// Copyright 2023 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_system_access_observer_observation.h"

#include <memory>
#include <string>
#include <variant>
#include <vector>

#include "base/files/file_path.h"
#include "base/functional/bind.h"
#include "base/metrics/histogram_functions.h"
#include "build/buildflag.h"
#include "content/browser/file_system_access/file_system_access_change_source.h"
#include "content/browser/file_system_access/file_system_access_directory_handle_impl.h"
#include "content/browser/file_system_access/file_system_access_file_handle_impl.h"
#include "content/browser/file_system_access/file_system_access_handle_base.h"
#include "content/browser/file_system_access/file_system_access_manager_impl.h"
#include "content/browser/file_system_access/file_system_access_observer_host.h"
#include "content/browser/file_system_access/file_system_access_watch_scope.h"
#include "content/browser/file_system_access/file_system_access_watcher_manager.h"
#include "content/browser/renderer_host/render_frame_host_impl.h"
#include "content/public/browser/file_system_access_permission_context.h"
#include "content/public/browser/global_routing_id.h"
#include "content/public/browser/web_contents.h"
#include "storage/browser/file_system/file_system_context.h"
#include "storage/browser/file_system/file_system_url.h"
#include "third_party/blink/public/mojom/file_system_access/file_system_access_directory_handle.mojom.h"
#include "third_party/blink/public/mojom/file_system_access/file_system_access_observer.mojom.h"
#include "third_party/blink/public/mojom/permissions/permission_status.mojom-shared.h"

#if BUILDFLAG(IS_WIN)
#include "base/strings/utf_string_conversions.h"
#endif  // BUILDFLAG(IS_WIN)

namespace content {

namespace {

// A visitor for a variant of file system access handles that returns the
// appropriate `FileSystemAccessPermissionContext::HandleType`.
struct GetHandleTypeVisitor {
  FileSystemAccessPermissionContext::HandleType operator()(
      const std::unique_ptr<FileSystemAccessDirectoryHandleImpl>&) const {
    return FileSystemAccessPermissionContext::HandleType::kDirectory;
  }
  FileSystemAccessPermissionContext::HandleType operator()(
      const std::unique_ptr<FileSystemAccessFileHandleImpl>&) const {
    return FileSystemAccessPermissionContext::HandleType::kFile;
  }
};

FileSystemAccessHandleBase& AsHandleBase(
    const std::variant<std::unique_ptr<FileSystemAccessDirectoryHandleImpl>,
                       std::unique_ptr<FileSystemAccessFileHandleImpl>>&
        handle) {
  return std::visit(
      [](const auto& h) -> FileSystemAccessHandleBase& { return *h; }, handle);
}

// TODO(crbug.com/40105284): Move this to a helper shared with
// `FileSystemAccessDirectoryHandleImpl`.
std::vector<std::string> GetRelativePathAsVectorOfStrings(
    const base::FilePath& relative_path) {
  CHECK(!relative_path.IsAbsolute());
  CHECK(!relative_path.ReferencesParent());

  std::vector<base::FilePath::StringType> components =
      relative_path.GetComponents();
#if BUILDFLAG(IS_WIN)
  std::vector<std::string> result;
  result.reserve(components.size());
  for (const auto& component : components) {
    result.push_back(base::WideToUTF8(component));
  }
  return result;
#else
  return components;
#endif  //  BUILDFLAG(IS_WIN)
}

blink::mojom::FileSystemAccessEntryPtr CreateEntryForUrl(
    FileSystemAccessManagerImpl& manager,
    const FileSystemAccessManagerImpl::BindingContext& binding_context,
    const FileSystemAccessManagerImpl::SharedHandleState& handle_state,
    const storage::FileSystemURL& url,
    FileSystemAccessPermissionContext::HandleType handle_type) {
  switch (handle_type) {
    case FileSystemAccessPermissionContext::HandleType::kFile:
      return blink::mojom::FileSystemAccessEntry::New(
          blink::mojom::FileSystemAccessHandle::NewFile(
              manager.CreateFileHandle(
                  binding_context, url,
                  url.virtual_path().BaseName().AsUTF8Unsafe(), handle_state)),
          url.virtual_path().BaseName().AsUTF8Unsafe());
    case FileSystemAccessPermissionContext::HandleType::kDirectory:
      return blink::mojom::FileSystemAccessEntry::New(
          blink::mojom::FileSystemAccessHandle::NewDirectory(
              manager.CreateDirectoryHandle(binding_context, url,
                                            handle_state)),
          url.virtual_path().BaseName().AsUTF8Unsafe());
  }
}

