#pragma once
#include <string>
#include <unordered_map>
class DataBase
{
public:
 ~DataBase() = default;
 static DataBase &GetInstance()
 {
 static DataBase db;
 return db;
 }
 std::string getNameByEmail(const std::string &email) const
 {
 auto it = m_map.find(email);
 if (it != m_map.end())
 {
 return it->second;
 }
 else
 {
 return {};
 }
 }

protected:
 DataBase(const DataBase &) = delete;
 DataBase(DataBase &&) = delete;
 DataBase &operator=(const DataBase &) = delete;
 DataBase &operator=(DataBase &&) = delete;

private:
 DataBase() {}

private:
 std::unordered_map<std::string, std::string> m_map{ { "zhangsan@zhangsan.com", "zhangsan" },
 { "lisi@lisi.com", "lisi" },
 { "wangwu@wangwu.com", "wangwu" } };
};