//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
//
// 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/MessagesDb.h"

#include "td/telegram/logevent/LogEvent.h"
#include "td/telegram/Version.h"

#include "td/db/SqliteConnectionSafe.h"
#include "td/db/SqliteDb.h"
#include "td/db/SqliteStatement.h"

#include "td/actor/actor.h"
#include "td/actor/PromiseFuture.h"
#include "td/actor/SchedulerLocalStorage.h"

#include "td/utils/format.h"
#include "td/utils/logging.h"
#include "td/utils/ScopeGuard.h"
#include "td/utils/Slice.h"
#include "td/utils/StackAllocator.h"
#include "td/utils/StringBuilder.h"
#include "td/utils/Time.h"
#include "td/utils/tl_helpers.h"
#include "td/utils/unicode.h"
#include "td/utils/utf8.h"

#include <algorithm>
#include <array>
#include <iterator>
#include <limits>
#include <tuple>

namespace td {

static constexpr int32 MESSAGES_DB_INDEX_COUNT = 30;
static constexpr int32 MESSAGES_DB_INDEX_COUNT_OLD = 9;

// NB: must happen inside a transaction
Status init_messages_db(SqliteDb &db, int32 version) {
  LOG(INFO) << "Init message database " << tag("version", version);

  // Check if database exists
  TRY_RESULT(has_table, db.has_table("messages"));
  if (!has_table) {
    version = 0;
  } else if (version < static_cast<int32>(DbVersion::DialogDbCreated) || version > current_db_version()) {
    TRY_STATUS(drop_messages_db(db, version));
    version = 0;
  }

  auto add_media_indices = [&db](int begin, int end) {
    for (int i = begin; i < end; i++) {
      TRY_STATUS(db.exec(PSLICE() << "CREATE INDEX IF NOT EXISTS message_index_" << i
                                  << " ON messages (dialog_id, message_id) WHERE (index_mask & " << (1 << i)
                                  << ") != 0"));
    }
    return Status::OK();
  };

  auto add_fts = [&db] {
    TRY_STATUS(
        db.exec("CREATE INDEX IF NOT EXISTS message_by_search_id ON messages "
                "(search_id) WHERE search_id IS NOT NULL"));

    TRY_STATUS(
        db.exec("CREATE VIRTUAL TABLE IF NOT EXISTS messages_fts USING fts5(text, content='messages', "
                "content_rowid='search_id', tokenize = \"unicode61 remove_diacritics 0 tokenchars '\a'\")"));
    TRY_STATUS(db.exec(
        "CREATE TRIGGER IF NOT EXISTS trigger_fts_delete BEFORE DELETE ON messages WHEN OLD.search_id IS NOT NULL"
        " BEGIN INSERT INTO messages_fts(messages_fts, rowid, text) VALUES(\'delete\', OLD.search_id, OLD.text); END"));
    TRY_STATUS(db.exec(
        "CREATE TRIGGER IF NOT EXISTS trigger_fts_insert AFTER INSERT ON messages WHEN NEW.search_id IS NOT NULL"
        " BEGIN INSERT INTO messages_fts(rowid, text) VALUES(NEW.search_id, NEW.text); END"));
    //TRY_STATUS(db.exec(
    //"CREATE TRIGGER IF NOT EXISTS trigger_fts_update AFTER UPDATE ON messages WHEN NEW.search_id IS NOT NULL OR "
    //"OLD.search_id IS NOT NULL"
    //" BEGIN "
    //"INSERT INTO messages_fts(messages_fts, rowid, text) VALUES(\'delete\', OLD.search_id, OLD.text); "
    //"INSERT INTO messages_fts(rowid, text) VALUES(NEW.search_id, NEW.text); "
    //" END"));

    return Status::OK();
  };
  auto add_call_index = [&db]() {
    for (int i = static_cast<int>(SearchMessagesFilter::Call) - 1;
         i < static_cast<int>(SearchMessagesFilter::MissedCall); i++) {
      TRY_STATUS(db.exec(PSLICE() << "CREATE INDEX IF NOT EXISTS full_message_index_" << i
                                  << " ON messages (unique_message_id) WHERE (index_mask & " << (1 << i) << ") != 0"));
    }
    return Status::OK();
  };
  auto add_notification_id_index = [&db]() {
    TRY_STATUS(
        db.exec("CREATE INDEX IF NOT EXISTS message_by_notification_id ON messages (dialog_id, notification_id) "
                "WHERE notification_id IS NOT NULL"));
    return Status::OK();
  };

  if (version == 0) {
    LOG(INFO) << "Create new message database";
    TRY_STATUS(
        db.exec("CREATE TABLE IF NOT EXISTS messages (dialog_id INT8, message_id INT8, "
                "unique_message_id INT4, sender_user_id INT4, random_id INT8, data BLOB, "
                "ttl_expires_at INT4, index_mask INT4, search_id INT8, text STRING, notification_id INT4, PRIMARY KEY "
                "(dialog_id, message_id))"));

    TRY_STATUS(
        db.exec("CREATE INDEX IF NOT EXISTS message_by_random_id ON messages (dialog_id, random_id) "
                "WHERE random_id IS NOT NULL"));

    TRY_STATUS(
        db.exec("CREATE INDEX IF NOT EXISTS message_by_unique_message_id ON messages "
                "(unique_message_id) WHERE unique_message_id IS NOT NULL"));

    TRY_STATUS(
        db.exec("CREATE INDEX IF NOT EXISTS message_by_ttl ON messages "
                "(ttl_expires_at) WHERE ttl_expires_at IS NOT NULL"));

    TRY_STATUS(add_media_indices(0, MESSAGES_DB_INDEX_COUNT));

    TRY_STATUS(add_fts());

    TRY_STATUS(add_call_index());

