// Implementation file for the Hash class
// Written By: Iurii Tatishchev
// Changed by: Iurii Tatishchev

#include <string>
#include <utility>

#include "HashTable.h"

using namespace std;

/*~*~*~*
  A simple hash function 
 *~**/
int HashTable::_hash(string key) const {
    int sum = 0;
    for (char c : key)
        sum += c;
    return sum % hashSize;
};

/*~*~*~*
  hash insert - linear probe
*~**/
bool HashTable::insert(const Student &itemIn) {
    if (count == hashSize)
        return false;
    int pos = _hash(itemIn.getName());
    int collisions = 0;
    while (hashAry[pos].getOccupied() == 1) {
        ++pos;
        ++collisions;
        pos = pos % hashSize;
    }
    hashAry[pos].setItem(itemIn);
    hashAry[pos].setOccupied(1);
    hashAry[pos].setNoCollisions(collisions);
    count++;

    return true;
}

/*~*~*~*
   hash delete - linear probe
*~**/
bool HashTable::remove(Student &itemOut, string key) {
    int pos = _hash(key);
    for (int collisions = 0; collisions < count; collisions++) {
        if (hashAry[pos].getOccupied() == 1 && hashAry[pos].getItem().getName() == key) {
            itemOut = hashAry[pos].getItem();
            // -1 means freed
            hashAry[pos].setOccupied(-1);
            count--;
            return true;
        }
        pos = (pos + 1) % hashSize;
    }
    return false;
}

/*~*~*~*
   hash search - linear probe
   search for key
   if found: 
      - copy data to itemOut
      - copy number of collisions for this key to noCol
      - returns true
   if not found, returns false
*~**/
int HashTable::search(Student &itemOut, string key) const {
    int pos = _hash(key);
    for (int collisions = 0; collisions < count; collisions++) {
        if (hashAry[pos].getOccupied() == 0) return -1;
        if (hashAry[pos].getOccupied() == 1 && hashAry[pos].getItem().getName() == key) {
            itemOut = hashAry[pos].getItem();
            return hashAry[pos].getNoCollisions();
        }
        pos = (pos + 1) % hashSize;
    }
    return -1;
}