#include <stdio.h>
#include <stdbool.h>
#include <process.h>

int yearstartday(int Year);
bool isLeapYear(int Year);
int monthDays(int Year, int Month);
int getWeekDay(int Year, int Month, int Day);
void outMonthDays(int Year, int Month);
void outMonthDays1582(int Year, int Month);
void menu();
void MenuChoice(int Choice);
void printYearCalendar(int Year);

const char* weekDays[] = {"日", "一", "二", "三", "四", "五", "六"};

int main() {
	menu();
	return 0;
}

int yearstartday(int Year) {
	int detayear, corday, weekstartday, detaday;
	detayear = Year - 2000;
	if (detayear > 0) {
		corday = 2;
		detayear -= 1;
	} else {
		corday = 0;
		if (detayear <= -418) {
			corday = -3;
			if (detayear <= -2000) {
				corday = -1;
			}
		}
	}
	detaday = (detayear / 400) * 2 - detayear / 100 + detayear / 4 + detayear + corday;
	weekstartday = (6 + detaday % 7) % 7;
	return weekstartday;
}

bool isLeapYear(int Year) {
	return (Year % 4 == 0 && Year % 100 != 0) || (Year % 400 == 0);
}

int monthDays(int Year, int Month) {
	if (Month == 1 || Month == 3 || Month == 5 || Month == 7 || Month == 8 || Month == 10 || Month == 12) {
		return 31;
	} else if (Month == 4 || Month == 6 || Month == 9 || Month == 11) {
		return 30;
	} else {
		return isLeapYear(Year) ? 29 : 28;
	}
}

int getWeekDay(int Year, int Month, int Day) {
	int i, temp, weekday, Days = 0;
	for (i = 1; i <= Month - 1; i++) {
		Days += monthDays(Year, i);
	}
	Days = Days + Day - 1;
	temp = yearstartday(Year) + Days;
	weekday = temp % 7;
	if (Year == 1582 && Month > 10) {
		weekday -= 3;
	}
	return weekday;
}

void outMonthDays(int Year, int Month) {
	int i, j, weekday;
	printf("           %d月日历\n", Month);
	printf("  日  一   二   三   四   五  六\n");
	weekday = getWeekDay(Year, Month, 1);
	for (i = 0; i < weekday; i++) {
		printf("    ");
	}
	for (j = 1; j <= monthDays(Year, Month); j++) {
		printf("%4d", j);
		if ((j + weekday) % 7 == 0) {
			printf("\n");
		}
	}
	printf("\n");
	printf("-------------------------------------\n");
}

void outMonthDays1582(int Year, int Month) {
	int i, j, weekday;
	printf("           %d月日历\n", Month);
	printf("  日  一  二  三  四  五  六\n");
	weekday = getWeekDay(Year, Month, 1);
	for (i = 0; i < weekday; i++) {
		printf("    ");
	}
	for (j = 1; j <= monthDays(Year, Month); j++) {
		if (Month == 10) {
			if (j > 4 && j < 15) {
			} else {
				printf("%4d", j);
				if (j == 16 || j == 23 || j == 30) {
					printf("\n");
				}
			}
		} else {
			printf("%4d", j);
			if ((j + weekday) % 7 == 0) {
				printf("\n");
			}
		}
	}
	printf("\n");
	printf("-------------------------------------\n");
}

void printYearCalendar(int Year) {
	printf("Calendar for %d\n\n", Year);
	for (int month = 1; month <= 12; month += 2) {
		outMonthDays(Year, month);
		printf("\n");
		if (month + 1 <= 12) {
			outMonthDays(Year, month + 1);
			printf("\n");
		}
	}
}

void menu() {
	int choice;
	while (1) {
		printf("万年历\n1. 输入年月日输出星期几\n");
		printf("2. 判断闰平年\n");
		printf("3. 单列输出某年日历\n");
		printf("4. 双列输出某年日历\n");
		printf("5. 退出\n");
		printf("请输入选择：");
		scanf("%d", &choice);
		MenuChoice(choice);
	}
}

void MenuChoice(int Choice) {
	int Year, Month, Day;
	switch (Choice) {
		case 1:
			printf("请输入年 月 日：");
			scanf("%d %d %d", &Year, &Month, &Day);
			if (Year == 1582 && Month == 10 && Day > 4 && Day < 15) {
				printf("1582年10月5日至10月14日不存在\n");
			} else {
				int weekday = getWeekDay(Year, Month, Day);
				printf("%d年%d月%d日是星期%s\n", Year, Month, Day, weekDays[weekday]);
			}
			break;
		case 2:
			printf("请输入年份：");
			scanf("%d", &Year);
			if (isLeapYear(Year)) {
				printf("%d年是闰年\n", Year);
			} else {
				printf("%d年是平年\n", Year);
			}
			break;
		case 3:
			printf("请输入年份：");
			scanf("%d", &Year);
			if (Year == 0) {
				printf("输入错误，没有公元零年\n");
			} else {
				if (Year > 0) {
					printf("       公元%d年日历为:\n", Year);
				} else {
					printf("      公元前%d年日历为:\n", -Year);
				}
				printf("=====================================\n");
				if (Year != 1582) {
					for (Month = 1; Month <= 12; Month++) {
						outMonthDays(Year, Month);
					}
				} else {
					for (Month = 1; Month <= 12; Month++) {
						outMonthDays1582(Year, Month);
					}
				}
			}
			break;
		case 4:
			printf("请输入年份：");
			scanf("%d", &Year);
			if (Year == 0) {
				printf("输入错误，没有公元零年\n");
			} else {
				printYearCalendar(Year);
			}
			break;
		case 5:
			printf("退出程序\n");
			exit(0);
		default:
			printf("无效的选择\n");
	}
}