    TRY_STATUS(add_notification_id_index());

    version = current_db_version();
  }
  if (version < static_cast<int32>(DbVersion::MessagesDbMediaIndex)) {
    TRY_STATUS(db.exec("ALTER TABLE messages ADD COLUMN index_mask INT4"));
    TRY_STATUS(add_media_indices(0, MESSAGES_DB_INDEX_COUNT_OLD));
  }
  if (version < static_cast<int32>(DbVersion::MessagesDb30MediaIndex)) {
    TRY_STATUS(add_media_indices(MESSAGES_DB_INDEX_COUNT_OLD, MESSAGES_DB_INDEX_COUNT));
  }
  if (version < static_cast<int32>(DbVersion::MessagesDbFts)) {
    TRY_STATUS(db.exec("ALTER TABLE messages ADD COLUMN search_id INT8"));
    TRY_STATUS(db.exec("ALTER TABLE messages ADD COLUMN text STRING"));
    TRY_STATUS(add_fts());
  }
  if (version < static_cast<int32>(DbVersion::MessagesCallIndex)) {
    TRY_STATUS(add_call_index());
  }
  if (version < static_cast<int32>(DbVersion::AddNotificationsSupport)) {
    TRY_STATUS(db.exec("ALTER TABLE messages ADD COLUMN notification_id INT4"));
    TRY_STATUS(add_notification_id_index());
  }
  return Status::OK();
}

// NB: must happen inside a transaction
Status drop_messages_db(SqliteDb &db, int32 version) {
  LOG(WARNING) << "Drop message database " << tag("version", version)
               << tag("current_db_version", current_db_version());
  return db.exec("DROP TABLE IF EXISTS messages");
}

class MessagesDbImpl : public MessagesDbSyncInterface {
 public:
  explicit MessagesDbImpl(SqliteDb db) : db_(std::move(db)) {
    init().ensure();
  }

  Status init() {
    TRY_RESULT(
        add_message_stmt,
        db_.get_statement("INSERT OR REPLACE INTO messages VALUES(?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9, ?10, ?11)"));
    TRY_RESULT(delete_message_stmt, db_.get_statement("DELETE FROM messages WHERE dialog_id = ?1 AND message_id = ?2"));
    TRY_RESULT(delete_all_dialog_messages_stmt,
               db_.get_statement("DELETE FROM messages WHERE dialog_id = ?1 AND message_id <= ?2"));
    TRY_RESULT(delete_dialog_messages_from_user_stmt,
               db_.get_statement("DELETE FROM messages WHERE dialog_id = ?1 AND sender_user_id == ?2"));

    TRY_RESULT(get_message_stmt,
               db_.get_statement("SELECT data FROM messages WHERE dialog_id = ?1 AND message_id = ?2"));
    TRY_RESULT(get_message_by_random_id_stmt,
               db_.get_statement("SELECT data FROM messages WHERE dialog_id = ?1 AND random_id = ?2"));
    TRY_RESULT(get_message_by_unique_message_id_stmt,
               db_.get_statement("SELECT dialog_id, data FROM messages WHERE unique_message_id = ?1"));

    TRY_RESULT(get_expiring_messages_stmt,
               db_.get_statement("SELECT dialog_id, data FROM messages WHERE ?1 < ttl_expires_at AND ttl_expires_at <= "
                                 "?2"));
    TRY_RESULT(get_expiring_messages_helper_stmt,
               db_.get_statement("SELECT MAX(ttl_expires_at), COUNT(*) FROM (SELECT ttl_expires_at FROM messages WHERE "
                                 "?1 < ttl_expires_at LIMIT ?2) AS T"));

    TRY_RESULT(get_messages_asc_stmt,
               db_.get_statement("SELECT data, message_id FROM messages WHERE dialog_id = ?1 AND "
                                 "message_id > ?2 ORDER BY message_id ASC LIMIT ?3"));
    TRY_RESULT(get_messages_desc_stmt, db_.get_statement("SELECT data, message_id FROM messages WHERE dialog_id = ?1 "
                                                         "AND message_id < ?2 ORDER BY message_id DESC LIMIT ?3"));
    TRY_RESULT(get_messages_from_notification_id_stmt,
               db_.get_statement("SELECT data, message_id FROM messages WHERE dialog_id = ?1 "
                                 "AND notification_id < ?2 ORDER BY notification_id DESC LIMIT ?3"));
    TRY_RESULT(
        get_messages_fts_stmt,
        db_.get_statement("SELECT dialog_id, data, search_id FROM messages WHERE search_id IN (SELECT rowid FROM "
                          "messages_fts WHERE messages_fts MATCH ?1 AND rowid < ?2 ORDER BY rowid DESC LIMIT "
                          "?3) ORDER BY search_id DESC"));

    for (int32 i = 0; i < MESSAGES_DB_INDEX_COUNT; i++) {
      TRY_RESULT(get_messages_from_index_desc_stmt,
                 db_.get_statement(PSLICE() << "SELECT data, message_id FROM messages WHERE dialog_id = ?1 "
                                               "AND message_id < ?2 AND (index_mask & "
                                            << (1 << i) << ") != 0 ORDER BY message_id DESC LIMIT ?3"));
      get_messages_from_index_stmts_[i].desc_stmt_ = std::move(get_messages_from_index_desc_stmt);

      TRY_RESULT(get_messages_from_index_asc_stmt,
                 db_.get_statement(PSLICE() << "SELECT data, message_id FROM messages WHERE dialog_id = ?1 "
                                               "AND message_id > ?2 AND (index_mask & "
                                            << (1 << i) << ") != 0 ORDER BY message_id ASC LIMIT ?3"));
      get_messages_from_index_stmts_[i].asc_stmt_ = std::move(get_messages_from_index_asc_stmt);

