tdlight/td/telegram/DocumentsManager.cpp

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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#include "td/telegram/DocumentsManager.h"
#include "td/telegram/AnimationsManager.h"
#include "td/telegram/AudiosManager.h"
#include "td/telegram/AuthManager.h"
#include "td/telegram/Document.h"
#include "td/telegram/files/FileEncryptionKey.h"
#include "td/telegram/files/FileLocation.h"
#include "td/telegram/files/FileManager.h"
#include "td/telegram/files/FileType.h"
#include "td/telegram/misc.h"
#include "td/telegram/net/DcId.h"
#include "td/telegram/Photo.h"
#include "td/telegram/StickersManager.h"
#include "td/telegram/Td.h"
#include "td/telegram/VideoNotesManager.h"
#include "td/telegram/VideosManager.h"
#include "td/telegram/VoiceNotesManager.h"
#include "td/telegram/secret_api.h"
#include "td/telegram/td_api.h"
#include "td/telegram/telegram_api.h"
#include "td/utils/common.h"
#include "td/utils/format.h"
#include "td/utils/HttpUrl.h"
#include "td/utils/logging.h"
#include "td/utils/MimeType.h"
#include "td/utils/misc.h"
#include "td/utils/PathView.h"
#include "td/utils/Random.h"
#include "td/utils/Slice.h"
#include "td/utils/StackAllocator.h"
#include "td/utils/Status.h"
#include "td/utils/StringBuilder.h"
#include "td/utils/utf8.h"
#include <limits>
namespace td {
DocumentsManager::DocumentsManager(Td *td) : td_(td) {
}
tl_object_ptr<td_api::document> DocumentsManager::get_document_object(FileId file_id, PhotoFormat thumbnail_format) {
if (!file_id.is_valid()) {
return nullptr;
}
LOG(INFO) << "Return document " << file_id << " object";
auto &document = documents_[file_id];
LOG_CHECK(document != nullptr) << tag("file_id", file_id);
document->is_changed = false;
return make_tl_object<td_api::document>(
document->file_name, document->mime_type, get_minithumbnail_object(document->minithumbnail),
get_thumbnail_object(td_->file_manager_.get(), document->thumbnail, thumbnail_format),
td_->file_manager_->get_file_object(file_id));
}
Document DocumentsManager::on_get_document(RemoteDocument remote_document, DialogId owner_dialog_id,
MultiPromiseActor *load_data_multipromise_ptr,
Document::Type default_document_type, bool is_background, bool is_pattern) {
tl_object_ptr<telegram_api::documentAttributeAnimated> animated;
tl_object_ptr<telegram_api::documentAttributeVideo> video;
tl_object_ptr<telegram_api::documentAttributeAudio> audio;
tl_object_ptr<telegram_api::documentAttributeSticker> sticker;
Dimensions dimensions;
string file_name;
bool has_stickers = false;
int32 type_attributes = 0;
for (auto &attribute : remote_document.attributes) {
switch (attribute->get_id()) {
case telegram_api::documentAttributeImageSize::ID: {
auto image_size = move_tl_object_as<telegram_api::documentAttributeImageSize>(attribute);
dimensions = get_dimensions(image_size->w_, image_size->h_);
break;
}
case telegram_api::documentAttributeAnimated::ID:
animated = move_tl_object_as<telegram_api::documentAttributeAnimated>(attribute);
type_attributes++;
break;
case telegram_api::documentAttributeSticker::ID:
sticker = move_tl_object_as<telegram_api::documentAttributeSticker>(attribute);
type_attributes++;
break;
case telegram_api::documentAttributeVideo::ID:
video = move_tl_object_as<telegram_api::documentAttributeVideo>(attribute);
type_attributes++;
break;
case telegram_api::documentAttributeAudio::ID:
audio = move_tl_object_as<telegram_api::documentAttributeAudio>(attribute);
type_attributes++;
break;
case telegram_api::documentAttributeFilename::ID:
file_name = std::move(static_cast<telegram_api::documentAttributeFilename *>(attribute.get())->file_name_);
break;
case telegram_api::documentAttributeHasStickers::ID:
has_stickers = true;
break;
default:
UNREACHABLE();
}
}
int32 video_duration = 0;
if (video != nullptr) {
video_duration = video->duration_;
if (dimensions.width == 0) {
dimensions = get_dimensions(video->w_, video->h_);
