/**

 * \file uid.c -- UIDL handling for POP3 servers without LAST

 *

 * For license terms, see the file COPYING in this directory.

 */

#include "config.h"

#include <sys/stat.h>

#include <errno.h>

#include <stdio.h>

#include <limits.h>

#if defined(STDC_HEADERS)

#include <stdlib.h>

#include <string.h>

#endif

#if defined(HAVE_UNISTD_H)

#include <unistd.h>

#endif

#include "fetchmail.h"

#include "i18n.h"

#include "sdump.h"

/*

 * Machinery for handling UID lists live here.  This is mainly to support

 * RFC1725/RFC1939-conformant POP3 servers without a LAST command, but may also

 * be useful for making the IMAP4 querying logic UID-oriented, if a future

 * revision of IMAP forces me to.

 *

 * These functions are also used by the rest of the code to maintain

 * string lists.

 *

 * Here's the theory:

 *

 * At start of a query, we have a (possibly empty) list of UIDs to be

 * considered seen in `oldsaved'.  These are messages that were left in

 * the mailbox and *not deleted* on previous queries (we don't need to

 * remember the UIDs of deleted messages because ... well, they're gone!)

 * This list is initially set up by initialize_saved_list() from the

 * .fetchids file.

 *

 * Early in the query, during the execution of the protocol-specific

 * getrange code, the driver expects that the host's `newsaved' member

 * will be filled with a list of UIDs and message numbers representing

 * the mailbox state.  If this list is empty, the server did

 * not respond to the request for a UID listing.

 *

 * Each time a message is fetched, we can check its UID against the

 * `oldsaved' list to see if it is old.

 *

 * Each time a message-id is seen, we mark it with MARK_SEEN.

 *

 * Each time a message is deleted, we mark its id UID_DELETED in the

 * `newsaved' member.  When we want to assert that an expunge has been

 * done on the server, we call expunge_uid() to register that all

 * deleted messages are gone by marking them UID_EXPUNGED.

 *

 * At the end of the query, the `newsaved' member becomes the

 * `oldsaved' list.  The old `oldsaved' list is freed.

 *

 * At the end of the fetchmail run, seen and non-EXPUNGED members of all

 * current `oldsaved' lists are flushed out to the .fetchids file to

 * be picked up by the next run.  If there are no un-expunged

 * messages, the file is deleted.

 *

 * One disadvantage of UIDL is that all the UIDs have to be downloaded

 * before a search for new messages can be done. Typically, new messages

 * are appended to mailboxes. Hence, downloading all UIDs just to download

 * a few new mails is a waste of bandwidth. If new messages are always at

 * the end of the mailbox, fast UIDL will decrease the time required to

 * download new mails.

 *

 * During fast UIDL, the UIDs of all messages are not downloaded! The first

 * unseen message is searched for by using a binary search on UIDs. UIDs

 * after the first unseen message are downloaded as and when needed.

 *

 * The advantages of fast UIDL are (this is noticeable only when the

 * mailbox has too many mails):

 *

 * - There is no need to download the UIDs of all mails right at the start.

 * - There is no need to save all the UIDs in memory separately in

 * `newsaved' list.

 * - There is no need to download the UIDs of seen mail (except for the

 * first binary search).

 * - The first new mail is downloaded considerably faster.

 *

 * The disadvantages are:

 *

 * - Since all UIDs are not downloaded, it is not possible to swap old and

 * new list. The current state of the mailbox is essentially a merged state

 * of old and new mails.

 * - If an intermediate mail has been temporarily refused (say, due to 4xx

 * code from the smtp server), this mail may not get downloaded.

 * - If 'flush' is used, such intermediate mails will also get deleted.

 *

 * The first two disadvantages can be overcome by doing a linear search

 * once in a while (say, every 10th poll). Also, with flush, fast UIDL

 * should be disabled.

 *

 * Note: some comparisons (those used for DNS address lists) are caseblind!

