//********************************************************
//
// Assignment 9 - Linked Lists
//
// Name: Baba Alhassan
//
// Class: C Programming, Summer 2026
//
// Date: July 22, 2026
//
// Description: Program which determines overtime and 
// gross pay for a set of employees with outputs sent 
// to standard output (the screen).
//
// This assignment also adds the employee name, their tax state,
// and calculates the state tax, federal tax, and net pay.   It
// also calculates totals, averages, minimum, and maximum values.
//
// Array and Structure references have all been replaced with
// pointer references to speed up the processing of this code.
// A linked list has been created and deployed to dynamically
// allocate and process employees as needed.
//
// Call by Reference design (using pointers)
//
//********************************************************

// necessary header files
#include <stdio.h>
#include <string.h>
#include <ctype.h>   // for char functions
#include <stdlib.h>  // for malloc

// define constants
#define STD_HOURS 40.0
#define OT_RATE 1.5
#define MA_TAX_RATE 0.05
#define NH_TAX_RATE 0.0
#define VT_TAX_RATE 0.06
#define CA_TAX_RATE 0.07
#define DEFAULT_TAX_RATE 0.08
#define NAME_SIZE 20
#define TAX_STATE_SIZE 3
#define FED_TAX_RATE 0.25
#define FIRST_NAME_SIZE 10
#define LAST_NAME_SIZE 10

// Define a global structure type to store an employee name
struct name
{
    char firstName[FIRST_NAME_SIZE];
    char lastName [LAST_NAME_SIZE];
};

// Define a global structure type to pass employee data between functions
struct employee
{
    struct name empName;
    char taxState [TAX_STATE_SIZE];
    long int clockNumber;
    float wageRate;
    float hours;
    float overtimeHrs;
    float grossPay;
    float stateTax;
    float fedTax;
    float netPay;
    struct employee * next;
};

// this structure type defines the totals of all floating point items
struct totals
{
    float total_wageRate;
    float total_hours;
    float total_overtimeHrs;
    float total_grossPay;
    float total_stateTax;
    float total_fedTax;
    float total_netPay;
};

// this structure type defines the min and max values of all floating point items
struct min_max
{
    float min_wageRate;
    float min_hours;
    float min_overtimeHrs;
    float min_grossPay;
    float min_stateTax;
    float min_fedTax;
    float min_netPay;
    float max_wageRate;
    float max_hours;
    float max_overtimeHrs;
    float max_grossPay;
    float max_stateTax;
    float max_fedTax;
    float max_netPay;
};

// define prototypes here for each function except main
struct employee * getEmpData (void);
int isEmployeeSize (struct employee * head_ptr);
void calcOvertimeHrs (struct employee * head_ptr);
void calcGrossPay (struct employee * head_ptr);
void printHeader (void);
void printEmp (struct employee * head_ptr);
void calcStateTax (struct employee * head_ptr);
void calcFedTax (struct employee * head_ptr);
void calcNetPay (struct employee * head_ptr);
void calcEmployeeTotals (struct employee * head_ptr,
                         struct totals * emp_totals_ptr);
                                 
void calcEmployeeMinMax (struct employee * head_ptr,
                         struct min_max * emp_minMax_ptr);
                                  
void printEmpStatistics (struct totals * emp_totals_ptr, 
                         struct min_max * emp_minMax_ptr,
                         int theSize);

int main ()
{
    struct employee * head_ptr; // always points to first linked list node
    int theSize; // number of employees processed
    
    struct totals employeeTotals  = {0,0,0,0,0,0,0};
    struct totals * emp_totals_ptr = &employeeTotals;
    
    struct min_max employeeMinMax = {0,0,0,0,0,0,0,0,0,0,0,0,0,0};
    struct min_max * emp_minMax_ptr = &employeeMinMax;

    head_ptr = getEmpData ();

    theSize = isEmployeeSize (head_ptr);
    
    if (theSize <= 0)
    {
        printf("\n\n**** There was no employee input to process ***\n");
    }
    
