/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 8; tab-width: 8 -*- */
/* mail-mlist-magic.c
 *
 * Copyright (C) 2000  Helix Code, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Author: Ettore Perazzoli
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

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

#include "camel.h"

#include "mail-mlist-magic.h"

/* FIXME: This really should just use regexps... */


/* Utility functions.  */

static char *
extract_until_at_sign (const char *s)
{
	const char *at_sign;

	at_sign = strchr (s, '@');
	if (at_sign == NULL)
		return g_strdup (s);

	if (at_sign == s)
		return NULL;

	return g_strndup (s, at_sign - s);
}

static const char *
get_header (CamelMimeMessage *message,
	    const char *header_name)
{
	const char *value;

	value = camel_medium_get_header (CAMEL_MEDIUM (message), header_name);
	if (value == NULL)
		return NULL;

	/* FIXME: Correct?  */
	while (isspace ((int) *value))
		value++;

	return value;
}


/* The checks.  */

/* Sender: (owner-([^@]+)|([^@+]-owner)@ */
static char *
check_sender (CamelMimeMessage *message,
	      const char **header_name_return,
	      char **header_value_return)
{
	const char *value;
	char *owner, *list_name;

	value = get_header (message, "Sender");
	if (value == NULL)
		return NULL;

	owner = strstr (value, "owner");
	if (!owner)
		return NULL;

	if (owner == value && value[5] == '-' && value[6] && value[6] != '@')
		list_name = extract_until_at_sign (value + 6);
	else if (owner > value + 1 && *(owner - 1) == '-' && owner[5] == '@')
		list_name = g_strndup (value, owner - 1 - value);
	else
		return NULL;

	if (header_name_return != NULL)
		*header_name_return = "Sender";
	if (header_value_return != NULL)
		*header_value_return = g_strdup (value);
	return list_name;
}
   
/* X-BeenThere: ([^@]+) */
static char *
check_x_been_there (CamelMimeMessage *message,
		    const char **header_name_return,
		    char **header_value_return)
{
	const char *value;

	value = get_header (message, "X-BeenThere");
	if (value == NULL || *value == '@')
		return NULL;

	if (header_name_return != NULL)
		*header_name_return = "X-BeenThere";
	if (header_value_return != NULL)
		*header_value_return = g_strdup (value);

	return extract_until_at_sign (value);
}
   
/* Delivered-To: mailing list ([^@]+) */
static char *
check_delivered_to (CamelMimeMessage *message,
		    const char **header_name_return,
		    char **header_value_return)
{
	const char *value;

	value = get_header (message, "Delivered-To");
	if (value == NULL)
		return NULL;

	/* FIXME uh? */
	if (strncmp (value, "mailing list ", 13) != 0)
		return NULL;

	if (value[13] == '\0' || value[13] == '@')
		return NULL;

	if (header_name_return != NULL)
		*header_name_return = "Delivered-To";
	if (header_value_return != NULL)
		*header_value_return = g_strdup (value);
	return extract_until_at_sign (value + 13);
}
   
/* X-Mailing-List: <([^@]+) */
static char *
check_x_mailing_list (CamelMimeMessage *message,
		      const char **header_name_return,
		      char **header_value_return)
{
	const char *value;
	int value_length;

	value = get_header (message, "X-Mailing-List");
	if (value == NULL)
		return NULL;

	if (value[0] != '<' || value[1] == '\0' || value[1] == '@')
		return NULL;

	value_length = strlen (value);
	if (value[value_length - 1] != '>')
		return NULL;

	if (header_name_return != NULL)
		*header_name_return = "X-Mailing-List";
	if (header_value_return != NULL)
		*header_value_return = g_strdup (value);
	return extract_until_at_sign (value + 1);
}
   
/* X-Loop: ([^@]+) */
static char *
check_x_loop (CamelMimeMessage *message,
	      const char **header_name_return,
	      char **header_value_return)
{
	const char *value;

	value = get_header (message, "X-Loop");
	if (value == NULL)
		return NULL;

	if (*value == '\0' || *value == '@')
		return NULL;

	if (header_name_return != NULL)
		*header_name_return = "X-Loop";
	if (header_value_return != NULL)
		*header_value_return = g_strdup (value);

	return extract_until_at_sign (value);
}

/* List-Post: <mailto:([^@]+) */
static char *
check_list_post (CamelMimeMessage *message,
		 const char **header_name_return,
		 char **header_value_return)
{
	const char *value;
	int value_length;

	value = get_header (message, "List-Post");
	if (value == NULL)
		return NULL;

	if (strncmp (value, "<mailto:", 8) != 0 || value[8] == '@')
		return NULL;

	value_length = strlen (value);
	if (value[value_length - 1] != '>')
		return NULL;

	if (header_name_return != NULL)
		*header_name_return = "List-Post";
	if (header_value_return != NULL)
		*header_value_return = g_strdup (value);
	return extract_until_at_sign (value + 8);
}

typedef char *(*MagicDetectorFunc) (CamelMimeMessage *, const char **, char **);

MagicDetectorFunc magic_detector[] = {
	check_sender,
	check_x_been_there,
	check_delivered_to,
	check_x_mailing_list,
	check_x_loop,
	check_list_post
};
static const int num_detectors = sizeof (magic_detector) / sizeof (magic_detector[0]);


/**
 * mail_mlist_magic_detect_list:
 * @message:
 * @header_name_return:
 * @header_value_return:
 * 
 * Detect if message was delivered by a mailing list.
 * 
 * Return value: The name of the mailing list, if the message appears to be
 * sent from a mailing list.  NULL otherwise.
 **/
char *
mail_mlist_magic_detect_list (CamelMimeMessage *message,
			      const char **header_name_return,
			      char **header_value_return)
{
	char *list_name;
	int i;

	g_return_val_if_fail (message != NULL, NULL);
	g_return_val_if_fail (CAMEL_IS_MIME_MESSAGE (message), NULL);

	for (i = 0; i < num_detectors; i++) {
		list_name = magic_detector[i] (message, header_name_return, header_value_return);
		if (list_name != NULL)
			return list_name;
	}

	return NULL;
}