/* $Id: imap-common.c,v 1.66 2007/09/25 21:34:51 nicm Exp $ */

/*
 * Copyright (c) 2006 Nicholas Marriott <nicm@users.sourceforge.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 MIND, 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/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>

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

#include <openssl/bio.h>
#include <openssl/buffer.h>
#include <openssl/evp.h>
#include <openssl/hmac.h>

#include "fdm.h"
#include "fetch.h"

int	imap_putln(struct account *, const char *, ...);
int	imap_getln(struct account *, struct fetch_ctx *, int, char **);

void	imap_free(void *);

int	imap_okay(char *);
int	imap_parse(struct account *, int, char *);
int	imap_tag(char *);

char   *imap_base64_encode(char *);
char   *imap_base64_decode(char *);

int	imap_bad(struct account *, const char *);
int	imap_invalid(struct account *, const char *);

int	imap_state_connect(struct account *, struct fetch_ctx *);
int	imap_state_connected(struct account *, struct fetch_ctx *);
int	imap_state_capability1(struct account *, struct fetch_ctx *);
int	imap_state_capability2(struct account *, struct fetch_ctx *);
int	imap_state_cram_md5_auth(struct account *, struct fetch_ctx *);
int	imap_state_login(struct account *, struct fetch_ctx *);
int	imap_state_user(struct account *, struct fetch_ctx *);
int	imap_state_pass(struct account *, struct fetch_ctx *);
int	imap_state_select1(struct account *, struct fetch_ctx *);
int	imap_state_select2(struct account *, struct fetch_ctx *);
int	imap_state_select3(struct account *, struct fetch_ctx *);
int	imap_state_select4(struct account *, struct fetch_ctx *);
int	imap_state_search1(struct account *, struct fetch_ctx *);
int	imap_state_search2(struct account *, struct fetch_ctx *);
int	imap_state_search3(struct account *, struct fetch_ctx *);
int	imap_state_next(struct account *, struct fetch_ctx *);
int	imap_state_uid1(struct account *, struct fetch_ctx *);
int	imap_state_uid2(struct account *, struct fetch_ctx *);
int	imap_state_body(struct account *, struct fetch_ctx *);
int	imap_state_line(struct account *, struct fetch_ctx *);
int	imap_state_mail(struct account *, struct fetch_ctx *);
int	imap_state_delete(struct account *, struct fetch_ctx *);
int	imap_state_expunge(struct account *, struct fetch_ctx *);
int	imap_state_quit1(struct account *, struct fetch_ctx *);
int	imap_state_quit2(struct account *, struct fetch_ctx *);

#define IMAP_TAG_NONE -1
#define IMAP_TAG_CONTINUE -2
#define IMAP_TAG_ERROR -3

#define IMAP_TAGGED 0
#define IMAP_CONTINUE 1
#define IMAP_UNTAGGED 2
#define IMAP_RAW 3

#define IMAP_CAPA_AUTH_CRAM_MD5 0x1

/* Put line to server. */
int
imap_putln(struct account *a, const char *fmt, ...)
{
	struct fetch_imap_data	*data = a->data;
	va_list			 ap;
	int			 n;

	va_start(ap, fmt);
	n = data->putln(a, fmt, ap);
	va_end(ap);

	return (n);
}

/*
 * Get line from server. Returns -1 on error, 0 on success, a NULL line when
 * out of data.
 */
int
imap_getln(struct account *a, struct fetch_ctx *fctx, int type, char **line)
{
	struct fetch_imap_data	*data = a->data;
 	int			 n;

	do {
		if (data->getln(a, fctx, line) != 0)
			return (-1);
		if (*line == NULL)
			return (0);
	} while ((n = imap_parse(a, type, *line)) == 1);
	return (n);
}

/* Free auxiliary data. */
void
imap_free(void *ptr)
{
	xfree(ptr);
}

/* Check for okay from server. */
int
imap_okay(char *line)
{
	char	*ptr;

	ptr = strchr(line, ' ');
	if (ptr == NULL || strncmp(ptr + 1, "OK ", 3) != 0)
		return (0);
	return (1);
}

