// Copyright (c) 2011 The Chromium 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 "content/browser/appcache/appcache_request_handler.h"

#include <utility>

#include "base/bind.h"
#include "content/browser/appcache/appcache.h"
#include "content/browser/appcache/appcache_backend_impl.h"
#include "content/browser/appcache/appcache_policy.h"
#include "content/browser/appcache/appcache_url_request_job.h"
#include "content/browser/service_worker/service_worker_request_handler.h"
#include "net/url_request/url_request.h"
#include "net/url_request/url_request_job.h"

namespace content {

AppCacheRequestHandler::AppCacheRequestHandler(AppCacheHost* host,
                                               ResourceType resource_type,
                                               bool should_reset_appcache)
    : host_(host),
      resource_type_(resource_type),
      should_reset_appcache_(should_reset_appcache),
      is_waiting_for_cache_selection_(false),
      found_group_id_(0),
      found_cache_id_(0),
      found_network_namespace_(false),
      cache_entry_not_found_(false),
      is_delivering_network_response_(false),
      maybe_load_resource_executed_(false),
      old_process_id_(0),
      old_host_id_(kAppCacheNoHostId),
      cache_id_(kAppCacheNoCacheId),
      service_(host_->service()) {
  DCHECK(host_);
  DCHECK(service_);
  host_->AddObserver(this);
  service_->AddObserver(this);
}

AppCacheRequestHandler::~AppCacheRequestHandler() {
  if (host_) {
    storage()->CancelDelegateCallbacks(this);
    host_->RemoveObserver(this);
  }
  if (service_)
    service_->RemoveObserver(this);
}

AppCacheStorage* AppCacheRequestHandler::storage() const {
  DCHECK(host_);
  return host_->storage();
}

AppCacheURLRequestJob* AppCacheRequestHandler::MaybeLoadResource(
    net::URLRequest* request,
    net::NetworkDelegate* network_delegate) {
  maybe_load_resource_executed_ = true;
  if (!host_ || !IsSchemeAndMethodSupportedForAppCache(request) ||
      cache_entry_not_found_) {
    return NULL;
  }

  // This method can get called multiple times over the life
  // of a request. The case we detect here is having scheduled
  // delivery of a "network response" using a job set up on an
  // earlier call through this method. To send the request through
  // to the network involves restarting the request altogether,
  // which will call through to our interception layer again.
  // This time through, we return NULL so the request hits the wire.
  if (is_delivering_network_response_) {
    is_delivering_network_response_ = false;
    return NULL;
  }

  // Clear out our 'found' fields since we're starting a request for a
  // new resource, any values in those fields are no longer valid.
  found_entry_ = AppCacheEntry();
  found_fallback_entry_ = AppCacheEntry();
  found_cache_id_ = kAppCacheNoCacheId;
  found_manifest_url_ = GURL();
  found_network_namespace_ = false;

  std::unique_ptr<AppCacheURLRequestJob> job;
  if (is_main_resource())
    job = MaybeLoadMainResource(request, network_delegate);
  else
    job = MaybeLoadSubResource(request, network_delegate);

  // If its been setup to deliver a network response, we can just delete
  // it now and return NULL instead to achieve that since it couldn't
  // have been started yet.
  if (job && job->is_delivering_network_response()) {
    DCHECK(!job->has_been_started());
    job.reset();
  }

  return job.release();
}

AppCacheURLRequestJob* AppCacheRequestHandler::MaybeLoadFallbackForRedirect(
    net::URLRequest* request,
    net::NetworkDelegate* network_delegate,
    const GURL& location) {
  if (!host_ || !IsSchemeAndMethodSupportedForAppCache(request) ||
      cache_entry_not_found_)
    return NULL;
  if (is_main_resource())
    return NULL;
  // TODO(vabr) This is a temporary fix (see crbug/141114). We should get rid of
  // it once a more general solution to crbug/121325 is in place.
  if (!maybe_load_resource_executed_)
    return NULL;
  if (request->url().GetOrigin() == location.GetOrigin())
    return NULL;

