using System;
using UnityEngine;

public class RWTCameraOrbit : MonoBehaviour
{
    public Camera camera;
    public Vector3 pivot = new Vector3(512, 0, 512);
    public bool relativeY = true;
    public float distance = 1000;
    public float scrollSpeed = 100;
    public Vector2 rotation = new Vector2(0, 0);
    public Vector2 rotationSpeed = new Vector2(1, 1);
    public float maxRotationX = 80;

    private Vector3 _pivot;
    private float _distance;
    private Vector2 _rotation;
    private Vector2 lastInputPosition;
    private bool isDrag;
    private Plane? plane;

    private void Start()
    {
        lastInputPosition = Input.mousePosition;
        UpdateCamera();
    }

    private void Update()
    {
        Vector2 inputPosition = Input.mousePosition;

        if (Input.GetMouseButton(0))
        {
            if (plane == null)
            {
                Vector3? hit = GetHitPoint(inputPosition);
                if (hit != null)
                {
                    plane = new Plane(Vector3.up, hit.Value);
                    lastInputPosition = inputPosition;
                }
            }
        }
        else plane = null;

        if (lastInputPosition != inputPosition)
        {
            if (plane != null)
            {
                float d1, d2;
                Ray r1 = camera.ScreenPointToRay(lastInputPosition);
                Ray r2 = camera.ScreenPointToRay(inputPosition);
                bool s1 = plane.Value.Raycast(r1, out d1);
                bool s2 = plane.Value.Raycast(r2, out d2);
                if (s1 && s2)
                {
                    Vector3 p1 = r1.GetPoint(d1);
                    Vector3 p2 = r2.GetPoint(d2);
                    Vector3 offset = p1 - p2;
                    pivot.x += offset.x;
                    pivot.z += offset.z;
                }
            }

            if (Input.GetMouseButton(1))
            {
                Vector2 offset = lastInputPosition - inputPosition;
                rotation.x -= offset.y / 10f * rotationSpeed.x;
                rotation.y -= offset.x / 10f * rotationSpeed.y;
            }
        }

        float wheel = Input.GetAxis("Mouse ScrollWheel");
        if (Math.Abs(wheel) > float.Epsilon)
        {
            distance -= wheel * scrollSpeed;
        }

        if (_pivot != pivot || _distance != distance || _rotation != rotation) UpdateCamera();

        lastInputPosition = inputPosition;
    }

    private Vector3? GetHitPoint(Vector2 inputPosition)
    {
        RaycastHit[] hits = Physics.RaycastAll(camera.ScreenPointToRay(inputPosition));
        foreach (RaycastHit hit in hits)
        {
            if (hit.transform.GetComponent<Terrain>() != null) return hit.point;
        }

        return null;
    }

    private void UpdateCamera()
    {
        _pivot = pivot;
        _distance = distance;
        _rotation = rotation;

        if (camera == null) return;

        if (rotation.x > maxRotationX) rotation.x = maxRotationX;
        else if (rotation.x < 0) rotation.x = 0;

        float rx = 90 - rotation.x;
        if (rx > 89.9) rx = 89.9f;

        double px = Math.Cos(rx * Mathf.Deg2Rad) * distance;
        double py = Math.Sin(rx * Mathf.Deg2Rad) * distance;
        double pz = Math.Cos(rotation.y * Mathf.Deg2Rad) * px;
        px = Math.Sin(rotation.y * Mathf.Deg2Rad) * px;
        float oy = 0;

        if (relativeY)
        {
            RaycastHit[] hits = Physics.RaycastAll(new Vector3(pivot.x, 100000, pivot.z), Vector3.down);
            foreach (RaycastHit hit in hits)
            {
                if (hit.transform.GetComponent<Terrain>() != null)
                {
                    oy = hit.point.y;
                    break;
                }
            }
        }

        Vector3 target = pivot + new Vector3(0, oy, 0);

        Vector3 newPosition = new Vector3((float)px, (float)py, (float)pz) + target;

        camera.transform.position = newPosition;
        camera.transform.LookAt(target);
    }
}