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

#include "md5.h"

#define min_t(type,x,y) \
	({ type __x = (x); type __y = (y); __x < __y ? __x: __y; })

static const char *hstr = "0123456789ABCDEF";

typedef struct {
	size_t len;
	char *buf;
} string_t;
#define s_buf(x) ((x)->buf)
#define s_len(x) ((x)->len)

static inline void set_str(string_t *s, void *buf, int len)
{
	s_buf(s) = buf;
	s_len(s) = len;
}

static inline void add_str(string_t *a, string_t *b)
{
	memcpy(s_buf(a) + s_len(a), s_buf(b), s_len(b));
	s_len(a) += s_len(b);
}

static void pack_h(string_t *src, string_t *dst, int bytes_of_src)
{
	int count, i;
	char *s, *d;

	if (!src || !s_buf(src) || !dst) {
		fprintf(stderr, "%s(): -.-;\n", __func__);
		return;
	}

	count = min_t(int, bytes_of_src, s_len(src));
	set_str(dst, realloc(s_buf(dst), count * 2), 0);

	s = s_buf(src);
	d = s_buf(dst);

	for (i = 0; i < count; i++) {
		int a = *s++ & 0xff;
		*d++ = *(hstr + (a >> 4));
		*d++ = *(hstr + (a & 0xf));
	}
	s_len(dst) = count * 2;
}

static void bytexor(string_t *src, string_t *dst, string_t *key, int len)
{
	int i;
	unsigned char *s, *d, *k;
	int count;

	count = len;
	count = min_t(int, s_len(src), count);
	count = min_t(int, s_len(dst), count);
	count = min_t(int, s_len(dst), count);

	s = (unsigned char*)s_buf(src);
	d = (unsigned char*)s_buf(dst);
	k = (unsigned char*)s_buf(key);

	for (i = 0; i < count; i++) {
		*d++ = *s++ ^ *k++;
	}
}

static int crypt_md5(const char *_msg, int msglen, const char *_key,
		char *tmp, int tmps)
{
	string_t key, key1, key2;
	string_t buffer, dst, md;
	int left, this_len;
	int key_len;
	char md5buf[16];

	/* char* -> string_t */
	set_str(&md, &md5buf[0], 16);
	set_str(&dst, tmp, tmps);
	set_str(&key, (char*)_key, strlen(_key));

	set_str(&buffer, NULL, 0);
	set_str(&key1, NULL, 0);
	set_str(&key2, NULL, 0);

	left = msglen;

	while (left) {
		this_len = min_t(int, 16, left);

		/* $key1 = $key.$key2.$buffer; */
		key_len = s_len(&key) + s_len(&key2) + s_len(&buffer);
		set_str(&key1, realloc(s_buf(&key1), key_len), 0);
		add_str(&key1, &key);
		add_str(&key1, &key2);
		add_str(&key1, &buffer);

		/* $md = md5($key1); */
		md5_buffer(s_buf(&key1), s_len(&key1), s_buf(&md));	

		/* $key2=pack("H*",$md); */
		pack_h(&md, &key2, s_len(&md));

		/* $buffer=substr($msg,0,16); */
		set_str(&buffer, (char*)_msg, this_len);
		
		/* $str = bytexor($buffer,$key2); */
		bytexor(&buffer, &dst, &key2, this_len);
		memcpy(s_buf(&dst), s_buf(&buffer), this_len);

 		/* $string.=$str; */
		set_str(&dst, s_buf(&dst) + this_len, s_len(&dst) - this_len);

		/* $msg=substr($msg,16); */
		_msg += this_len;

		left -= this_len;
	}

	free(s_buf(&key1));
	free(s_buf(&key2));

	return s_buf(&dst) - tmp;
}

int main(int argc, char **argv)
{
	char tmp_buf[256];
	char tmp_buf2[256];
	char *msg = "☆━2008년*♡*┐┃설날부턴 ° ː│。°더많이°│ː 。사랑할께~┃└*♡* *‥─━★";
	char *key = "9857861";
	int ret;

	printf("source len %d\n", strlen(msg));

	ret = crypt_md5(msg, strlen(msg), key, tmp_buf, sizeof(tmp_buf));
	printf("encrypted len %d\n", ret);

#if 1
	ret = crypt_md5(tmp_buf, ret, key, tmp_buf2, sizeof(tmp_buf2));
	printf("decrypted len %d\n", ret);

	tmp_buf2[ret] = 0;
	printf("result: %s\n", tmp_buf2);
#endif
	
	return 0;
}