/*

    Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)

    Copyright (C) 2001 Dirk Mueller (mueller@kde.org)

    Copyright (C) 2002 Waldo Bastian (bastian@kde.org)

    Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)

    Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.

    This library is free software; you can redistribute it and/or

    modify it under the terms of the GNU Library General Public

    License as published by the Free Software Foundation; either

    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of

    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public License

    along with this library; see the file COPYING.LIB.  If not, write to

    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,

    Boston, MA 02110-1301, USA.

*/

#include "config.h"

#include "CachedResource.h"

#include "Cache.h"

#include "CachedResourceHandle.h"

#include "DocLoader.h"

#include "Frame.h"

#include "FrameLoader.h"

#include "KURL.h"

#include "PurgeableBuffer.h"

#include "Request.h"

#include <wtf/CurrentTime.h>

#include <wtf/MathExtras.h>

#include <wtf/RefCountedLeakCounter.h>

#include <wtf/StdLibExtras.h>

#include <wtf/Vector.h>

using namespace WTF;

namespace WebCore {

#ifndef NDEBUG

static RefCountedLeakCounter cachedResourceLeakCounter("CachedResource");

#endif

CachedResource::CachedResource(const String& url, Type type)

    : m_url(url)

    , m_responseTimestamp(currentTime())

    , m_lastDecodedAccessTime(0)

    , m_sendResourceLoadCallbacks(true)

    , m_preloadCount(0)

    , m_preloadResult(PreloadNotReferenced)

    , m_requestedFromNetworkingLayer(false)

    , m_inCache(false)

    , m_loading(false)

    , m_docLoader(0)

    , m_handleCount(0)

    , m_resourceToRevalidate(0)

    , m_proxyResource(0)

{

#ifndef NDEBUG

    cachedResourceLeakCounter.increment();

#endif

    m_type = type;

    m_status = Pending;

    m_encodedSize = 0;

    m_decodedSize = 0;

    m_request = 0;

    m_accessCount = 0;

    m_inLiveDecodedResourcesList = false;

    m_nextInAllResourcesList = 0;

    m_prevInAllResourcesList = 0;

    m_nextInLiveResourcesList = 0;

    m_prevInLiveResourcesList = 0;

#ifndef NDEBUG

    m_deleted = false;

    m_lruIndex = 0;

#endif

    m_errorOccurred = false;

}

CachedResource::~CachedResource()

{

    ASSERT(!m_resourceToRevalidate); // Should be true because canDelete() checks this.

    ASSERT(canDelete());

    ASSERT(!inCache());

    ASSERT(!m_deleted);

    ASSERT(url().isNull() || cache()->resourceForURL(url()) != this);

#ifndef NDEBUG

    m_deleted = true;

    cachedResourceLeakCounter.decrement();

#endif

    if (m_docLoader)

        m_docLoader->removeCachedResource(this);

}

void CachedResource::load(DocLoader* docLoader, bool incremental, bool skipCanLoadCheck, bool sendResourceLoadCallbacks)

{

    m_sendResourceLoadCallbacks = sendResourceLoadCallbacks;

    cache()->loader()->load(docLoader, this, incremental, skipCanLoadCheck, sendResourceLoadCallbacks);

    m_loading = true;

}

void CachedResource::finish()

{

    m_status = Cached;

}

bool CachedResource::isExpired() const

{

    if (m_response.isNull())

        return false;

    return currentAge() > freshnessLifetime();

}

double CachedResource::currentAge() const

{

    // RFC2616 13.2.3

    // No compensation for latency as that is not terribly important in practice

    double dateValue = m_response.date();

    double apparentAge = isfinite(dateValue) ? max(0., m_responseTimestamp - dateValue) : 0;

    double ageValue = m_response.age();

    double correctedReceivedAge = isfinite(ageValue) ? max(apparentAge, ageValue) : apparentAge;

    double residentTime = currentTime() - m_responseTimestamp;

    return correctedReceivedAge + residentTime;