    else // there are employees to be processed
    {    
        calcOvertimeHrs (head_ptr);
        calcGrossPay (head_ptr); 
        calcStateTax (head_ptr);
        calcFedTax (head_ptr);
        calcNetPay (head_ptr); 
        
        calcEmployeeTotals (head_ptr, 
                            &employeeTotals);
                            
        calcEmployeeMinMax (head_ptr, 
                            &employeeMinMax);
                        
        printHeader();

        printEmp (head_ptr); 
    
        printEmpStatistics (&employeeTotals, 
                            &employeeMinMax, 
                            theSize);
    }
    
    printf ("\n\n *** End of Program *** \n");

    return (0); // success

} // main

//**************************************************************
// Function: getEmpData 
//**************************************************************

struct employee * getEmpData (void)
{
 
    char   answer[80];
    int    more_data = 1;
    char   value;
 
    struct employee *current_ptr,
                    *head_ptr;
 
    head_ptr = (struct employee *) malloc (sizeof(struct employee));
    current_ptr = head_ptr;
 
    while (more_data)
    {
        printf ("\nEnter employee first name: ");
        scanf ("%s", current_ptr->empName.firstName);
        printf ("\nEnter employee last name: ");
        scanf ("%s", current_ptr->empName.lastName);
 
        printf ("\nEnter employee two character tax state: ");
        scanf ("%s", current_ptr->taxState);
 
        printf("\nEnter employee clock number: ");
        scanf("%li", & current_ptr -> clockNumber);
 
        printf("\nEnter employee hourly wage: ");
        scanf("%f", & current_ptr -> wageRate);
 
        printf("\nEnter hours worked this week: ");
        scanf("%f", & current_ptr -> hours);
 
        printf("\nWould you like to add another employee? (y/n): ");
        scanf("%s", answer);
 
        if ((value = toupper(answer[0])) != 'Y')
        {
           current_ptr->next = (struct employee *) NULL;
           more_data = 0; 
        }
        else
        {
           current_ptr->next = (struct employee *) malloc (sizeof(struct employee));
           current_ptr = current_ptr->next;
        }
         
    } // while
 
    return(head_ptr);
}

//*************************************************************
// Function: isEmployeeSize
//**************************************************************

int isEmployeeSize (struct employee * head_ptr)
{
    
    struct employee * current_ptr;
    int theSize;

    theSize = 0;

    if (head_ptr->empName.firstName[0] != '\0')
    {
        for (current_ptr = head_ptr; current_ptr; current_ptr = current_ptr->next)
        {  
            ++theSize;
        } // for
    }

    return (theSize);

} // isEmployeeSize

//**************************************************************
// Function: printHeader
//**************************************************************

void printHeader (void) 
{ 

    printf ("\n\n*** Pay Calculator ***\n");

    printf("\n--------------------------------------------------------------");
    printf("-------------------");
    printf("\nName                Tax  Clock# Wage   Hours  OT   Gross ");
    printf("  State  Fed      Net");
    printf("\n                   State                           Pay   ");
    printf("  Tax    Tax      Pay");
    
    printf("\n--------------------------------------------------------------");
    printf("-------------------");

} // printHeader

//************************************************************* 
// Function: printEmp 
//**************************************************************

void printEmp (struct employee * head_ptr)
{
    
    char name [FIRST_NAME_SIZE + LAST_NAME_SIZE + 1];

    struct employee * current_ptr;

    for (current_ptr = head_ptr; current_ptr; current_ptr = current_ptr->next)
    {
        strcpy (name, current_ptr->empName.firstName);
        strcat (name, " ");
        strcat (name, current_ptr->empName.lastName);
    
        printf("\n%-20.20s %-2.2s  %06li %5.2f  %4.1f  %4.1f %7.2f %6.2f %7.2f %8.2f",
               name, current_ptr->taxState, current_ptr->clockNumber, 
               current_ptr->wageRate, current_ptr->hours,
               current_ptr->overtimeHrs, current_ptr->grossPay, 
               current_ptr->stateTax, current_ptr->fedTax, 
               current_ptr->netPay);
               