 */

int dofastuidl = 0;

#ifdef POP3_ENABLE

/** UIDs associated with un-queried hosts */

static struct idlist *scratchlist;

/** Read saved IDs from \a idfile and attach to each host in \a hostlist. */

void initialize_saved_lists(struct query *hostlist, const char *idfile)

{

    struct stat statbuf;

    FILE	*tmpfp;

    struct query *ctl;

    /* make sure lists are initially empty */

    for (ctl = hostlist; ctl; ctl = ctl->next) {

	ctl->skipped = (struct idlist *)NULL;

	ctl->oldsaved = (struct idlist *)NULL;

	ctl->newsaved = (struct idlist *)NULL;

	ctl->oldsavedend = &ctl->oldsaved;

    }

    errno = 0;

    /*

     * Croak if the uidl directory does not exist.

     * This probably means an NFS mount failed and we can't

     * see a uidl file that ought to be there.

     * Question: is this a portable check? It's not clear

     * that all implementations of lstat() will return ENOTDIR

     * rather than plain ENOENT in this case...

     */

    if (lstat(idfile, &statbuf) < 0) {

	if (errno == ENOTDIR)

	{

	    report(stderr, "lstat: %s: %s\n", idfile, strerror(errno));

	    exit(PS_IOERR);

	}

    }

    /* let's get stored message UIDs from previous queries */

    if ((tmpfp = fopen(idfile, "r")) != (FILE *)NULL)

    {

	char buf[POPBUFSIZE+1];

	char *host = NULL;	/* pacify -Wall */

	char *user;

	char *id;

	char *atsign;	/* temp pointer used in parsing user and host */

	char *delimp1;

	char saveddelim1;

	char *delimp2;

	char saveddelim2 = '\0';	/* pacify -Wall */

	while (fgets(buf, POPBUFSIZE, tmpfp) != (char *)NULL)

	{

	    /*

	     * At this point, we assume the bug has two fields -- a user@host 

	     * part, and an ID part. Either field may contain spurious @ signs.

	     * The previous version of this code presumed one could split at 

	     * the rightmost '@'.  This is not correct, as InterMail puts an 

	     * '@' in the UIDL.

	     */

	    /* first, skip leading spaces */

	    user = buf + strspn(buf, " \t");

	    /*

	     * First, we split the buf into a userhost part and an id

	     * part ... but id doesn't necessarily start with a '<',

	     * espescially if the POP server returns an X-UIDL header

	     * instead of a Message-ID, as GMX's (www.gmx.net) POP3

	     * StreamProxy V1.0 does.

	     *

	     * this is one other trick. The userhost part 

	     * may contain ' ' in the user part, at least in

	     * the lotus notes case.

	     * So we start looking for the '@' after which the

	     * host will follow with the ' ' separator with the id.

	     *

	     * XXX FIXME: There is a case this code cannot handle:

	     * the user name cannot have blanks after a '@'.

	     */

	    if ((delimp1 = strchr(user, '@')) != NULL &&

		(id = strchr(delimp1,' ')) != NULL)

	    {

	        for (delimp1 = id; delimp1 >= user; delimp1--)

		    if ((*delimp1 != ' ') && (*delimp1 != '\t'))

			break;

		/* 

		 * It should be safe to assume that id starts after

		 * the " " - after all, we're writing the " "

		 * ourselves in write_saved_lists() :-)

		 */

		id = id + strspn(id, " ");

		delimp1++; /* but what if there is only white space ?!? */

		/* we have at least one @, else we are not in this branch */

		saveddelim1 = *delimp1;		/* save char after token */

		*delimp1 = '\0';		/* delimit token with \0 */

		/* now remove trailing white space chars from id */

		if ((delimp2 = strpbrk(id, " \t\n")) != NULL ) {

		    saveddelim2 = *delimp2;

		    *delimp2 = '\0';

		}

		atsign = strrchr(user, '@');

		/* we have at least one @, else we are not in this branch */

		*atsign = '\0';

		host = atsign + 1;

		/* find proper list and save it */

		for (ctl = hostlist; ctl; ctl = ctl->next) {

		    if (strcasecmp(host, ctl->server.queryname) == 0

			    && strcasecmp(user, ctl->remotename) == 0) {

			save_str(&ctl->oldsaved, id, UID_SEEN);

			break;

		    }

		}

		/* 

		 * If it's not in a host we're querying,

		 * save it anyway.  Otherwise we'd lose UIDL

		 * information any time we queried an explicit

		 * subset of hosts.

