using UnityEngine;
using UnityEngine.Rendering;
using UnityEditor;

[RequireComponent(typeof(Camera))]
[ExecuteInEditMode]
public class FlipView : MonoBehaviour
{
	Camera _camera;
	public Camera Camera
	{
		get
		{
			if (_camera == null)
			{
				_camera = this.GetComponent<Camera>();
			}
			return _camera;
		}
	}

	[SerializeField]
	protected bool flipHorizontal;
	public bool FlipHorizontal
	{
		get => flipHorizontal;
		set
		{
			flipHorizontal = value;
			UpdateCameraMatrix();
		}
	}

	[SerializeField]
	protected bool flipVertical;
	public bool FlipVertical
	{
		get => flipVertical;
		set
		{
			flipVertical = value;
			UpdateCameraMatrix();
		}
	}

	protected float aspectRatio = 0;

	void Awake()
	{
		RenderPipelineManager.beginCameraRendering += beginCameraRendering;
		RenderPipelineManager.endCameraRendering += endCameraRendering;
	}

	void beginCameraRendering(ScriptableRenderContext context, Camera camera)
	{
		// Flip only if ONE of the two axis is mirrored but not if both are mirrored.
		if (this == null || !this.gameObject.activeInHierarchy)
			return;

		GL.invertCulling = flipHorizontal ^ flipVertical;

		// update is aspect ratio changed
		if (Mathf.Abs(aspectRatio - Camera.aspect) > 0.01f)
		{
			aspectRatio = Camera.aspect;
			UpdateCameraMatrix();
		}
	}

	void endCameraRendering(ScriptableRenderContext context, Camera camera)
	{
		if (this == null || !this.gameObject.activeInHierarchy)
			return;

		GL.invertCulling = false;
	}

	public void UpdateCameraMatrix()
	{
		Camera.ResetWorldToCameraMatrix();
		Camera.ResetProjectionMatrix();
		Vector3 scale = new Vector3(
			flipHorizontal ? -1 : 1,
			flipVertical ? -1 : 1,
			1);
		Camera.projectionMatrix = Camera.projectionMatrix * Matrix4x4.Scale(scale);

	}

	void OnValidate()
	{
		if (Camera == null)
			return;

		UpdateCameraMatrix();

#if UNITY_EDITOR
		RenderPipelineManager.beginCameraRendering -= beginCameraRendering;
		RenderPipelineManager.endCameraRendering -= endCameraRendering;
		if (!EditorApplication.isPlayingOrWillChangePlaymode)
		{
			RenderPipelineManager.beginCameraRendering += beginCameraRendering;
			RenderPipelineManager.endCameraRendering += endCameraRendering;
		}
#endif
	}
}