// Copyright (c) 2012 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 "base/files/file_path.h"
#include "base/metrics/field_trial.h"
#include "base/task/task_scheduler/task_scheduler.h"
#include "net/base/cache_type.h"
#include "net/base/net_errors.h"
#include "net/disk_cache/backend_cleanup_tracker.h"
#include "net/disk_cache/cache_util.h"
#include "net/disk_cache/cobalt/cobalt_backend_impl.h"
#include "net/disk_cache/disk_cache.h"
#include "net/disk_cache/memory/mem_backend_impl.h"

namespace {

// Builds an instance of the backend depending on platform, type, experiments
// etc. Takes care of the retry state. This object will self-destroy when
// finished.
class CacheCreator {
 public:
  CacheCreator(const base::FilePath& path,
               bool force,
               int64_t max_bytes,
               net::CacheType type,
               net::NetLog* net_log,
               std::unique_ptr<disk_cache::Backend>* backend,
               base::OnceClosure post_cleanup_callback,
               net::CompletionOnceCallback callback);

  net::Error TryCreateCleanupTrackerAndRun();

  // Creates the backend, the cleanup context for it having been already
  // established... or purposefully left as null.
  net::Error Run();

 private:
  ~CacheCreator();

  void DoCallback(int result);

  void OnIOComplete(int result);

  const base::FilePath path_;
  bool force_;
  bool retry_;
  int64_t max_bytes_;
  net::CacheType type_;
  std::unique_ptr<disk_cache::Backend>* backend_;
  base::OnceClosure post_cleanup_callback_;
  net::CompletionOnceCallback callback_;
  std::unique_ptr<disk_cache::Backend> created_cache_;
  net::NetLog* net_log_;
  scoped_refptr<disk_cache::BackendCleanupTracker> cleanup_tracker_;

  DISALLOW_COPY_AND_ASSIGN(CacheCreator);
};

CacheCreator::CacheCreator(const base::FilePath& path,
                           bool force,
                           int64_t max_bytes,
                           net::CacheType type,
                           net::NetLog* net_log,
                           std::unique_ptr<disk_cache::Backend>* backend,
                           base::OnceClosure post_cleanup_callback,
                           net::CompletionOnceCallback callback)
    : path_(path),
      force_(force),
      retry_(false),
      max_bytes_(max_bytes),
      type_(type),
      backend_(backend),
      post_cleanup_callback_(std::move(post_cleanup_callback)),
      callback_(std::move(callback)),
      net_log_(net_log) {}

CacheCreator::~CacheCreator() = default;

net::Error CacheCreator::Run() {
  disk_cache::CobaltBackendImpl* cobalt_cache =
      new disk_cache::CobaltBackendImpl(path_, cleanup_tracker_.get(),
                                        max_bytes_, type_, net_log_);
  created_cache_.reset(cobalt_cache);
  return cobalt_cache->Init(
      base::Bind(&CacheCreator::OnIOComplete, base::Unretained(this)));
}

net::Error CacheCreator::TryCreateCleanupTrackerAndRun() {
  // Before creating a cache Backend, a BackendCleanupTracker object is needed
  // so there is a place to keep track of outstanding I/O even after the backend
  // object itself is destroyed, so that further use of the directory
  // doesn't race with those outstanding disk I/O ops.

  // This method's purpose it to grab exlusive ownership of a fresh
  // BackendCleanupTracker for the cache path, and then move on to Run(),
  // which will take care of creating the actual cache backend. It's possible
  // that something else is currently making use of the directory, in which
  // case BackendCleanupTracker::TryCreate will fail, but will just have
  // TryCreateCleanupTrackerAndRun run again at an opportune time to make
  // another attempt.

  // The resulting BackendCleanupTracker is stored into a scoped_refptr member
  // so that it's kept alive while |this| CacheCreator exists , so that in the
  // case Run() needs to retry Backend creation the same BackendCleanupTracker
  // is used for both attempts, and |post_cleanup_callback_| gets called after
  // the second try, not the first one.
  cleanup_tracker_ = disk_cache::BackendCleanupTracker::TryCreate(
      path_, base::BindOnce(base::IgnoreResult(
                                &CacheCreator::TryCreateCleanupTrackerAndRun),
                            base::Unretained(this)));
  if (!cleanup_tracker_)
    return net::ERR_IO_PENDING;
  if (!post_cleanup_callback_.is_null())
    cleanup_tracker_->AddPostCleanupCallback(std::move(post_cleanup_callback_));
  return Run();
}

void CacheCreator::DoCallback(int result) {
  DCHECK_NE(net::ERR_IO_PENDING, result);
  if (result == net::OK) {
    *backend_ = std::move(created_cache_);
  } else {
    LOG(ERROR) << "Unable to create cache";
    created_cache_.reset();
  }
  std::move(callback_).Run(result);
  delete this;
}