		 */

		if (ctl == (struct query *)NULL) {

		    /* restore string */

		    *delimp1 = saveddelim1;

		    *atsign = '@';

		    if (delimp2 != NULL) {

			*delimp2 = saveddelim2;

		    }

		    save_str(&scratchlist, buf, UID_SEEN);

		}

	    }

	}

	fclose(tmpfp);	/* not checking should be safe, mode was "r" */

    }

    if (outlevel >= O_DEBUG)

    {

	struct idlist	*idp;

	for (ctl = hostlist; ctl; ctl = ctl->next)

	    {

		report_build(stdout, GT_("Old UID list from %s:"), 

			     ctl->server.pollname);

		idp = ctl->oldsaved;

		if (!idp)

		    report_build(stdout, GT_(" <empty>"));

		else for (idp = ctl->oldsaved; idp; idp = idp->next) {

		    char *t = sdump(idp->id, strlen(idp->id)-1);

		    report_build(stdout, " %s\n", t);

		    free(t);

		}

		report_complete(stdout, "\n");

	    }

	report_build(stdout, GT_("Scratch list of UIDs:"));

	if (!scratchlist)

		report_build(stdout, GT_(" <empty>"));

	else for (idp = scratchlist; idp; idp = idp->next) {

		char *t = sdump(idp->id, strlen(idp->id)-1);

		report_build(stdout, " %s\n", t);

		free(t);

	}

	report_complete(stdout, "\n");

    }

}

/** Assert that all UIDs marked deleted in query \a ctl have actually been

expunged. */

void expunge_uids(struct query *ctl)

{

    struct idlist *idl;

    for (idl = dofastuidl ? ctl->oldsaved : ctl->newsaved; idl; idl = idl->next)

	if (idl->val.status.mark == UID_DELETED)

	    idl->val.status.mark = UID_EXPUNGED;

}

static const char *str_uidmark(int mark)

{

	static char buf[20];

	switch(mark) {

		case UID_UNSEEN:

			return "UNSEEN";

		case UID_SEEN:

			return "SEEN";

		case UID_EXPUNGED:

			return "EXPUNGED";

		case UID_DELETED:

			return "DELETED";

		default:

			if (snprintf(buf, sizeof(buf), "MARK=%d", mark) < 0)

				return "ERROR";

			else

				return buf;

	}

}

static void dump_list(const struct idlist *idp)

{

	if (!idp) {

		report_build(stdout, GT_(" <empty>"));

	} else while (idp) {

	    char *t = sdump(idp->id, strlen(idp->id));

	    report_build(stdout, " %s = %s%s", t, str_uidmark(idp->val.status.mark), idp->next ? "," : "");

	    free(t);

	    idp = idp->next;

	}

}

/* finish a query */

void uid_swap_lists(struct query *ctl) 

{

    /* debugging code */

    if (outlevel >= O_DEBUG)

    {

	if (dofastuidl) {

	    report_build(stdout, GT_("Merged UID list from %s:"), ctl->server.pollname);

	    dump_list(ctl->oldsaved);

	} else {

	    report_build(stdout, GT_("New UID list from %s:"), ctl->server.pollname);

	    dump_list(ctl->newsaved);

	}

	report_complete(stdout, "\n");

    }

    /*

     * Don't swap UID lists unless we've actually seen UIDLs.

     * This is necessary in order to keep UIDL information

     * from being heedlessly deleted later on.

     *

     * Older versions of fetchmail did

     *

     *     free_str_list(&scratchlist);

     *

     * after swap.  This was wrong; we need to preserve the UIDL information

     * from unqueried hosts.  Unfortunately, not doing this means that

     * under some circumstances UIDLs can end up being stored forever --

     * specifically, if a user description is removed from .fetchmailrc

     * with UIDLs from that account in .fetchids, there is no way for

     * them to ever get garbage-collected.

