/*----------------------------------------------------------
 *				HTBLA-Leonding
 * ---------------------------------------------------------
 * Title:			Trim String
 * Author:			Marc Tismonar
 * ----------------------------------------------------------
 * Description:
 * Implementation of 'trim' functionality.
 * ----------------------------------------------------------
 */

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include "trim.h"

// private functions
bool is_whitespace(char c) {
    return c == ' ' || c == '\t' || c == '\n' || c == '\r';
}

void shift(char* string, int start, int end) {
    int i;
    for (i = 0; i <= end - start; i++) {
        string[i] = string[i + start];
    }
    string[i] = '\0';
}

void override_all(char* string) {
    for (int i = 0; i < strlen(string); i++) {
        string[i] = ' ';
    }
}

/**
* Provides the trimmed string WITHOUT making a copy 
* of the source string.
* Trimming means that leading and trailing whitespace 
* characters are removed.
*
* Whitespace characters are:
* - space (' '),
* - tabulator ('\t')
* - new line ('\n')
* - line feed ('\r')
* @param string The string to be trimmed.
* @return The trimmed string.
*/
char* trim(char* string) {
    if (string == 0) {
        return 0;
    }

    int start = 0;
    while (string[start] != '\0' && is_whitespace(string[start])) {
        start++;
    }
    
    // if empty or only whitespace
    if (string[start] == '\0') {
        string[0] = '\0';
        return string;
    }
    
    int end = strlen(string) - 1;
    while (end > start && is_whitespace(string[end])) {
        end--;
    }
    
    // shift
    if (start > 0) {
        shift(string, start, end);
    } else {
        string[end + 1] = '\0';
    }
    
    return string;
}

/**
* Provides the trimmed string as COPY of the source string.
* Trimming means that leading and trailing whitespace 
* characters are removed.
*
* Whitespace characters are:
* - space (' '),
* - tabulator ('\t')
* - new line ('\n')
* - line feed ('\r')
* @param string The string to be trimmed.
* @param trimmed_string Container which takes the trimmed
* version of source. This function expects a buffer that
* is large enough for carrying the trimmed string.
*/
void trim_cpy(char* string, char* trimmed_string) {
    if (string == 0 || trimmed_string == 0) {
        return;
    }

    if (strlen(string) == 0) {
        trimmed_string[0] = '\0';
        return;
    }

    override_all(trimmed_string);
    trimmed_string = strncpy(trimmed_string, string, strlen(string));
    trimmed_string = trim(trimmed_string);
}