}

double CachedResource::freshnessLifetime() const

{

    // Cache non-http resources liberally

    if (!m_response.url().protocolInHTTPFamily())

        return std::numeric_limits<double>::max();

    // RFC2616 13.2.4

    double maxAgeValue = m_response.cacheControlMaxAge();

    if (isfinite(maxAgeValue))

        return maxAgeValue;

    double expiresValue = m_response.expires();

    double dateValue = m_response.date();

    double creationTime = isfinite(dateValue) ? dateValue : m_responseTimestamp;

    if (isfinite(expiresValue))

        return expiresValue - creationTime;

    double lastModifiedValue = m_response.lastModified();

    if (isfinite(lastModifiedValue))

        return (creationTime - lastModifiedValue) * 0.1;

    // If no cache headers are present, the specification leaves the decision to the UA. Other browsers seem to opt for 0.

    return 0;

}

void CachedResource::setResponse(const ResourceResponse& response)

{

    m_response = response;

    m_responseTimestamp = currentTime();

}

void CachedResource::setRequest(Request* request)

{

    if (request && !m_request)

        m_status = Pending;

    m_request = request;

    if (canDelete() && !inCache())

        delete this;

}

void CachedResource::addClient(CachedResourceClient* client)

{

    addClientToSet(client);

    didAddClient(client);

}

void CachedResource::addClientToSet(CachedResourceClient* client)

{

    ASSERT(!isPurgeable());

    if (m_preloadResult == PreloadNotReferenced) {

        if (isLoaded())

            m_preloadResult = PreloadReferencedWhileComplete;

        else if (m_requestedFromNetworkingLayer)

            m_preloadResult = PreloadReferencedWhileLoading;

        else

            m_preloadResult = PreloadReferenced;

    }

    if (!hasClients() && inCache())

        cache()->addToLiveResourcesSize(this);

    m_clients.add(client);

}

void CachedResource::removeClient(CachedResourceClient* client)

{

    ASSERT(m_clients.contains(client));

    m_clients.remove(client);

    if (canDelete() && !inCache())

        delete this;

    else if (!hasClients() && inCache()) {

        cache()->removeFromLiveResourcesSize(this);

        cache()->removeFromLiveDecodedResourcesList(this);

        allClientsRemoved();

        if (response().cacheControlContainsNoStore()) {

            // RFC2616 14.9.2:

            // "no-store: ...MUST make a best-effort attempt to remove the information from volatile storage as promptly as possible"

            cache()->remove(this);

        } else

            cache()->prune();

    }

    // This object may be dead here.

}

void CachedResource::deleteIfPossible()

{

    if (canDelete() && !inCache())

        delete this;

}

void CachedResource::setDecodedSize(unsigned size)

{

    if (size == m_decodedSize)

        return;

    int delta = size - m_decodedSize;

    // The object must now be moved to a different queue, since its size has been changed.

    // We have to remove explicitly before updating m_decodedSize, so that we find the correct previous

    // queue.

    if (inCache())

        cache()->removeFromLRUList(this);

    m_decodedSize = size;

    if (inCache()) { 

        // Now insert into the new LRU list.

        cache()->insertInLRUList(this);

        // Insert into or remove from the live decoded list if necessary.

        // When inserting into the LiveDecodedResourcesList it is possible

        // that the m_lastDecodedAccessTime is still zero or smaller than

        // the m_lastDecodedAccessTime of the current list head. This is a

        // violation of the invariant that the list is to be kept sorted

        // by access time. The weakening of the invariant does not pose

        // a problem. For more details please see: https://bugs.webkit.org/show_bug.cgi?id=30209

        if (m_decodedSize && !m_inLiveDecodedResourcesList && hasClients())

            cache()->insertInLiveDecodedResourcesList(this);

        else if (!m_decodedSize && m_inLiveDecodedResourcesList)

            cache()->removeFromLiveDecodedResourcesList(this);

        // Update the cache's size totals.

        cache()->adjustSize(hasClients(), delta);

    }

}

void CachedResource::setEncodedSize(unsigned size)

{

    if (size == m_encodedSize)

        return;

    // The size cannot ever shrink (unless it is being nulled out because of an error).  If it ever does, assert.