      // LOG(ERROR) << get_messages_from_index_stmts_[i].explain().ok();
    }

    for (int i = static_cast<int>(SearchMessagesFilter::Call) - 1, pos = 0;
         i < static_cast<int>(SearchMessagesFilter::MissedCall); i++, pos++) {
      TRY_RESULT(get_messages_from_index_stmt,
                 db_.get_statement(PSLICE() << "SELECT dialog_id, data FROM messages "
                                               "WHERE unique_message_id < ?1 AND (index_mask & "
                                            << (1 << i) << ") != 0 ORDER BY unique_message_id DESC LIMIT ?2"));
      get_calls_stmts_[pos] = std::move(get_messages_from_index_stmt);
      // LOG(ERROR) << get_messages_from_index_stmts_[i].explain().ok();
    }

    add_message_stmt_ = std::move(add_message_stmt);
    delete_message_stmt_ = std::move(delete_message_stmt);
    delete_all_dialog_messages_stmt_ = std::move(delete_all_dialog_messages_stmt);
    delete_dialog_messages_from_user_stmt_ = std::move(delete_dialog_messages_from_user_stmt);

    get_message_stmt_ = std::move(get_message_stmt);
    get_message_by_random_id_stmt_ = std::move(get_message_by_random_id_stmt);
    get_message_by_unique_message_id_stmt_ = std::move(get_message_by_unique_message_id_stmt);

    get_expiring_messages_stmt_ = std::move(get_expiring_messages_stmt);
    get_expiring_messages_helper_stmt_ = std::move(get_expiring_messages_helper_stmt);

    get_messages_stmt_.asc_stmt_ = std::move(get_messages_asc_stmt);
    get_messages_stmt_.desc_stmt_ = std::move(get_messages_desc_stmt);
    get_messages_from_notification_id_stmt_ = std::move(get_messages_from_notification_id_stmt);

    get_messages_fts_stmt_ = std::move(get_messages_fts_stmt);

    // LOG(ERROR) << get_message_stmt_.explain().ok();
    // LOG(ERROR) << get_messages_from_notification_id_stmt.explain().ok();
    // LOG(ERROR) << get_message_by_random_id_stmt_.explain().ok();
    // LOG(ERROR) << get_message_by_unique_message_id_stmt_.explain().ok();

    // LOG(ERROR) << get_expiring_messages_stmt_.explain().ok();
    // LOG(ERROR) << get_expiring_messages_helper_stmt_.explain().ok();

    // LOG(ERROR) << get_messages_asc_stmt_.explain().ok();
    // LOG(ERROR) << get_messages_desc_stmt_.explain().ok();
    // LOG(FATAL) << "EXPLAINED";

    return Status::OK();
  }

  Status add_message(FullMessageId full_message_id, ServerMessageId unique_message_id, UserId sender_user_id,
                     int64 random_id, int32 ttl_expires_at, int32 index_mask, int64 search_id, string text,
                     NotificationId notification_id, BufferSlice data) override {
    LOG(INFO) << "Add " << full_message_id << " to database";
    auto dialog_id = full_message_id.get_dialog_id();
    auto message_id = full_message_id.get_message_id();
    LOG_CHECK(dialog_id.is_valid()) << dialog_id << ' ' << message_id << ' ' << full_message_id;
    CHECK(message_id.is_valid());
    SCOPE_EXIT {
      add_message_stmt_.reset();
    };
    add_message_stmt_.bind_int64(1, dialog_id.get()).ensure();
    add_message_stmt_.bind_int64(2, message_id.get()).ensure();

    if (unique_message_id.is_valid()) {
      add_message_stmt_.bind_int32(3, unique_message_id.get()).ensure();
    } else {
      add_message_stmt_.bind_null(3).ensure();
    }

    if (sender_user_id.is_valid()) {
      add_message_stmt_.bind_int32(4, sender_user_id.get()).ensure();
    } else {
      add_message_stmt_.bind_null(4).ensure();
    }

    if (random_id != 0) {
      add_message_stmt_.bind_int64(5, random_id).ensure();
    } else {
      add_message_stmt_.bind_null(5).ensure();
    }

    add_message_stmt_.bind_blob(6, data.as_slice()).ensure();

    if (ttl_expires_at != 0) {
      add_message_stmt_.bind_int32(7, ttl_expires_at).ensure();
    } else {
      add_message_stmt_.bind_null(7).ensure();
    }

    if (index_mask != 0) {
      add_message_stmt_.bind_int32(8, index_mask).ensure();
    } else {
      add_message_stmt_.bind_null(8).ensure();
    }
    if (search_id != 0) {
      // add dialog_id to text
      text += PSTRING() << " \a" << dialog_id.get();
      if (index_mask) {
        for (int i = 0; i < MESSAGES_DB_INDEX_COUNT; i++) {
          if ((index_mask & (1 << i))) {
            text += PSTRING() << " \a\a" << i;
          }
        }
      }
      add_message_stmt_.bind_int64(9, search_id).ensure();
    } else {
      text = "";
      add_message_stmt_.bind_null(9).ensure();
    }
    if (!text.empty()) {
      add_message_stmt_.bind_string(10, text).ensure();
    } else {
      add_message_stmt_.bind_null(10).ensure();
    }
    if (notification_id.is_valid()) {
      add_message_stmt_.bind_int32(11, notification_id.get()).ensure();
    } else {
      add_message_stmt_.bind_null(11).ensure();
    }

    add_message_stmt_.step().ensure();

    return Status::OK();
  }

  Status delete_message(FullMessageId full_message_id) override {
    auto dialog_id = full_message_id.get_dialog_id();
    auto message_id = full_message_id.get_message_id();
    CHECK(dialog_id.is_valid());
    CHECK(message_id.is_valid());
    SCOPE_EXIT {
      delete_message_stmt_.reset();
    };
    delete_message_stmt_.bind_int64(1, dialog_id.get()).ensure();
    delete_message_stmt_.bind_int64(2, message_id.get()).ensure();
    delete_message_stmt_.step().ensure();
    return Status::OK();
  }

