/*
 *  Project   : tin - a Usenet reader
 *  Module    : rfc1524.c
 *  Author    : Urs Janssen <urs@tin.org>, Jason Faultless <jason@altarstone.com>
 *  Created   : 2000-05-15
 *  Updated   : 2021-02-23
 *  Notes     : mailcap parsing as defined in RFC 1524
 *
 * Copyright (c) 2000-2023 Urs Janssen <urs@tin.org>, Jason Faultless <jason@altarstone.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.
 *
 * 3. Neither the name of the copyright holder nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * 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 COPYRIGHT HOLDER 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.
 */

#ifndef TIN_H
#	include "tin.h"
#endif /* !TIN_H */


/*
 * As defined in RFC 1524, Appendix A
 */
#define DEFAULT_MAILCAPS "~/.mailcap:/etc/mailcap:/usr/etc/mailcap:/usr/local/etc/mailcap:/etc/mail/mailcap"

/* maximum number of mailcap fields */
#define MAILCAPFIELDS 13

/* local prototypes */
static char *expand_mailcap_meta(const char *mailcap, t_part *part, t_bool escape_shell_meta_chars, const char *path);
static char *get_mailcap_field(char *mailcap);
static t_mailcap *parse_mailcap_line(const char *mailcap, t_part *part, const char *path);


/*
 * mainloop:
 * 	scan mailcap file(s), look for a matching entry, extract fields,
 * 	expand metas
 *
 * TODO: don't used fixed length buffers
 */
t_mailcap *
get_mailcap_entry(
	t_part *part,
	const char *path)
{
	FILE *fp;
	char *ptr, *ptr2, *nptr;
	char buf[LEN];
	char filename[LEN];	/* name of current mailcap file */
	char mailcap[LEN];	/* full match */
	char *mailcaps;		/* possible mailcap files */
	char wildcap[LEN];	/* basetype match */
	t_mailcap *foo = (t_mailcap *) 0;

	/* build list of mailcap files */
	if ((ptr = getenv("MAILCAPS")) != NULL && strlen(ptr)) {
		mailcaps = my_malloc(strlen(ptr) + strlen(DEFAULT_MAILCAPS) + 2);
		sprintf(mailcaps, "%s:%s", ptr, DEFAULT_MAILCAPS);
	} else
		mailcaps = my_strdup(DEFAULT_MAILCAPS);

	mailcap[0] = '\0';
	wildcap[0] = '\0';
	buf[0] = '\0';

	ptr = buf;

	nptr = strtok(mailcaps, ":");
	while (nptr != NULL) {
		/* expand ~ and/or $HOME etc. */
		if (strfpath(nptr, filename, sizeof(filename) - 1, &CURR_GROUP, FALSE)) {
			if ((fp = fopen(filename, "r")) != NULL) {
				while ((fgets(ptr, (int) (sizeof(buf) - strlen(buf)), fp)) != NULL) {
					if (*ptr == '#' || *ptr == '\n')		/* skip comments & blank lines */
						continue;

					ptr = buf + strlen(buf) - 1;

					if (*ptr == '\n')		/* remove linebreaks */
						*ptr-- = '\0';

					if (*ptr == '\\')		/* continuation line */
						continue;			/* append */
					else
						ptr = buf;

