/*-----------------------------------------------------------------------------
 *				HTBLA-Leonding
 *-----------------------------------------------------------------------------
 * Exercise Number: S07
 * Title:			Binary search implementation
 * Author:			Marc Tismonar
 *-----------------------------------------------------------------------------
 * Description:
 * Implements the binary search algorithm
 *-----------------------------------------------------------------------------
*/

#include "binary_search.h"

/**
 * Searches the given needle within the given haystack using binary search approach.
 * 
 * Implementation hint: delegate the invocation to function `binary_search_list_limited(…)`.
 * 
 * @param haystack The sorted list in which the `needle` is searched.
 * @param criterion The pointer to the function that implements the sorting criterion of the list.
 * That function accepts two integer parameters and returns a boolean value.
 * @param needle The value to find within the haystack.
 * @return The index of the `needle` within the list if it was found or the position where the needle need to
 * be inserted into the sorted list if it is not included in the list. The insertion position is 
 * expressed as index with negative sign, so that the value can be inserted at index (-1 * result).
 */
int binary_search_list(IntList haystack, criterion_fn criterion, int needle) {
    if (!list_is_valid(haystack)) {
        return -1;
    }
    
    return binary_search_list_limited(haystack, list_get_size(haystack), criterion, needle);
}

/**
 * Searches the given needle within the given haystack up the given length using binary search approach.
 * 
 * @param haystack The sorted list in which the `needle` is searched.
 * @param length The number of items to consider starting from the beginning of the haystack.
 * If the haystack contains more items, the remaining items are omitted from the search. If it contains
 * less items, the number of items are clipped to the size of the haystack.
 * @param criterion The pointer to the function that implements the sorting criterion of the list.
 * That function accepts two integer parameters and returns a boolean value.
 * @param needle The value to find within the haystack.
 * @return The index of the `needle` within the list if it was found or the position where the needle need to
 * be inserted into the sorted list if it is not included in the list. The insertion position is 
 * expressed as index with negative sign, so that the value can be inserted at index (-1 * result).
 */
int binary_search_list_limited(IntList haystack, int length, criterion_fn criterion, int needle) {
    if (!list_is_valid(haystack) || criterion == 0) {
        return -1;
    }
    
    int list_size = list_get_size(haystack);
    if (length > list_size) {
        length = list_size;
    }
    
    if (length <= 0) {
        return -1;
    }
    
    int left = 0;
    int right = length - 1;
    
    while (left <= right) {
        int mid = left + (right - left) / 2;
        int mid_value = list_get_at(haystack, mid);
        
        if (mid_value == needle) {
            return mid;
        }
        
        if (criterion(mid_value, needle)) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    
    return -left;
}

/* ARRAY VARIANT */

/**
 * Searches the given needle within the given haystack using binary search approach.
 *  
 * @param haystack The sorted list in which the `needle` is searched.
 * @param length The length of the haystack array.
 * @param criterion The pointer to the function that implements the sorting criterion of the list.
 * That function accepts two integer parameters and returns a boolean value.
 * @param needle The value to find within the haystack.
 * @return The index of the `needle` within the list if it was found or the position where the needle need to
 * be inserted into the sorted list if it is not included in the list. The insertion position is 
 * expressed as index with negative sign, so that the value can be inserted at index (-1 * result).
 */
int binary_search_array(int haystack[], int length, criterion_fn criterion, int needle) {
    return -1;
}