using System;
using UnityEngine;

namespace Rigging.Debugging
{

    public class GLScope : IDisposable
    {
        bool bScopeBefore;

        public GLScope(bool enabled)
        {
            bScopeBefore = GLHandle.bScopeEnabled;
            GLHandle.EnterScope(enabled);
        }

        public void Dispose()
        {
            GLHandle.EndScope(bScopeBefore);
        }
    }

    [DefaultExecutionOrder(-100)]
    public class GLHandle : MonoBehaviour
    {

        private static GLHandle instance;
        private static event System.Action onGL;
        private static event System.Action onGLFixedUpdate;

        private static Material lineMaterial;

        public static bool bScopeEnabled;

        static GLHandle()
        {
            bScopeEnabled = true;
        }

        static void CreateLineMaterial()
        {
            if (!lineMaterial)
            {
                // Unity has a built-in shader that is useful for drawing
                // simple colored things.
                Shader shader = Shader.Find("Hidden/Internal-Colored");
                lineMaterial = new Material(shader);
                lineMaterial.hideFlags = HideFlags.HideAndDontSave;
                // Turn on alpha blending
                lineMaterial.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
                lineMaterial.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                // Turn backface culling off
                lineMaterial.SetInt("_Cull", (int)UnityEngine.Rendering.CullMode.Off);
                // Turn off depth writes
                lineMaterial.SetInt("_ZWrite", 0);
                lineMaterial.SetInt("_ZTest", 0);
            }
        }

        private void FixedUpdate()
        {
            onGLFixedUpdate = null;
        }

        public void OnRenderObject()
        {
            CreateLineMaterial();

            // Apply the line material
            lineMaterial.SetPass(0);

            onGL?.Invoke();
            onGL = null;

            onGLFixedUpdate?.Invoke();
        }

        static void Check()
        {
            if(instance == null)
            {
                GameObject gl = new GameObject();
                gl.name = "GLHandle";
                instance = gl.AddComponent<GLHandle>();
            }
        }

        public static void EnterScope(bool enabled = true)
        {
            bScopeEnabled = enabled;
        }

        public static void EndScope(bool enabled = true)
        {
            bScopeEnabled = true;
        }

        public static void DrawSphere(Vector3 pos, float radius, int verticalSegments = 1, int radialSegments = 2)
        {
            Check();

            if (!bScopeEnabled) return;

            if(Time.inFixedTimeStep)
            {
                onGLFixedUpdate += () =>
                {
                    Draw.Sphere(pos, radius, verticalSegments, radialSegments);
                };
            }
            else
            {
                onGL += () =>
                {
                    Draw.Sphere(pos, radius, verticalSegments, radialSegments);
                };
            }
        }

        public static void DrawLine(Vector3 p1, Vector3 p2)
        {
            Check();

            if (!bScopeEnabled) return;

            if (Time.inFixedTimeStep)
            {
                onGLFixedUpdate += () =>
                {
                    Draw.Line3D(p1, p2);
                };
            }
            else
            {
                onGL += () =>
                {
                    Draw.Line3D(p1, p2);
                };
            }
        }

    }

}