/*
 * Copyright (c) 2003-2015 Hypertriton, Inc. <http://hypertriton.com/>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This input filter processes a text/html stream. It performs the following
 * substitutions:
 *
 * - percgi(3) variable values: "$foo" => (Value of foo)
 *                              "%24foo" => (Value of foo)
 * - Gettext translation: "$_(String)" => (Translation of String)
 * - Quoted instances of "&amp;" => "&"
 */

#include "cgi.h"

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

#define VARSUBST_TRANSLATE_MAX	256	/* Max string length for $_(foo) */

enum varsubst_mode {
	VARSUBST_NORMAL,
	VARSUBST_VAR,
	VARSUBST_ESCAPE,
	VARSUBST_TRANSLATE
};

static __inline__ const char *
FetchVar(const char *key)
{
	char *s;

	s = VAR_Get(key);
	return (s != NULL) ? s : "";
}

static __inline__ int
VarnameChar(const char c)
{
	return (isalnum(c) || c == '_');
}

static size_t
Filter(struct cgi_query *q, void **pBuf, size_t src_len)
{
	char vName[VARSUBST_TRANSLATE_MAX], *pName;
	char *src = *(char **)pBuf, *p, *endp;
	int quot = 0;
	enum varsubst_mode mode;
	TEXT te;

	TEXT_Init(&te, src_len, q->cset);

	for (p = src; p < &src[src_len];) {
#if 0
		if (*p == '"' || *p == '\'') {
			quot = !quot;
		}
		if (quot && p < &src[src_len-5] &&	/* Quoted &amp; => & */
		    strncmp(p, "&amp;", 5) == 0) {
			TEXT_CatC(&te, '&');
			p += 5;
		}
#endif
		mode = VARSUBST_NORMAL;

		if (p[0] == '%' && p < &src[src_len-3] &&	/* %24foo */
		    p[1] == '2' && p[2] == '4') {
			if (p[3] == '%' && &p[3] < &src[src_len-3] &&
			    p[4] == '2' && p[5] == '4') {
				mode = VARSUBST_ESCAPE;
			} else {
				mode = VARSUBST_VAR;
			}
			p+=3;
			if (p[0] == '_' && p[1] == '(') {
				mode = VARSUBST_TRANSLATE;
				p+=2;
				for (pName = &vName[0];
				     p < &src[src_len-1] &&
				      *p != ')' && isprint(*p) &&
				      pName < &vName[sizeof(vName)-1];
				     p++) {
					*pName = *p;
					pName++;
				}
				p++;
			} else {
				for (pName = &vName[0];
				     p < &src[src_len-1] && VarnameChar(*p) &&
				      pName < &vName[sizeof(vName)-1];
				     p++, pName++) {
					*pName = *p;
				}
			}
			*pName = '\0';
		} else if (p[0] == '$') {
			if (p[1] == '$') {
				mode = VARSUBST_ESCAPE;
			} else {
				mode = VARSUBST_VAR;
			}
			p++;
			if (p[0] == '_' && p[1] == '(') {
				mode = VARSUBST_TRANSLATE;
				p+=2;
				for (pName = &vName[0];
				     p < &src[src_len-1] &&
				      *p != ')' && isprint(*p) &&
				      pName < &vName[sizeof(vName)-1];
				     p++) {
					*pName = *p;
					pName++;
				}
				p++;
			} else {
				for (pName = &vName[0];
				     p < &src[src_len-1] && VarnameChar(*p) &&
				      pName < &vName[sizeof(vName)-1];
				     p++, pName++) {
					*pName = *p;
				}
			}
			*pName = '\0';
		}
		
		switch (mode) {
		case VARSUBST_NORMAL:
			TEXT_CatC(&te, *(p++));
			break;
		case VARSUBST_ESCAPE:
			TEXT_CatC(&te, '$');
			TEXT_CatS(&te, vName);
			break;
		case VARSUBST_TRANSLATE:
			TEXT_CatS_UTF8(&te, gettext(vName));
			break;
		case VARSUBST_VAR:
			if (vName[0] != '\0') {
				char *s = VAR_Get(vName);

				if (s != NULL) {
					TEXT_CatS_UTF8(&te, FetchVar(vName));
				} else {
					CGI_Log(CGI_LOG_ERR,
					    "Uninitialized variable: $%s",
					    vName);
				}
			}
			break;
		}
	}

	*pBuf = Realloc(*pBuf, te.len);
	memcpy(*pBuf, te.buf, te.len);
	TEXT_Destroy(&te);
	return (te.len);
}

struct cgi_filter cgiVarSubstFilter = {
	CGI_INPUT_FILTER,
	"text/html",
	Filter
};