  DCHECK(!job_.get());  // our jobs never generate redirects

  std::unique_ptr<AppCacheURLRequestJob> job;
  if (found_fallback_entry_.has_response_id()) {
    // 6.9.6, step 4: If this results in a redirect to another origin,
    // get the resource of the fallback entry.
    job = CreateJob(request, network_delegate);
    DeliverAppCachedResponse(found_fallback_entry_, found_cache_id_,
                             found_manifest_url_, true,
                             found_namespace_entry_url_);
  } else if (!found_network_namespace_) {
    // 6.9.6, step 6: Fail the resource load.
    job = CreateJob(request, network_delegate);
    DeliverErrorResponse();
  } else {
    // 6.9.6 step 3 and 5: Fetch the resource normally.
  }

  return job.release();
}

AppCacheURLRequestJob* AppCacheRequestHandler::MaybeLoadFallbackForResponse(
    net::URLRequest* request,
    net::NetworkDelegate* network_delegate) {
  if (!host_ || !IsSchemeAndMethodSupportedForAppCache(request) ||
      cache_entry_not_found_)
    return NULL;
  if (!found_fallback_entry_.has_response_id())
    return NULL;

  if (request->status().status() == net::URLRequestStatus::CANCELED) {
    // 6.9.6, step 4: But not if the user canceled the download.
    return NULL;
  }

  // We don't fallback for responses that we delivered.
  if (job_.get()) {
    DCHECK(!job_->is_delivering_network_response());
    return NULL;
  }

  if (request->status().is_success()) {
    int code_major = request->GetResponseCode() / 100;
    if (code_major !=4 && code_major != 5)
      return NULL;

    // Servers can override the fallback behavior with a response header.
    const std::string kFallbackOverrideHeader(
        "x-chromium-appcache-fallback-override");
    const std::string kFallbackOverrideValue(
        "disallow-fallback");
    std::string header_value;
    request->GetResponseHeaderByName(kFallbackOverrideHeader, &header_value);
    if (header_value == kFallbackOverrideValue)
      return NULL;
  }

  // 6.9.6, step 4: If this results in a 4xx or 5xx status code
  // or there were network errors, get the resource of the fallback entry.
  std::unique_ptr<AppCacheURLRequestJob> job =
      CreateJob(request, network_delegate);
  DeliverAppCachedResponse(found_fallback_entry_, found_cache_id_,
                           found_manifest_url_, true,
                           found_namespace_entry_url_);
  return job.release();
}

void AppCacheRequestHandler::GetExtraResponseInfo(int64_t* cache_id,
                                                  GURL* manifest_url) {
  *cache_id = cache_id_;
  *manifest_url = manifest_url_;
}

void AppCacheRequestHandler::PrepareForCrossSiteTransfer(int old_process_id) {
  if (!host_)
    return;
  AppCacheBackendImpl* backend = host_->service()->GetBackend(old_process_id);
  DCHECK(backend) << "appcache detected likely storage partition mismatch";
  old_process_id_ = old_process_id;
  old_host_id_ = host_->host_id();
  host_for_cross_site_transfer_ = backend->TransferHostOut(host_->host_id());
  DCHECK_EQ(host_, host_for_cross_site_transfer_.get());
}

void AppCacheRequestHandler::CompleteCrossSiteTransfer(
    int new_process_id, int new_host_id) {
  if (!host_for_cross_site_transfer_.get())
    return;
  DCHECK_EQ(host_, host_for_cross_site_transfer_.get());
  AppCacheBackendImpl* backend = host_->service()->GetBackend(new_process_id);
  DCHECK(backend) << "appcache detected likely storage partition mismatch";
  backend->TransferHostIn(new_host_id,
                          std::move(host_for_cross_site_transfer_));
}

void AppCacheRequestHandler::MaybeCompleteCrossSiteTransferInOldProcess(
    int old_process_id) {
  if (!host_ || !host_for_cross_site_transfer_.get() ||
      old_process_id != old_process_id_) {
    return;
  }
  CompleteCrossSiteTransfer(old_process_id_, old_host_id_);
}

void AppCacheRequestHandler::OnDestructionImminent(AppCacheHost* host) {
  storage()->CancelDelegateCallbacks(this);
  host_ = NULL;  // no need to RemoveObserver, the host is being deleted

  // Since the host is being deleted, we don't have to complete any job
  // that is current running. It's destined for the bit bucket anyway.
  if (job_.get()) {
    job_->Kill();
    job_.reset();
  }
}

void AppCacheRequestHandler::OnServiceDestructionImminent(
    AppCacheServiceImpl* service) {
  service_ = nullptr;
  if (!host_) {
    DCHECK(!host_for_cross_site_transfer_);
    DCHECK(!job_);
    return;
  }
  host_->RemoveObserver(this);
  OnDestructionImminent(host_);
  host_for_cross_site_transfer_.reset();
}

void AppCacheRequestHandler::DeliverAppCachedResponse(
    const AppCacheEntry& entry,
    int64_t cache_id,
    const GURL& manifest_url,
    bool is_fallback,
    const GURL& namespace_entry_url) {
  DCHECK(host_ && job_.get() && job_->is_waiting());
  DCHECK(entry.has_response_id());