}
if (animated != nullptr) {
// video animation
type_attributes--;
video = nullptr;
}
}
if (animated != nullptr && audio != nullptr) {
// animation send as audio
type_attributes--;
audio = nullptr;
}
if (animated != nullptr && sticker != nullptr) {
// animation send as sticker
type_attributes--;
sticker = nullptr;
}
auto document_type = default_document_type;
FileType file_type = FileType::Document;
Slice default_extension;
bool supports_streaming = false;
PhotoFormat thumbnail_format = PhotoFormat::Jpeg;
if (type_attributes == 1 || default_document_type != Document::Type::General) { // not a general document
if (animated != nullptr || default_document_type == Document::Type::Animation) {
document_type = Document::Type::Animation;
file_type = FileType::Animation;
default_extension = Slice("mp4");
} else if (audio != nullptr || default_document_type == Document::Type::Audio ||
default_document_type == Document::Type::VoiceNote) {
bool is_voice_note = default_document_type == Document::Type::VoiceNote;
if (audio != nullptr) {
is_voice_note = (audio->flags_ & telegram_api::documentAttributeAudio::VOICE_MASK) != 0;
}
if (is_voice_note) {
document_type = Document::Type::VoiceNote;
file_type = FileType::VoiceNote;
default_extension = Slice("oga");
file_name.clear();
} else {
document_type = Document::Type::Audio;
file_type = FileType::Audio;
default_extension = Slice("mp3");
}
} else if (sticker != nullptr || default_document_type == Document::Type::Sticker) {
document_type = Document::Type::Sticker;
file_type = FileType::Sticker;
default_extension = Slice("webp");
owner_dialog_id = DialogId();
file_name.clear();
if (td_->stickers_manager_->has_webp_thumbnail(sticker) && remote_document.secret_file == nullptr) {
thumbnail_format = PhotoFormat::Webp;
}
} else if (video != nullptr || default_document_type == Document::Type::Video ||
default_document_type == Document::Type::VideoNote) {
bool is_video_note = default_document_type == Document::Type::VideoNote;
if (video != nullptr) {
is_video_note = (video->flags_ & telegram_api::documentAttributeVideo::ROUND_MESSAGE_MASK) != 0;
if (!is_video_note) {
supports_streaming = (video->flags_ & telegram_api::documentAttributeVideo::SUPPORTS_STREAMING_MASK) != 0;
}
}
if (is_video_note) {
document_type = Document::Type::VideoNote;
file_type = FileType::VideoNote;
file_name.clear();
} else {
document_type = Document::Type::Video;
file_type = FileType::Video;
}
default_extension = Slice("mp4");
}
} else if (type_attributes >= 2) {
LOG(WARNING) << "Receive document with more than 1 type attribute: animated = " << to_string(animated)
<< ", sticker = " << to_string(sticker) << ", video = " << to_string(video)
<< ", audio = " << to_string(audio) << ", file_name = " << file_name << ", dimensions = " << dimensions
<< ", has_stickers = " << has_stickers;
}
if (is_background) {
if (document_type != Document::Type::General) {
LOG(ERROR) << "Receive background of type " << document_type;
document_type = Document::Type::General;
}
file_type = FileType::Background;
if (is_pattern) {
default_extension = Slice("png");
thumbnail_format = PhotoFormat::Png;
} else {
default_extension = Slice("jpg");
}
}
int64 id;
int64 access_hash;
int32 dc_id;
int32 size;
string mime_type;
string file_reference;
string minithumbnail;
PhotoSize thumbnail;
AnimationSize animated_thumbnail;
FileEncryptionKey encryption_key;
bool is_animated_sticker = false;
bool is_web = false;
bool is_web_no_proxy = false;
string url;
FileLocationSource source = FileLocationSource::FromServer;
auto fix_animated_sticker_type = [&] {
if (mime_type != "application/x-tgsticker") {
return;
}
is_animated_sticker = true;
if (document_type == Document::Type::General) {
document_type = Document::Type::Sticker;
file_type = FileType::Sticker;
default_extension = Slice("tgs");
owner_dialog_id = DialogId();
file_name.clear();
thumbnail_format = PhotoFormat::Webp;