std::optional<base::FilePath> GetRelativePath(const base::FilePath& root_path,
                                              const base::FilePath& target) {
  if (root_path.empty()) {
    return base::FilePath(target);
  }

  if (root_path == target) {
    return base::FilePath();
  }

  if (root_path.IsParent(target)) {
    base::FilePath relative_path;
    CHECK(root_path.AppendRelativePath(target, &relative_path));
    return relative_path;
  }

  return std::nullopt;
}

bool RenderFrameHostIsActive(
    const FileSystemAccessManagerImpl::BindingContext& binding_context) {
  GlobalRenderFrameHostId render_frame_host_id = binding_context.frame_id;
  RenderFrameHostImpl* rfh = RenderFrameHostImpl::FromID(render_frame_host_id);

  // Frames without an associated render frame host (e.g. Service Workers,
  // Shared Workers) are considered active.
  if (!rfh) {
    return true;
  }

  return rfh->IsActive();
}

}  // namespace

FileSystemAccessObserverObservation::FileSystemAccessObserverObservation(
    FileSystemAccessObserverHost* host,
    std::unique_ptr<FileSystemAccessObservationGroup::Observer> observation,
    mojo::PendingRemote<blink::mojom::FileSystemAccessObserver> remote,
    std::variant<std::unique_ptr<FileSystemAccessDirectoryHandleImpl>,
                 std::unique_ptr<FileSystemAccessFileHandleImpl>> handle)
    : WebContentsObserver(
          WebContents::FromRenderFrameHost(RenderFrameHostImpl::FromID(
              AsHandleBase(handle).context().frame_id))),
      host_(host),
      handle_(std::move(handle)),
      observation_(std::move(observation)),
      remote_(std::move(remote)) {
  CHECK(host);
  CHECK(observation_);

  CHECK(observation_->scope().Contains(AsHandleBase(handle_).url()));

  // Observe `read_grant` changes in case we lose read permission.
  const FileSystemAccessManagerImpl::SharedHandleState& handle_state =
      AsHandleBase(handle_).handle_state();
  handle_state.read_grant->AddObserver(this);

  observation_->SetCallback(
      base::BindRepeating(&FileSystemAccessObserverObservation::OnChanges,
                          weak_factory_.GetWeakPtr()));

  // `base::Unretained` is safe here because this instance owns
  // `remote_`.
  remote_.set_disconnect_handler(
      base::BindOnce(&FileSystemAccessObserverObservation::OnReceiverDisconnect,
                     base::Unretained(this)));
}

FileSystemAccessObserverObservation::~FileSystemAccessObserverObservation() {
  const FileSystemAccessManagerImpl::SharedHandleState& handle_state =
      AsHandleBase(handle_).handle_state();
  handle_state.read_grant->RemoveObserver(this);
}

const storage::FileSystemURL& FileSystemAccessObserverObservation::handle_url()
    const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return AsHandleBase(handle_).url();
}

void FileSystemAccessObserverObservation::OnChanges(
    const std::optional<std::list<FileSystemAccessObservationGroup::Change>>&
        changes_or_error) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  // We should never receive changes for an observation with
  // `WatchType::kAllBucketFileSystems`.
  CHECK(observation_->scope().GetWatchType() !=
        FileSystemAccessWatchScope::WatchType::kAllBucketFileSystems);

  if (received_error_while_in_bf_cache_) {
    return;
  }

  if (!changes_or_error.has_value()) {
    HandleError();
    return;
  }

  FileSystemAccessHandleBase& handle_base = AsHandleBase(handle_);
  const FileSystemAccessManagerImpl::BindingContext& binding_context =
      handle_base.context();

