#include <stdio.h>
#include <stdlib.h>

#define BASIC_PAY_RATE_ONE    8.75
#define BASIC_PAY_RATE_TWO    9.33
#define BASIC_PAY_RATE_THREE 10.00
#define BASIC_PAY_RATE_FOUR  11.20

#define EXCESS   40.0
#define OVERTIME  1.5

#define FIRST_BORDER 300.00
#define NEXT_BORDER  150.00
#define SECOND_BORDER (FIRST_BORDER + NEXT_BORDER)

#define TAX_RATE_ONE   0.15
#define TAX_RATE_TWO   0.20
#define DIFFERENCE_BETWEEN_TAX_RATE_TWO_AND_TAX_RATE_ONE   (TAX_RATE_TWO - TAX_RATE_ONE)
#define TAX_RATE_THREE 0.25
#define DIFFERENCE_BETWEEN_TAX_RATE_THREE_AND_TAX_RATE_TWO (TAX_RATE_THREE - TAX_RATE_TWO)

int    get_num_decision(void);
double get_basic_pay_rate(int num_decision);
double get_additional_pay_rate(double basic_pay_rate);
double get_non_negative_not_too_big(void);
double gross_pay_calc(double hours, double basic_pay_rate, double additional_pay_rate);
double the_taxes_calc(double gross_pay);
void   response_output(double gross_pay, double the_taxes);

int main(void) {
    int num_decision = 0;
    double basic_pay_rate = 0, additional_pay_rate = 0;
    double hours = 0, gross_pay = 0, the_taxes = 0;
    while ((num_decision    = get_num_decision()) != 5) {
        basic_pay_rate      = get_basic_pay_rate(num_decision);
        additional_pay_rate = get_additional_pay_rate(basic_pay_rate);
        hours     = get_non_negative_not_too_big();
        gross_pay = gross_pay_calc(hours, basic_pay_rate, additional_pay_rate);
        the_taxes = the_taxes_calc(gross_pay);
        response_output(gross_pay, the_taxes);
    }
    return 0;
}

int get_num_decision(void) {
    printf("Enter the number corresponding to the desired pay rate or action:\n");
    printf("1) $%.2f/hr\n", BASIC_PAY_RATE_ONE);
    printf("2) $%.2f/hr\n", BASIC_PAY_RATE_TWO);
    printf("3) $%.2f/hr\n", BASIC_PAY_RATE_THREE);
    printf("4) $%.2f/hr\n", BASIC_PAY_RATE_FOUR);
    printf("5) quit\n\n");
    int num = 0;
    int num_decision = 0;
    while (((num = scanf("%d", &num_decision)) != 1) || (num_decision > 5) || (num_decision < 1)) {
        if ((num == EOF) || (num == 0))
            exit(EXIT_SUCCESS);
        printf("You were mistaken\n"
               "Enter the value greater than or equal to 1\n"
               "And less than or equal to 5: ");
    }
    while((num = getchar()) != '\n')
            if (num == EOF)
                exit(EXIT_SUCCESS);
    return num_decision;
}

double get_basic_pay_rate(int num_decision) {
        switch (num_decision) {
            case 1  : return BASIC_PAY_RATE_ONE;
            case 2  : return BASIC_PAY_RATE_TWO;
            case 3  : return BASIC_PAY_RATE_THREE;
            case 4  : return BASIC_PAY_RATE_FOUR;
            default : exit(EXIT_SUCCESS);
    }
}

double get_additional_pay_rate(double basic_pay_rate) {
    return  basic_pay_rate * OVERTIME - basic_pay_rate;
}

double get_non_negative_not_too_big(void) {
    int num = 0;
    double hours = 0;
    printf("\nEnter the hours worked in a week: ");
    while (((num = scanf("%lf", &hours)) != 1) || (hours < 0) || (hours > 168)) {
        if ((num == EOF) || (num == 0))
            exit(EXIT_SUCCESS);
        printf("You were mistaken\n"
               "Enter the value greater than or equal to 0\n"
               "And less than or equal to 168: ");
    }
    while ((num = getchar()) != '\n')
        if (num == EOF)
            exit(EXIT_SUCCESS);
    return hours;
}

double gross_pay_calc(double hours, double basic_pay_rate, double additional_pay_rate) {
    double gross_pay = hours * basic_pay_rate;
    if (hours > EXCESS)
        gross_pay += (hours - EXCESS) * additional_pay_rate;
    return gross_pay;
}

double the_taxes_calc(double gross_pay) {
    double the_taxes = gross_pay * TAX_RATE_ONE;
    if (gross_pay > FIRST_BORDER)
        the_taxes += (gross_pay -  FIRST_BORDER) * DIFFERENCE_BETWEEN_TAX_RATE_TWO_AND_TAX_RATE_ONE;
    if (gross_pay > SECOND_BORDER)
        the_taxes += (gross_pay - SECOND_BORDER) * DIFFERENCE_BETWEEN_TAX_RATE_THREE_AND_TAX_RATE_TWO;
    return the_taxes;
}

void response_output(double gross_pay, double the_taxes) {
    printf("\nGross pay: %.2f\n", gross_pay);
    printf("The taxes: %.2f\n", the_taxes);
    printf("Net   pay: %.2f\n\n", gross_pay - the_taxes);
}