using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using System;

public class ConvertToSubstance : EditorWindow
{
    private MonoScript targetMonoScript;
    private Vector2 scrollPos;
    Texture2D texture;

    [MenuItem("UMA/Tools/Convert ZB Alpha to Substance Alpha")]
    public static void ShowWindow()
    {
        GetWindow<ConvertToSubstance>(true, "Convert Grayscale to Subtance Alpha", true);
    }

    void OnGUI()
    {
        texture = (Texture2D)EditorGUILayout.ObjectField("Texture (2D)", texture, typeof(Texture2D), false);
        if (GUILayout.Button("Convert"))
        {
            if (texture == null)
            {
                EditorUtility.DisplayDialog("Error", "Please select a texture", "OK");
                return;
            }
            string path = EditorUtility.SaveFilePanel("Save Texture", "","file.png", "png");

            if (!string.IsNullOrEmpty(path))
            {
                var newTex = ConvertTexture(texture);
                if (newTex == null)
                {
                    EditorUtility.DisplayDialog("Error", "Texture is not readable", "OK");
                    return;
                }
                byte[] bytes = newTex.EncodeToPNG();
                System.IO.File.WriteAllBytes(path, bytes);
                GameObject.DestroyImmediate(newTex);
            }
        }
    }

    private static Texture2D ConvertTexture(Texture TextureToConvert)
    {
        if (TextureToConvert != null)
        {
            Texture2D tex = (Texture2D)TextureToConvert;
            Color32[] pixels = tex.GetPixels32();
            byte alphabase = pixels[0].r;

            for (int i = 0; i < pixels.Length; i++)
            {
                Color32 pixel = pixels[i];
                float alpha = 1.0f;
                float dist = Mathf.Abs(pixel.r - alphabase);
                if (pixel.r > alphabase)
                {
                     
                    float upperRange = 255 - alphabase;
                    if (upperRange == 0)
                    {
                        alpha = 1;
                    }
                    else
                    {
                        alpha = dist / upperRange;
                    }
                }
                else
                {
                    float lowerRange = alphabase;
                    if (lowerRange == 0)
                    {
                        alpha = 0;
                    }
                    else
                    {
                        alpha = dist / lowerRange;
                    }
                }
                pixels[i].a = (byte)(alpha * 255);
            }
            Texture2D newTex = new Texture2D(tex.width, tex.height, TextureFormat.RGBA32,false);
            newTex.SetPixels32(pixels);
            newTex.Apply();
        }
        return null;
    }
}