  Status delete_all_dialog_messages(DialogId dialog_id, MessageId from_message_id) override {
    CHECK(dialog_id.is_valid());
    CHECK(from_message_id.is_valid());
    SCOPE_EXIT {
      delete_all_dialog_messages_stmt_.reset();
    };
    delete_all_dialog_messages_stmt_.bind_int64(1, dialog_id.get()).ensure();
    delete_all_dialog_messages_stmt_.bind_int64(2, from_message_id.get()).ensure();
    auto status = delete_all_dialog_messages_stmt_.step();
    if (status.is_error()) {
      LOG(ERROR) << status;
    }
    return status;
  }

  Status delete_dialog_messages_from_user(DialogId dialog_id, UserId sender_user_id) override {
    CHECK(dialog_id.is_valid());
    CHECK(sender_user_id.is_valid());
    SCOPE_EXIT {
      delete_dialog_messages_from_user_stmt_.reset();
    };
    delete_dialog_messages_from_user_stmt_.bind_int64(1, dialog_id.get()).ensure();
    delete_dialog_messages_from_user_stmt_.bind_int32(2, sender_user_id.get()).ensure();
    delete_dialog_messages_from_user_stmt_.step().ensure();
    return Status::OK();
  }

  Result<BufferSlice> get_message(FullMessageId full_message_id) override {
    auto dialog_id = full_message_id.get_dialog_id();
    auto message_id = full_message_id.get_message_id();
    CHECK(dialog_id.is_valid());
    CHECK(message_id.is_valid());

    SCOPE_EXIT {
      get_message_stmt_.reset();
    };
    get_message_stmt_.bind_int64(1, dialog_id.get()).ensure();
    get_message_stmt_.bind_int64(2, message_id.get()).ensure();
    get_message_stmt_.step().ensure();
    if (!get_message_stmt_.has_row()) {
      return Status::Error("Not found");
    }
    return BufferSlice(get_message_stmt_.view_blob(0));
  }

  Result<std::pair<DialogId, BufferSlice>> get_message_by_unique_message_id(
      ServerMessageId unique_message_id) override {
    if (!unique_message_id.is_valid()) {
      return Status::Error("unique_message_id is invalid");
    }
    SCOPE_EXIT {
      get_message_by_unique_message_id_stmt_.reset();
    };
    get_message_by_unique_message_id_stmt_.bind_int32(1, unique_message_id.get()).ensure();
    get_message_by_unique_message_id_stmt_.step().ensure();
    if (!get_message_by_unique_message_id_stmt_.has_row()) {
      return Status::Error("Not found");
    }
    DialogId dialog_id(get_message_by_unique_message_id_stmt_.view_int64(0));
    return std::make_pair(dialog_id, BufferSlice(get_message_by_unique_message_id_stmt_.view_blob(1)));
  }

  Result<BufferSlice> get_message_by_random_id(DialogId dialog_id, int64 random_id) override {
    SCOPE_EXIT {
      get_message_by_random_id_stmt_.reset();
    };
    get_message_by_random_id_stmt_.bind_int64(1, dialog_id.get()).ensure();
    get_message_by_random_id_stmt_.bind_int64(2, random_id).ensure();
    get_message_by_random_id_stmt_.step().ensure();
    if (!get_message_by_random_id_stmt_.has_row()) {
      return Status::Error("Not found");
    }
    return BufferSlice(get_message_by_random_id_stmt_.view_blob(0));
  }

  Result<BufferSlice> get_dialog_message_by_date(DialogId dialog_id, MessageId first_message_id,
                                                 MessageId last_message_id, int32 date) override {
    int64 left_message_id = first_message_id.get();
    int64 right_message_id = last_message_id.get();
    LOG_CHECK(left_message_id <= right_message_id) << first_message_id << " " << last_message_id;
    TRY_RESULT(first_messages,
               get_messages_inner(get_messages_stmt_.asc_stmt_, dialog_id.get(), left_message_id - 1, 1));
    if (!first_messages.empty()) {
      MessageId real_first_message_id;
      int32 real_first_message_date;
      std::tie(real_first_message_id, real_first_message_date) = get_message_info(first_messages[0]);
      if (real_first_message_date <= date) {
        // we definitely have at least one suitable message, let's do a binary search
        left_message_id = real_first_message_id.get();

        MessageId prev_found_message_id;
        while (left_message_id <= right_message_id) {
          auto middle_message_id = left_message_id + ((right_message_id - left_message_id) >> 1);
          TRY_RESULT(messages, get_messages_inner(get_messages_stmt_.asc_stmt_, dialog_id.get(), middle_message_id, 1));

          MessageId message_id;
          int32 message_date = std::numeric_limits<int32>::max();
          if (!messages.empty()) {
            std::tie(message_id, message_date) = get_message_info(messages[0]);
          }
          if (message_date <= date) {
            left_message_id = message_id.get();
          } else {
            right_message_id = middle_message_id - 1;
          }

          if (prev_found_message_id == message_id) {
            // we may be very close to the result, let's check
            TRY_RESULT(left_messages,
                       get_messages_inner(get_messages_stmt_.asc_stmt_, dialog_id.get(), left_message_id - 1, 2));
            CHECK(!left_messages.empty());
            if (left_messages.size() == 1) {
              // only one message has left, result is found
              break;
            }

