/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
 * Copyright (C) 2016 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include "config.h"
#include "LinkLoader.h"

#include "CSSStyleSheet.h"
#include "CachedCSSStyleSheet.h"
#include "CachedResourceLoader.h"
#include "CachedResourceRequest.h"
#include "ContainerNode.h"
#include "CrossOriginAccessControl.h"
#include "Document.h"
#include "Frame.h"
#include "FrameLoaderClient.h"
#include "FrameView.h"
#include "LinkHeader.h"
#include "LinkPreloadResourceClients.h"
#include "LinkRelAttribute.h"
#include "RuntimeEnabledFeatures.h"
#include "Settings.h"
#include "StyleResolver.h"

namespace WebCore {

LinkLoader::LinkLoader(LinkLoaderClient& client)
    : m_client(client)
    , m_weakPtrFactory(this)
{
}

LinkLoader::~LinkLoader()
{
    if (m_cachedLinkResource)
        m_cachedLinkResource->removeClient(*this);
    if (m_preloadResourceClient)
        m_preloadResourceClient->clear();
}

void LinkLoader::triggerEvents(const CachedResource& resource)
{
    if (resource.errorOccurred())
        m_client.linkLoadingErrored();
    else
        m_client.linkLoaded();
}

void LinkLoader::notifyFinished(CachedResource& resource)
{
    ASSERT_UNUSED(resource, m_cachedLinkResource.get() == &resource);

    triggerEvents(*m_cachedLinkResource);

    m_cachedLinkResource->removeClient(*this);
    m_cachedLinkResource = nullptr;
}

void LinkLoader::loadLinksFromHeader(const String& headerValue, const URL& baseURL, Document& document)
{
    if (headerValue.isEmpty())
        return;
    LinkHeaderSet headerSet(headerValue);
    for (auto& header : headerSet) {
        if (!header.valid() || header.url().isEmpty() || header.rel().isEmpty())
            continue;

        LinkRelAttribute relAttribute(header.rel());
        URL url(baseURL, header.url());
        // Sanity check to avoid re-entrancy here.
        if (equalIgnoringFragmentIdentifier(url, baseURL))
            continue;
        preloadIfNeeded(relAttribute, url, document, header.as(), header.crossOrigin(), nullptr, nullptr);
    }
}

std::optional<CachedResource::Type> LinkLoader::resourceTypeFromAsAttribute(const String& as)
{
    if (as.isEmpty())
        return CachedResource::RawResource;
    if (equalLettersIgnoringASCIICase(as, "image"))
        return CachedResource::ImageResource;
    if (equalLettersIgnoringASCIICase(as, "script"))
        return CachedResource::Script;
    if (equalLettersIgnoringASCIICase(as, "style"))
        return CachedResource::CSSStyleSheet;
    if (equalLettersIgnoringASCIICase(as, "media"))
        return CachedResource::MediaResource;
    if (equalLettersIgnoringASCIICase(as, "font"))
        return CachedResource::FontResource;
#if ENABLE(VIDEO_TRACK)
    if (equalLettersIgnoringASCIICase(as, "track"))
        return CachedResource::TextTrackResource;
#endif
    return std::nullopt;
}

static std::unique_ptr<LinkPreloadResourceClient> createLinkPreloadResourceClient(CachedResource& resource, LinkLoader& loader, CachedResource::Type type)
{
    switch (type) {
    case CachedResource::ImageResource:
        return LinkPreloadImageResourceClient::create(loader, static_cast<CachedImage&>(resource));
    case CachedResource::Script:
        return LinkPreloadScriptResourceClient::create(loader, static_cast<CachedScript&>(resource));
    case CachedResource::CSSStyleSheet:
        return LinkPreloadStyleResourceClient::create(loader, static_cast<CachedCSSStyleSheet&>(resource));
    case CachedResource::FontResource:
        return LinkPreloadFontResourceClient::create(loader, static_cast<CachedFont&>(resource));
    case CachedResource::MediaResource:
#if ENABLE(VIDEO_TRACK)
    case CachedResource::TextTrackResource:
#endif
    case CachedResource::RawResource:
        return LinkPreloadRawResourceClient::create(loader, static_cast<CachedRawResource&>(resource));
    case CachedResource::MainResource:
#if ENABLE(SVG_FONTS)
    case CachedResource::SVGFontResource:
#endif
    case CachedResource::SVGDocumentResource:
#if ENABLE(XSLT)
    case CachedResource::XSLStyleSheet:
#endif
#if ENABLE(LINK_PREFETCH)
    case CachedResource::LinkSubresource:
    case CachedResource::LinkPrefetch:
#endif
        // None of these values is currently supported as an `as` value.
        ASSERT_NOT_REACHED();
    }
    return nullptr;
}

