/* ----------------------------------------------------------------------------
 * --  _____       ______  _____                                              -
 * -- |_   _|     |  ____|/ ____|                                             -
 * --   | |  _ __ | |__  | (___    Institute of Embedded Systems              -
 * --   | | | '_ \|  __|  \___ \   Zuercher Hochschule Winterthur             -
 * --  _| |_| | | | |____ ____) |  (University of Applied Sciences)           -
 * -- |_____|_| |_|______|_____/   8401 Winterthur, Switzerland               -
 * ----------------------------------------------------------------------------
 */
/**
 * @file
 * @brief Lab P02 weekday
 */
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>


// *** TASK1: typedef enum types for month_t (Jan=1,...Dec} ***
// BEGIN-STUDENTS-TO-ADD-CODE
typedef enum {Jan=1, Feb, Mar, Apr, May, June, July, Aug, Sept, Oct, Nov, Dec} month_t;

// END-STUDENTS-TO-ADD-CODE



// *** TASK1: typedef struct for date_t ***
// BEGIN-STUDENTS-TO-ADD-CODE
typedef struct {int year, month, day;} date_t;

// END-STUDENTS-TO-ADD-CODE



// *** TASK2: typedef enum weekday_t (Sun=0, Mon, ...Sat) ***
// BEGIN-STUDENTS-TO-ADD-CODE
typedef enum {Sun=0, Mon, Tue, Wed, Thu, Fri, Sat} weekday_t;

// END-STUDENTS-TO-ADD-CODE

/**
 * @brief   TASK1: Checks if the given date is a leap year.
 * @returns 0 = is not leap year, 1 = is leap year
 */
// BEGIN-STUDENTS-TO-ADD-CODE
int is_leap_year(date_t date){
    int ergebnis;
    if(date.year % 400 == 0){
        ergebnis = 1;
    }
    else if (date.year % 100 == 0){
        ergebnis = 0;
    }
    else if(date.year % 4 == 0){
        ergebnis = 1;
    }
    else {
        ergebnis = 0;
    }
    return ergebnis;
}

// END-STUDENTS-TO-ADD-CODE


/**
 * @brief   TASK1: Calculates the length of the month given by the data parameter
 * @returns 28, 29, 30, 31 if a valid month, else 0
 */
// BEGIN-STUDENTS-TO-ADD-CODE
int get_month_length(date_t date){
    int ergebnis = 0;
    switch (date.month) {
        case Jan:
            ergebnis = 31;
            break;
        case Feb:
            if(is_leap_year(date)){
                ergebnis = 29;
            }
            else {
                ergebnis = 28;
            }
            break;
        case Mar:
            ergebnis = 31;
            break;
        case Apr:
            ergebnis = 30;
            break;
        case May:
            ergebnis = 31;
            break;
        case June:
            ergebnis = 30;
            break;
        case July:
            ergebnis = 31;
            break;
        case Aug:
            ergebnis = 31;
            break;
        case Sept:
            ergebnis = 30;
            break;
        case Oct:
            ergebnis = 31;
            break;
        case Nov:
            ergebnis = 30;
            break;
        case Dec:
            ergebnis = 31;
            break;
    }
    return ergebnis;
}

// END-STUDENTS-TO-ADD-CODE

/**
 * @brief   TASK1: Checks if the given date is in the gregorian date range
 * @returns 0 = no, 1 = yes
 */
// BEGIN-STUDENTS-TO-ADD-CODE
int is_gregorian_date(date_t date) {
    int ergebnis = 1;
    if((date.year == 1582 && date.month <= Oct && date.day < 15) || date.year < 1582 || (date.year > 9999)){
        return 0;
    }
    else {
        return 1;
    }

}

// END-STUDENTS-TO-ADD-CODE


/**
 * @brief   TASK1: Checks if the given date is a valid date.
 * @returns 0 = is not valid date, 1 = is valid date
 */
// BEGIN-STUDENTS-TO-ADD-CODE
int is_valid_date(date_t date) {
    int ergebnis = 1;
    int ml = get_month_length(date);


    if((int)ml < (int)date.day ){//|| date.month < 1 || date.month > 12 || is_gregorian_date == 0){

        return 0;
    }
    else {
        printf("Länge Monat: %d\n", get_month_length(date));
         printf("Länge Monat: %d\n", ml);
    printf("Tag: %d\n", date.day);
    printf("Monat: %d\n", date.month);
    printf("Jahr: %d\n", date.year);
        return 1;

    }

}


// END-STUDENTS-TO-ADD-CODE


/**
 * @brief   TASK2: calculated from a valid date the weekday
 * @returns returns a weekday in the range Sun...Sat
 */
// BEGIN-STUDENTS-TO-ADD-CODE
weekday_t calculate_weekday(date_t date) {
    int m = 1 + (date.month + 9) % 12;
    int a;
    if(date.month < Mar){
        a = date.year - 1;
    }
    else {
        a = date.year;
    }
    int y = a % 100;
    int c = a / 100;
    weekday_t weekday = ((date.day + (13 * m - 1) / 5 + y + y / 4 + c / 4 - 2 * c) % 7 + 7) % 7;
    return weekday;
}

// END-STUDENTS-TO-ADD-CODE



/**
 * @brief   TASK2: print weekday as 3-letter abreviated English day name
 */
// BEGIN-STUDENTS-TO-ADD-CODE
void print_weekday(weekday_t day) {
    int ergebnis = 0;
    switch (day) {
        case Sun:
            printf("Sun");
            break;
        case Mon:
            printf("Mon");
            break;
        case Tue:
            printf("Tue");
            break;
        case Wed:
            printf("Wed");
            break;
        case Thu:
            printf("Thu");
            break;
        case Fri:
            printf("Fri");
            break;
        case Sat:
            printf("Sat");
            break;
        default:
            assert(!"day is out-of-range");
            break;
            }

}

// END-STUDENTS-TO-ADD-CODE

/**
 * @brief   main function
 * @param   argc [in] number of entries in argv
 * @param   argv [in] program name plus command line arguments
 * @returns returns success if valid date is given, failure otherwise
 */
int main(int argc, const char *argv[])
{
    // TASK1: parse the mandatory argument into a date_t variable and check if the date is valid
    // BEGIN-STUDENTS-TO-ADD-CODE
    date_t date;
    int res = sscanf(argv[1]
                , "%d-%d-%d"
                , &date.year, &date.month, &date.day
                );
    if (res != 3 || is_valid_date(date) == 0) {
        printf("Fehler\n");
        return EXIT_FAILURE;
    }

    // END-STUDENTS-TO-ADD-CODE


    // TASK2: calculate the weekday and print it in this format: "%04d-%02d-%02d is a %s\n"
    // BEGIN-STUDENTS-TO-ADD-CODE
    printf("%04d-%02d-%02d is a ", date.year, date.month, date.day);
    print_weekday(calculate_weekday(date));
    printf("\n");

    // END-STUDENTS-TO-ADD-CODE

    return EXIT_SUCCESS;
}