            MessageId next_message_id;
            int32 next_message_date;
            std::tie(next_message_id, next_message_date) = get_message_info(left_messages[1]);
            if (next_message_date <= date) {
              // next message has lesser date, adjusting left message
              left_message_id = next_message_id.get();
            } else {
              // next message has bigger date, result is found
              break;
            }
          }

          prev_found_message_id = message_id;
        }

        // left_message_id is always an id of suitable message, let's return it
        return get_message({dialog_id, MessageId(left_message_id)});
      }
    }

    return Status::Error("Not found");
  }

  Result<std::pair<std::vector<std::pair<DialogId, BufferSlice>>, int32>> get_expiring_messages(int32 expires_from,
                                                                                                int32 expires_till,
                                                                                                int32 limit) override {
    SCOPE_EXIT {
      get_expiring_messages_stmt_.reset();
      get_expiring_messages_helper_stmt_.reset();
    };

    std::vector<std::pair<DialogId, BufferSlice>> messages;
    // load messages
    if (expires_from <= expires_till) {
      get_expiring_messages_stmt_.bind_int32(1, expires_from).ensure();
      get_expiring_messages_stmt_.bind_int32(2, expires_till).ensure();
      get_expiring_messages_stmt_.step().ensure();

      while (get_expiring_messages_stmt_.has_row()) {
        DialogId dialog_id(get_expiring_messages_stmt_.view_int64(0));
        BufferSlice data(get_expiring_messages_stmt_.view_blob(1));
        messages.push_back(std::make_pair(dialog_id, std::move(data)));
        get_expiring_messages_stmt_.step().ensure();
      }
    }

    // calc next expires_till
    get_expiring_messages_helper_stmt_.bind_int32(1, expires_till).ensure();
    get_expiring_messages_helper_stmt_.bind_int32(2, limit).ensure();
    get_expiring_messages_helper_stmt_.step().ensure();
    CHECK(get_expiring_messages_helper_stmt_.has_row());
    int32 count = get_expiring_messages_helper_stmt_.view_int32(1);
    int32 next_expires_till = -1;
    if (count != 0) {
      next_expires_till = get_expiring_messages_helper_stmt_.view_int32(0);
    }
    return std::make_pair(std::move(messages), next_expires_till);
  }

  Result<std::vector<BufferSlice>> get_messages(MessagesDbMessagesQuery query) override {
    if (query.index_mask != 0) {
      return get_messages_from_index(query.dialog_id, query.from_message_id, query.index_mask, query.offset,
                                     query.limit);
    }
    return get_messages_impl(get_messages_stmt_, query.dialog_id, query.from_message_id, query.offset, query.limit);
  }

  Result<vector<BufferSlice>> get_messages_from_notification_id(DialogId dialog_id, NotificationId from_notification_id,
                                                                int32 limit) override {
    auto &stmt = get_messages_from_notification_id_stmt_;
    SCOPE_EXIT {
      stmt.reset();
    };
    stmt.bind_int64(1, dialog_id.get()).ensure();
    stmt.bind_int32(2, from_notification_id.get()).ensure();
    stmt.bind_int32(3, limit).ensure();

    std::vector<BufferSlice> result;
    stmt.step().ensure();
    while (stmt.has_row()) {
      auto data_slice = stmt.view_blob(0);
      result.emplace_back(data_slice);
      auto message_id = stmt.view_int64(1);
      LOG(INFO) << "Load " << MessageId(message_id) << " in " << dialog_id << " from database";
      stmt.step().ensure();
    }
    return std::move(result);
  }

  static string prepare_query(Slice query) {
    auto is_word_character = [](uint32 a) {
      switch (get_unicode_simple_category(a)) {
        case UnicodeSimpleCategory::Letter:
        case UnicodeSimpleCategory::DecimalNumber:
        case UnicodeSimpleCategory::Number:
          return true;
        default:
          return a == '_';
      }
    };

    const size_t MAX_QUERY_SIZE = 1024;
    query = utf8_truncate(query, MAX_QUERY_SIZE);
    auto buf = StackAllocator::alloc(query.size() * 4 + 100);
    StringBuilder sb(buf.as_slice());
    bool in_word{false};

    for (auto ptr = query.ubegin(), end = query.uend(); ptr < end;) {
      uint32 code;
      auto code_ptr = ptr;
      ptr = next_utf8_unsafe(ptr, &code, "prepare_query");
      if (is_word_character(code)) {
        if (!in_word) {
          in_word = true;
          sb << "\"";
        }
        sb << Slice(code_ptr, ptr);
      } else {
        if (in_word) {
          in_word = false;
          sb << "\" ";
        }
      }
    }
    if (in_word) {
      sb << "\" ";
    }

    if (sb.is_error()) {
      LOG(ERROR) << "StringBuilder buffer overflow";
      return "";
    }

    return sb.as_cslice().str();
  }

  Result<MessagesDbFtsResult> get_messages_fts(MessagesDbFtsQuery query) override {
    SCOPE_EXIT {
      get_messages_fts_stmt_.reset();
    };

    LOG(INFO) << tag("query", query.query) << query.dialog_id << tag("index_mask", query.index_mask)
              << tag("from_search_id", query.from_search_id) << tag("limit", query.limit);
    string words = prepare_query(query.query);
    LOG(INFO) << tag("from", query.query) << tag("to", words);

    // dialog_id kludge
    if (query.dialog_id.is_valid()) {
      words += PSTRING() << " \"\a" << query.dialog_id.get() << "\"";
    }

    // index_mask kludge
    if (query.index_mask != 0) {
      int index_i = -1;
      for (int i = 0; i < MESSAGES_DB_INDEX_COUNT; i++) {
        if (query.index_mask == (1 << i)) {
          index_i = i;
          break;
        }
      }
      if (index_i == -1) {
        return Status::Error("Union of index types is not supported");
      }
      words += PSTRING() << " \"\a\a" << index_i << "\"";
    }

    auto &stmt = get_messages_fts_stmt_;
    stmt.bind_string(1, words).ensure();
    if (query.from_search_id == 0) {
      query.from_search_id = std::numeric_limits<int64>::max();
    }
    stmt.bind_int64(2, query.from_search_id).ensure();
    stmt.bind_int32(3, query.limit).ensure();
    MessagesDbFtsResult result;
    auto status = stmt.step();
    if (status.is_error()) {
      LOG(ERROR) << status;
      return std::move(result);
    }
    while (stmt.has_row()) {
      auto dialog_id = stmt.view_int64(0);
      auto data_slice = stmt.view_blob(1);
      auto search_id = stmt.view_int64(2);
      result.next_search_id = search_id;
      result.messages.push_back(MessagesDbMessage{DialogId(dialog_id), BufferSlice(data_slice)});
      stmt.step().ensure();
    }
    return std::move(result);
  }