/*
 * Parse line based on type. Returns -1 on error, 0 on success, 1 to ignore
 * this line.
 */
int
imap_parse(struct account *a, int type, char *line)
{
	struct fetch_imap_data	*data = a->data;
	int			 tag;

	if (type == IMAP_RAW)
		return (0);

	tag = imap_tag(line);
	switch (type) {
	case IMAP_TAGGED:
		if (tag == IMAP_TAG_NONE)
			return (1);
		if (tag == IMAP_TAG_CONTINUE)
			goto invalid;
		if (tag != data->tag)
			goto invalid;
		break;
	case IMAP_UNTAGGED:
		if (tag != IMAP_TAG_NONE)
			goto invalid;
		break;
	case IMAP_CONTINUE:
		if (tag == IMAP_TAG_NONE)
			return (1);
		if (tag != IMAP_TAG_CONTINUE)
			goto invalid;
		break;
	}

	return (0);

invalid:
	imap_bad(a, line);
	return (-1);
}

/* Parse IMAP tag. */
int
imap_tag(char *line)
{
	int	 	 tag;
	const char	*errstr;
	char		*ptr;

	if (line[0] == '*' && line[1] == ' ')
		return (IMAP_TAG_NONE);
	if (line[0] == '+')
		return (IMAP_TAG_CONTINUE);

	if ((ptr = strchr(line, ' ')) == NULL)
		return (IMAP_TAG_ERROR);
	*ptr = '\0';

	tag = strtonum(line, 0, INT_MAX, &errstr);
	*ptr = ' ';
	if (errstr != NULL)
		return (IMAP_TAG_ERROR);

	return (tag);
}

/* Base64 encode string. */
char *
imap_base64_encode(char *in)
{
	char	*out;
	size_t	 size;

	size = (strlen(in) * 2) + 1;
	out = xcalloc(1, size);
	if (b64_ntop(in, strlen(in), out, size) < 0) {
		xfree(out);
		return (NULL);
	}
	return (out);
}

/* Base64 decode string. */
char *
imap_base64_decode(char *in)
{
	char	*out;
	size_t	 size;

	size = (strlen(in) * 4) + 1;
	out = xcalloc(1, size);
	if (b64_pton(in, out, size) < 0) {
		xfree(out);
		return (NULL);
	}
	return (out);
}

int
imap_bad(struct account *a, const char *line)
{
	log_warnx("%s: unexpected data: %s", a->name, line);
	return (FETCH_ERROR);
}

int
imap_invalid(struct account *a, const char *line)
{
	log_warnx("%s: invalid response: %s", a->name, line);
	return (FETCH_ERROR);
}

/* Commit mail. */
int
imap_commit(struct account *a, struct mail *m)
{
	struct fetch_imap_data	*data = a->data;
	struct fetch_imap_mail	*aux = m->auxdata;

	if (m->decision == DECISION_DROP) {
		TAILQ_INSERT_TAIL(&data->dropped, aux, entry);
	} else {
		ARRAY_ADD(&data->kept, aux->uid);
		xfree(aux);

		data->committed++;
	}
	m->auxdata = m->auxfree = NULL;

	return (FETCH_AGAIN);
}

/* Abort fetch. */
void
imap_abort(struct account *a)
{
	struct fetch_imap_data	*data = a->data;
	struct fetch_imap_mail	*aux;

	while (!TAILQ_EMPTY(&data->dropped)) {
		aux = TAILQ_FIRST(&data->dropped);
		TAILQ_REMOVE(&data->dropped, aux, entry);
		imap_free(aux);
	}

	ARRAY_FREE(&data->kept);

	data->disconnect(a);
}

/* Return total mails available. */
u_int
imap_total(struct account *a)
{
	struct fetch_imap_data	*data = a->data;

	return (data->total);
}

/* Common initialisatio state. */
int
imap_state_init(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;

 	TAILQ_INIT(&data->dropped);
	ARRAY_INIT(&data->kept);

	data->tag = 0;

	fctx->state = imap_state_connect;
	return (FETCH_AGAIN);
}

/* Connect state. */
int
imap_state_connect(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;

	if (data->connect(a) != 0)
		return (FETCH_ERROR);

	fctx->state = imap_state_connected;
	return (FETCH_BLOCK);
}

/* Connected state: wait for initial line from server. */
int
imap_state_connected(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_UNTAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	if (strncmp(line, "* PREAUTH", 9) == 0) {
		fctx->state = imap_state_select1;
		return (FETCH_AGAIN);
	}
	if (data->user == NULL || data->pass == NULL) {
		log_warnx("%s: not PREAUTH and no user or password", a->name);
		return (FETCH_ERROR);
	}

	if (imap_putln(a, "%u CAPABILITY", ++data->tag) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_capability1;
	return (FETCH_BLOCK);
}

