/*

 * Copyright (c) 2014 Sunil Nimmagadda <sunil@nimmagadda.net>

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

#include <sys/param.h>

#include <sys/types.h>

#include <sys/queue.h>

#include <sys/socket.h>

#include <sys/stat.h>

#include <errno.h>

#include <fcntl.h>

#include <stdio.h>

#include <string.h>

#include <syslog.h>

#include <unistd.h>

#include "pop3d.h"

static int init(struct mdrop *, size_t *, size_t *);

static int retr(struct mdrop *, unsigned int, size_t *, long *);

static int update(struct mdrop *);

struct m_backend m_backend_mbox = {

	init,

	retr,

	update

};

/* 

 * Parse mbox calculating each message's offset, size and hash.

 * A message is identified by "From " at the start of a line.

 * Returns 0 on success with nmsgs and sz populated.

 */

int

init(struct mdrop *m, size_t *nmsgs, size_t *sz)

{

	SHA1_CTX	ctx;

	FILE		*fp;

	struct msg	*msg = NULL;

	size_t		i, len;

	long		offset;

	char		*line;

	*nmsgs = 0;

	*sz = 0;

	if (flock(m->fd, LOCK_EX|LOCK_NB) == -1) {

		switch (errno) {

		case EWOULDBLOCK:

			logit(LOG_INFO, "mbox: locked by other process");

			return (-1);

		default:

			fatal("flock(LOCK_EX)");

		}

	}

	if ((fp = fdopen(dup(m->fd), "r+")) == NULL) {

		logit(LOG_INFO, "mbox: fdopen failed");

		return (-1);

	}

	SIMPLEQ_INIT(&m->e.q_msgs);

	offset = ftell(fp);

	while ((line = fgetln(fp, &len))) {

		if ((len > 5) && strncmp("From ", line, 5) == 0) {

			if (msg)

				SHA1End(&ctx, msg->hash);

			msg = xcalloc(1, sizeof(*msg), "init");

			SHA1Init(&ctx);

			msg->u.offset = offset;

			m->nmsgs += 1;

			SIMPLEQ_INSERT_TAIL(&m->e.q_msgs, msg, e.q_entry);

		} else {

			if (msg == NULL)

				fatalx("mbox corrupted: no \"From \" line");

			msg->sz += len;

			msg->nlines += 1;

			SHA1Update(&ctx, (u_int8_t *)line, len);

			offset = ftell(fp);

		}

	}

	if (msg)

		SHA1End(&ctx, msg->hash);

	/* allocate space for nmsgs of struct msg pointers */

	m->msgs_index = xcalloc(m->nmsgs, sizeof(msg), "make_index");

	i = 0;

	SIMPLEQ_FOREACH(msg, &m->e.q_msgs, e.q_entry) {

		m->msgs_index[i++] = msg;

		/* calculate mbox size by counting newline as 2 (CRLF) */

		m->sz += msg->sz + msg->nlines;

	}

	*nmsgs = m->nmsgs;

	*sz = m->sz;

	fclose(fp);

	return (0);

}

static int

retr(struct mdrop *m, unsigned int idx, size_t *nlines, long *offset)

{

	if (m->msgs_index[idx]->flags & F_DELE)

		return (-1);

	*offset = m->msgs_index[idx]->u.offset;

	*nlines = m->msgs_index[idx]->nlines;

	return (dup(m->fd)); /* imsg closes sender's fd */

}

/* 

 * No resource management as this process is blown away

 * upon success or error.

 */

static int

update(struct mdrop *m)

{

	struct msg	*cur;

	size_t		i, j = 0, len, nlines;

	char		buf[MAXBSIZE], fn[22], *line;

	FILE		*tmp_fp, *m_fp;

	mode_t		old_mask;

	int		tmp_fd;

	for (i = 0; i < m->nmsgs; i++)

		if (m->msgs_index[i]->flags & F_DELE)

			j += 1;

	if ((m_fp = fdopen(dup(m->fd), "r+")) == NULL) {

		logit(LOG_INFO, "mbox: fdopen failed");

		return (-1);

	}

	if (j == 0)

		return (0);

	else if (j == m->nmsgs) {

		if (ftruncate(fileno(m_fp), 0) == -1) {

			logit(LOG_CRIT, "update: ftruncate failed");

			return (1);

		}

		return (0);

	}

	strlcpy(fn, "/tmp/pop3d.XXXXXXXXXX", sizeof(fn));

	old_mask = umask(S_IXUSR|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH);

	if ((tmp_fd = mkstemp(fn)) == -1 ||

	    (tmp_fp = fdopen(tmp_fd, "r+")) == NULL) {

		logit(LOG_CRIT, "mbox: mkstemp failed");

		return (1);

	}

	umask(old_mask);

	for (i = 0; i < m->nmsgs; i++) {

		cur = m->msgs_index[i];

		if (cur->flags & F_DELE)

			continue;

		if (fseek(m_fp, cur->u.offset, SEEK_SET) == -1) {

			logit(LOG_CRIT, "update: fseek failed");

			return (1);

		}

		/*

		 * "From " line isn't counted in nlines but offset starts

		 * there, adjust nlines here 

		 */

		nlines = m->msgs_index[i]->nlines + 1;

		while (nlines--) {

			if ((line = fgetln(m_fp, &len)))

				if (fwrite(line, len, 1, tmp_fp) != 1)

					fatalx("update: short write");

		}

	}

	fflush(tmp_fp);

	rewind(m_fp);

	rewind(tmp_fp);

	while (!feof(tmp_fp)) {

		fread(buf, sizeof(buf), 1, tmp_fp);

		if (fwrite(buf, sizeof(buf), 1, m_fp) != 1)

			fatalx("update: short write");

	}

	fflush(m_fp);

	if (ftruncate(fileno(m_fp), ftello(tmp_fp)) == -1)

		fatal("update: failed to truncate");

	fclose(m_fp);

	return (0);

}