#include <iostream>
#include <string>

#define ARRAY_SIZE(a) (sizeof(a)/sizeof(a[0]))

using namespace std;
// Declare the struct

#define EMPTY_STUDENT_ID 0 // An Id of 0 means an empty record.
struct Student
{
    int id;
    std::string name;
    std::string telephone;
    std::string email;

    Student* pNext;
};

/*
The HashTable is a structure of 2 elements, the first element records the size of the prime area
and the second element is a pointer to the start of the prime area.
*/
struct HashTable
{
    int size;       /* the size of the table */
    Student *primeArea; /* the table elements */
};

HashTable  *my_hash_table;
int size_of_table = 12;


// Create an array of students.
// These will be put into a hash table
Student studentList[] =
{
    {379452, "Mary Odd", "5555555", "mary@gmail.com" },
    {367173, "Sarah Alice", "5555555", "sarah@gmail.com" },
    {166702, "Harry Joy", "5555555", "harry@gmail.com" },
    {572556, "Hidayah", "5555555", "harry@gmail.com"},
};

HashTable* create_hash_table(int size)
{
    HashTable* new_table;

    if (size<1) return NULL; /* invalid size for table */

    // Allocate the hash table main structure
    if ((new_table = new HashTable) == NULL) {
        return NULL;
    }

    // Allocate the primeArea
    if ((new_table->primeArea = new Student[size]) == NULL) {
        return NULL;
    }

    /* Initialize the elements of the table */
    for(int i=0; i<size; i++)
    {
        new_table->primeArea[i].pNext = NULL;
        // An id of 0 means an empty record.
        new_table->primeArea[i].id = EMPTY_STUDENT_ID;

    }

    /* Set the table's size */
    new_table->size = size;

    return new_table;
}

// This is a hashing function.
unsigned int moduloDivisionHashFunction(Student *pStudent, unsigned int listSize)
{
    return pStudent->id % listSize;
}


void insert_to_hash_table(HashTable* ht, Student* record)
{

     //This is where the chaining solution should be taken

    unsigned int hashValue = moduloDivisionHashFunction(record, my_hash_table->size);
    cout<< "Student ID " << record->id << " hashes to " << hashValue << endl;

    ht->primeArea[hashValue].id = record->id;
    ht->primeArea[hashValue].name = record->name;
    ht->primeArea[hashValue].telephone= record->telephone;
    ht->primeArea[hashValue].email = record->email;

}

int main(void)
{
    cout<<"Modulo-Division Hashing Function"<<endl;

    my_hash_table = create_hash_table(size_of_table);

    // go through the studentList using a loop
    int studentListSize = ARRAY_SIZE(studentList);
    for(int i = 0; i < studentListSize ; i++)
    {

        insert_to_hash_table(my_hash_table, &studentList[i]);
    }

    system("pause");
    return 0;
}