/*
 * mailing backend for dovecot antispam plugin
 *
 * Copyright (C) 2009       Alexander Sulfrian <alexander@sulfrian.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License Version 2 as
 * published by the Free Software Foundation.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */

#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <dirent.h>
#include <openssl/sha.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <libgen.h>

#include "lib.h"
#include "dict.h"
#include "mail-storage-private.h"
#include "ostream.h"
#include "istream.h"

#include "antispam-plugin.h"

static const char *spamdir = NULL;
static const char *hamdir = NULL;

struct antispam_transaction_context {
	int count;
};

int mkdir_rec(const char *dir, mode_t mask) {
	char *parent;
	struct stat sb;
	int status;

	if (stat(dir, &sb) == 0) {
		if (! S_ISDIR(sb.st_mode)) {
			return -1;
		}

		return 0;
	}

	t_push();

	parent = t_malloc(strlen(dir) + 1);
	strcpy(parent, dir);

	if ((status = mkdir_rec(dirname(parent), mask)) == 0) {
		mkdir(dir, mask);

		status = 0;
	}

	t_pop();

	return status;
}

struct antispam_transaction_context *
backend_start(struct mailbox *box __attr_unused__)
{
	struct antispam_transaction_context *ast;

	ast = i_new(struct antispam_transaction_context, 1);
	ast->count = 0;

	/* Create spam and hamdir */
	mkdir_rec(spamdir, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
	mkdir_rec(hamdir, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);

	return ast;
}

void backend_rollback(struct antispam_transaction_context *ast)
{
	i_free(ast);
}

int backend_commit(struct mailbox_transaction_context *ctx __attr_unused__,
		   struct antispam_transaction_context *ast)
{
	i_free(ast);
	return 0;
}

static char *create_unique_mailname(const char *date, const char *mail_id, char *sha1)
{
	char *unique_string;
	unsigned char *sha_bytes;

	t_push();

	unique_string = t_malloc(strlen(date) + strlen(mail_id) + 1);
	i_snprintf(unique_string, strlen(date) + strlen(mail_id) + 1, "%s%s", date, mail_id);

	sha_bytes = t_malloc(20);
	sha_bytes = SHA1((unsigned char*)unique_string, strlen(date) + strlen(mail_id), sha_bytes);

	int i;
	for (i = 0; i < 20; i++) {
		i_snprintf(sha1+(i*2), 3, "%02hhx", sha_bytes[i]);
	}
	sha1[40] = 0;

	t_pop();

	return sha1;
}

int backend_handle_mail(struct mailbox_transaction_context *t,
			struct antispam_transaction_context *ast,
			struct mail *mail, enum classification wanted)
{
	struct istream *mailstream;
	struct ostream *outstream;
	int ret;
	char *file;
	const unsigned char *beginning;
	size_t size;
	int fd;
	char *name = NULL, *check_file = NULL;
	const char *date = NULL, *mail_id = NULL, *dest = NULL, *other = NULL;
	struct stat sb;

	if (!hamdir || !spamdir) {
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "antispam plugin not configured");
		return -1;
	}

	mailstream = get_mail_stream(mail);
	if (!mailstream) {
		mail_storage_set_error(t->box->storage,
				       ME(EXPUNGED)
				       "Failed to get mail contents");
		return -1;
	}

 	t_push();

	/* Generate unique id for mail */

	/* get date header */
	if (mail_get_first_header(mail, "Date", &date) == 0) {
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "Invalid mail with no date header");
		ret = -1;
		goto out;
	}

	/* get message id */
	if (mail_get_first_header(mail, "Message-Id", &mail_id) == 0) {
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "Invalid mail with no message id header");
		ret = -1;
		goto out;
	}

	/* hash name and message id */
	name = t_malloc(41 * sizeof(char));
	name = create_unique_mailname(date, mail_id, name);

	/* switch weather this should be ham or spam */
	switch (wanted) {
	case CLASS_SPAM:
		dest = spamdir;
		other = hamdir;
		break;
	case CLASS_NOTSPAM:
		dest = hamdir;
		other = spamdir;
		break;
	}

	if (dest == NULL) {
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "Failed to determine whether mail is ham or spam");
		ret = -1;
		goto out;
	}

	/* check if this mail is already marked as the opposit */
	check_file = t_malloc(2 + strlen(other) + strlen(name));
	i_snprintf(check_file, 1 + strlen(other) + strlen(name), "%s/%s", other, name);

	if (stat(check_file, &sb) == 0) {
		debug("mail is marked opposit, remove it there");
		unlink(check_file);
	}

	/* create file name */
	file = t_malloc(2 + strlen(dest) + strlen(name));
	i_snprintf(file, 1 + strlen(dest) + strlen(name), "%s/%s", dest, name);

	if (stat(file, &sb) == 0) {
		debug("mail is already there, nothing to do");
		ret = 0;
		goto out;
	}

	fd = creat(file, 0600);
	if (fd < 0) {
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "Failed to create temporary file");
		ret = -1;
		goto out;
	}

	ast->count++;

	outstream = o_stream_create_from_fd(fd, t->box->pool);
	if (!outstream) {
		ret = -1;
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "Failed to stream temporary file");
		goto out_close;
	}

	if (o_stream_send(outstream, &wanted, sizeof(wanted))
			!= sizeof(wanted)) {
		ret = -1;
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "Failed to write marker to temp file");
		goto failed_to_copy;
	}

	if (i_stream_read_data(mailstream, &beginning, &size, 5) < 0 ||
	    size < 5) {
		ret = -1;
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "Failed to read mail beginning");
		goto failed_to_copy;
	}

	/* "From "? skip line */
	if (memcmp("From ", beginning, 5) == 0)
		i_stream_read_next_line(mailstream);

	if (o_stream_send_istream(outstream, mailstream) < 0) {
		ret = -1;
		mail_storage_set_error(t->box->storage,
				       ME(NOTPOSSIBLE)
				       "Failed to copy to temporary file");
		goto failed_to_copy;
	}

	ret = 0;

 failed_to_copy:
	o_stream_destroy(&outstream);
 out_close:
	close(fd);
 out:
	t_pop();

	return ret;
}

void backend_init(pool_t pool __attr_unused__)
{
	const char *tmp;

	tmp = get_setting("DIR_SPAM");
	if (tmp) {
		spamdir = tmp;
		debug("mail backend spam directory %s\n", tmp);
	}

	tmp = get_setting("DIR_NOTSPAM");
	if (tmp) {
		hamdir = tmp;
		debug("mail backend not-spam directory %s\n", tmp);
	}
}

void backend_exit(void)
{
}