  Result<std::vector<BufferSlice>> get_messages_from_index(DialogId dialog_id, MessageId from_message_id,
                                                           int32 index_mask, int32 offset, int32 limit) {
    CHECK(index_mask != 0);
    LOG_CHECK(index_mask < (1 << MESSAGES_DB_INDEX_COUNT)) << tag("index_mask", index_mask);
    int index_i = -1;
    for (int i = 0; i < MESSAGES_DB_INDEX_COUNT; i++) {
      if (index_mask == (1 << i)) {
        index_i = i;
        break;
      }
    }
    if (index_i == -1) {
      return Status::Error("Union is not supported");
    }

    auto &stmt = get_messages_from_index_stmts_[index_i];
    return get_messages_impl(stmt, dialog_id, from_message_id, offset, limit);
  }

  Result<MessagesDbCallsResult> get_calls(MessagesDbCallsQuery query) override {
    CHECK(query.index_mask != 0);
    LOG_CHECK(query.index_mask < (1 << MESSAGES_DB_INDEX_COUNT)) << tag("index_mask", query.index_mask);
    int index_i = -1;
    for (int i = 0; i < MESSAGES_DB_INDEX_COUNT; i++) {
      if (query.index_mask == (1 << i)) {
        index_i = i;
        break;
      }
    }
    if (index_i == -1) {
      return Status::Error("Union is not supported");
    }
    int32 pos;
    if (index_i + 1 == static_cast<int>(SearchMessagesFilter::Call)) {
      pos = 0;
    } else if (index_i + 1 == static_cast<int>(SearchMessagesFilter::MissedCall)) {
      pos = 1;
    } else {
      return Status::Error(PSLICE() << "Index_mask is not Call or MissedCall " << query.index_mask);
    }

    auto &stmt = get_calls_stmts_[pos];
    SCOPE_EXIT {
      stmt.reset();
    };

    stmt.bind_int32(1, query.from_unique_message_id).ensure();
    stmt.bind_int32(2, query.limit).ensure();

    MessagesDbCallsResult result;
    stmt.step().ensure();
    while (stmt.has_row()) {
      auto dialog_id = stmt.view_int64(0);
      auto data_slice = stmt.view_blob(1);
      result.messages.push_back(MessagesDbMessage{DialogId(dialog_id), BufferSlice(data_slice)});
      stmt.step().ensure();
    }
    return std::move(result);
  }

  Status begin_transaction() override {
    return db_.begin_transaction();
  }
  Status commit_transaction() override {
    return db_.commit_transaction();
  }

 private:
  SqliteDb db_;

  SqliteStatement add_message_stmt_;

  SqliteStatement delete_message_stmt_;
  SqliteStatement delete_all_dialog_messages_stmt_;
  SqliteStatement delete_dialog_messages_from_user_stmt_;

  SqliteStatement get_message_stmt_;
  SqliteStatement get_message_by_random_id_stmt_;
  SqliteStatement get_message_by_unique_message_id_stmt_;
  SqliteStatement get_expiring_messages_stmt_;
  SqliteStatement get_expiring_messages_helper_stmt_;

  struct GetMessagesStmt {
    SqliteStatement asc_stmt_;
    SqliteStatement desc_stmt_;
  };
  GetMessagesStmt get_messages_stmt_;
  SqliteStatement get_messages_from_notification_id_stmt_;

  std::array<GetMessagesStmt, MESSAGES_DB_INDEX_COUNT> get_messages_from_index_stmts_;
  std::array<SqliteStatement, 2> get_calls_stmts_;

  SqliteStatement get_messages_fts_stmt_;

  Result<std::vector<BufferSlice>> get_messages_impl(GetMessagesStmt &stmt, DialogId dialog_id,
                                                     MessageId from_message_id, int32 offset, int32 limit) {
    LOG_CHECK(dialog_id.is_valid()) << dialog_id;
    CHECK(from_message_id.is_valid());

    LOG(INFO) << "Loading messages in " << dialog_id << " from " << from_message_id << " with offset = " << offset
              << " and limit = " << limit;

    auto message_id = from_message_id.get();

    if (message_id >= MessageId::max().get()) {
      message_id--;
    }

    auto left_message_id = message_id;
    auto left_cnt = limit + offset;

    auto right_message_id = message_id - 1;
    auto right_cnt = -offset;

    std::vector<BufferSlice> left;
    std::vector<BufferSlice> right;

    if (left_cnt != 0) {
      if (right_cnt == 1 && false) {
        left_message_id++;
        left_cnt++;
      }

      TRY_RESULT(left_tmp, get_messages_inner(stmt.desc_stmt_, dialog_id.get(), left_message_id, left_cnt));
      left = std::move(left_tmp);

      if (right_cnt == 1 && !left.empty() && false /*get_message_id(left[0].as_slice()) == message_id*/) {
        right_cnt = 0;
      }
    }
    if (right_cnt != 0) {
      TRY_RESULT(right_tmp, get_messages_inner(stmt.asc_stmt_, dialog_id.get(), right_message_id, right_cnt));
      right = std::move(right_tmp);
      std::reverse(right.begin(), right.end());
    }
    if (left.empty()) {
      return std::move(right);
    }
    if (right.empty()) {
      return std::move(left);
    }

    right.reserve(right.size() + left.size());
    std::move(left.begin(), left.end(), std::back_inserter(right));

    return std::move(right);
  }

  Result<std::vector<BufferSlice>> get_messages_inner(SqliteStatement &stmt, int64 dialog_id, int64 from_message_id,
                                                      int32 limit) {
    SCOPE_EXIT {
      stmt.reset();
    };
    stmt.bind_int64(1, dialog_id).ensure();
    stmt.bind_int64(2, from_message_id).ensure();
    stmt.bind_int32(3, limit).ensure();