    } // for
          
} // printEmp

//************************************************************* 
// Function: printEmpStatistics 
//**************************************************************

void printEmpStatistics (struct totals   * emp_totals_ptr,
                         struct min_max  * emp_minMax_ptr,
                         int theSize)
{
    
    printf("\n--------------------------------------------------------------");
    printf("-------------------");
    
    printf("\nTotals:                         %5.2f %5.1f %5.1f %7.2f %6.2f %7.2f %8.2f",
           emp_totals_ptr->total_wageRate,
           emp_totals_ptr->total_hours,
           emp_totals_ptr->total_overtimeHrs,
           emp_totals_ptr->total_grossPay,
           emp_totals_ptr->total_stateTax,
           emp_totals_ptr->total_fedTax,
           emp_totals_ptr->total_netPay);
    
    if (theSize > 0)       
    {
        printf("\nAverages:                       %5.2f %5.1f %5.1f %7.2f %6.2f %7.2f %8.2f",
               emp_totals_ptr->total_wageRate/theSize,
               emp_totals_ptr->total_hours/theSize,
               emp_totals_ptr->total_overtimeHrs/theSize,
               emp_totals_ptr->total_grossPay/theSize,
               emp_totals_ptr->total_stateTax/theSize,
               emp_totals_ptr->total_fedTax/theSize,
               emp_totals_ptr->total_netPay/theSize);
   
    } // if
    
    printf("\nMinimum:                        %5.2f %5.1f %5.1f %7.2f %6.2f %7.2f %8.2f",
           emp_minMax_ptr->min_wageRate,
           emp_minMax_ptr->min_hours,
           emp_minMax_ptr->min_overtimeHrs,
           emp_minMax_ptr->min_grossPay,
           emp_minMax_ptr->min_stateTax,
           emp_minMax_ptr->min_fedTax,
           emp_minMax_ptr->min_netPay);
    
    printf("\nMaximum:                        %5.2f %5.1f %5.1f %7.2f %6.2f %7.2f %8.2f",
           emp_minMax_ptr->max_wageRate,
           emp_minMax_ptr->max_hours,
           emp_minMax_ptr->max_overtimeHrs,
           emp_minMax_ptr->max_grossPay,
           emp_minMax_ptr->max_stateTax,
           emp_minMax_ptr->max_fedTax,
           emp_minMax_ptr->max_netPay);
           
    printf ("\n\nThe total employees processed was: %i\n", theSize);

}  // printEmpStatistics

//*************************************************************
// Function: calcOvertimeHrs
//**************************************************************

void calcOvertimeHrs (struct employee * head_ptr)
{
    
    struct employee * current_ptr;

    for (current_ptr = head_ptr; current_ptr; current_ptr = current_ptr->next)
    {  
        if (current_ptr->hours >= STD_HOURS)
        {
            current_ptr->overtimeHrs = current_ptr->hours - STD_HOURS;
        }
        else
        {
              current_ptr->overtimeHrs = 0;
        }
        
    } // for


} // calcOvertimeHrs

//*************************************************************
// Function: calcGrossPay
//**************************************************************

void calcGrossPay (struct employee * head_ptr)
{

    float theNormalPay;
    float theOvertimePay;

    struct employee * current_ptr;

    for (current_ptr = head_ptr; current_ptr; current_ptr = current_ptr->next)
    {
        theNormalPay = current_ptr->wageRate * 
                       (current_ptr->hours - current_ptr->overtimeHrs);
        theOvertimePay = current_ptr->overtimeHrs * 
                         (OT_RATE * current_ptr->wageRate);
  
        current_ptr->grossPay = theNormalPay + theOvertimePay;

