using System.Collections;
using UnityEngine;

public class CamOrthoTransition : MonoBehaviour
{
    public Camera cam;
    private float fov = 90f;
    private float dist = 10f;
    private bool m_Ortho;
    private bool m_Animating = false;

    public string distText = "10";
    public Vector3 pos;
    public float size;
    public Transform[] objs;

    private void OnGUI()
    {
        GUI.enabled = !m_Animating;
        distText = GUILayout.TextField(distText);
        if (float.TryParse(distText, out float d))
            dist = d;
        if (!m_Ortho && GUILayout.Button("Orthographic") )
        {
            dist = float.Parse(distText);
            StartCoroutine(Perspective2Ortho());
        }
        if (m_Ortho && GUILayout.Button("Perspective"))
        {
            dist = float.Parse(distText);
            StartCoroutine(Ortho2Perspective());
        }
        for(int i = 0; i < objs.Length; i++)
            GUILayout.Label("O"+i+":" + cam.transform.InverseTransformPoint(objs[i].position).z);
    }
    private void OnDrawGizmos()
    {
        if (!m_Animating)
        {
            m_Ortho = cam.orthographic;
            if (cam.orthographic)
            {
                size = cam.orthographicSize;
            }
            else
            {
                if (float.TryParse(distText, out float d))
                    dist = d;
                size = dist * Mathf.Tan(fov * 0.5f * Mathf.Deg2Rad);
                fov = cam.fieldOfView;
                var trans = cam.transform;
                pos = trans.position + trans.forward * dist;
            }
        }
        float a = cam.aspect;
        Gizmos.color = Color.green;
        var u = cam.transform.up * size;
        var r = cam.transform.right * size*a;
        Gizmos.DrawLine(pos + u + r, pos - u + r);
        Gizmos.DrawLine(pos + u - r, pos - u - r);
        Gizmos.DrawLine(pos + u + r, pos + u - r);
        Gizmos.DrawLine(pos - u + r, pos - u - r);
        Gizmos.DrawLine(pos + u + r, pos - u - r);
        Gizmos.DrawLine(pos - u + r, pos - u + r);
    }
    IEnumerator Perspective2Ortho()
    {
        m_Animating = true;
        var trans = cam.transform;
        fov = cam.fieldOfView;
        pos = trans.position + trans.forward * dist;
        size = dist * Mathf.Tan(fov * 0.5f * Mathf.Deg2Rad);

        for (float t = 0; t < 1.1f; t+=Time.deltaTime*1f)
        {
            float f = Mathf.Lerp(fov, 0, t);
            float d = size / Mathf.Tan(f * 0.5f * Mathf.Deg2Rad);
            cam.fieldOfView = f;
            trans.position = pos - trans.forward * d;
            if (f < 1f || d > 700)
                break;
            yield return null;
        }
        cam.orthographic = true;
        cam.orthographicSize = size;
        cam.fieldOfView = fov;
        m_Ortho = true;
        m_Animating = false;
    }
    IEnumerator Ortho2Perspective()
    {
        m_Animating = true;
        var trans = cam.transform;
        size = cam.orthographicSize;
        cam.orthographic = false;
        for (float t = 0; t < 1.1f; t += Time.deltaTime * 1f)
        {
            float f = Mathf.Lerp(1f, fov, t);
            float d = size / Mathf.Tan(f * 0.5f * Mathf.Deg2Rad);
            cam.fieldOfView = f;
            trans.position = pos - trans.forward * d;
            yield return null;
        }
        m_Ortho = false;
        m_Animating = false;
    }
}