/* Capability state 1. Parse capabilities and set flags. */
int
imap_state_capability1(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_UNTAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	data->capa = 0;
	if (strstr(line, "AUTH=CRAM-MD5") != NULL)
		data->capa |= IMAP_CAPA_AUTH_CRAM_MD5;

	fctx->state = imap_state_capability2;
	return (FETCH_AGAIN);
}

/* Capability state 2. Check capabilities and choose login type. */
int
imap_state_capability2(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	if (data->capa & IMAP_CAPA_AUTH_CRAM_MD5) {
		if (imap_putln(a,
		    "%u AUTHENTICATE CRAM-MD5", ++data->tag) != 0)
			return (FETCH_ERROR);
		fctx->state = imap_state_cram_md5_auth;
		return (FETCH_BLOCK);
	}

	if (imap_putln(a,
	    "%u LOGIN {%zu}", ++data->tag, strlen(data->user)) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_login;
	return (FETCH_BLOCK);
}

/* CRAM-MD5 auth state. */
int
imap_state_cram_md5_auth(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line, *ptr, *src, *b64;
	char			 out[EVP_MAX_MD_SIZE * 2 + 1];
	u_char			 digest[EVP_MAX_MD_SIZE];
	u_int			 i, n;

	if (imap_getln(a, fctx, IMAP_CONTINUE, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	ptr = line +  1;
	while (isspace((u_char) *ptr))
		ptr++;
	if (*ptr == '\0')
		return (imap_invalid(a, line));

	b64 = imap_base64_decode(ptr);
	HMAC(EVP_md5(),
	    data->pass, strlen(data->pass), b64, strlen(b64), digest, &n);
	xfree(b64);

	for (i = 0; i < n; i++)
		xsnprintf(out + i * 2, 3, "%02hhx", digest[i]);
	xasprintf(&src, "%s %s", data->user, out);
	b64 = imap_base64_encode(src);
	xfree(src);

	if (imap_putln(a, "%s", b64) != 0) {
		xfree(b64);
		return (FETCH_ERROR);
	}
	xfree(b64);

	fctx->state = imap_state_pass;
	return (FETCH_BLOCK);
}

/* Login state. */
int
imap_state_login(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_CONTINUE, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	if (imap_putln(a, "%s {%zu}", data->user, strlen(data->pass)) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_user;
	return (FETCH_BLOCK);
}

/* User state. */
int
imap_state_user(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_CONTINUE, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	if (imap_putln(a, "%s", data->pass) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_pass;
	return (FETCH_BLOCK);
}

/* Pass state. */
int
imap_state_pass(struct account *a, struct fetch_ctx *fctx)
{
	char	*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	fctx->state = imap_state_select1;
	return (FETCH_AGAIN);
}

/* Select state 1. */
int
imap_state_select1(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;

	if (imap_putln(a,
	    "%u SELECT {%zu}", ++data->tag, strlen(data->folder)) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_select2;
	return (FETCH_BLOCK);
}

/* Select state 2. Wait for continuation and send folder name. */
int
imap_state_select2(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_CONTINUE, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	if (imap_putln(a, "%s", data->folder) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_select3;
	return (FETCH_BLOCK);
}

/* Select state 3. Hold until select returns message count. */
int
imap_state_select3(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	for (;;) {
		if (imap_getln(a, fctx, IMAP_UNTAGGED, &line) != 0)
			return (FETCH_ERROR);
		if (line == NULL)
			return (FETCH_BLOCK);

		if (sscanf(line, "* %u EXISTS", &data->num) == 1)
			break;
	}
	data->cur = 0;

	/* Save total, if no previous total. */
	if (data->total == 0) {
		data->total = data->num;

		/*
		 * If not reconnecting and a subset of mail is required,
		 * skip to search for the right flags.
		 */
		if (data->only != FETCH_ONLY_ALL) {
			fctx->state = imap_state_search1;
			return (FETCH_AGAIN);
		}
	}

	fctx->state = imap_state_select4;
	return (FETCH_AGAIN);
}

/* Select state 4. Hold until select completes then get next mail. */
int
imap_state_select4(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	/* If polling, stop here. */
	if (fctx->flags & FETCH_POLL) {
		if (imap_putln(a, "%u CLOSE", ++data->tag) != 0)
			return (FETCH_ERROR);
		fctx->state = imap_state_quit1;
		return (FETCH_BLOCK);
	}

	fctx->state = imap_state_next;
	return (FETCH_AGAIN);
}

/* Search state 1. Request list of mail required. */
int
imap_state_search1(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	/* Search for a list of the mail UIDs we want to ignore. */
	if (data->only == FETCH_ONLY_NEW) {
		if (imap_putln(a, "%u UID SEARCH SEEN", ++data->tag) != 0)
			return (FETCH_ERROR);
	} else {
		if (imap_putln(a, "%u UID SEARCH UNSEEN", ++data->tag) != 0)
			return (FETCH_ERROR);
	}

	fctx->state = imap_state_search2;
	return (FETCH_BLOCK);
}

/* Search state 2. */
int
imap_state_search2(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line, *ptr;
	u_int			 uid;

	if (imap_getln(a, fctx, IMAP_UNTAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	/* Skip the header. */
	if (strncasecmp(line, "* SEARCH", 8) != 0)
		return (imap_bad(a, line));
	line += 8;

