/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* 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 "mozilla/dom/Promise.h"

#include "nsICSSLoaderObserver.h"

#include "nsLayoutUtils.h"

namespace mozilla {

PreloadedStyleSheet::PreloadedStyleSheet(nsIURI* aURI,

                                         css::SheetParsingMode aParsingMode)

  : mLoaded(false)

  , mURI(aURI)

  , mParsingMode(aParsingMode)

{

}

/* static */ nsresult

PreloadedStyleSheet::Create(nsIURI* aURI,

                            css::SheetParsingMode aParsingMode,

                            PreloadedStyleSheet** aResult)

{

  *aResult = nullptr;

  RefPtr<PreloadedStyleSheet> preloadedSheet =

    new PreloadedStyleSheet(aURI, aParsingMode);

  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, mSheet)

nsresult

PreloadedStyleSheet::GetSheet(StyleSheet** aResult)

{

  *aResult = nullptr;

  MOZ_DIAGNOSTIC_ASSERT(mLoaded);

  if (!mSheet) {

    RefPtr<css::Loader> loader = new css::Loader;

    nsresult rv = loader->LoadSheetSync(mURI, mParsingMode, true, &mSheet);

    NS_ENSURE_SUCCESS(rv, rv);

    MOZ_ASSERT(mSheet);

  }

  *aResult = mSheet;

  return NS_OK;

}

nsresult

PreloadedStyleSheet::Preload()

{

  MOZ_DIAGNOSTIC_ASSERT(!mLoaded);

  // 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.

  mLoaded = true;

  StyleSheet* sheet;

  return GetSheet(&sheet);

}

NS_IMPL_ISUPPORTS(PreloadedStyleSheet::StylesheetPreloadObserver,

                  nsICSSLoaderObserver)

NS_IMETHODIMP

PreloadedStyleSheet::StylesheetPreloadObserver::StyleSheetLoaded(

  StyleSheet* aSheet, bool aWasDeferred, nsresult aStatus)

{

  MOZ_DIAGNOSTIC_ASSERT(!mPreloadedSheet->mLoaded);

  mPreloadedSheet->mLoaded = true;

  if (NS_FAILED(aStatus)) {

    mPromise->MaybeReject(aStatus);

  } else {

    mPromise->MaybeResolve(mPreloadedSheet);

  }

  return NS_OK;

}

// Note: After calling this method, the preloaded sheet *must not* be used

// until the observer is notified that the sheet has finished loading.

nsresult

PreloadedStyleSheet::PreloadAsync(NotNull<dom::Promise*> aPromise)

{

  MOZ_DIAGNOSTIC_ASSERT(!mLoaded);

  RefPtr<css::Loader> loader = new css::Loader;

  RefPtr<StylesheetPreloadObserver> obs =

    new StylesheetPreloadObserver(aPromise, this);

  return loader->LoadSheet(mURI, mParsingMode, false, obs, &mSheet);

}

} // namespace mozilla