  // Make sure the RenderFrameHost is Active before sending changes to the
  // renderer.
  if (!RenderFrameHostIsActive(binding_context)) {
    received_changes_while_in_bf_cache_ = true;
    return;
  }

  const FileSystemAccessManagerImpl::SharedHandleState& handle_state =
      handle_base.handle_state();
  // Do not relay changes if the site has lost read permission to the handle.
  // TODO(crbug.com/321980366): Add tests for this.
  if (handle_state.read_grant->GetStatus() !=
      blink::mojom::PermissionStatus::GRANTED) {
    return;
  }

  FileSystemAccessManagerImpl* manager = handle_base.manager();
  const storage::FileSystemURL& handle_url = handle_base.url();
  std::vector<blink::mojom::FileSystemAccessChangePtr> mojo_changes;
  bool observation_root_disappeared = false;
  for (const auto& change : changes_or_error.value()) {
    // TODO(crbug.com/40105284): Consider refactoring to keep the "scope"
    // concept within the WatcherManager and its associated classes. This method
    // just needs the root url.
    //
    // It is illegal to receive a change outside of the observed scope.
    CHECK(observation_->scope().Contains(change.url));

    const auto handle_type = std::visit(GetHandleTypeVisitor(), handle_);
    blink::mojom::FileSystemAccessEntryPtr root_entry = CreateEntryForUrl(
        *manager, binding_context, handle_state, handle_url, handle_type);
    const auto& change_info = change.change_info;
    FileSystemAccessPermissionContext::HandleType changed_entry_handle_type;
    switch (change_info.file_path_type) {
      case FileSystemAccessChangeSource::FilePathType::kUnknown:
        // Fall back to using the same handle type as the root handle.
        changed_entry_handle_type = handle_type;
        break;
      case FileSystemAccessChangeSource::FilePathType::kDirectory:
        changed_entry_handle_type =
            FileSystemAccessPermissionContext::HandleType::kDirectory;
        break;
      case FileSystemAccessChangeSource::FilePathType::kFile:
        changed_entry_handle_type =
            FileSystemAccessPermissionContext::HandleType::kFile;
        break;
    }
    // TODO(crbug.com/377903461): Don't send a changedHandle for `kDisappeared`
    // or `kUnknown` events. Renderer side, changedHandle() getter returns null
    // for these cases.
    blink::mojom::FileSystemAccessEntryPtr changed_entry =
        CreateEntryForUrl(*manager, binding_context, handle_state, change.url,
                          changed_entry_handle_type);

    // Some platforms do not support ChangeInfo for Local FS changes, in which
    // case a default, empty ChangeInfo is passed. In this case, report an event
    // without metadata. Remove this section once ChangeInfo is supported in all
    // platforms.
    if (change_info == FileSystemAccessChangeSource::ChangeInfo()) {
      mojo_changes.emplace_back(blink::mojom::FileSystemAccessChange::New(
          blink::mojom::FileSystemAccessChangeMetadata::New(
              std::move(root_entry), std::move(changed_entry),
              std::vector<std::string>()),
          blink::mojom::FileSystemAccessChangeType::NewUnknown(
              blink::mojom::FileSystemAccessChangeTypeUnknown::New())));
      continue;
    }