}
};
if (remote_document.document != nullptr) {
auto document = std::move(remote_document.document);
id = document->id_;
access_hash = document->access_hash_;
dc_id = document->dc_id_;
size = document->size_;
mime_type = std::move(document->mime_type_);
file_reference = document->file_reference_.as_slice().str();
fix_animated_sticker_type();
if (owner_dialog_id.get_type() == DialogType::SecretChat) {
// secret_api::decryptedMessageMediaExternalDocument
if (document_type != Document::Type::Sticker) {
LOG(ERROR) << "Receive " << document_type << " in " << owner_dialog_id;
return {};
}
source = FileLocationSource::FromUser;
}
if (document_type != Document::Type::VoiceNote) {
for (auto &thumb : document->thumbs_) {
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auto photo_size = get_photo_size(td_->file_manager_.get(), {FileType::Thumbnail, 0}, id, access_hash,
file_reference, DcId::create(dc_id), owner_dialog_id, std::move(thumb),
thumbnail_format, document_type != Document::Type::Sticker);
if (photo_size.get_offset() == 0) {
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if (!thumbnail.file_id.is_valid()) {
thumbnail = std::move(photo_size.get<0>());
}
} else {
minithumbnail = std::move(photo_size.get<1>());
}
}
}
for (auto &thumb : document->video_thumbs_) {
if (thumb->type_ == "v") {
animated_thumbnail = get_animation_size(td_->file_manager_.get(), {FileType::Thumbnail, 0}, id, access_hash,
file_reference, DcId::create(dc_id), owner_dialog_id, std::move(thumb));
if (animated_thumbnail.file_id.is_valid()) {
break;
}
}
}
} else if (remote_document.secret_file != nullptr) {
CHECK(remote_document.secret_document != nullptr);
auto file = std::move(remote_document.secret_file);
auto document = std::move(remote_document.secret_document);
id = file->id_;
access_hash = file->access_hash_;
dc_id = file->dc_id_;
size = document->size_;
mime_type = std::move(document->mime_type_);
file_type = FileType::Encrypted;
encryption_key = FileEncryptionKey{document->key_.as_slice(), document->iv_.as_slice()};
if (encryption_key.empty()) {
return {};
}
// do not allow encrypted animated stickers
// fix_animated_sticker_type();
if (document_type != Document::Type::VoiceNote) {
thumbnail = get_secret_thumbnail_photo_size(td_->file_manager_.get(), std::move(document->thumb_),
owner_dialog_id, document->thumb_w_, document->thumb_h_);
}
} else {
is_web = true;
id = Random::fast(0, std::numeric_limits<int32>::max());
dc_id = 0;
access_hash = 0;
if (remote_document.thumbnail.type == 'v') {
static_cast<PhotoSize &>(animated_thumbnail) = std::move(remote_document.thumbnail);
} else {
thumbnail = std::move(remote_document.thumbnail);
if (remote_document.thumbnail.type == 'g') {
thumbnail_format = PhotoFormat::Gif;
}
}
auto web_document_ptr = std::move(remote_document.web_document);
switch (web_document_ptr->get_id()) {
case telegram_api::webDocument::ID: {
auto web_document = move_tl_object_as<telegram_api::webDocument>(web_document_ptr);
auto r_http_url = parse_url(web_document->url_);
if (r_http_url.is_error()) {
LOG(ERROR) << "Can't parse URL " << web_document->url_;
return {};
}
auto http_url = r_http_url.move_as_ok();
access_hash = web_document->access_hash_;
url = http_url.get_url();
file_name = get_url_query_file_name(http_url.query_);
mime_type = std::move(web_document->mime_type_);
size = web_document->size_;
break;
}
case telegram_api::webDocumentNoProxy::ID: {
is_web_no_proxy = true;
auto web_document = move_tl_object_as<telegram_api::webDocumentNoProxy>(web_document_ptr);
if (web_document->url_.find('.') == string::npos) {
LOG(ERROR) << "Receive invalid URL " << web_document->url_;
return {};
}
url = std::move(web_document->url_);
file_name = get_url_file_name(url);
mime_type = std::move(web_document->mime_type_);
size = web_document->size_;
break;
}
default:
UNREACHABLE();
}
// do not allow web animated stickers
// fix_animated_sticker_type();
}
