#include "string_utils.h"

#include <ctype.h>
#include <stdlib.h>
#include <string.h>

char *trim_blank_left(char *str)
{
    if (str == NULL)
        return NULL;

    while (*str != '\0' && isblank(*str))
        str++;

    return str;
}

char *insert_into(char *dest, const char *src, size_t pos, size_t len)
{
    size_t res_len = strlen(dest);
    size_t prefix_len = pos;
    size_t suffix_len = res_len - (pos + len);
    size_t src_len = strlen(src);
    size_t new_len = prefix_len + src_len + suffix_len;

    if (dest == NULL || src == NULL || pos + len > res_len)
        return NULL;

    if (res_len < new_len)
    {
        char *p = realloc(dest, new_len + 1);
        if (p == NULL)
            return NULL; // allocation failure
        dest = p;
    }

    memmove(dest + pos + src_len, dest + pos + len, suffix_len);
    memcpy(dest + pos, src, src_len);
    dest[new_len] = 0;

    if (res_len > new_len)
        return realloc(dest, new_len + 1);
    return dest;
}