    }

} // calcGrossPay

//*************************************************************
// Function: calcStateTax
//
// Purpose: Calculates the State Tax owed based on gross pay
//          for each employee, using the employee's tax state
//          to determine the correct tax rate.
//**************************************************************

void calcStateTax (struct employee * head_ptr)
{
    
    struct employee * current_ptr; // pointer to current node

    // traverse through the linked list to calculate the state tax
    for (current_ptr = head_ptr; current_ptr; current_ptr = current_ptr->next)
    {
        // Make sure tax state is all uppercase
        if (islower(current_ptr->taxState[0]))
            current_ptr->taxState[0] = toupper(current_ptr->taxState[0]);
        if (islower(current_ptr->taxState[1]))
            current_ptr->taxState[1] = toupper(current_ptr->taxState[1]);
       
        // calculate state tax based on where employee resides
        if (strcmp(current_ptr->taxState, "MA") == 0)
            current_ptr->stateTax = current_ptr->grossPay * MA_TAX_RATE;
        else if (strcmp(current_ptr->taxState, "VT") == 0)
            current_ptr->stateTax = current_ptr->grossPay * VT_TAX_RATE;
        else if (strcmp(current_ptr->taxState, "NH") == 0)
            current_ptr->stateTax = current_ptr->grossPay * NH_TAX_RATE;
        else if (strcmp(current_ptr->taxState, "CA") == 0)
            current_ptr->stateTax = current_ptr->grossPay * CA_TAX_RATE;
        else
            // any other state is the default rate
            current_ptr->stateTax = current_ptr->grossPay * DEFAULT_TAX_RATE;
        
    } // for
       
} // calcStateTax

//*************************************************************
// Function: calcFedTax
//
// Purpose: Calculates the Federal Tax owed based on the gross 
//          pay for each employee. The rate is the same
//          regardless of tax state.
//**************************************************************

void calcFedTax (struct employee * head_ptr)
{
    
    struct employee * current_ptr; // pointer to current node

    // traverse through the linked list to calculate the federal tax
    for (current_ptr = head_ptr; current_ptr; current_ptr = current_ptr->next)
    {
        // Fed Tax is the same for all regardless of state
        current_ptr->fedTax = current_ptr->grossPay * FED_TAX_RATE;

    } // for

} // calcFedTax

//*************************************************************
// Function: calcNetPay
//**************************************************************

void calcNetPay (struct employee * head_ptr)
{
    float theTotalTaxes;
    
    struct employee * current_ptr;

    for (current_ptr = head_ptr; current_ptr; current_ptr = current_ptr->next)
    {
        theTotalTaxes = current_ptr->stateTax + current_ptr->fedTax;
    
        current_ptr->netPay = current_ptr->grossPay - theTotalTaxes;

    } // for
    
} // calcNetPay

//*************************************************************
// Function: calcEmployeeTotals
//
// Purpose: Performs a running total (sum) of each employee
//          floating point member item stored in our linked list,
//          including state and federal tax.
//**************************************************************

void calcEmployeeTotals (struct employee * head_ptr,
                         struct totals * emp_totals_ptr)
{
       
    struct employee * current_ptr; // pointer to current node

    for (current_ptr = head_ptr; current_ptr; current_ptr = current_ptr->next)
    {
        emp_totals_ptr->total_wageRate += current_ptr->wageRate;
        emp_totals_ptr->total_hours += current_ptr->hours;
        emp_totals_ptr->total_overtimeHrs += current_ptr->overtimeHrs;
        emp_totals_ptr->total_grossPay += current_ptr->grossPay;
        
        // keep a running total of the state and federal taxes
        emp_totals_ptr->total_stateTax += current_ptr->stateTax;
        emp_totals_ptr->total_fedTax += current_ptr->fedTax;
        
        emp_totals_ptr->total_netPay += current_ptr->netPay;
        
    } // for
    
} // calcEmployeeTotals

//*************************************************************
// Function: calcEmployeeMinMax
//
// Purpose: Accepts various floating point values from an
//          employee and adds to a running update of min
//          and max values, including state and federal tax.
//**************************************************************

void calcEmployeeMinMax (struct employee * head_ptr,
                         struct min_max * emp_minMax_ptr)
{

    struct employee * current_ptr; // pointer to current node
   
    current_ptr = head_ptr;
    