    ASSERT(size == 0 || size >= m_encodedSize);

    int delta = size - m_encodedSize;

    // The object must now be moved to a different queue, since its size has been changed.

    // We have to remove explicitly before updating m_encodedSize, so that we find the correct previous

    // queue.

    if (inCache())

        cache()->removeFromLRUList(this);

    m_encodedSize = size;

    if (inCache()) { 

        // Now insert into the new LRU list.

        cache()->insertInLRUList(this);

        // Update the cache's size totals.

        cache()->adjustSize(hasClients(), delta);

    }

}

void CachedResource::didAccessDecodedData(double timeStamp)

{

    m_lastDecodedAccessTime = timeStamp;

    if (inCache()) {

        if (m_inLiveDecodedResourcesList) {

            cache()->removeFromLiveDecodedResourcesList(this);

            cache()->insertInLiveDecodedResourcesList(this);

        }

        cache()->prune();

    }

}

void CachedResource::setResourceToRevalidate(CachedResource* resource) 

{ 

    ASSERT(resource);

    ASSERT(!m_resourceToRevalidate);

    ASSERT(resource != this);

    ASSERT(m_handlesToRevalidate.isEmpty());

    ASSERT(resource->type() == type());

    // The following assert should be investigated whenever it occurs. Although it should never fire, it currently does in rare circumstances.

    // https://bugs.webkit.org/show_bug.cgi?id=28604.

    // So the code needs to be robust to this assert failing thus the "if (m_resourceToRevalidate->m_proxyResource == this)" in CachedResource::clearResourceToRevalidate.

    ASSERT(!resource->m_proxyResource);

    resource->m_proxyResource = this;

    m_resourceToRevalidate = resource;

}

void CachedResource::clearResourceToRevalidate() 

{ 

    ASSERT(m_resourceToRevalidate);

    // A resource may start revalidation before this method has been called, so check that this resource is still the proxy resource before clearing it out.

    if (m_resourceToRevalidate->m_proxyResource == this) {

        m_resourceToRevalidate->m_proxyResource = 0;

        m_resourceToRevalidate->deleteIfPossible();

    }

    m_handlesToRevalidate.clear();

    m_resourceToRevalidate = 0;

    deleteIfPossible();

}

void CachedResource::switchClientsToRevalidatedResource()

{

    ASSERT(m_resourceToRevalidate);

    ASSERT(m_resourceToRevalidate->inCache());

    ASSERT(!inCache());

    HashSet<CachedResourceHandleBase*>::iterator end = m_handlesToRevalidate.end();

    for (HashSet<CachedResourceHandleBase*>::iterator it = m_handlesToRevalidate.begin(); it != end; ++it) {

        CachedResourceHandleBase* handle = *it;

        handle->m_resource = m_resourceToRevalidate;

        m_resourceToRevalidate->registerHandle(handle);

        --m_handleCount;

    }

    ASSERT(!m_handleCount);

    m_handlesToRevalidate.clear();

    Vector<CachedResourceClient*> clientsToMove;

    HashCountedSet<CachedResourceClient*>::iterator end2 = m_clients.end();

    for (HashCountedSet<CachedResourceClient*>::iterator it = m_clients.begin(); it != end2; ++it) {

        CachedResourceClient* client = it->first;

        unsigned count = it->second;

        while (count) {

            clientsToMove.append(client);

            --count;

        }

    }

    // Equivalent of calling removeClient() for all clients

    m_clients.clear();

    unsigned moveCount = clientsToMove.size();

    for (unsigned n = 0; n < moveCount; ++n)

        m_resourceToRevalidate->addClientToSet(clientsToMove[n]);

    for (unsigned n = 0; n < moveCount; ++n) {

        // Calling didAddClient for a client may end up removing another client. In that case it won't be in the set anymore.

