database.h

#pragma once
#include "date.h"
#include <map>
#include <set>
#include <vector>
#include <memory>
#include <algorithm>

using namespace std;

class Database
{
public:
    void Add(const Date& _Date, const string& _Event);

    void Print(ostream& os) const;

    string Last(const Date& _Date) const;

    template <typename FuncName>
    int RemoveIf(const FuncName& _Func);

    template <typename FuncName>
    vector <pair <Date, string>> FindIf(const FuncName& _Func);

private:
    map <Date, pair <set <string>, vector <set <string>::iterator>>> Records;
};


template <typename FuncName>
int Database::RemoveIf(const FuncName& _Func)
{
    int counter = 0;

    for (auto& [key, value] : Records)
    {
        auto it = stable_partition(value.second.begin(), value.second.end(), [&_Func, &key, &value, &counter](const auto& _Event) -> bool
        {
            if (_Func(key, *_Event))
            {
                ++counter;
                value.first.erase(*_Event);
                return false;
            }
            return true;
        });
        value.second.erase(it, value.second.end());
    }

    for (auto eraseIt = Records.cbegin(), nextIt = eraseIt; eraseIt != Records.end(); eraseIt = nextIt)
    {
        ++nextIt;
        if (eraseIt->second.first.empty())
        {
            Records.erase(eraseIt);
        }

    }

    return counter;
}

template <typename FuncName>
vector <pair <Date, string>> Database::FindIf(const FuncName& _Func)
{
    vector <pair <Date, string>> ans;

    for (const auto& [_Key, _Value] : Records)
    {
        auto it = find_if(_Value.second.begin(), _Value.second.end(), [&_Key, &ans, &_Func](const auto& _Event)
            {
                if (_Func(_Key, *_Event))
                {
                    ans.push_back({ _Key, *_Event });
                }
                return false;
            });
    }

    return ans;
}