    // set the min to the first employee members
    emp_minMax_ptr->min_wageRate = current_ptr->wageRate; 
    emp_minMax_ptr->min_hours = current_ptr->hours;
    emp_minMax_ptr->min_overtimeHrs = current_ptr->overtimeHrs; 
    emp_minMax_ptr->min_grossPay = current_ptr->grossPay;
    emp_minMax_ptr->min_stateTax = current_ptr->stateTax;
    emp_minMax_ptr->min_fedTax = current_ptr->fedTax;
    emp_minMax_ptr->min_netPay = current_ptr->netPay;
        
    // set the max to the first employee members
    emp_minMax_ptr->max_wageRate = current_ptr->wageRate; 
    emp_minMax_ptr->max_hours = current_ptr->hours;
    emp_minMax_ptr->max_overtimeHrs = current_ptr->overtimeHrs;
    emp_minMax_ptr->max_grossPay = current_ptr->grossPay;
    emp_minMax_ptr->max_stateTax = current_ptr->stateTax;
    emp_minMax_ptr->max_fedTax = current_ptr->fedTax;
    emp_minMax_ptr->max_netPay = current_ptr->netPay;

    current_ptr = current_ptr->next;
    
    // traverse the linked list
    for (; current_ptr; current_ptr = current_ptr->next) 
    {
        
        if (current_ptr->wageRate < emp_minMax_ptr->min_wageRate)
        {
            emp_minMax_ptr->min_wageRate = current_ptr->wageRate;
        }
        
        if (current_ptr->wageRate > emp_minMax_ptr->max_wageRate)
        {
            emp_minMax_ptr->max_wageRate = current_ptr->wageRate;
        }
        
        if (current_ptr->hours < emp_minMax_ptr->min_hours)
        {
            emp_minMax_ptr->min_hours = current_ptr->hours;
        }
        
        if (current_ptr->hours > emp_minMax_ptr->max_hours)
        {
            emp_minMax_ptr->max_hours = current_ptr->hours;
        }
        
        if (current_ptr->overtimeHrs < emp_minMax_ptr->min_overtimeHrs)
        {
            emp_minMax_ptr->min_overtimeHrs = current_ptr->overtimeHrs;
        }
        
        if (current_ptr->overtimeHrs > emp_minMax_ptr->max_overtimeHrs)
        {
            emp_minMax_ptr->max_overtimeHrs = current_ptr->overtimeHrs;
        }
        
        if (current_ptr->grossPay < emp_minMax_ptr->min_grossPay)
        {
            emp_minMax_ptr->min_grossPay = current_ptr->grossPay;
        }
        
        if (current_ptr->grossPay > emp_minMax_ptr->max_grossPay)
        {
            emp_minMax_ptr->max_grossPay = current_ptr->grossPay;
        }
        
        // check if current State Tax is the new min and/or max
        if (current_ptr->stateTax < emp_minMax_ptr->min_stateTax)
        {
            emp_minMax_ptr->min_stateTax = current_ptr->stateTax;
        }
        
        if (current_ptr->stateTax > emp_minMax_ptr->max_stateTax)
        {
            emp_minMax_ptr->max_stateTax = current_ptr->stateTax;
        }
        
        // check if current Federal Tax is the new min and/or max
        if (current_ptr->fedTax < emp_minMax_ptr->min_fedTax)
        {
            emp_minMax_ptr->min_fedTax = current_ptr->fedTax;
        }
        
        if (current_ptr->fedTax > emp_minMax_ptr->max_fedTax)
        {
            emp_minMax_ptr->max_fedTax = current_ptr->fedTax;
        }
        
        if (current_ptr->netPay < emp_minMax_ptr->min_netPay)
        {
            emp_minMax_ptr->min_netPay = current_ptr->netPay;
        }
        
        if (current_ptr->netPay > emp_minMax_ptr->max_netPay)
        {
            emp_minMax_ptr->max_netPay = current_ptr->netPay;
        }
        
    } // for
    
} // calcEmployeeMinMax