LOG(DEBUG) << "Receive document with id = " << id << " of type " << document_type;
if (!is_web && !DcId::is_valid(dc_id)) {
LOG(ERROR) << "Wrong dc_id = " << dc_id;
return {};
}
file_name = strip_empty_characters(file_name, 255, true);
auto suggested_file_name = file_name;
if (suggested_file_name.empty()) {
suggested_file_name = to_string(static_cast<uint64>(id));
auto extension = MimeType::to_extension(mime_type, default_extension);
if (!extension.empty()) {
suggested_file_name += '.';
suggested_file_name += extension;
}
}
FileId file_id;
if (!is_web) {
file_id = td_->file_manager_->register_remote(
FullRemoteFileLocation(file_type, id, access_hash, DcId::internal(dc_id), std::move(file_reference)), source,
owner_dialog_id, size, 0, suggested_file_name);
if (!encryption_key.empty()) {
td_->file_manager_->set_encryption_key(file_id, std::move(encryption_key));
}
} else if (!is_web_no_proxy) {
file_id = td_->file_manager_->register_remote(FullRemoteFileLocation(file_type, url, access_hash), source,
owner_dialog_id, 0, size, file_name);
} else {
auto r_file_id = td_->file_manager_->from_persistent_id(url, file_type);
if (r_file_id.is_error()) {
LOG(ERROR) << "Can't register URL: " << r_file_id.error();
return {};
}
file_id = r_file_id.move_as_ok();
}
if (dimensions.width != 0 && thumbnail.dimensions.width != 0) {
if ((thumbnail.dimensions.width < thumbnail.dimensions.height && dimensions.width > dimensions.height) ||
(thumbnail.dimensions.width > thumbnail.dimensions.height && dimensions.width < dimensions.height)) {
// fix for wrong dimensions specified by the Android application
std::swap(dimensions.width, dimensions.height);
}
}
switch (document_type) {
case Document::Type::Animation:
td_->animations_manager_->create_animation(
file_id, std::move(minithumbnail), std::move(thumbnail), std::move(animated_thumbnail), has_stickers,
vector<FileId>(), std::move(file_name), std::move(mime_type), video_duration, dimensions, !is_web);
break;
case Document::Type::Audio: {
int32 duration = 0;
string title;
string performer;
if (audio != nullptr) {
duration = audio->duration_;
title = std::move(audio->title_);
performer = std::move(audio->performer_);
}
td_->audios_manager_->create_audio(file_id, std::move(minithumbnail), std::move(thumbnail), std::move(file_name),
std::move(mime_type), duration, std::move(title), std::move(performer),
!is_web);
break;
}
case Document::Type::General:
create_document(file_id, std::move(minithumbnail), std::move(thumbnail), std::move(file_name),
std::move(mime_type), !is_web);
break;
case Document::Type::Sticker:
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td_->stickers_manager_->create_sticker(file_id, std::move(minithumbnail), std::move(thumbnail), dimensions,
std::move(sticker), is_animated_sticker, load_data_multipromise_ptr);
break;
case Document::Type::Video:
td_->videos_manager_->create_video(file_id, std::move(minithumbnail), std::move(thumbnail),
std::move(animated_thumbnail), has_stickers, vector<FileId>(),
std::move(file_name), std::move(mime_type), video_duration, dimensions,
supports_streaming, !is_web);
break;
case Document::Type::VideoNote:
td_->video_notes_manager_->create_video_note(file_id, std::move(minithumbnail), std::move(thumbnail),
video_duration, dimensions, !is_web);
break;
case Document::Type::VoiceNote: {
int32 duration = 0;
string waveform;
if (audio != nullptr) {
duration = audio->duration_;
waveform = audio->waveform_.as_slice().str();
}
td_->voice_notes_manager_->create_voice_note(file_id, std::move(mime_type), duration, std::move(waveform),
!is_web);
break;
}
case Document::Type::Unknown:
default:
UNREACHABLE();
}
return {document_type, file_id};
}
FileId DocumentsManager::on_get_document(unique_ptr<GeneralDocument> new_document, bool replace) {
auto file_id = new_document->file_id;
CHECK(file_id.is_valid());
LOG(INFO) << "Receive document " << file_id;
auto &d = documents_[new_document->file_id];