     */

    if (ctl->newsaved)

    {

	/* old state of mailbox may now be irrelevant */

	struct idlist *temp = ctl->oldsaved;

	if (outlevel >= O_DEBUG)

	    report(stdout, GT_("swapping UID lists\n"));

	ctl->oldsaved = ctl->newsaved;

	ctl->newsaved = (struct idlist *) NULL;

	free_str_list(&temp);

    }

    /* in fast uidl, there is no need to swap lists: the old state of

     * mailbox cannot be discarded! */

    else if (outlevel >= O_DEBUG && !dofastuidl)

	report(stdout, GT_("not swapping UID lists, no UIDs seen this query\n"));

}

/* finish a query which had errors */

void uid_discard_new_list(struct query *ctl)

{

    /* debugging code */

    if (outlevel >= O_DEBUG)

    {

	/* this is now a merged list! the mails which were seen in this

	 * poll are marked here. */

	report_build(stdout, GT_("Merged UID list from %s:"), ctl->server.pollname);

	dump_list(ctl->oldsaved);

	report_complete(stdout, "\n");

    }

    if (ctl->newsaved)

    {

	/* new state of mailbox is not reliable */

	if (outlevel >= O_DEBUG)

	    report(stdout, GT_("discarding new UID list\n"));

	free_str_list(&ctl->newsaved);

	ctl->newsaved = (struct idlist *) NULL;

    }

}

/** Reset the number associated with each id */

void uid_reset_num(struct query *ctl)

{

    struct idlist *idp;

    for (idp = ctl->oldsaved; idp; idp = idp->next)

	idp->val.status.num = 0;

}

/** Write list of seen messages, at end of run. */

void write_saved_lists(struct query *hostlist, const char *idfile)

{

    long	idcount;

    FILE	*tmpfp;

    struct query *ctl;

    struct idlist *idp;

    /* if all lists are empty, nuke the file */

    idcount = 0;

    for (ctl = hostlist; ctl; ctl = ctl->next) {

	for (idp = ctl->oldsaved; idp; idp = idp->next)

	    if (idp->val.status.mark == UID_SEEN

		    || idp->val.status.mark == UID_DELETED)

		idcount++;

    }

    /* either nuke the file or write updated last-seen IDs */

    if (!idcount && !scratchlist)

    {

	if (outlevel >= O_DEBUG) {

	    if (access(idfile, F_OK) == 0)

		    report(stdout, GT_("Deleting fetchids file.\n"));

	}

	if (unlink(idfile) && errno != ENOENT)

	    report(stderr, GT_("Error deleting %s: %s\n"), idfile, strerror(errno));

    } else {

	char *newnam = (char *)xmalloc(strlen(idfile) + 2);

	strcpy(newnam, idfile);

	strcat(newnam, "_");

	if (outlevel >= O_DEBUG)

	    report(stdout, GT_("Writing fetchids file.\n"));

	(void)unlink(newnam); /* remove file/link first */

	if ((tmpfp = fopen(newnam, "w")) != (FILE *)NULL) {

	    int errflg = 0;

	    for (ctl = hostlist; ctl; ctl = ctl->next) {

		for (idp = ctl->oldsaved; idp; idp = idp->next)

		    if (idp->val.status.mark == UID_SEEN

				|| idp->val.status.mark == UID_DELETED)

			if (fprintf(tmpfp, "%s@%s %s\n",

			    ctl->remotename, ctl->server.queryname, idp->id) < 0) {

			    int e = errno;

			    report(stderr, GT_("Write error on fetchids file %s: %s\n"), newnam, strerror(e));

			    errflg = 1;

			    goto bailout;

			}

	    }

	    for (idp = scratchlist; idp; idp = idp->next)

		if (EOF == fputs(idp->id, tmpfp)) {

			    int e = errno;

			    report(stderr, GT_("Write error on fetchids file %s: %s\n"), newnam, strerror(e));

			    errflg = 1;

			    goto bailout;

		}

bailout:

	    (void)fflush(tmpfp); /* return code ignored, we check ferror instead */

	    errflg |= ferror(tmpfp);

	    fclose(tmpfp);

	    /* if we could write successfully, move into place;

	     * otherwise, drop */

	    if (errflg) {

		report(stderr, GT_("Error writing to fetchids file %s, old file left in place.\n"), newnam);

		unlink(newnam);

	    } else {

		if (rename(newnam, idfile)) {

		    report(stderr, GT_("Cannot rename fetchids file %s to %s: %s\n"), newnam, idfile, strerror(errno));

		}

	    }

	} else {

	    report(stderr, GT_("Cannot open fetchids file %s for writing: %s\n"), newnam, strerror(errno));

	}

	free(newnam);

    }

}

#endif /* POP3_ENABLE */

/* uid.c ends here */