  // Cache information about the response, for use by GetExtraResponseInfo.
  cache_id_ = cache_id;
  manifest_url_ = manifest_url;

  if (IsResourceTypeFrame(resource_type_) && !namespace_entry_url.is_empty())
    host_->NotifyMainResourceIsNamespaceEntry(namespace_entry_url);

  job_->DeliverAppCachedResponse(manifest_url, cache_id, entry, is_fallback);
}

void AppCacheRequestHandler::DeliverErrorResponse() {
  DCHECK(job_.get() && job_->is_waiting());
  DCHECK_EQ(kAppCacheNoCacheId, cache_id_);
  DCHECK(manifest_url_.is_empty());
  job_->DeliverErrorResponse();
}

void AppCacheRequestHandler::DeliverNetworkResponse() {
  DCHECK(job_.get() && job_->is_waiting());
  DCHECK_EQ(kAppCacheNoCacheId, cache_id_);
  DCHECK(manifest_url_.is_empty());
  job_->DeliverNetworkResponse();
}

void AppCacheRequestHandler::OnPrepareToRestart() {
  DCHECK(job_->is_delivering_network_response() ||
         job_->cache_entry_not_found());

  // Any information about the source of the response is no longer relevant.
  cache_id_ = kAppCacheNoCacheId;
  manifest_url_ = GURL();

  cache_entry_not_found_ = job_->cache_entry_not_found();
  is_delivering_network_response_ = job_->is_delivering_network_response();

  storage()->CancelDelegateCallbacks(this);

  job_.reset();
}

std::unique_ptr<AppCacheURLRequestJob> AppCacheRequestHandler::CreateJob(
    net::URLRequest* request,
    net::NetworkDelegate* network_delegate) {
  std::unique_ptr<AppCacheURLRequestJob> job(new AppCacheURLRequestJob(
      request, network_delegate, storage(), host_, is_main_resource(),
      base::Bind(&AppCacheRequestHandler::OnPrepareToRestart,
                 base::Unretained(this))));
  job_ = job->GetWeakPtr();
  return job;
}

// Main-resource handling ----------------------------------------------

std::unique_ptr<AppCacheURLRequestJob>
AppCacheRequestHandler::MaybeLoadMainResource(
    net::URLRequest* request,
    net::NetworkDelegate* network_delegate) {
  DCHECK(!job_.get());
  DCHECK(host_);

  // If a page falls into the scope of a ServiceWorker, any matching AppCaches
  // should be ignored. This depends on the ServiceWorker handler being invoked
  // prior to the AppCache handler.
  if (ServiceWorkerRequestHandler::IsControlledByServiceWorker(request)) {
    host_->enable_cache_selection(false);
    return nullptr;
  }

  host_->enable_cache_selection(true);

  const AppCacheHost* spawning_host =
      (resource_type_ == RESOURCE_TYPE_SHARED_WORKER) ?
      host_ : host_->GetSpawningHost();
  GURL preferred_manifest_url = spawning_host ?
      spawning_host->preferred_manifest_url() : GURL();

  // We may have to wait for our storage query to complete, but
  // this query can also complete syncrhonously.
  std::unique_ptr<AppCacheURLRequestJob> job =
      CreateJob(request, network_delegate);
  storage()->FindResponseForMainRequest(
      request->url(), preferred_manifest_url, this);
  return job;
}

void AppCacheRequestHandler::OnMainResponseFound(
    const GURL& url,
    const AppCacheEntry& entry,
    const GURL& namespace_entry_url,
    const AppCacheEntry& fallback_entry,
    int64_t cache_id,
    int64_t group_id,
    const GURL& manifest_url) {
  DCHECK(host_);
  DCHECK(is_main_resource());
  DCHECK(!entry.IsForeign());
  DCHECK(!fallback_entry.IsForeign());
  DCHECK(!(entry.has_response_id() && fallback_entry.has_response_id()));

  // Request may have been canceled, but not yet deleted, while waiting on
  // the cache.
  if (!job_.get())
    return;

  AppCachePolicy* policy = host_->service()->appcache_policy();
  bool was_blocked_by_policy = !manifest_url.is_empty() && policy &&
      !policy->CanLoadAppCache(manifest_url, host_->first_party_url());

  if (was_blocked_by_policy) {
    if (IsResourceTypeFrame(resource_type_)) {
      host_->NotifyMainResourceBlocked(manifest_url);
    } else {
      DCHECK_EQ(resource_type_, RESOURCE_TYPE_SHARED_WORKER);
      host_->frontend()->OnContentBlocked(host_->host_id(), manifest_url);
    }
    DeliverNetworkResponse();
    return;
  }

  if (should_reset_appcache_ && !manifest_url.is_empty()) {
    host_->service()->DeleteAppCacheGroup(
        manifest_url, net::CompletionCallback());
    DeliverNetworkResponse();
    return;
  }

  if (IsMainResourceType(resource_type_) && cache_id != kAppCacheNoCacheId) {
    // AppCacheHost loads and holds a reference to the main resource cache
    // for two reasons, firstly to preload the cache into the working set
    // in advance of subresource loads happening, secondly to prevent the
    // AppCache from falling out of the working set on frame navigations.
    host_->LoadMainResourceCache(cache_id);
    host_->set_preferred_manifest_url(manifest_url);
  }

