// 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 "flutter/shell/common/snapshot_controller_skia.h"

#include "display_list/display_list_image.h"
#include "flutter/flow/surface.h"
#include "flutter/fml/trace_event.h"
#include "flutter/shell/common/snapshot_controller.h"
#include "third_party/skia/include/core/SkSurface.h"

namespace flutter {

namespace {
sk_sp<SkImage> DrawSnapshot(
    sk_sp<SkSurface> surface,
    const std::function<void(SkCanvas*)>& draw_callback) {
  if (surface == nullptr || surface->getCanvas() == nullptr) {
    return nullptr;
  }

  draw_callback(surface->getCanvas());
  surface->getCanvas()->flush();

  sk_sp<SkImage> device_snapshot;
  {
    TRACE_EVENT0("flutter", "MakeDeviceSnpashot");
    device_snapshot = surface->makeImageSnapshot();
  }

  if (device_snapshot == nullptr) {
    return nullptr;
  }

  {
    TRACE_EVENT0("flutter", "DeviceHostTransfer");
    if (auto raster_image = device_snapshot->makeRasterImage()) {
      return raster_image;
    }
  }

  return nullptr;
}
}  // namespace

sk_sp<DlImage> SnapshotControllerSkia::DoMakeRasterSnapshot(
    SkISize size,
    std::function<void(SkCanvas*)> draw_callback) {
  TRACE_EVENT0("flutter", __FUNCTION__);
  sk_sp<SkImage> result;
  SkImageInfo image_info = SkImageInfo::MakeN32Premul(
      size.width(), size.height(), SkColorSpace::MakeSRGB());

  std::unique_ptr<Surface> pbuffer_surface;
  Surface* snapshot_surface = nullptr;
  auto& delegate = GetDelegate();
  if (delegate.GetSurface() && delegate.GetSurface()->GetContext()) {
    snapshot_surface = delegate.GetSurface().get();
  } else if (delegate.GetSnapshotSurfaceProducer()) {
    pbuffer_surface =
        delegate.GetSnapshotSurfaceProducer()->CreateSnapshotSurface();
    if (pbuffer_surface && pbuffer_surface->GetContext()) {
      snapshot_surface = pbuffer_surface.get();
    }
  }

  if (!snapshot_surface) {
    // Raster surface is fine if there is no on screen surface. This might
    // happen in case of software rendering.
    sk_sp<SkSurface> sk_surface = SkSurface::MakeRaster(image_info);
    result = DrawSnapshot(sk_surface, draw_callback);
  } else {
    delegate.GetIsGpuDisabledSyncSwitch()->Execute(
        fml::SyncSwitch::Handlers()
            .SetIfTrue([&] {
              sk_sp<SkSurface> surface = SkSurface::MakeRaster(image_info);
              result = DrawSnapshot(surface, draw_callback);
            })
            .SetIfFalse([&] {
              FML_DCHECK(snapshot_surface);
              auto context_switch =
                  snapshot_surface->MakeRenderContextCurrent();
              if (!context_switch->GetResult()) {
                return;
              }

              GrRecordingContext* context = snapshot_surface->GetContext();
              auto max_size = context->maxRenderTargetSize();
              double scale_factor = std::min(
                  1.0, static_cast<double>(max_size) /
                           static_cast<double>(std::max(image_info.width(),
                                                        image_info.height())));

              // Scale down the render target size to the max supported by the
              // GPU if necessary. Exceeding the max would otherwise cause a
              // null result.
              if (scale_factor < 1.0) {
                image_info = image_info.makeWH(
                    static_cast<double>(image_info.width()) * scale_factor,
                    static_cast<double>(image_info.height()) * scale_factor);
              }

              // When there is an on screen surface, we need a render target
              // SkSurface because we want to access texture backed images.
              sk_sp<SkSurface> sk_surface =
                  SkSurface::MakeRenderTarget(context,          // context
                                              SkBudgeted::kNo,  // budgeted
                                              image_info        // image info
                  );
              if (!sk_surface) {
                FML_LOG(ERROR)
                    << "DoMakeRasterSnapshot can not create GPU render target";
                return;
              }

              sk_surface->getCanvas()->scale(scale_factor, scale_factor);
              result = DrawSnapshot(sk_surface, draw_callback);
            }));
  }

  return DlImage::Make(result);
}

sk_sp<DlImage> SnapshotControllerSkia::MakeRasterSnapshot(
    sk_sp<DisplayList> display_list,
    SkISize size) {
  return DoMakeRasterSnapshot(size, [display_list](SkCanvas* canvas) {
    display_list->RenderTo(canvas);
  });
}

sk_sp<SkImage> SnapshotControllerSkia::ConvertToRasterImage(
    sk_sp<SkImage> image) {
  // If the rasterizer does not have a surface with a GrContext, then it will
  // be unable to render a cross-context SkImage.  The caller will need to
  // create the raster image on the IO thread.
  if (GetDelegate().GetSurface() == nullptr ||
      GetDelegate().GetSurface()->GetContext() == nullptr) {
    return nullptr;
  }

  if (image == nullptr) {
    return nullptr;
  }

  SkISize image_size = image->dimensions();

  auto result = DoMakeRasterSnapshot(
      image_size, [image = std::move(image)](SkCanvas* canvas) {
        canvas->drawImage(image, 0, 0);
      });
  return result->skia_image();
}

}  // namespace flutter