// monthviewgen.cpp - Xestia Calendar month view generation functions.
//
// (c) 2016-2017 Xestia Software Development.
//
// This file is part of Xestia Calendar.
//
// Xestia Calendar is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by the
// Free Software Foundation, version 3 of the license.
//
// Xestia Calendar is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with Xestia Calendar. If not, see <http://www.gnu.org/licenses/>

#include "monthviewgen.h"

using namespace std;

int PreviousMonthNumberofDays(int month, int year){
	
	// Work out what the previous month is.
	
	// Return 31 if month matches.
	
	if (month == 1 || month == 2 || month == 4 || 
		month == 6 || month == 8 || month == 9 || month == 11){
	
		return 31;
			
	}
	
	// Return 30 if month matches.
	
	if (month == 5 || month == 7 || month == 10 || month == 12){
		
		return 30;
		
	}
	
	// Work out if year is a leap year and return 28 or 29
	// for february.
	
	if (year % 4 == 0){
		
		if (year % 100 == 0){
			
			if (year % 400 == 0){
			
				return 29;
				
			} else {
				
				return 28;
				
			}
			
		}
		
		return 29;
		
	} else {
		
		return 28;
		
	}
	
}

XCCalendarMonthViewGrid GenerateMonthGrid(int month, int year){
	
	XCCalendarMonthViewGrid monthViewOutput;
	
	// Work out which day of the week the first day of 
	// the month is.
		
	time_t emptyTime;
	struct tm * firstDay;
	int previousMonthNumDays = PreviousMonthNumberofDays(month, year);
	int previousMonthDays = 0;
	int previousMonth = 0;
	int previousYear = year;
	int dayWeekCount = 0;
	bool processGrid = true;
	bool firstWeekProcessing = true;
	
	time(&emptyTime);
	
	firstDay = localtime(&emptyTime);
	firstDay->tm_year = year - 1900;
	firstDay->tm_mon = month - 1;
	firstDay->tm_mday = 1;
	
	mktime(firstDay);
	
	if (firstDay->tm_wday == 0){
		previousMonthDays = 6;
	} else {
		previousMonthDays = firstDay->tm_wday - 1;
	}
	
	if (month == 1){
		
		previousMonth = 12;
		previousYear--;
		
	} else {

		previousMonth = month - 1;
		
	}
	
	// Workout the days of the previous month for the
	// first week to be displayed.
	
	XCCalendarMonthViewGridDayWeek firstWeek;
	
	for (int previousMonthDaysProcessing = 0; 
		previousMonthDaysProcessing < previousMonthDays; 
		previousMonthDaysProcessing++){
		
		XCCalendarMonthViewGridDayData dayItem;
			
		dayItem.day = previousMonthNumDays - previousMonthDaysProcessing;
		dayItem.month = previousMonth;
		dayItem.year = previousYear;
		dayItem.isInMonth = false;
			
		firstWeek.dayList.insert(firstWeek.dayList.begin(), dayItem);
			
		dayWeekCount++;
			
	}
	
	// Process the actual days of the month.

	XCCalendarMonthViewGridDayWeek monthWeek;
	int processDay = 1;
	
	while (processGrid == true){
		
		if (dayWeekCount == 7){
			
			// Add to the month view grid.
			
			if (firstWeekProcessing == true){
				
				firstWeekProcessing = false;
				monthViewOutput.weekList.push_back(firstWeek);
				
			} else {
			
				monthViewOutput.weekList.push_back(monthWeek);
				monthWeek.dayList.clear();
				
			}
			
			dayWeekCount = 0;
			continue;
			
		}

		XCCalendarMonthViewGridDayData dayItem;
		
		dayItem.day = processDay;
		dayItem.month = month;
		dayItem.year = year;
		dayItem.isInMonth = true;
		
		if (firstWeekProcessing == true){
			
			firstWeek.dayList.push_back(dayItem);
			
		} else {
			
			monthWeek.dayList.push_back(dayItem);
			
		}

		dayWeekCount++;
		
		if ((month == 1 || month == 3 || month == 5 || 
			month == 7 || month == 8 || month == 10 || month == 12) && 
			processDay == 31){
	
			break;
			
		}
	
		if ((month == 4 || month == 6 || month == 9 || month == 11) &&
			processDay == 30){
		
			break;
		
		}
		
		if (year % 4 == 0){
		
			if (year % 100 == 0){
			
				if (year % 400 == 0){
			
					if (month == 2 && processDay == 29){
					
						break;
						
					}
				
				} else {
				
					if (month == 2 && processDay == 28){
						
						break;
						
					}
				
				}
			
			}
		
			if (month == 2 && processDay == 29){

				break;
				
			}
		
		} else if ((month == 2 && processDay == 28) && year % 4 != 0){
		
			break;
		
		}
		
		processDay++;
		
		
	}
	
	// At the end of the month add any remaining days
	// (if required).
	
	int nextMonthYear = year;
	int nextMonth = 0;
	int nextMonthDay = 1;
	
	if (month == 12){
		
		nextMonth = 1;
		nextMonthYear++;
		
	} else {
		
		nextMonth = month + 1;
		
	}
	
	for (; dayWeekCount < 7; dayWeekCount++){
	
		XCCalendarMonthViewGridDayData dayItem;
		
		dayItem.day = nextMonthDay;
		dayItem.month = nextMonth;
		dayItem.year = nextMonthYear;
		dayItem.isInMonth = false;

		monthWeek.dayList.push_back(dayItem);
		nextMonthDay++;
		
	}
	
	if (dayWeekCount == 7){

		monthViewOutput.weekList.push_back(monthWeek);
		
	}
	
	return monthViewOutput;
	
}