    LOG(INFO) << "Begin to load " << limit << " messages in " << DialogId(dialog_id) << " from "
              << MessageId(from_message_id) << " from database";
    std::vector<BufferSlice> result;
    stmt.step().ensure();
    while (stmt.has_row()) {
      auto data_slice = stmt.view_blob(0);
      result.emplace_back(data_slice);
      auto message_id = stmt.view_int64(1);
      LOG(INFO) << "Loaded " << MessageId(message_id) << " in " << DialogId(dialog_id) << " from database";
      stmt.step().ensure();
    }
    return std::move(result);
  }

  static std::tuple<MessageId, int32> get_message_info(const BufferSlice &message) {
    LogEventParser message_date_parser(message.as_slice());
    int32 flags;
    td::parse(flags, message_date_parser);
    int32 flags2 = 0;
    if ((flags & (1 << 29)) != 0) {
      td::parse(flags2, message_date_parser);
    }
    bool has_sender = (flags >> 10) & 1;
    MessageId message_id;
    td::parse(message_id, message_date_parser);
    UserId sender_user_id;
    if (has_sender) {
      td::parse(sender_user_id, message_date_parser);
    }
    int32 date;
    td::parse(date, message_date_parser);
    LOG(INFO) << "Loaded " << message_id << " sent at " << date << " by " << sender_user_id;
    return std::make_tuple(message_id, date);
  }
};

std::shared_ptr<MessagesDbSyncSafeInterface> create_messages_db_sync(
    std::shared_ptr<SqliteConnectionSafe> sqlite_connection) {
  class MessagesDbSyncSafe : public MessagesDbSyncSafeInterface {
   public:
    explicit MessagesDbSyncSafe(std::shared_ptr<SqliteConnectionSafe> sqlite_connection)
        : lsls_db_([safe_connection = std::move(sqlite_connection)] {
          return make_unique<MessagesDbImpl>(safe_connection->get().clone());
        }) {
    }
    MessagesDbSyncInterface &get() override {
      return *lsls_db_.get();
    }

   private:
    LazySchedulerLocalStorage<unique_ptr<MessagesDbSyncInterface>> lsls_db_;
  };
  return std::make_shared<MessagesDbSyncSafe>(std::move(sqlite_connection));
}

class MessagesDbAsync : public MessagesDbAsyncInterface {
 public:
  MessagesDbAsync(std::shared_ptr<MessagesDbSyncSafeInterface> sync_db, int32 scheduler_id) {
    impl_ = create_actor_on_scheduler<Impl>("MessagesDbActor", scheduler_id, std::move(sync_db));
  }

  void add_message(FullMessageId full_message_id, ServerMessageId unique_message_id, UserId sender_user_id,
                   int64 random_id, int32 ttl_expires_at, int32 index_mask, int64 search_id, string text,
                   NotificationId notification_id, BufferSlice data, Promise<> promise) override {
    send_closure_later(impl_, &Impl::add_message, full_message_id, unique_message_id, sender_user_id, random_id,
                       ttl_expires_at, index_mask, search_id, std::move(text), notification_id, std::move(data),
                       std::move(promise));
  }

  void delete_message(FullMessageId full_message_id, Promise<> promise) override {
    send_closure_later(impl_, &Impl::delete_message, full_message_id, std::move(promise));
  }
  void delete_all_dialog_messages(DialogId dialog_id, MessageId from_message_id, Promise<> promise) override {
    send_closure_later(impl_, &Impl::delete_all_dialog_messages, dialog_id, from_message_id, std::move(promise));
  }
  void delete_dialog_messages_from_user(DialogId dialog_id, UserId sender_user_id, Promise<> promise) override {
    send_closure_later(impl_, &Impl::delete_dialog_messages_from_user, dialog_id, sender_user_id, std::move(promise));
  }

  void get_message(FullMessageId full_message_id, Promise<BufferSlice> promise) override {
    send_closure_later(impl_, &Impl::get_message, full_message_id, std::move(promise));
  }
  void get_message_by_unique_message_id(ServerMessageId unique_message_id,
                                        Promise<std::pair<DialogId, BufferSlice>> promise) override {
    send_closure_later(impl_, &Impl::get_message_by_unique_message_id, unique_message_id, std::move(promise));
  }
  void get_message_by_random_id(DialogId dialog_id, int64 random_id, Promise<BufferSlice> promise) override {
    send_closure_later(impl_, &Impl::get_message_by_random_id, dialog_id, random_id, std::move(promise));
  }
  void get_dialog_message_by_date(DialogId dialog_id, MessageId first_message_id, MessageId last_message_id, int32 date,
                                  Promise<BufferSlice> promise) override {
    send_closure_later(impl_, &Impl::get_dialog_message_by_date, dialog_id, first_message_id, last_message_id, date,
                       std::move(promise));
  }

  void get_messages(MessagesDbMessagesQuery query, Promise<std::vector<BufferSlice>> promise) override {
    send_closure_later(impl_, &Impl::get_messages, std::move(query), std::move(promise));
  }
  void get_messages_from_notification_id(DialogId dialog_id, NotificationId from_notification_id, int32 limit,
                                         Promise<vector<BufferSlice>> promise) override {
    send_closure_later(impl_, &Impl::get_messages_from_notification_id, dialog_id, from_notification_id, limit,
                       std::move(promise));
  }
  void get_calls(MessagesDbCallsQuery query, Promise<MessagesDbCallsResult> promise) override {
    send_closure_later(impl_, &Impl::get_calls, std::move(query), std::move(promise));
  }
  void get_messages_fts(MessagesDbFtsQuery query, Promise<MessagesDbFtsResult> promise) override {
    send_closure_later(impl_, &Impl::get_messages_fts, std::move(query), std::move(promise));
  }
  void get_expiring_messages(
      int32 expires_from, int32 expires_till, int32 limit,
      Promise<std::pair<std::vector<std::pair<DialogId, BufferSlice>>, int32>> promise) override {
    send_closure_later(impl_, &Impl::get_expiring_messages, expires_from, expires_till, limit, std::move(promise));
  }