	/* Read each UID and save it. */
	do {
		while (isspace((u_char) *line))
			line++;
		ptr = strchr(line, ' ');
		if (ptr == NULL)
			ptr = strchr(line, '\0');
		if (ptr == line)
			break;

		if (sscanf(line, "%u", &uid) != 1)
			return (imap_bad(a, line));
		ARRAY_ADD(&data->kept, uid);
		log_debug3("%s: skipping UID: %u", a->name, uid);

		line = ptr;
	} while (*line == ' ');

	fctx->state = imap_state_search3;
	return (FETCH_AGAIN);
}

/* Search state 3. */
int
imap_state_search3(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	/* Adjust the total. */
	data->total -= ARRAY_LENGTH(&data->kept);

	/* If no mails left, or polling, stop here. */
	if (data->total == 0 || fctx->flags & FETCH_POLL) {
		if (imap_putln(a, "%u CLOSE", ++data->tag) != 0)
			return (FETCH_ERROR);
		fctx->state = imap_state_quit1;
		return (FETCH_BLOCK);
	}

	fctx->state = imap_state_next;
	return (FETCH_AGAIN);
}

/*
 * Next state. Get next mail. This is also the idle state when completed, so
 * check for finished mail, exiting, and so on.
 */
int
imap_state_next(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	struct fetch_imap_mail	*aux;

	/* Handle dropped mail. */
	if (!TAILQ_EMPTY(&data->dropped)) {
		aux = TAILQ_FIRST(&data->dropped);

		if (imap_putln(a,
		    "%u STORE %u +FLAGS \\Deleted", ++data->tag, aux->idx) != 0)
			return (FETCH_ERROR);
		fctx->state = imap_state_delete;
		return (FETCH_BLOCK);
	}

	/* Need to purge, switch to purge state. */
	if (fctx->flags & FETCH_PURGE) {
		/*
		 * If can't purge now, loop through this state until there is
		 * no mail on the dropped queue and FETCH_EMPTY is set. Can't
		 * have a seperate state to loop through without returning
		 * here: mail could potentially be added to the dropped list
		 * while in that state.
		 */
		if (fctx->flags & FETCH_EMPTY) {
			fctx->flags &= ~FETCH_PURGE;

			if (imap_putln(a, "%u EXPUNGE", ++data->tag) != 0)
				return (FETCH_ERROR);
			fctx->state = imap_state_expunge;
			return (FETCH_BLOCK);
		}

		/*
		 * Must be waiting for delivery, so permit blocking even though
		 * we (fetch) aren't waiting for any data.
		 */
		return (FETCH_BLOCK);
	}

	/* Move to the next mail if possible. */
	if (data->cur <= data->num)
		data->cur++;

	/* If last mail, wait for everything to be committed then close down. */
	if (data->cur > data->num) {
		if (data->committed != data->total)
			return (FETCH_BLOCK);
		if (imap_putln(a, "%u CLOSE", ++data->tag) != 0)
			return (FETCH_ERROR);
		fctx->state = imap_state_quit1;
		return (FETCH_BLOCK);
	}

	/* List the next mail. */
	if (imap_putln(a, "%u FETCH %u UID", ++data->tag, data->cur) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_uid1;
	return (FETCH_BLOCK);
}

/* UID state 1. */
int
imap_state_uid1(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;
	u_int			 n;

	if (imap_getln(a, fctx, IMAP_UNTAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	if (sscanf(line, "* %u FETCH (UID %u)", &n, &data->uid) != 2)
		return (imap_invalid(a, line));
	if (n != data->cur)
		return (imap_bad(a, line));

	fctx->state = imap_state_uid2;
	return (FETCH_AGAIN);
}

/* UID state 2. */
int
imap_state_uid2(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;
	u_int			 i;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	for (i = 0; i < ARRAY_LENGTH(&data->kept); i++) {
		if (ARRAY_ITEM(&data->kept, i) == data->uid) {
			/* Had this message before and kept, so skip. */
			fctx->state = imap_state_next;
			return (FETCH_AGAIN);
		}
	}

	if (imap_putln(a, "%u FETCH %u BODY[]", ++data->tag, data->cur) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_body;
	return (FETCH_BLOCK);
}

