using UnityEditor;
using UnityEditor.U2D;
using UnityEngine;

/// <summary>
/// 贴图平台压缩格式的公共常量、工具方法，以及平台设置的核心逻辑。
/// Batch 和 Import 只需调用 Apply 方法，不重复编写设置代码。
/// </summary>
public static class TexturePlatformFormatHelper
{
    // ---- 格式常量 ----
    public const TextureImporterFormat ANDROID_RGBA = TextureImporterFormat.ASTC_6x6;
    public const TextureImporterFormat ANDROID_RGB  = TextureImporterFormat.ASTC_6x6;
    public const TextureImporterFormat IOS_FORMAT   = TextureImporterFormat.ASTC_6x6;
    public const TextureImporterFormat WEBGL_FORMAT = TextureImporterFormat.ASTC_6x6;

    // ---- 目标文件夹 ----
    public const string TARGET_FOLDER = "Assets/ResourcesOut";

    // ---- 图集固定尺寸 ----
    public const int ATLAS_MAX_SIZE = 2048;

    // ---- 压缩质量 ----
    public const int COMPRESSION_QUALITY = 50;

    // ============================================================
    // 核心：对单个 importer 应用平台格式设置
    // ============================================================

    /// <summary>
    /// 对 TextureImporter 设置 Android=ETC2 / iPhone=ASTC / WebGL=ASTC。
    /// 返回 true 表示有改动，调用方负责 SaveAndReimport。
    /// </summary>
    public static bool ApplyTexturePlatformSettings(TextureImporter importer)
    {
        bool needsAlpha = NeedsAlpha(importer);
        var androidTarget = needsAlpha ? ANDROID_RGBA : ANDROID_RGB;
        int maxSize = GetMaxTextureSize(importer);
        bool changed = false;

        // Android → ETC2
        {
            var s = importer.GetPlatformTextureSettings("Android");
            if (!s.overridden || s.format != androidTarget)
            {
                s.overridden = true;
                s.maxTextureSize = maxSize;
                s.textureCompression = TextureImporterCompression.Compressed;
                s.format = androidTarget;
                s.compressionQuality = COMPRESSION_QUALITY;
                importer.SetPlatformTextureSettings(s);
                changed = true;
            }
        }

        // iPhone → ASTC
        {
            var s = importer.GetPlatformTextureSettings("iPhone");
            if (!s.overridden || s.format != IOS_FORMAT)
            {
                s.overridden = true;
                s.maxTextureSize = maxSize;
                s.textureCompression = TextureImporterCompression.Compressed;
                s.format = IOS_FORMAT;
                s.compressionQuality = COMPRESSION_QUALITY;
                importer.SetPlatformTextureSettings(s);
                changed = true;
            }
        }

        // WebGL → ASTC
        {
            var s = importer.GetPlatformTextureSettings("WebGL");
            if (!s.overridden || s.format != WEBGL_FORMAT)
            {
                s.overridden = true;
                s.maxTextureSize = maxSize;
                s.textureCompression = TextureImporterCompression.Compressed;
                s.format = WEBGL_FORMAT;
                s.compressionQuality = COMPRESSION_QUALITY;
                importer.SetPlatformTextureSettings(s);
                changed = true;
            }
        }

        return changed;
    }

    /// <summary>
    /// 对 SpriteAtlasImporter 设置 Android=ETC2_RGBA8 / iPhone=ASTC / WebGL=ASTC。
    /// 返回 true 表示有改动，调用方负责 SaveAndReimport。
    /// </summary>
    public static bool ApplyAtlasPlatformSettings(SpriteAtlasImporter importer)
    {
        bool changed = false;

        // Android → ETC2_RGBA8（图集始终含 Alpha）
        {
            var s = importer.GetPlatformSettings("Android");
            if (!s.overridden || s.format != ANDROID_RGBA)
            {
                s.overridden = true;
                s.maxTextureSize = ATLAS_MAX_SIZE;
                s.textureCompression = TextureImporterCompression.Compressed;
                s.format = ANDROID_RGBA;
                s.compressionQuality = COMPRESSION_QUALITY;
                importer.SetPlatformSettings(s);
                changed = true;
            }
        }

        // iPhone → ASTC
        {
            var s = importer.GetPlatformSettings("iPhone");
            if (!s.overridden || s.format != IOS_FORMAT)
            {
                s.overridden = true;
                s.maxTextureSize = ATLAS_MAX_SIZE;
                s.textureCompression = TextureImporterCompression.Compressed;
                s.format = IOS_FORMAT;
                s.compressionQuality = COMPRESSION_QUALITY;
                importer.SetPlatformSettings(s);
                changed = true;
            }
        }

        // WebGL → ASTC
        {
            var s = importer.GetPlatformSettings("WebGL");
            if (!s.overridden || s.format != WEBGL_FORMAT)
            {
                s.overridden = true;
                s.maxTextureSize = ATLAS_MAX_SIZE;
                s.textureCompression = TextureImporterCompression.Compressed;
                s.format = WEBGL_FORMAT;
                s.compressionQuality = COMPRESSION_QUALITY;
                importer.SetPlatformSettings(s);
                changed = true;
            }
        }

        return changed;
    }

    // ============================================================
    // 工具方法
    // ============================================================

    public static bool NeedsAlpha(TextureImporter importer)
    {
        if (importer.DoesSourceTextureHaveAlpha())
            return true;

        foreach (var platform in new[] { "Android", "iPhone", "Standalone" })
        {
            var s = importer.GetPlatformTextureSettings(platform);
            if (s.overridden && IsAlphaFormat(s.format))
                return true;
        }

        if (importer.alphaSource != TextureImporterAlphaSource.None)
            return importer.DoesSourceTextureHaveAlpha();

        return false;
    }

    public static bool IsAlphaFormat(TextureImporterFormat format)
    {
        switch (format)
        {
            case TextureImporterFormat.RGBA32:
            case TextureImporterFormat.RGBA16:
            case TextureImporterFormat.ARGB32:
            case TextureImporterFormat.ARGB16:
            case TextureImporterFormat.DXT5:
            case TextureImporterFormat.ETC2_RGBA8:
            case TextureImporterFormat.ASTC_4x4:
            case TextureImporterFormat.ASTC_5x5:
            case TextureImporterFormat.ASTC_6x6:
            case TextureImporterFormat.ASTC_8x8:
            case TextureImporterFormat.ASTC_10x10:
            case TextureImporterFormat.ASTC_12x12:
            case TextureImporterFormat.PVRTC_RGBA2:
            case TextureImporterFormat.PVRTC_RGBA4:
                return true;
            default:
                return false;
        }
    }

    public static int GetMaxTextureSize(TextureImporter importer)
    {
        foreach (var platform in new[] { "Android", "iPhone", "Standalone" })
        {
            var s = importer.GetPlatformTextureSettings(platform);
            if (s.overridden)
                return s.maxTextureSize;
        }
        return importer.maxTextureSize;
    }
}