  void close(Promise<> promise) override {
    send_closure_later(impl_, &Impl::close, std::move(promise));
  }

  void force_flush() override {
    send_closure_later(impl_, &Impl::force_flush);
  }

 private:
  class Impl : public Actor {
   public:
    explicit Impl(std::shared_ptr<MessagesDbSyncSafeInterface> sync_db_safe) : sync_db_safe_(std::move(sync_db_safe)) {
    }
    void add_message(FullMessageId full_message_id, ServerMessageId unique_message_id, UserId sender_user_id,
                     int64 random_id, int32 ttl_expires_at, int32 index_mask, int64 search_id, string text,
                     NotificationId notification_id, BufferSlice data, Promise<> promise) {
      add_write_query([=, promise = std::move(promise), data = std::move(data), text = std::move(text)](Unit) mutable {
        promise.set_result(sync_db_->add_message(full_message_id, unique_message_id, sender_user_id, random_id,
                                                 ttl_expires_at, index_mask, search_id, std::move(text),
                                                 notification_id, std::move(data)));
      });
    }

    void delete_message(FullMessageId full_message_id, Promise<> promise) {
      add_write_query([=, promise = std::move(promise)](Unit) mutable {
        promise.set_result(sync_db_->delete_message(full_message_id));
      });
    }
    void delete_all_dialog_messages(DialogId dialog_id, MessageId from_message_id, Promise<> promise) {
      add_read_query();
      promise.set_result(sync_db_->delete_all_dialog_messages(dialog_id, from_message_id));
    }
    void delete_dialog_messages_from_user(DialogId dialog_id, UserId sender_user_id, Promise<> promise) {
      add_read_query();
      promise.set_result(sync_db_->delete_dialog_messages_from_user(dialog_id, sender_user_id));
    }

    void get_message(FullMessageId full_message_id, Promise<BufferSlice> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_message(full_message_id));
    }
    void get_message_by_unique_message_id(ServerMessageId unique_message_id,
                                          Promise<std::pair<DialogId, BufferSlice>> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_message_by_unique_message_id(unique_message_id));
    }
    void get_message_by_random_id(DialogId dialog_id, int64 random_id, Promise<BufferSlice> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_message_by_random_id(dialog_id, random_id));
    }
    void get_dialog_message_by_date(DialogId dialog_id, MessageId first_message_id, MessageId last_message_id,
                                    int32 date, Promise<BufferSlice> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_dialog_message_by_date(dialog_id, first_message_id, last_message_id, date));
    }

    void get_messages(MessagesDbMessagesQuery query, Promise<std::vector<BufferSlice>> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_messages(std::move(query)));
    }
    void get_messages_from_notification_id(DialogId dialog_id, NotificationId from_notification_id, int32 limit,
                                           Promise<vector<BufferSlice>> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_messages_from_notification_id(dialog_id, from_notification_id, limit));
    }
    void get_calls(MessagesDbCallsQuery query, Promise<MessagesDbCallsResult> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_calls(std::move(query)));
    }
    void get_messages_fts(MessagesDbFtsQuery query, Promise<MessagesDbFtsResult> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_messages_fts(std::move(query)));
    }
    void get_expiring_messages(int32 expires_from, int32 expires_till, int32 limit,
                               Promise<std::pair<std::vector<std::pair<DialogId, BufferSlice>>, int32>> promise) {
      add_read_query();
      promise.set_result(sync_db_->get_expiring_messages(expires_from, expires_till, limit));
    }

    void close(Promise<> promise) {
      do_flush();
      sync_db_safe_.reset();
      sync_db_ = nullptr;
      promise.set_value(Unit());
      stop();
    }

    void force_flush() {
      LOG(INFO) << "MessagesDb flushed";
      do_flush();
    }

   private:
    std::shared_ptr<MessagesDbSyncSafeInterface> sync_db_safe_;
    MessagesDbSyncInterface *sync_db_ = nullptr;

    static constexpr size_t MAX_PENDING_QUERIES_COUNT{50};
    static constexpr double MAX_PENDING_QUERIES_DELAY{0.01};
    std::vector<Promise<>> pending_writes_;
    double wakeup_at_ = 0;
    template <class F>
    void add_write_query(F &&f) {
      pending_writes_.push_back(PromiseCreator::lambda(std::forward<F>(f), PromiseCreator::Ignore()));
      if (pending_writes_.size() > MAX_PENDING_QUERIES_COUNT) {
        do_flush();
        wakeup_at_ = 0;
      } else if (wakeup_at_ == 0) {
        wakeup_at_ = Time::now_cached() + MAX_PENDING_QUERIES_DELAY;
      }
      if (wakeup_at_ != 0) {
        set_timeout_at(wakeup_at_);
      }
    }
    void add_read_query() {
      do_flush();
    }
    void do_flush() {
      if (pending_writes_.empty()) {
        return;
      }
      sync_db_->begin_transaction().ensure();
      for (auto &query : pending_writes_) {
        query.set_value(Unit());
      }
      sync_db_->commit_transaction().ensure();
      pending_writes_.clear();
      cancel_timeout();
    }
    void timeout_expired() override {
      do_flush();
    }

    void start_up() override {
      sync_db_ = &sync_db_safe_->get();
    }
  };
  ActorOwn<Impl> impl_;
};

std::shared_ptr<MessagesDbAsyncInterface> create_messages_db_async(std::shared_ptr<MessagesDbSyncSafeInterface> sync_db,
                                                                   int32 scheduler_id) {
  return std::make_shared<MessagesDbAsync>(std::move(sync_db), scheduler_id);
}

}  // namespace td