/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
// vim:cindent:tabstop=2:expandtab:shiftwidth=2:
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* a CSS style sheet returned from nsIStyleSheetService.preloadSheet */

#include "PreloadedStyleSheet.h"

#include "mozilla/css/Loader.h"
#include "nsLayoutUtils.h"

namespace mozilla {

PreloadedStyleSheet::PreloadedStyleSheet(nsIURI* aURI,
                                         css::SheetParsingMode aParsingMode)
  : mURI(aURI)
  , mParsingMode(aParsingMode)
{
}

/* static */ nsresult
PreloadedStyleSheet::Create(nsIURI* aURI,
                            css::SheetParsingMode aParsingMode,
                            PreloadedStyleSheet** aResult)
{
  *aResult = nullptr;

  // The nsIStyleSheetService.preloadSheet API doesn't tell us which backend
  // the sheet will be used with, and it seems wasteful to eagerly create
  // both a CSSStyleSheet and a ServoStyleSheet.  So instead, we guess that
  // the sheet type we will want matches the current value of the stylo pref,
  // and preload a sheet of that type.
  //
  // If we guess wrong, we will re-load the sheet later with the requested type,
  // and we won't really have front loaded the loading time as the name
  // "preload" might suggest.  Also, in theory we could get different data from
  // fetching the URL again, but for the usage patterns of this API this is
  // unlikely, and it doesn't seem worth trying to store the contents of the URL
  // and duplicating a bunch of css::Loader's logic.

  RefPtr<PreloadedStyleSheet> preloadedSheet =
    new PreloadedStyleSheet(aURI, aParsingMode);
  auto type = nsLayoutUtils::StyloEnabled() ? StyleBackendType::Servo
                                            : StyleBackendType::Gecko;
  StyleSheet* sheet;
  nsresult rv = preloadedSheet->GetSheet(type, &sheet);
  NS_ENSURE_SUCCESS(rv, rv);

  preloadedSheet.forget(aResult);
  return NS_OK;
}

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(PreloadedStyleSheet)
  NS_INTERFACE_MAP_ENTRY(nsIPreloadedStyleSheet)
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(PreloadedStyleSheet)
NS_IMPL_CYCLE_COLLECTING_RELEASE(PreloadedStyleSheet)

NS_IMPL_CYCLE_COLLECTION(PreloadedStyleSheet, mGecko, mServo)

nsresult
PreloadedStyleSheet::GetSheet(StyleBackendType aType, StyleSheet** aResult)
{
  *aResult = nullptr;

  RefPtr<StyleSheet>& sheet =
    aType == StyleBackendType::Gecko ? mGecko : mServo;

  if (!sheet) {
    RefPtr<css::Loader> loader = new css::Loader(aType);
    nsresult rv = loader->LoadSheetSync(mURI, mParsingMode, true, &sheet);
    NS_ENSURE_SUCCESS(rv, rv);
    MOZ_ASSERT(sheet);
  }

  *aResult = sheet;
  return NS_OK;
}

} // namespace mozilla