  // 6.11.1 Navigating across documents, steps 10 and 14.

  found_entry_ = entry;
  found_namespace_entry_url_ = namespace_entry_url;
  found_fallback_entry_ = fallback_entry;
  found_cache_id_ = cache_id;
  found_group_id_ = group_id;
  found_manifest_url_ = manifest_url;
  found_network_namespace_ = false;  // not applicable to main requests

  if (found_entry_.has_response_id()) {
    DCHECK(!found_fallback_entry_.has_response_id());
    DeliverAppCachedResponse(found_entry_, found_cache_id_, found_manifest_url_,
                             false, found_namespace_entry_url_);
  } else {
    DeliverNetworkResponse();
  }
}

// Sub-resource handling ----------------------------------------------

std::unique_ptr<AppCacheURLRequestJob>
AppCacheRequestHandler::MaybeLoadSubResource(
    net::URLRequest* request,
    net::NetworkDelegate* network_delegate) {
  DCHECK(!job_.get());

  if (host_->is_selection_pending()) {
    // We have to wait until cache selection is complete and the
    // selected cache is loaded.
    is_waiting_for_cache_selection_ = true;
    return CreateJob(request, network_delegate);
  }

  if (!host_->associated_cache() ||
      !host_->associated_cache()->is_complete() ||
      host_->associated_cache()->owning_group()->is_being_deleted()) {
    return nullptr;
  }

  std::unique_ptr<AppCacheURLRequestJob> job =
      CreateJob(request, network_delegate);
  ContinueMaybeLoadSubResource();
  return job;
}

void AppCacheRequestHandler::ContinueMaybeLoadSubResource() {
  // 6.9.6 Changes to the networking model
  // If the resource is not to be fetched using the HTTP GET mechanism or
  // equivalent ... then fetch the resource normally.
  DCHECK(job_.get());
  DCHECK(host_->associated_cache() && host_->associated_cache()->is_complete());

  const GURL& url = job_->request()->url();
  AppCache* cache = host_->associated_cache();
  storage()->FindResponseForSubRequest(
      host_->associated_cache(), url,
      &found_entry_, &found_fallback_entry_, &found_network_namespace_);

  if (found_entry_.has_response_id()) {
    // Step 2: If there's an entry, get it instead.
    DCHECK(!found_network_namespace_ &&
           !found_fallback_entry_.has_response_id());
    found_cache_id_ = cache->cache_id();
    found_group_id_ = cache->owning_group()->group_id();
    found_manifest_url_ = cache->owning_group()->manifest_url();
    DeliverAppCachedResponse(found_entry_, found_cache_id_, found_manifest_url_,
                             false, GURL());
    return;
  }

  if (found_fallback_entry_.has_response_id()) {
    // Step 4: Fetch the resource normally, if this results
    // in certain conditions, then use the fallback.
    DCHECK(!found_network_namespace_ &&
           !found_entry_.has_response_id());
    found_cache_id_ = cache->cache_id();
    found_manifest_url_ = cache->owning_group()->manifest_url();
    DeliverNetworkResponse();
    return;
  }

  if (found_network_namespace_) {
    // Step 3 and 5: Fetch the resource normally.
    DCHECK(!found_entry_.has_response_id() &&
           !found_fallback_entry_.has_response_id());
    DeliverNetworkResponse();
    return;
  }

  // Step 6: Fail the resource load.
  DeliverErrorResponse();
}

void AppCacheRequestHandler::OnCacheSelectionComplete(AppCacheHost* host) {
  DCHECK(host == host_);

  // Request may have been canceled, but not yet deleted, while waiting on
  // the cache.
  if (!job_.get())
    return;

  if (is_main_resource())
    return;
  if (!is_waiting_for_cache_selection_)
    return;

  is_waiting_for_cache_selection_ = false;

  if (!host_->associated_cache() ||
      !host_->associated_cache()->is_complete()) {
    DeliverNetworkResponse();
    return;
  }

  ContinueMaybeLoadSubResource();
}

}  // namespace content