std::unique_ptr<LinkPreloadResourceClient> LinkLoader::preloadIfNeeded(const LinkRelAttribute& relAttribute, const URL& href, Document& document, const String& as, const String& crossOriginMode, LinkLoader* loader, LinkLoaderClient* client)
{
    if (!document.loader() || !relAttribute.isLinkPreload)
        return nullptr;

    ASSERT(RuntimeEnabledFeatures::sharedFeatures().linkPreloadEnabled());
    if (!href.isValid()) {
        document.addConsoleMessage(MessageSource::Other, MessageLevel::Error, String("<link rel=preload> has an invalid `href` value"));
        return nullptr;
    }
    auto type = LinkLoader::resourceTypeFromAsAttribute(as);
    if (!type) {
        document.addConsoleMessage(MessageSource::Other, MessageLevel::Error, String("<link rel=preload> must have a valid `as` value"));
        if (client)
            client->linkLoadingErrored();
        return nullptr;
    }

    ResourceRequest resourceRequest(document.completeURL(href));
    resourceRequest.setIgnoreForRequestCount(true);
    CachedResourceRequest linkRequest(WTFMove(resourceRequest), CachedResourceLoader::defaultCachedResourceOptions(), CachedResource::defaultPriorityForResourceType(type.value()));
    linkRequest.setInitiator("link");
    linkRequest.setIsLinkPreload();

    linkRequest.setAsPotentiallyCrossOrigin(crossOriginMode, document);
    CachedResourceHandle<CachedResource> cachedLinkResource = document.cachedResourceLoader().preload(type.value(), WTFMove(linkRequest));

    if (cachedLinkResource && loader)
        return createLinkPreloadResourceClient(*cachedLinkResource, *loader, type.value());
    return nullptr;
}

void LinkLoader::cancelLoad()
{
    if (m_preloadResourceClient)
        m_preloadResourceClient->clear();
}

bool LinkLoader::loadLink(const LinkRelAttribute& relAttribute, const URL& href, const String& as, const String& crossOrigin, Document& document)
{
    if (relAttribute.isDNSPrefetch) {
        // FIXME: The href attribute of the link element can be in "//hostname" form, and we shouldn't attempt
        // to complete that as URL <https://bugs.webkit.org/show_bug.cgi?id=48857>.
        if (document.settings().dnsPrefetchingEnabled() && href.isValid() && !href.isEmpty() && document.frame())
            document.frame()->loader().client().prefetchDNS(href.host());
    }

    if (m_client.shouldLoadLink()) {
        auto resourceClient = preloadIfNeeded(relAttribute, href, document, as, crossOrigin, this, &m_client);
        if (resourceClient)
            m_preloadResourceClient = WTFMove(resourceClient);
        else if (m_preloadResourceClient)
            m_preloadResourceClient->clear();
    }

#if ENABLE(LINK_PREFETCH)
    if ((relAttribute.isLinkPrefetch || relAttribute.isLinkSubresource) && href.isValid() && document.frame()) {
        if (!m_client.shouldLoadLink())
            return false;

        std::optional<ResourceLoadPriority> priority;
        CachedResource::Type type = CachedResource::LinkPrefetch;
        if (relAttribute.isLinkSubresource) {
            // We only make one request to the cached resource loader if multiple rel types are specified;
            // this is the higher priority, which should overwrite the lower priority.
            priority = ResourceLoadPriority::Low;
            type = CachedResource::LinkSubresource;
        }

        if (m_cachedLinkResource) {
            m_cachedLinkResource->removeClient(*this);
            m_cachedLinkResource = nullptr;
        }
        ResourceLoaderOptions options = CachedResourceLoader::defaultCachedResourceOptions();
        options.contentSecurityPolicyImposition = ContentSecurityPolicyImposition::SkipPolicyCheck;
        m_cachedLinkResource = document.cachedResourceLoader().requestLinkResource(type, CachedResourceRequest(ResourceRequest(document.completeURL(href)), options, priority));
        if (m_cachedLinkResource)
            m_cachedLinkResource->addClient(*this);
    }
#endif

    return true;
}

}