using System.IO;
using UnityEditor;
using UnityEngine;

public class MetallicGloss : EditorWindow
{
    Texture2D metallicMap;
    Texture2D smoothnessMap;
    bool invertMetallic;
    bool invertSmoothness;

    [MenuItem("Tools/yum_food/Metallic Gloss")]
    static void ShowWindow()
    {
        var window = GetWindow<MetallicGloss>("Metallic Gloss");
        window.minSize = new Vector2(300, 180);
    }

    void OnGUI()
    {
        EditorGUILayout.Space(5);

        metallicMap = (Texture2D)EditorGUILayout.ObjectField("Metallic Map", metallicMap, typeof(Texture2D), false);
        invertMetallic = EditorGUILayout.Toggle("Invert", invertMetallic);

        EditorGUILayout.Space(5);

        smoothnessMap = (Texture2D)EditorGUILayout.ObjectField("Smoothness Map", smoothnessMap, typeof(Texture2D), false);
        invertSmoothness = EditorGUILayout.Toggle("Invert", invertSmoothness);

        if (metallicMap != null) EnforceLinear(metallicMap);
        if (smoothnessMap != null) EnforceLinear(smoothnessMap);

        EditorGUILayout.Space(10);

        using (new EditorGUI.DisabledScope(metallicMap == null && smoothnessMap == null))
        {
            if (GUILayout.Button("Merge"))
                Merge();
        }
    }

    static void EnforceLinear(Texture2D tex)
    {
        string path = AssetDatabase.GetAssetPath(tex);
        if (!string.IsNullOrEmpty(path)) EnforceSettings(path);
    }

    static void EnforceSettings(string path)
    {
        var importer = AssetImporter.GetAtPath(path) as TextureImporter;
        if (importer == null) return;
        bool dirty = false;
        if (importer.sRGBTexture) { importer.sRGBTexture = false; dirty = true; }
        if (importer.textureType != TextureImporterType.Default) { importer.textureType = TextureImporterType.Default; dirty = true; }
        if (importer.wrapMode != TextureWrapMode.Repeat) { importer.wrapMode = TextureWrapMode.Repeat; dirty = true; }
        if (importer.filterMode != FilterMode.Trilinear) { importer.filterMode = FilterMode.Trilinear; dirty = true; }
        if (importer.anisoLevel != 4) { importer.anisoLevel = 4; dirty = true; }
        if (dirty) importer.SaveAndReimport();
    }

    void Merge()
    {
        Texture2D reference = metallicMap != null ? metallicMap : smoothnessMap;
        int w = reference.width;
        int h = reference.height;

        Color[] mPixels = metallicMap != null ? ReadPixels(metallicMap, w, h) : null;
        Color[] sPixels = smoothnessMap != null ? ReadPixels(smoothnessMap, w, h) : null;

        var pixels = new Color[w * h];
        for (int i = 0; i < pixels.Length; i++)
        {
            float m = mPixels != null ? mPixels[i].r : 0;
            float s = sPixels != null ? sPixels[i].r : 0;
            if (invertMetallic) m = 1 - m;
            if (invertSmoothness) s = 1 - s;
            pixels[i] = new Color(m, 0, 0, s);
        }

        var output = new Texture2D(w, h, TextureFormat.RGBA32, false, true);
        output.SetPixels(pixels);
        output.Apply();

        string refPath = AssetDatabase.GetAssetPath(reference);
        string dir = Path.GetDirectoryName(refPath);
        string basename = Path.GetFileNameWithoutExtension(refPath);
        string outputPath = Path.Combine(dir, basename + "_metallic_gloss.png");

        File.WriteAllBytes(outputPath, output.EncodeToPNG());
        DestroyImmediate(output);
        AssetDatabase.ImportAsset(outputPath);

        EnforceSettings(outputPath);
        EditorGUIUtility.PingObject(AssetDatabase.LoadAssetAtPath<Texture2D>(outputPath));
    }

    static Color[] ReadPixels(Texture2D tex, int w, int h)
    {
        var rt = RenderTexture.GetTemporary(w, h, 0, RenderTextureFormat.ARGB32, RenderTextureReadWrite.Linear);
        Graphics.Blit(tex, rt);
        var prev = RenderTexture.active;
        RenderTexture.active = rt;
        var tmp = new Texture2D(w, h, TextureFormat.RGBA32, false, true);
        tmp.ReadPixels(new Rect(0, 0, w, h), 0, 0);
        tmp.Apply();
        RenderTexture.active = prev;
        RenderTexture.ReleaseTemporary(rt);
        var pixels = tmp.GetPixels();
        DestroyImmediate(tmp);
        return pixels;
    }
}