#include "string.h"

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

#ifndef HAVE_STRDUP
char *strdup(const char *s) {
	if (NULL == s) {
		return NULL;
	}

	size_t len = strlen(s);
	char *buf = malloc(len+1);

	if (buf) {
		memcpy(buf, s, len + 1);
	}
	return buf;
}
#endif

size_t stranjoin_r(
		char *restrict buf, size_t buflen, char sep, const char *restrict a[],
		size_t nmemb) {
	size_t len = 0;

	if (NULL != buf && 0 < buflen) {
		/* clear buf string */
		*buf = '\0';
	}

	for (size_t i = 0; i < nmemb; ++i) {
		if (0 < len) {
			/* add separator */
			if (NULL != buf && len < buflen) {
				*(buf+len) = sep;
			}
			++len;
		}

		if (NULL != buf) {
			/* append element */
			strncpy(buf+len, a[i], (buflen - len));
		}
		len += strlen(a[i]);
	}

	return len;
}

char *stranjoin(char sep, const char *a[], size_t nmemb) {
	/* determine length of result string */
	size_t len = stranjoin_r(NULL, 0, sep, a, nmemb);

	/* allocate destination buffer */
	char *dest = malloc(len+1);
	if (NULL != dest) {
		(void)stranjoin_r(dest, len+1, sep, a, nmemb);
	}

	return dest;
}

size_t _vstrjoin_r(char *restrict buf, size_t buflen, char sep, va_list ap) {
	const char *s;
	size_t len = 0;

	if (NULL != buf && 0 < buflen) {
		/* clear buf string */
		*buf = '\0';
	}

	while (NULL != (s = va_arg(ap, const char *restrict))) {
		if (0 < len) {
			/* add separator */
			if (NULL != buf && len < buflen) {
				*(buf+len) = sep;
			}
			++len;
		}

		if (NULL != buf) {
			/* append element */
			strncpy(buf+len, s, (buflen - len));
		}
		len += strlen(s);
	}

	return len;
}

size_t _strjoin_r(
		char *restrict buf, size_t buflen, char sep, /* const char *restrict */...) {
	va_list ap;
	va_start(ap, sep);
	size_t len = _vstrjoin_r(buf, buflen, sep, ap);
	va_end(ap);
	return len;
}

char *_strjoin(char sep, /* const char *restrict */...) {
	va_list ap;

	/* determine length of result string */
	va_start(ap, sep);
	size_t len = _vstrjoin_r(NULL, 0, sep, ap);
	va_end(ap);

	/* allocate destination buffer */
	char *dest = malloc(len+1);
	if (NULL != dest) {
		(void)_vstrjoin_r(dest, len+1, sep, ap);
	}

	return dest;
}


size_t strsplit(const char *restrict in, const char *restrict sep, void *buf) {
	size_t i = 0;
	char **arr = buf;

	if (0 == strlen(in)) {
		/* special case: empty string */
		if (arr) arr[0] = NULL;
		return sizeof(char *);
	}

	char *tok, *saveptr, *tmp = strdup(in);

	tok = strtok_r(tmp, sep, &saveptr);
	do {
		if (arr) {
			arr[i] = (char *)(tok - tmp);  /* save char offset */
		}
		i++;
	} while ((tok = strtok_r(NULL, sep, &saveptr)));

	size_t strtokoffset = ((i+1)*sizeof(*arr)),
	       strtoklen = strlen(in) + 1;

	if (arr) {
		/* update array pointers */
		for (int j = 0; j < i; j++) {
			arr[j] = (char *)((size_t)buf + strtokoffset + (size_t)arr[j]);
		}
		arr[i] = NULL;  /* NULL termination */

		/* copy tokenized string from tmp to the back of buf */
		(void)memcpy(buf + strtokoffset, tmp, strtoklen);
	}

	free(tmp);

	return (strtoklen + strtokoffset);
}