    // TODO(crbug.com/340583257): It is expected that `ChangeInfo.modified_path`
    // match the path of `Observation::Change.url`. Consider refactoring
    // Observation::Change so that we do not need to do this check.
    CHECK_EQ(change.url.virtual_path(), change_info.modified_path);

    const base::FilePath& root_path = handle_url.path();
    std::optional<base::FilePath> relative_modified_path =
        GetRelativePath(root_path, change_info.modified_path);
    // It is expected that modified_path is a descendent of the root,
    // or the same as the root.
    CHECK(relative_modified_path.has_value());
    std::optional<base::FilePath> relative_moved_from_path =
        change_info.moved_from_path.has_value()
            ? GetRelativePath(root_path, change_info.moved_from_path.value())
            : std::nullopt;

    blink::mojom::FileSystemAccessChangeTypePtr mojo_change_type;
    switch (change_info.change_type) {
      case FileSystemAccessChangeSource::ChangeType::kUnknown:
        mojo_change_type = blink::mojom::FileSystemAccessChangeType::NewUnknown(
            blink::mojom::FileSystemAccessChangeTypeUnknown::New());
        break;
      case FileSystemAccessChangeSource::ChangeType::kCreated:
        mojo_change_type =
            blink::mojom::FileSystemAccessChangeType::NewAppeared(
                blink::mojom::FileSystemAccessChangeTypeAppeared::New());
        break;
      case FileSystemAccessChangeSource::ChangeType::kDeleted:
        mojo_change_type =
            blink::mojom::FileSystemAccessChangeType::NewDisappeared(
                blink::mojom::FileSystemAccessChangeTypeDisappeared::New());
        break;
      case FileSystemAccessChangeSource::ChangeType::kModified:
        mojo_change_type =
            blink::mojom::FileSystemAccessChangeType::NewModified(
                blink::mojom::FileSystemAccessChangeTypeModified::New());
        break;
      case FileSystemAccessChangeSource::ChangeType::kMoved:
        if (relative_moved_from_path.has_value()) {
          mojo_change_type = blink::mojom::FileSystemAccessChangeType::NewMoved(
              blink::mojom::FileSystemAccessChangeTypeMoved::New(
                  GetRelativePathAsVectorOfStrings(
                      relative_moved_from_path.value())));
        } else {
          mojo_change_type = blink::mojom::FileSystemAccessChangeType::NewMoved(
              blink::mojom::FileSystemAccessChangeTypeMoved::New());
        }
        break;
    }

    observation_root_disappeared =
        mojo_change_type->is_disappeared() &&
        observation_->scope().root_url() == change.url;

    mojo_changes.emplace_back(blink::mojom::FileSystemAccessChange::New(
        blink::mojom::FileSystemAccessChangeMetadata::New(
            std::move(root_entry), std::move(changed_entry),
            GetRelativePathAsVectorOfStrings(relative_modified_path.value())),
        std::move(mojo_change_type)));

    if (observation_root_disappeared) {
      break;
    }
  }

  // Report the number of events in a 1s time window.
  if (callback_count_ == 0) {
    base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
        FROM_HERE,
        base::BindOnce(
            &FileSystemAccessObserverObservation::RecordCallbackCountUMA,
            weak_factory_.GetWeakPtr()),
        base::Seconds(1));
  }
  callback_count_++;

  remote_->OnFileChanges(std::move(mojo_changes));

  // Send an "errored" event and destruct if the root of the observation
  // disappeared.
  if (observation_root_disappeared) {
    HandleError();
  }
}

void FileSystemAccessObserverObservation::HandleError() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  FileSystemAccessHandleBase& handle_base = AsHandleBase(handle_);
  const FileSystemAccessManagerImpl::BindingContext& binding_context =
      handle_base.context();

  // Skip sending changes to the renderer if RenderFrameHost is not valid.
  if (!RenderFrameHostIsActive(binding_context)) {
    received_error_while_in_bf_cache_ = true;
    return;
  }