/* Body state. */
int
imap_state_body(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	struct mail		*m = fctx->mail;
	struct fetch_imap_mail	*aux;
	char			*line, *ptr;
	u_int			 n;

	if (imap_getln(a, fctx, IMAP_UNTAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);

	if (sscanf(line, "* %u FETCH (", &n) != 1)
		return (imap_invalid(a, line));
	if ((ptr = strstr(line, "BODY[] {")) == NULL)
		return (imap_invalid(a, line));

	if (sscanf(ptr, "BODY[] {%zu}", &data->size) != 1)
		return (imap_invalid(a, line));
	if (n != data->cur)
		return (imap_bad(a, line));
	data->lines = 0;

	/* Fill in local data. */
	aux = xcalloc(1, sizeof *aux);
	aux->idx = data->cur;
	aux->uid = data->uid;
	m->auxdata = aux;
	m->auxfree = imap_free;

	/* Open the mail. */
	if (mail_open(m, data->size) != 0) {
		log_warn("%s: failed to create mail", a->name);
		return (FETCH_ERROR);
	}
	m->size = 0;

	/* Tag mail. */
	default_tags(&m->tags, data->src);
	if (data->server.host != NULL) {
		add_tag(&m->tags, "server", "%s", data->server.host);
		add_tag(&m->tags, "port", "%s", data->server.port);
	}
	add_tag(&m->tags, "server_uid", "%u", data->uid);
	add_tag(&m->tags, "folder", "%s", data->folder);

	/* If we already know the mail is oversize, start off flushing it. */
	data->flushing = data->size > conf.max_size;

	fctx->state = imap_state_line;
	return (FETCH_AGAIN);
}

/* Line state. */
int
imap_state_line(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	struct mail		*m = fctx->mail;
	char			*line;
	size_t			 used, size, left;

	for (;;) {
		if (imap_getln(a, fctx, IMAP_RAW, &line) != 0)
			return (FETCH_ERROR);
		if (line == NULL)
			return (FETCH_BLOCK);

		if (data->flushing)
			continue;

		/* Check if this line would exceed the expected size. */
		used = m->size + data->lines;
		size = strlen(line);
		if (used + size + 2 > data->size)
			break;

		if (append_line(m, line, size) != 0) {
			log_warn("%s: failed to resize mail", a->name);
			return (FETCH_ERROR);
		}
		data->lines++;
	}

	/*
	 * Calculate the number of bytes still needed. The current line must be
	 * those bytes plus a trailing close bracket.
	 */
	left = data->size - used;
	if (size != left + 1)
		return (imap_invalid(a, line));
	if (line[left] != ')' || line[left + 1] != '\0')
		return (imap_invalid(a, line));

	/* If there was data left, add it as a new line without trailing \n. */
	if (left > 0) {
		if (append_line(m, line, left) != 0) {
			log_warn("%s: failed to resize mail", a->name);
			return (FETCH_ERROR);
		}
		data->lines++;

		/* Wipe out the trailing \n. */
		m->size--;
	}

	fctx->state = imap_state_mail;
	return (FETCH_AGAIN);
}

/* Mail state. */
int
imap_state_mail(struct account *a, struct fetch_ctx *fctx)
{
	char	*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	fctx->state = imap_state_next;
	return (FETCH_MAIL);
}

/* Delete state. */
int
imap_state_delete(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	struct fetch_imap_mail	*aux;
	char			*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	aux = TAILQ_FIRST(&data->dropped);
	TAILQ_REMOVE(&data->dropped, aux, entry);
	imap_free(aux);

	data->committed++;

	fctx->state = imap_state_next;
	return (FETCH_AGAIN);
}

/* Expunge state. */
int
imap_state_expunge(struct account *a, struct fetch_ctx *fctx)
{
	char	*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	fctx->state = imap_state_select1;
	return (FETCH_AGAIN);
}

/* Quit state 1. */
int
imap_state_quit1(struct account *a, struct fetch_ctx *fctx)
{
	struct fetch_imap_data	*data = a->data;
	char			*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	if (imap_putln(a, "%u LOGOUT", ++data->tag) != 0)
		return (FETCH_ERROR);
	fctx->state = imap_state_quit2;
	return (FETCH_BLOCK);
}

/* Quit state 2. */
int
imap_state_quit2(struct account *a, struct fetch_ctx *fctx)
{
	char	*line;

	if (imap_getln(a, fctx, IMAP_TAGGED, &line) != 0)
		return (FETCH_ERROR);
	if (line == NULL)
		return (FETCH_BLOCK);
	if (!imap_okay(line))
		return (imap_bad(a, line));

	imap_abort(a);
	return (FETCH_EXIT);
}