					if ((ptr2 = strchr(buf, '/')) != NULL) {
						if (!strncasecmp(ptr, content_types[part->type], strlen(ptr) - strlen(ptr2))) {
							if (!strncasecmp(ptr + strlen(content_types[part->type]) + 1, part->subtype, strlen(part->subtype))) {
								/* full match, so parse line and evaluate test if given. */
								STRCPY(mailcap, ptr);
								FreeIfNeeded(foo);
								foo = parse_mailcap_line(mailcap, part, path);
								if (foo != NULL) {
									fclose(fp); /* perfect match with test succeeded (if given) */
									free(mailcaps);
									return foo;
								}
							} else {
								if ((*(ptr2 + 1) == '*') || (*(ptr2 + 1) == ';')) { /* wildmat match */
									if (!strlen(wildcap)) { /* we don't already have a wildmat match */
										STRCPY(wildcap, buf);
										FreeIfNeeded(foo);
										foo = parse_mailcap_line(wildcap, part, path);
										if (foo == NULL) /* test failed */
											wildcap[0] = '\0'; /* ignore match */
									}
								} /* else subtype mismatch, no action required */
							}
						} /* else no match, no action required */
					} /* else invalid mailcap line (no /), no action required */
					if (*wildcap) {	/* we just had a wildmat match */
						fclose(fp);
						free(mailcaps);
						return foo;
					}
				} /* while ((fgets(ptr, ... */
				fclose(fp);
			}
		} /* else strfpath() failed, no action required */
		nptr = strtok(NULL, ":"); /* get next filename */
	}
	free(mailcaps);
	FreeAndNull(foo);
	return foo;
}


/*
 * extract fields, expand metas - called from get_mailcap_entry()
 */
static t_mailcap*
parse_mailcap_line(
	const char *mailcap,
	t_part *part,
	const char *path)
{
	char *ptr, *optr, *buf;
	int i = MAILCAPFIELDS - 2; /* max MAILCAPFIELDS - required fields */
	t_mailcap *tmailcap;

	/* malloc and init */
	tmailcap = my_malloc(sizeof(t_mailcap));
	tmailcap->type = NULL;
	tmailcap->command = NULL;
	tmailcap->needsterminal = FALSE;
	tmailcap->copiousoutput = FALSE;
	tmailcap->textualnewlines = 0;
	tmailcap->description = NULL;
	tmailcap->test = NULL;
	tmailcap->nametemplate = NULL;
	tmailcap->compose = NULL;
	tmailcap->composetyped = NULL;
	tmailcap->edit = NULL;
	tmailcap->print = NULL;
	tmailcap->x11bitmap = NULL;

	optr = ptr = my_strdup(mailcap);

	/* get required entries */
	ptr = get_mailcap_field(ptr);
	buf = my_calloc(1, strlen(content_types[part->type]) + strlen(part->subtype) + 2);
	sprintf(buf, "%s/%s", content_types[part->type], part->subtype);
	tmailcap->type = buf;
	ptr += strlen(ptr) + 1;
	if ((ptr = get_mailcap_field(ptr)) != NULL) {
		tmailcap->command = ptr;
		ptr += strlen(ptr) + 1;
	} else { /* required filed missing */
		free(optr);
		free_mailcap(tmailcap);
		return ((t_mailcap *) 0);
	}

	while ((ptr = get_mailcap_field(ptr)) != NULL) {
		if (i-- <= 0) /* number of possible fields exhausted */
			break;
		if (!strncasecmp(ptr, "needsterminal", 13)) {
			tmailcap->needsterminal = TRUE;
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "copiousoutput", 13)) {
			tmailcap->copiousoutput = TRUE;
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "description=", 12)) {
			tmailcap->description = ptr + 12;
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "nametemplate=", 13)) {
			tmailcap->nametemplate = expand_mailcap_meta(ptr + 13, part, FALSE, path);
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "test=", 5)) {
			tmailcap->test = ptr + 5;
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "textualnewlines=", 16)) {
			tmailcap->textualnewlines = atoi(ptr + 16);
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "compose=", 8)) {
			tmailcap->compose = ptr + 8;
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "composetyped=", 13)) {
			tmailcap->composetyped = ptr + 13;
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "edit=", 5)) {
			tmailcap->edit = ptr + 5;
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "print=", 6)) {
			tmailcap->print = ptr + 6;
			ptr += strlen(ptr) + 1;
		}
		if (!strncasecmp(ptr, "x11-bitmap=", 11)) {
			tmailcap->x11bitmap = ptr + 11;
			ptr += strlen(ptr) + 1;
		}
	}

