// .. in the pch.h
#include <boost/date_time/gregorian/gregorian.hpp> //include all types plus i/o
namespace bgdt= boost::gregorian;

// .   ......................................................
//The HEDate.hpp
#pragma once

class HEDate
{
    bgdt::date date;
    bool bValid;

public:
    HEDate( ):bValid(false){ }
    HEDate( const bgdt::date& in )//assumes a valid date.
        :date( in )
        ,bValid(true)
    { }
    HEDate( const COleDateTime& dtIn )
        :bValid( false )
    {
        try{
            if( dtIn.m_status != COleDateTime::valid )
                return;

            bgdt::date inDate( dtIn.GetYear( ), dtIn.GetMonth( ), dtIn.GetDay( ) );
            //didn't throw
            date= inDate;
            bValid= true;
        }
        catch( std::exception& e )  {e; }
    }
    void operator = (const COleDateTime& dtIn) {
        bValid = false;
        try {
            if (dtIn.m_status != COleDateTime::valid)
                return;

            bgdt::date inDate(dtIn.GetYear(), dtIn.GetMonth(), dtIn.GetDay());
            //didn't throw
            date = inDate;
            bValid = true;
        }
        catch (std::exception & e){e;}
    }
    //CString Format( ) const, depreciated, not using CString anymore.............
    void AddYear(size_t dur = 1)
    {
        ASSERT(bValid);
        try {
            bgdt::date::ymd_type ymd = date.year_month_day();
            ymd.year = ymd.year + (unsigned short)dur;
            date = bgdt::date(ymd);
        }
        catch (std::exception & e)  {
            bValid = false;
            e;
            //e; //no what, just throws
        }
    }
    void AddDay(size_t dur = 1)
    {
        ASSERT(bValid);
        try {
            date += bgdt::date_duration(dur);
        }
        catch (std::exception & e) {
            bValid = false;
            e;
        }
    }
    bgdt::date GetDate( ) const { return date; }
    bool IsValid( ) const { return bValid; }
    operator COleDateTime ( ) const { //check if valid....
        return COleDateTime( date.year( ), date.month( ), date.day( ), 0, 0, 0 );
    }
    operator const bgdt::date& ( ) const { return date; }
    friend bool operator < (const HEDate in1, const HEDate in2) { return in1.date < in2.date; }

    std::string format(const char* psFmt = "%D") const;
    std::wstring formatW(const char* psFmt = "%D") const { return to_wide(format(psFmt).c_str()); }
    int years_span(const HEDate& from) { if (!from.IsValid() || !IsValid()) return 0; return date.year() - ((bgdt::date)from).year(); }
    long get_year()const { return date.year(); }
    long get_month()const { return date.month(); }
protected:
    //return false if lookup fails ?
    //update this and return a composed std::wstring, then depreciate
    void FormatSub(std::string_view::iterator f, std::stringstream& val ) const;
};

inline std::ostream& operator << ( std::ostream& os, HEDate& date ){
    os << date.format("%N");
    return os;
}

//.   .................................................................
//the HEDate.cpp

//official flags:
//https://www.boost.org/doc/libs/1_35_0/doc/html/date_time/date_time_io.html#date_time.format_flags

namespace {
    using iterator = std::string_view::const_iterator;
}

void HEDate::FormatSub(iterator f, std::stringstream& hold) const
{
    switch (*f)
    {
    case 'B'://December
        hold << en_long_month_names[date.month() - 1];
        break;

    case 'd'://31
        hold << date.day();
        break;

    case 'm'://12
        hold << date.month().as_number();
        break;

    case 'Y'://2020
        hold << date.year();
        break;

    case 'y'://20
    {
        auto dt = date.year() - (date.year() / 100) * 100;
        hold << (dt < 10 ? "0" : "") << date.year() - (date.year() / 100) * 100;
        break;
    }
    case 'D'://2020/12/31
        hold << date.year() << "/" << date.month().as_number() << "/" << date.day();
        break;

    case 'N'://1/31/2020
        hold << date.month().as_number() << "/" << date.day() << "/" << date.year();
        break;

    default://??
        hold << "??";
        break;

    }//switch
}

std::string HEDate::format( const char* psFmt ) const
{
    if( ! bValid )
        return "Invalid Date";//or we can crash/exception below

    std::string_view s( psFmt );
    std::stringstream hold;
    std::vector< std::pair< iterator, iterator> > tokens;
    boost::split( tokens, s, boost::is_any_of("%") );

    for( auto it= tokens.begin( ); it != tokens.end( ); ++it)
    {
        //no leading char
        if (it->first == it->second)
            continue;

        //a leading char set.
        if (it == tokens.begin()) {
            hold << std::string(it->first, it->second);
            continue;
        }
        FormatSub(it->first++, hold);
        if(it->first != it->second)//more printables
            hold << std::string(it->first, it->second);
    }
    return hold.str( );
}