if (d == nullptr) {
d = std::move(new_document);
} else if (replace) {
CHECK(d->file_id == new_document->file_id);
if (d->mime_type != new_document->mime_type) {
LOG(DEBUG) << "Document " << file_id << " mime_type has changed";
d->mime_type = new_document->mime_type;
d->is_changed = true;
}
if (d->file_name != new_document->file_name) {
LOG(DEBUG) << "Document " << file_id << " file_name has changed";
d->file_name = new_document->file_name;
d->is_changed = true;
}
if (d->minithumbnail != new_document->minithumbnail) {
d->minithumbnail = std::move(new_document->minithumbnail);
d->is_changed = true;
}
if (d->thumbnail != new_document->thumbnail) {
if (!d->thumbnail.file_id.is_valid()) {
LOG(DEBUG) << "Document " << file_id << " thumbnail has changed";
} else {
LOG(INFO) << "Document " << file_id << " thumbnail has changed from " << d->thumbnail << " to "
<< new_document->thumbnail;
}
d->thumbnail = new_document->thumbnail;
d->is_changed = true;
}
}
return file_id;
}
void DocumentsManager::create_document(FileId file_id, string minithumbnail, PhotoSize thumbnail, string file_name,
string mime_type, bool replace) {
auto d = make_unique<GeneralDocument>();
d->file_id = file_id;
d->file_name = std::move(file_name);
d->mime_type = std::move(mime_type);
d->minithumbnail = std::move(minithumbnail);
d->thumbnail = std::move(thumbnail);
on_get_document(std::move(d), replace);
}
const DocumentsManager::GeneralDocument *DocumentsManager::get_document(FileId file_id) const {
auto document = documents_.find(file_id);
if (document == documents_.end()) {
return nullptr;
}
CHECK(document->second->file_id == file_id);
return document->second.get();
}
bool DocumentsManager::has_input_media(FileId file_id, FileId thumbnail_file_id, bool is_secret) const {
auto file_view = td_->file_manager_->get_file_view(file_id);
if (is_secret) {
if (!file_view.is_encrypted_secret() || file_view.encryption_key().empty() || !file_view.has_remote_location()) {
return false;
}
return !thumbnail_file_id.is_valid();
} else {
if (file_view.is_encrypted()) {
return false;
}
if (td_->auth_manager_->is_bot() && file_view.has_remote_location()) {
return true;
}
// having remote location is not enough to have InputMedia, because the file may not have valid file_reference
// also file_id needs to be duped, because upload can be called to repair the file_reference and every upload
// request must have unique file_id
return /* file_view.has_remote_location() || */ file_view.has_url();
}
}
SecretInputMedia DocumentsManager::get_secret_input_media(FileId document_file_id,
tl_object_ptr<telegram_api::InputEncryptedFile> input_file,
const string &caption, BufferSlice thumbnail) const {
const GeneralDocument *document = get_document(document_file_id);
CHECK(document != nullptr);
auto file_view = td_->file_manager_->get_file_view(document_file_id);
auto &encryption_key = file_view.encryption_key();
if (!file_view.is_encrypted_secret() || encryption_key.empty()) {
return SecretInputMedia{};
}
if (file_view.has_remote_location()) {
input_file = file_view.main_remote_location().as_input_encrypted_file();
}
if (!input_file) {
return SecretInputMedia{};
}
if (document->thumbnail.file_id.is_valid() && thumbnail.empty()) {
return SecretInputMedia{};
}
vector<tl_object_ptr<secret_api::DocumentAttribute>> attributes;
if (document->file_name.size()) {
attributes.push_back(make_tl_object<secret_api::documentAttributeFilename>(document->file_name));
}
return SecretInputMedia{
std::move(input_file),
make_tl_object<secret_api::decryptedMessageMediaDocument>(
std::move(thumbnail), document->thumbnail.dimensions.width, document->thumbnail.dimensions.height,
document->mime_type, narrow_cast<int32>(file_view.size()), BufferSlice(encryption_key.key_slice()),
BufferSlice(encryption_key.iv_slice()), std::move(attributes), caption)};
}
tl_object_ptr<telegram_api::InputMedia> DocumentsManager::get_input_media(
