// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "export.h"
#include "skwasm_support.h"
#include "surface.h"
#include "wrappers.h"

#include "third_party/skia/include/core/SkColorSpace.h"
#include "third_party/skia/include/core/SkData.h"
#include "third_party/skia/include/core/SkImage.h"
#include "third_party/skia/include/core/SkImageInfo.h"
#include "third_party/skia/include/core/SkPicture.h"
#include "third_party/skia/include/gpu/GpuTypes.h"
#include "third_party/skia/include/gpu/GrBackendSurface.h"
#include "third_party/skia/include/gpu/GrDirectContext.h"
#include "third_party/skia/include/gpu/ganesh/GrExternalTextureGenerator.h"
#include "third_party/skia/include/gpu/ganesh/SkImageGanesh.h"
#include "third_party/skia/include/gpu/ganesh/SkSurfaceGanesh.h"
#include "third_party/skia/include/gpu/ganesh/gl/GrGLBackendSurface.h"
#include "third_party/skia/include/gpu/gl/GrGLInterface.h"
#include "third_party/skia/include/gpu/gl/GrGLTypes.h"

#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>
#include <emscripten/html5_webgl.h>

using namespace SkImages;

namespace {

enum class PixelFormat {
  rgba8888,
  bgra8888,
  rgbaFloat32,
};

SkColorType colorTypeForPixelFormat(PixelFormat format) {
  switch (format) {
    case PixelFormat::rgba8888:
      return SkColorType::kRGBA_8888_SkColorType;
    case PixelFormat::bgra8888:
      return SkColorType::kBGRA_8888_SkColorType;
    case PixelFormat::rgbaFloat32:
      return SkColorType::kRGBA_F32_SkColorType;
  }
}

SkAlphaType alphaTypeForPixelFormat(PixelFormat format) {
  switch (format) {
    case PixelFormat::rgba8888:
    case PixelFormat::bgra8888:
      return SkAlphaType::kPremul_SkAlphaType;
    case PixelFormat::rgbaFloat32:
      return SkAlphaType::kUnpremul_SkAlphaType;
  }
}

class ExternalWebGLTexture : public GrExternalTexture {
 public:
  ExternalWebGLTexture(GrBackendTexture backendTexture,
                       GLuint textureId,
                       EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context)
      : _backendTexture(backendTexture),
        _textureId(textureId),
        _webGLContext(context) {}

  GrBackendTexture getBackendTexture() override { return _backendTexture; }

  void dispose() override {
    Skwasm::makeCurrent(_webGLContext);
    glDeleteTextures(1, &_textureId);
  }

 private:
  GrBackendTexture _backendTexture;
  GLuint _textureId;
  EMSCRIPTEN_WEBGL_CONTEXT_HANDLE _webGLContext;
};
}  // namespace

class TextureSourceImageGenerator : public GrExternalTextureGenerator {
 public:
  TextureSourceImageGenerator(SkImageInfo ii,
                              SkwasmObject textureSource,
                              Skwasm::Surface* surface)
      : GrExternalTextureGenerator(ii),
        _textureSourceWrapper(
            surface->createTextureSourceWrapper(textureSource)) {}

  std::unique_ptr<GrExternalTexture> generateExternalTexture(
      GrRecordingContext* context,
      skgpu::Mipmapped mipmapped) override {
    GrGLTextureInfo glInfo;
    glInfo.fID = skwasm_createGlTextureFromTextureSource(
        _textureSourceWrapper->getTextureSource(), fInfo.width(),
        fInfo.height());
    glInfo.fFormat = GL_RGBA8_OES;
    glInfo.fTarget = GL_TEXTURE_2D;

    auto backendTexture = GrBackendTextures::MakeGL(
        fInfo.width(), fInfo.height(), mipmapped, glInfo);

    // In order to bind the image source to the texture, makeTexture has changed
    // which texture is "in focus" for the WebGL context.
    GrAsDirectContext(context)->resetContext(kTextureBinding_GrGLBackendState);
    return std::make_unique<ExternalWebGLTexture>(
        backendTexture, glInfo.fID, emscripten_webgl_get_current_context());
  }

 private:
  std::unique_ptr<Skwasm::TextureSourceWrapper> _textureSourceWrapper;
};

SKWASM_EXPORT SkImage* image_createFromPicture(SkPicture* picture,
                                               int32_t width,
                                               int32_t height) {
  return DeferredFromPicture(sk_ref_sp<SkPicture>(picture), {width, height},
                             nullptr, nullptr, BitDepth::kU8,
                             SkColorSpace::MakeSRGB())
      .release();
}

SKWASM_EXPORT SkImage* image_createFromPixels(SkData* data,
                                              int width,
                                              int height,
                                              PixelFormat pixelFormat,
                                              size_t rowByteCount) {
  return SkImages::RasterFromData(
             SkImageInfo::Make(width, height,
                               colorTypeForPixelFormat(pixelFormat),
                               alphaTypeForPixelFormat(pixelFormat),
                               SkColorSpace::MakeSRGB()),
             sk_ref_sp(data), rowByteCount)
      .release();
}

SKWASM_EXPORT SkImage* image_createFromTextureSource(SkwasmObject textureSource,
                                                     int width,
                                                     int height,
                                                     Skwasm::Surface* surface) {
  return SkImages::DeferredFromTextureGenerator(
             std::unique_ptr<TextureSourceImageGenerator>(
                 new TextureSourceImageGenerator(
                     SkImageInfo::Make(width, height,
                                       SkColorType::kRGBA_8888_SkColorType,
                                       SkAlphaType::kPremul_SkAlphaType),
                     textureSource, surface)))
      .release();
}

SKWASM_EXPORT void image_ref(SkImage* image) {
  image->ref();
}

SKWASM_EXPORT void image_dispose(SkImage* image) {
  image->unref();
}

SKWASM_EXPORT int image_getWidth(SkImage* image) {
  return image->width();
}

SKWASM_EXPORT int image_getHeight(SkImage* image) {
  return image->height();
}