// If the initialization of the cache fails, and |force| is true, we will
// discard the whole cache and create a new one.
void CacheCreator::OnIOComplete(int result) {
  if (result == net::OK || !force_ || retry_)
    return DoCallback(result);

  // This is a failure and we are supposed to try again, so delete the object,
  // delete all the files, and try again.
  retry_ = true;
  created_cache_.reset();
  if (!disk_cache::DelayedCacheCleanup(path_))
    return DoCallback(result);

  // The worker thread will start deleting files soon, but the original folder
  // is not there anymore... let's create a new set of files.
  int rv = Run();
  DCHECK_EQ(net::ERR_IO_PENDING, rv);
}

}  // namespace

namespace disk_cache {

net::Error CreateCacheBackendImpl(net::CacheType type,
                                  const base::FilePath& path,
                                  int64_t max_bytes,
                                  bool force,
                                  net::NetLog* net_log,
                                  std::unique_ptr<Backend>* backend,
                                  base::OnceClosure post_cleanup_callback,
                                  net::CompletionOnceCallback callback) {
  DCHECK(!callback.is_null());

  if (type == net::MEMORY_CACHE) {
    std::unique_ptr<MemBackendImpl> mem_backend_impl =
        disk_cache::MemBackendImpl::CreateBackend(max_bytes, net_log);
    if (mem_backend_impl) {
      mem_backend_impl->SetPostCleanupCallback(
          std::move(post_cleanup_callback));
      *backend = std::move(mem_backend_impl);
      return net::OK;
    } else {
      if (!post_cleanup_callback.is_null())
        base::SequencedTaskRunnerHandle::Get()->PostTask(
            FROM_HERE, std::move(post_cleanup_callback));
      return net::ERR_FAILED;
    }
  }

  bool had_post_cleanup_callback = !post_cleanup_callback.is_null();
  CacheCreator* creator =
      new CacheCreator(path, force, max_bytes, type, net_log, backend,
                       std::move(post_cleanup_callback), std::move(callback));
  if (type == net::DISK_CACHE || type == net::MEDIA_CACHE) {
    DCHECK(!had_post_cleanup_callback);
    return creator->Run();
  }

  return creator->TryCreateCleanupTrackerAndRun();
}

net::Error CreateCacheBackend(net::CacheType type,
                              net::BackendType backend_type,
                              const base::FilePath& path,
                              int64_t max_bytes,
                              bool force,
                              net::NetLog* net_log,
                              std::unique_ptr<Backend>* backend,
                              net::CompletionOnceCallback callback) {
  return CreateCacheBackendImpl(type, path, max_bytes, force, net_log, backend,
                                base::OnceClosure(), std::move(callback));
}

net::Error CreateCacheBackend(net::CacheType type,
                              net::BackendType backend_type,
                              const base::FilePath& path,
                              int64_t max_bytes,
                              bool force,
                              net::NetLog* net_log,
                              std::unique_ptr<Backend>* backend,
                              base::OnceClosure post_cleanup_callback,
                              net::CompletionOnceCallback callback) {
  return CreateCacheBackendImpl(type, path, max_bytes, force, net_log, backend,
                                std::move(post_cleanup_callback),
                                std::move(callback));
}

void FlushCacheThreadForTesting() {
  // For simple backend.
  SimpleBackendImpl::FlushWorkerPoolForTesting();
  base::TaskScheduler::GetInstance()->FlushForTesting();
}

int64_t Backend::CalculateSizeOfEntriesBetween(
    base::Time initial_time,
    base::Time end_time,
    Int64CompletionOnceCallback callback) {
  return net::ERR_NOT_IMPLEMENTED;
}

uint8_t Backend::GetEntryInMemoryData(const std::string& key) {
  return 0;
}

void Backend::SetEntryInMemoryData(const std::string& key, uint8_t data) {}

}  // namespace disk_cache