FileId file_id, tl_object_ptr<telegram_api::InputFile> input_file,
tl_object_ptr<telegram_api::InputFile> input_thumbnail) const {
auto file_view = td_->file_manager_->get_file_view(file_id);
if (file_view.is_encrypted()) {
return nullptr;
}
if (file_view.has_remote_location() && !file_view.main_remote_location().is_web() && input_file == nullptr) {
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return make_tl_object<telegram_api::inputMediaDocument>(0, file_view.main_remote_location().as_input_document(), 0,
string());
}
if (file_view.has_url()) {
return make_tl_object<telegram_api::inputMediaDocumentExternal>(0, file_view.url(), 0);
}
if (input_file != nullptr) {
const GeneralDocument *document = get_document(file_id);
CHECK(document != nullptr);
vector<tl_object_ptr<telegram_api::DocumentAttribute>> attributes;
if (document->file_name.size()) {
attributes.push_back(make_tl_object<telegram_api::documentAttributeFilename>(document->file_name));
}
int32 flags = 0;
if (input_thumbnail != nullptr) {
flags |= telegram_api::inputMediaUploadedDocument::THUMB_MASK;
}
if (file_view.get_type() == FileType::DocumentAsFile) {
flags |= telegram_api::inputMediaUploadedDocument::FORCE_FILE_MASK;
}
return make_tl_object<telegram_api::inputMediaUploadedDocument>(
flags, false /*ignored*/, false /*ignored*/, std::move(input_file), std::move(input_thumbnail),
document->mime_type, std::move(attributes), vector<tl_object_ptr<telegram_api::InputDocument>>(), 0);
} else {
CHECK(!file_view.has_remote_location());
}
return nullptr;
}
FileId DocumentsManager::get_document_thumbnail_file_id(FileId file_id) const {
auto document = get_document(file_id);
CHECK(document != nullptr);
return document->thumbnail.file_id;
}
void DocumentsManager::delete_document_thumbnail(FileId file_id) {
auto &document = documents_[file_id];
CHECK(document != nullptr);
document->thumbnail = PhotoSize();
}
FileId DocumentsManager::dup_document(FileId new_id, FileId old_id) {
const GeneralDocument *old_document = get_document(old_id);
CHECK(old_document != nullptr);
auto &new_document = documents_[new_id];
CHECK(!new_document);
new_document = make_unique<GeneralDocument>(*old_document);
new_document->file_id = new_id;
new_document->thumbnail.file_id = td_->file_manager_->dup_file_id(new_document->thumbnail.file_id);
return new_id;
}
bool DocumentsManager::merge_documents(FileId new_id, FileId old_id, bool can_delete_old) {
if (!old_id.is_valid()) {
LOG(ERROR) << "Old file id is invalid";
return true;
}
LOG(INFO) << "Merge documents " << new_id << " and " << old_id;
const GeneralDocument *old_ = get_document(old_id);
CHECK(old_ != nullptr);
if (old_id == new_id) {
return old_->is_changed;
}
auto new_it = documents_.find(new_id);
if (new_it == documents_.end()) {
auto &old = documents_[old_id];
old->is_changed = true;
if (!can_delete_old) {
dup_document(new_id, old_id);
} else {
old->file_id = new_id;
documents_.emplace(new_id, std::move(old));
}
} else {
GeneralDocument *new_ = new_it->second.get();
CHECK(new_ != nullptr);
if (old_->thumbnail != new_->thumbnail) {
// LOG_STATUS(td_->file_manager_->merge(new_->thumbnail.file_id, old_->thumbnail.file_id));
}
new_->is_changed = true;
}
LOG_STATUS(td_->file_manager_->merge(new_id, old_id));
if (can_delete_old) {
documents_.erase(old_id);
}
return true;
}
string DocumentsManager::get_document_search_text(FileId file_id) const {
auto document = get_document(file_id);
CHECK(document);
if (document->file_name.size() > 32) {
return document->file_name;
}
auto buf = StackAllocator::alloc(256);
StringBuilder sb(buf.as_slice());
auto stem = PathView(document->file_name).file_stem();
sb << document->file_name;
for (size_t i = 1; i + 1 < stem.size(); i++) {
if (is_utf8_character_first_code_unit(stem[i])) {
sb << " " << stem.substr(0, i);
}
}
if (sb.is_error()) {
return document->file_name;
}
return sb.as_cslice().str();
}
} // namespace td