using System;
using UnityEngine;
using UnityEngine.InputSystem;

[RequireComponent(typeof(Rigidbody2D), typeof(BoxCollider2D))]
public class Player : MonoBehaviour
{
    private Rigidbody2D _rigidbody;
    private bool _wantsJump;
    private bool _isJumping;
    private bool _isGrounded;
    private float _jumpStartTime;
    private float _dir;
    private Vector3 _oldPos;
    
    public InputAction movement;
    public InputAction jump;
    public float speed = 4;
    [Tooltip("This is the desired height, relative to the initial jump point, in unity units (meters)")]
    public float jumpHeight;
    [Tooltip("This is how long it takes to achieve the `jumpHeight` value")]
    public float jumpDuration;

    private void Start()
    {
        _rigidbody = GetComponent<Rigidbody2D>();
        movement.Enable();
        jump.Enable();

        jump.started += JumpStart;
        jump.canceled += JumpEnd;

        Application.targetFrameRate = 144;
    }

    private void JumpStart(InputAction.CallbackContext callbackContext)
    {
        _wantsJump = true;
    }

    private void JumpEnd(InputAction.CallbackContext callbackContext)
    {
        _wantsJump = false;
        _isJumping = false;
    }

    private void Update()
    {
        _dir = movement.ReadValue<float>();
        _oldPos = _rigidbody.position;
        _oldPos.x += _dir * speed * Time.deltaTime;

        if (_wantsJump && _isGrounded)
        {
            _isJumping = true;
            _isGrounded = false;
            _jumpStartTime = Time.time;
        }

        if (_isJumping && _wantsJump && _jumpStartTime + jumpDuration > Time.time)
        {
            _rigidbody.gravityScale = 0;
            var metersPerSecond = jumpHeight / jumpDuration;
            // This simulates "acceleration" or rather the immediate force of a jump and the falloff due to gravity,
            // without actually using gravity. That sounds odd, and maybe it can be improved, but this was the first
            // solution that gives the designer a maximum height to hit over a duration while allowing the user to
            // end the jump early (like most SNES era platformers). All this while still looking good or "correct".
            // TODO: I think the closer the end value (b in the lerp function) is to 0 the more "correct" it will look.
            var accelerationCoefficient = Mathf.Lerp(1.5f, 0.5f, (Time.time - _jumpStartTime) / jumpDuration);
            _oldPos.y += accelerationCoefficient * metersPerSecond * Time.deltaTime;
        }
        else
        {
            _rigidbody.gravityScale = 1;
        }

        _rigidbody.position = _oldPos;
    }

    private void OnCollisionEnter2D(Collision2D other)
    {
        foreach (var contacts in other.contacts)
        {
            if (contacts.point.y < _rigidbody.position.y)
            {
                // we are grounded and can exit!
                _isGrounded = true;
                return;
            }
        }
    }
}