// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/file_system_access/file_path_watcher/file_path_watcher.h"

#include <memory>

#include "base/memory/ptr_util.h"
#include "build/build_config.h"
#include "content/browser/file_system_access/features.h"
#include "content/browser/file_system_access/file_path_watcher/file_path_watcher_kqueue.h"

#if !BUILDFLAG(IS_IOS)
#include "content/browser/file_system_access/file_path_watcher/file_path_watcher_fsevents.h"
#endif

namespace content {

namespace {

// From experiment, we determined that the max calls to FSEventStreamCreate per
// process is 512. There is a higher system wide limit (at least 970), but we
// use the process limit since we'll hit it first.
constexpr size_t kMaxCreateFSEventCalls = 512u;

class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate {
 public:
  FilePathWatcherImpl() = default;
  FilePathWatcherImpl(const FilePathWatcherImpl&) = delete;
  FilePathWatcherImpl& operator=(const FilePathWatcherImpl&) = delete;
  ~FilePathWatcherImpl() override = default;

  size_t current_usage() const override { return impl_->current_usage(); }

  bool Watch(const base::FilePath& path,
             Type type,
             const FilePathWatcher::Callback& callback) override {
    // Use kqueue for non-recursive watches and FSEvents for recursive ones.
    DCHECK(!impl_.get());
    if (type == Type::kRecursive) {
      if (!FilePathWatcher::RecursiveWatchAvailable()) {
        return false;
      }
#if !BUILDFLAG(IS_IOS)
      impl_ = std::make_unique<FilePathWatcherFSEvents>();
#endif  // BUILDFLAG(IS_IOS)
    } else {
      impl_ = std::make_unique<FilePathWatcherKQueue>();
    }
    DCHECK(impl_.get());
    return impl_->Watch(path, type, callback);
  }

  bool WatchWithChangeInfo(
      const base::FilePath& path,
      const WatchOptions& options,
      const FilePathWatcher::CallbackWithChangeInfo& callback,
      const FilePathWatcher::UsageChangeCallback& usage_callback) override {
    impl_ = std::make_unique<FilePathWatcherFSEvents>();
    return impl_->WatchWithChangeInfo(path, options, callback, usage_callback);
  }

  void Cancel() override {
    if (impl_.get()) {
      impl_->Cancel();
    }
    set_cancelled();
  }

 private:
  std::unique_ptr<PlatformDelegate> impl_;
};

}  // namespace

FilePathWatcher::FilePathWatcher()
    : FilePathWatcher(std::make_unique<FilePathWatcherImpl>()) {}

// static
size_t FilePathWatcher::GetQuotaLimitImpl() {
  // TODO(crbug.com/383148762): This is only applicable to the
  // `FilePathWatcherFSEvents` implementation. `FilePathWatcherKQueue` is unused
  // so this shouldn't matter.
  return kMaxCreateFSEventCalls *
         features::kFileSystemObserverQuotaLimitMacPercent.Get();
}

// static
std::unique_ptr<FilePathWatcher>
FilePathWatcher::CreateWithFSEventsHookForTesting(base::RepeatingClosure hook) {
  auto delegate = std::make_unique<FilePathWatcherFSEvents>();
  delegate->SetOnFSEventsCallbackForTesting(std::move(hook));

  // Use the private constructor of FilePathWatcher
  return base::WrapUnique(new FilePathWatcher(std::move(delegate)));
}

}  // namespace content