//ProjectEulerTS/Problems/Problem18.ts
//Matthew Ellison
// Created: 04-06-21
//Modified: 07-14-21
//How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
/*
You are given the following information, but you may prefer to do some research for yourself.
1 Jan 1900 was a Monday.
Thirty days has September,
April, June and November.
All the rest have thirty-one,
Saving February alone,
Which has twenty-eight, rain or shine.
And on leap years, twenty-nine.
A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.
*/
//Unless otherwise listed all non-standard includes are my own creation and available from https://bibucket.org/Mattrixwv/typescriptClasses
/*
	Copyright (C) 2021  Matthew Ellison

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program 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 Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/


import { Problem } from "./Problem";


//An easier way to signal day of the week
enum DAYS {SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FIRDAY, SATURDAY, NUMBER_OF_DAYS, ERROR};


export class Problem19 extends Problem{
	//Variables
	//Static variables
	private static START_YEAR: number = 1901;	//The first year we are going to test
	private static END_YEAR: number = 2000;		//The last year we are going to test
	//Instance variables
	private totalSundays: number;	//Keep track of the number of sundays

	//Functions
	//Constructor
	public constructor(){
		super(`How many Sundays fell on the first of the month during the twentieth century (1 Jan ${Problem19.START_YEAR} to 31 Dec ${Problem19.END_YEAR})?`);
		this.totalSundays = 0;
	}
	//Operational functions
	//Solve the problem
	public solve(): void{
		//If the problem has already been solved do nothing and end the function
		if(this.solved){
			return;
		}

		//Start the timer
		this.timer.start();


		//Run for all years 1901-2000
		for(let year = Problem19.START_YEAR;year <= Problem19.END_YEAR;++year){
			//Run for all months in the year
			for(let month = 1;month <= 12;++month){
				let day: DAYS = this.getDay(month, 1, year);
				if(day == DAYS.ERROR){
					console.log("There was an error with the day");
				}
				else if(day == DAYS.SUNDAY){
					++this.totalSundays;
				}
			}
		}


		//Stop the timer
		this.timer.stop();

		//Throw a flag to show the problem is solved
		this.solved = true;
	}
	//Return the day of the week that the data you pass into it is on
	private getDay(month: number, day: number, year: number): DAYS{
		//Make sure the numbers are within propper bounds
		if((month < 1) || (month > 12) || (day < 1) || (day > 31) || (year < 1)){
			return DAYS.ERROR;
		}
		let numDays: number = 0;
		let currentYear: number = 1;
		let currentMonth: number = 1;
		let currentDay: number = DAYS.SATURDAY;
		--day;

		//Add the correct number of days for every year
		while(currentYear < year){
			if(this.isLeapYear(currentYear)){
				numDays += 366;
			}
			else{
				numDays += 365;
			}
			++currentYear;
		}
		//Add the correct number of days for every month
		while(currentMonth < month){
			switch(currentMonth){
				case  1:
				case  3:
				case  5:
				case  7:
				case  8:
				case 10:
				case 12: numDays += 31; break;
				case  4:
				case  6:
				case  9:
				case 11: numDays += 30; break;
				case  2:
					if(this.isLeapYear(currentYear)){
						numDays += 29;
					}
					else{
						numDays += 28;
					}
					break;
			}
			++currentMonth;
		}
		//Account for the weird year of 1752
		if(year > 1752){
			numDays -= 11;
		}
		else if(year == 1752){
			if(month > 9){
				numDays -= 11;
			}
			else if(month == 9){
				if(day >= 14){
					numDays -= 11;
				}
				else if((day > 2) && (day < 14)){
					console.log("Hit 1752 error");
					return DAYS.ERROR;
				}
			}
		}
		//Add the correct number of days for every day
		numDays += day;

		currentDay += numDays;
		currentDay = currentDay % DAYS.NUMBER_OF_DAYS;
		switch(currentDay){
			case DAYS.SUNDAY: return DAYS.SUNDAY;
			case DAYS.MONDAY: return DAYS.MONDAY;
			case DAYS.TUESDAY: return DAYS.TUESDAY;
			case DAYS.WEDNESDAY: return DAYS.WEDNESDAY;
			case DAYS.THURSDAY: return DAYS.THURSDAY;
			case DAYS.FIRDAY: return DAYS.FIRDAY;
			case DAYS.SATURDAY: return DAYS.SATURDAY;
			default:	console.log("Hit default error"); return DAYS.ERROR;
		}
	}
	//Returns true if the year passed to it is a leap year
	private isLeapYear(year: number): boolean{
		if(year < 1){
			return false;
		}
		else if((year % 100) == 0){
			//This rule only applies at and after 1800
			if(year <= 1700){
				return true;
			}
			else if((year % 400) == 0){
				return true;
			}
		}
		else if((year % 4) == 0){
			return true;
		}
		return false;
	}
	//Reset the problem so it can be run again
	public reset(): void{
		super.reset();
		this.totalSundays = 0;
	}
	//Gets
	//Returns the result of solving the problem
	public getResult(): string{
		this.solvedCheck("result");
		return `There are ${this.totalSundays} Sundays that landed on the first of the months from ${Problem19.START_YEAR} to ${Problem19.END_YEAR}`;
	}
	//Returns the total sundays that were asked for
	public getTotalSundays(): number{
		this.solvedCheck("total number of sundays");
		return this.totalSundays;
	}
}


/* Results:
There are 171 Sundays that landed on the first of the months from 1901 to 2000
It took an average of 4.314 milliseconds to run this problem through 100 iterations
*/