        if (m_resourceToRevalidate->m_clients.contains(clientsToMove[n]))

            m_resourceToRevalidate->didAddClient(clientsToMove[n]);

    }

}

void CachedResource::updateResponseAfterRevalidation(const ResourceResponse& validatingResponse)

{

    m_responseTimestamp = currentTime();

    DEFINE_STATIC_LOCAL(const AtomicString, contentHeaderPrefix, ("content-"));

    // RFC2616 10.3.5

    // Update cached headers from the 304 response

    const HTTPHeaderMap& newHeaders = validatingResponse.httpHeaderFields();

    HTTPHeaderMap::const_iterator end = newHeaders.end();

    for (HTTPHeaderMap::const_iterator it = newHeaders.begin(); it != end; ++it) {

        // Don't allow 304 response to update content headers, these can't change but some servers send wrong values.

        if (it->first.startsWith(contentHeaderPrefix, false))

            continue;

        m_response.setHTTPHeaderField(it->first, it->second);

    }

}

bool CachedResource::canUseCacheValidator() const

{

    if (m_loading || m_errorOccurred)

        return false;

    if (m_response.cacheControlContainsNoStore())

        return false;

    DEFINE_STATIC_LOCAL(const AtomicString, lastModifiedHeader, ("last-modified"));

    DEFINE_STATIC_LOCAL(const AtomicString, eTagHeader, ("etag"));

    return !m_response.httpHeaderField(lastModifiedHeader).isEmpty() || !m_response.httpHeaderField(eTagHeader).isEmpty();

}

bool CachedResource::mustRevalidate(CachePolicy cachePolicy) const

{

    if (m_errorOccurred)

        return true;

    if (m_loading)

        return false;

    if (m_response.cacheControlContainsNoCache() || m_response.cacheControlContainsNoStore())

        return true;

    if (cachePolicy == CachePolicyCache)

        return m_response.cacheControlContainsMustRevalidate() && isExpired();

    return isExpired();

}

bool CachedResource::isSafeToMakePurgeable() const

{ 

    return !hasClients() && !m_proxyResource && !m_resourceToRevalidate;

}

bool CachedResource::makePurgeable(bool purgeable) 

{ 

    if (purgeable) {

        ASSERT(isSafeToMakePurgeable());

        if (m_purgeableData) {

            ASSERT(!m_data);

            return true;

        }

        if (!m_data)

            return false;

        // Should not make buffer purgeable if it has refs othen than this since we don't want two copies.

        if (!m_data->hasOneRef())

            return false;

        // Purgeable buffers are allocated in multiples of the page size (4KB in common CPUs) so it does not make sense for very small buffers.

        const size_t purgeableThreshold = 4 * 4096;

        if (m_data->size() < purgeableThreshold)

            return false;

        if (m_data->hasPurgeableBuffer()) {

            m_purgeableData.set(m_data->releasePurgeableBuffer());

        } else {

            m_purgeableData.set(PurgeableBuffer::create(m_data->data(), m_data->size()));

            if (!m_purgeableData)

                return false;

        }

        m_purgeableData->makePurgeable(true);

        m_data.clear();

        return true;

    }

    if (!m_purgeableData)

        return true;

    ASSERT(!m_data);

    ASSERT(!hasClients());

    if (!m_purgeableData->makePurgeable(false))

        return false; 

    m_data = SharedBuffer::adoptPurgeableBuffer(m_purgeableData.release());

    return true;

}

bool CachedResource::isPurgeable() const

{

    return m_purgeableData && m_purgeableData->isPurgeable();

}

bool CachedResource::wasPurged() const

{

    return m_purgeableData && m_purgeableData->wasPurged();

}

unsigned CachedResource::overheadSize() const

{

    return sizeof(CachedResource) + m_response.memoryUsage() + 576;

    /*

        576 = 192 +                   // average size of m_url

              384;                    // average size of m_clients hash map

    */

}

}