	/*
	 * expand metas - we do it in a 2nd pass to be able to honor
	 * nametemplate
	 */
	if (tmailcap->command != NULL) /* TODO: pass body part to command on stdin if no % found */
		tmailcap->command = expand_mailcap_meta(tmailcap->command, part, TRUE, tmailcap->nametemplate ? tmailcap->nametemplate : path);
	if (tmailcap->description != NULL)
		tmailcap->description = expand_mailcap_meta(tmailcap->description, part, FALSE, tmailcap->nametemplate ? tmailcap->nametemplate : path);
	if (tmailcap->test != NULL)
		tmailcap->test = expand_mailcap_meta(tmailcap->test, part, TRUE, tmailcap->nametemplate ? tmailcap->nametemplate : path);
	if (tmailcap->compose != NULL)
		tmailcap->compose = expand_mailcap_meta(tmailcap->compose, part, TRUE, tmailcap->nametemplate ? tmailcap->nametemplate : path);
	if (tmailcap->composetyped != NULL)
		tmailcap->composetyped = expand_mailcap_meta(tmailcap->composetyped, part, TRUE, tmailcap->nametemplate ? tmailcap->nametemplate : path);
	if (tmailcap->edit != NULL)
		tmailcap->edit = expand_mailcap_meta(tmailcap->edit, part, TRUE, tmailcap->nametemplate ? tmailcap->nametemplate : path);
	if (tmailcap->print != NULL)
		tmailcap->print = expand_mailcap_meta(tmailcap->print, part, TRUE, tmailcap->nametemplate ? tmailcap->nametemplate : path);
	if (tmailcap->x11bitmap != NULL)
		tmailcap->x11bitmap = expand_mailcap_meta(tmailcap->x11bitmap, part, TRUE, tmailcap->nametemplate ? tmailcap->nametemplate : path);

	free(optr);

	if (tmailcap->test != NULL) { /* test field given */
		/*
		 * TODO: EndWin()/InitWin() around system needed?
		 *       use invoke_cmd()?
		 */
		if (system(tmailcap->test)) { /* test failed? */
			free_mailcap(tmailcap);
			return ((t_mailcap *) 0);
		}
	}
	return tmailcap;
}


/*
 * extract fields - called from parse_mailcap_line()
 *
 * TODO: add handling for singlequotes
 */
static char *
get_mailcap_field(
	char *mailcap)
{
	char *ptr;
	t_bool backquote = FALSE;
	t_bool doublequote = FALSE;

	ptr = str_trim(mailcap);

	while (*ptr != '\0') {
		switch (*ptr) {
			case '\\':
				backquote = bool_not(backquote);
				break;

			case '"':
				if (!backquote)
					doublequote = bool_not(doublequote);
				backquote = FALSE;
				break;

			case ';':
				if (!backquote && !doublequote) { /* field separator (plain ;) */
					*ptr = '\0';
					return mailcap;
				}
				if (backquote && !doublequote) /* remove \ in \; if not inside "" or '' */
					*(ptr - 1) = ' ';
				backquote = FALSE;
				break;

			default:
				backquote = FALSE;
				break;
		}
		ptr++;
	}
	return mailcap;
}


#define CHECK_SPACE(minlen) { \
	while (space <= (minlen)) { /* need more space? */ \
		olen = strlen(line); \
		space += linelen; \
		linelen <<= 1; \
		line = my_realloc(line, linelen); \
		memset(line + olen, 0, linelen - olen); \
	} \
}


/*
 * expand metas - called from parse_mailcap_line()
 *
 * TODO: expand %F, %n
 */
static char *
expand_mailcap_meta(
	const char *mailcap,
	t_part *part,
	t_bool escape_shell_meta_chars,
	const char *path)
{
	const char *ptr;
	char *line, *lptr;
	int quote = no_quote;
	size_t linelen, space, olen;

	if (!(strchr(mailcap, '%'))) /* nothing to expand */
		return my_strdup(mailcap); /* waste of mem, but simplifies the frees */

	linelen = LEN * 2;					/* initial maxlen */
	space = linelen - 1;					/* available space in string */
	line = my_calloc(1, linelen);
	lptr = line;
	ptr = mailcap;