  std::vector<blink::mojom::FileSystemAccessChangePtr> mojo_changes;
  const FileSystemAccessManagerImpl::SharedHandleState& handle_state =
      handle_base.handle_state();
  FileSystemAccessManagerImpl* manager = handle_base.manager();
  const storage::FileSystemURL& handle_url = handle_base.url();
  // TODO(crbug.com/377903461): Don't send changedHandle for `kErrored` events.
  // Renderer side, changedHandle() getter returns null for this case.
  const auto handle_type = std::visit(GetHandleTypeVisitor(), handle_);
  mojo_changes.emplace_back(blink::mojom::FileSystemAccessChange::New(
      blink::mojom::FileSystemAccessChangeMetadata::New(
          CreateEntryForUrl(*manager, binding_context, handle_state, handle_url,
                            handle_type),
          CreateEntryForUrl(*manager, binding_context, handle_state, handle_url,
                            handle_type),
          std::vector<std::string>()),
      blink::mojom::FileSystemAccessChangeType::NewErrored(
          blink::mojom::FileSystemAccessChangeTypeErrored::New())));
  remote_->OnFileChanges(std::move(mojo_changes));

  // Destroys `this`. It not only removes this observation but also its
  // corresponding watch set up by FileSystemAccessWatcherManager if this
  // observation is the only one using the watch.
  host_->RemoveObservation(this);
}

void FileSystemAccessObserverObservation::RenderFrameHostStateChanged(
    RenderFrameHost* render_frame_host,
    RenderFrameHost::LifecycleState old_state,
    RenderFrameHost::LifecycleState new_state) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  bool transitioned_from_bf_cache_to_active =
      new_state == RenderFrameHost::LifecycleState::kActive &&
      old_state == RenderFrameHost::LifecycleState::kInBackForwardCache;

  if (render_frame_host !=
          RenderFrameHost::FromID(AsHandleBase(handle_).context().frame_id) ||
      !transitioned_from_bf_cache_to_active) {
    return;
  }

  if (received_error_while_in_bf_cache_) {
    HandleError();
    return;
  }

  if (!received_changes_while_in_bf_cache_) {
    return;
  }

  // RFH's state changed to kActive from kInBackForwardCache. File System
  // changes are not sent while the page is in BFCache. So, we use
  // ChangeType::kUnknown to signal to the renderer that some changes could be
  // missing.
  std::vector<blink::mojom::FileSystemAccessChangePtr> mojo_changes;
  FileSystemAccessManagerImpl* manager = AsHandleBase(handle_).manager();
  const FileSystemAccessManagerImpl::BindingContext& binding_context =
      AsHandleBase(handle_).context();
  const FileSystemAccessManagerImpl::SharedHandleState& handle_state =
      AsHandleBase(handle_).handle_state();
  const storage::FileSystemURL& handle_url = AsHandleBase(handle_).url();

  const auto handle_type = std::visit(GetHandleTypeVisitor(), handle_);
  mojo_changes.emplace_back(blink::mojom::FileSystemAccessChange::New(
      blink::mojom::FileSystemAccessChangeMetadata::New(
          CreateEntryForUrl(*manager, binding_context, handle_state, handle_url,
                            handle_type),
          CreateEntryForUrl(*manager, binding_context, handle_state, handle_url,
                            handle_type),
          std::vector<std::string>()),
      blink::mojom::FileSystemAccessChangeType::NewUnknown(
          blink::mojom::FileSystemAccessChangeTypeUnknown::New())));
  remote_->OnFileChanges(std::move(mojo_changes));
  received_changes_while_in_bf_cache_ = false;
}

void FileSystemAccessObserverObservation::OnReceiverDisconnect() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  // Destroys `this`.
  host_->RemoveObservation(this);
}

void FileSystemAccessObserverObservation::OnPermissionStatusChanged() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  if (received_error_while_in_bf_cache_) {
    return;
  }

  const FileSystemAccessManagerImpl::SharedHandleState& handle_state =
      AsHandleBase(handle_).handle_state();
  if (handle_state.read_grant->GetStatus() ==
      blink::mojom::PermissionStatus::GRANTED) {
    return;
  }

  // The read permission has been revoked. Send an "errored" event and destroy
  // this observation.
  HandleError();
}

void FileSystemAccessObserverObservation::RecordCallbackCountUMA() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  base::UmaHistogramCounts1000(
      "Storage.FileSystemAccess.ObservationCallbackRate", callback_count_);
  callback_count_ = 0;
}

}  // namespace content