	while (*ptr != '\0') {
		/*
		 * to avoid reallocs() for the all the single char cases
		 * we do a check here
		 */
		if (space < 10) {				/* 'worst'case are two chars ... */
			olen = strlen(line);		/* get current length of string */
			space += linelen;			/* recalc available space */
			linelen <<= 1;				/* double maxlen */
			line = my_realloc(line, linelen);
			memset(line + olen, 0, linelen - olen); /* weed out junk */
			lptr = line + olen;		/* adjust pointer to current position */
		}

		if (*ptr == '\\') {
			ptr++;
			if ((*ptr == '\\') || (*ptr == '%')) {
				*lptr++ = *ptr++;
				space--;
			}
			continue;
		}
		if (*ptr == '%') {
			ptr++;
			if (*ptr == '{') {	/* Content-Type parameter */
				char *end;

				if ((end = strchr(ptr, '}')) != NULL) {
					if (part->params != NULL) {
						char *parameter;
						const char *value;

						parameter = my_calloc(1, end - ptr + 1);
						strncpy(parameter, ptr + 1, (size_t) (end - ptr - 1));	/* extract parameter name */
						if ((value = get_param(part->params, parameter)) != NULL) { /* match? */
							const char *nptr = escape_shell_meta_chars ? escape_shell_meta(value, quote) : value;

							CHECK_SPACE(strlen(nptr));
							strcat(line, nptr);
							lptr = line + strlen(line);
							space -= strlen(line);
						}
						free(parameter);
					}
					ptr = end;	/* skip past closing } */
					ptr++;
				} else {
					/* sequence broken, output literally */
					*lptr++ = '%';
					*lptr++ = *ptr++;
					space -= 2;
				}
				continue;
#if 0 /* TODO */
			} else if (*ptr == 'F') {	/* Content-Types and Filenames of sub parts */
			} else if (*ptr == 'n') {	/* Number of sub parts */
			}
#endif /* 0 */
			} else if (*ptr == 's') {	/* Filename */
				const char *nptr = escape_shell_meta_chars ? escape_shell_meta(path, quote) : path;

				CHECK_SPACE(strlen(nptr) + 2);
				strcat(line, nptr);
				lptr = line + strlen(line);
				space -= strlen(line);
				ptr++;
				continue;
			} else if (*ptr == 't') {	/* Content-Type */
				const char *nptr = escape_shell_meta_chars ? escape_shell_meta(part->subtype, quote) : part->subtype;

				CHECK_SPACE((strlen(content_types[part->type]) + 1 + strlen(nptr)));
				strcat(line, content_types[part->type]);
				strcat(line, "/");
				strcat(line, nptr);
				lptr = line + strlen(line);
				space -= strlen(line);
				ptr++;
				continue;
			} else {	/* unknown % sequence */
				*lptr++ = '%';
				space--;
				continue;
			}
		}

		if (escape_shell_meta_chars) {
			if ((*ptr == '\'') && (quote != dbl_quote))
				quote = (quote == no_quote ? sgl_quote : no_quote);
			else if ((*ptr == '"') && (quote != sgl_quote))
				quote = (quote == no_quote ? dbl_quote : no_quote);
		}

		/* any other char */
		*lptr++ = *ptr++;
		space--;
	}
	return line;
}


/*
 * frees the malloced space
 */
void
free_mailcap(
	t_mailcap *tmailcap)
{
	FreeIfNeeded(tmailcap->type);
	FreeIfNeeded(tmailcap->command);
	FreeIfNeeded(tmailcap->compose);
	FreeIfNeeded(tmailcap->composetyped);
	FreeIfNeeded(tmailcap->description);
	FreeIfNeeded(tmailcap->edit);
	FreeIfNeeded(tmailcap->nametemplate);
	FreeIfNeeded(tmailcap->print);
	FreeIfNeeded(tmailcap->test);
	FreeIfNeeded(tmailcap->x11bitmap);
	free(tmailcap);
}
