/* Copyright (c) 2015-2017 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "ioloop.h"
#include "file-create-locked.h"
#include "mailbox-list-iter.h"
#include "mail-storage-private.h"
#include "mail-namespace.h"
#include "mail-user.h"
#include "mail-autoexpunge.h"

#define AUTOEXPUNGE_LOCK_FNAME "dovecot.autoexpunge.lock"

struct mailbox_autoexpunge_lock {
	const char *path;
	struct file_lock *lock;
	int fd;
};

static bool mailbox_autoexpunge_lock(struct mail_user *user,
				     struct mailbox_autoexpunge_lock *lock)
{
	struct file_create_settings lock_set;
	bool created;
	const char *home, *error;
	int ret;

	if (lock->fd != -1)
		return TRUE;

	/* Try to lock the autoexpunging. If the lock already exists, another
	   process is already busy with expunging, so we don't have to do it.
	   The easiest place where to store the lock file to is the home
	   directory, but allow autoexpunging to work even if we can't get
	   it. The lock isn't really required; it 1) improves performance
	   so that multiple processes won't do the same work unnecessarily,
	   and 2) it helps to avoid duplicate mails being added with
	   lazy_expunge. */
	if ((ret = mail_user_get_home(user, &home)) > 0) {
		const struct mail_storage_settings *mail_set =
			mail_user_set_get_storage_set(user);
		i_zero(&lock_set);
		lock_set.lock_method = mail_set->parsed_lock_method,
		lock->path = t_strdup_printf("%s/"AUTOEXPUNGE_LOCK_FNAME, home);
		lock->fd = file_create_locked(lock->path, &lock_set,
					      &lock->lock, &created, &error);
		if (lock->fd == -1) {
			if (errno == EAGAIN)
				return FALSE;
			if (errno != ENOENT)
				i_error("autoexpunge: Couldn't lock %s: %s", lock->path, error);
			return TRUE;
		}
	} else if (ret == 0) {
		i_warning("autoexpunge: User has no home directory, can't lock");
	}
	return TRUE;
}

static int
mailbox_autoexpunge(struct mailbox *box, unsigned int interval_time,
		    unsigned int max_mails)
{
	struct mailbox_transaction_context *t;
	struct mail *mail;
	struct mailbox_metadata metadata;
	const struct mail_index_header *hdr;
	struct mailbox_status status;
	uint32_t seq;
	time_t timestamp, expire_time, last_rename_stamp = 0;
	const void *data;
	size_t size;
	int ret = 0;

	if ((unsigned int)ioloop_time < interval_time)
		expire_time = 0;
	else
		expire_time = ioloop_time - interval_time;

	/* first try to check quickly from mailbox list index if we should
	   bother opening this mailbox. */
	if (mailbox_get_status(box, STATUS_MESSAGES, &status) < 0) {
		if (mailbox_get_last_mail_error(box) == MAIL_ERROR_NOTFOUND) {
			/* autocreated mailbox doesn't exist yet */
			return 0;
		}
		return -1;
	}
	if (interval_time == 0 && status.messages <= max_mails)
		return 0;

	if (max_mails == 0 || status.messages <= max_mails) {
		if (mailbox_get_metadata(box, MAILBOX_METADATA_FIRST_SAVE_DATE,
					 &metadata) < 0)
			return -1;
		if (metadata.first_save_date == (time_t)-1 ||
		    metadata.first_save_date > expire_time)
			return 0;
	}

	if (mailbox_sync(box, MAILBOX_SYNC_FLAG_FAST) < 0)
		return -1;

	mail_index_get_header_ext(box->view, box->box_last_rename_stamp_ext_id,
				  &data, &size);

	if (size >= sizeof(uint32_t))
		last_rename_stamp = *(const uint32_t*)data;

	t = mailbox_transaction_begin(box, 0);
	mail = mail_alloc(t, 0, NULL);

	hdr = mail_index_get_header(box->view);
	for (seq = 1; seq <= hdr->messages_count; seq++) {
		mail_set_seq(mail, seq);
		if (max_mails > 0 && hdr->messages_count - seq + 1 > max_mails) {
			/* max_mails is still being reached -> expunge.
			   don't even check saved-dates before we're
			   below max_mails. */
			mail_expunge(mail);
		} else if (interval_time == 0) {
			/* only max_mails is used. nothing further to do. */
			break;
		} else if (mail_get_save_date(mail, &timestamp) == 0) {
			if (I_MAX(last_rename_stamp, timestamp) > expire_time)
				break;
			mail_expunge(mail);
		} else if (mailbox_get_last_mail_error(box) == MAIL_ERROR_EXPUNGED) {
			/* already expunged */
		} else {
			/* failed */
			ret = -1;
			break;
		}
	}
	mail_free(&mail);
	if (mailbox_transaction_commit(&t) < 0)
		ret = -1;
	return ret;
}

static void
mailbox_autoexpunge_set(struct mail_namespace *ns, const char *vname,
			unsigned int autoexpunge,
			unsigned int autoexpunge_max_mails)
{
	struct mailbox *box;

	/* autoexpunge is configured by admin, so we can safely ignore
	   any ACLs the user might normally have against expunging in
	   the mailbox. */
	box = mailbox_alloc(ns->list, vname, MAILBOX_FLAG_IGNORE_ACLS);
	if (mailbox_autoexpunge(box, autoexpunge, autoexpunge_max_mails) < 0) {
		i_error("Failed to autoexpunge mailbox '%s': %s",
			mailbox_get_vname(box),
			mailbox_get_last_error(box, NULL));
	}
	mailbox_free(&box);
}

static void
mailbox_autoexpunge_wildcards(struct mail_namespace *ns,
			      const struct mailbox_settings *set)
{
	struct mailbox_list_iterate_context *iter;
	const struct mailbox_info *info;
	const char *iter_name;

	iter_name = t_strconcat(ns->prefix, set->name, NULL);
	iter = mailbox_list_iter_init(ns->list, iter_name,
				      MAILBOX_LIST_ITER_NO_AUTO_BOXES |
				      MAILBOX_LIST_ITER_SKIP_ALIASES |
				      MAILBOX_LIST_ITER_RETURN_NO_FLAGS);
	while ((info = mailbox_list_iter_next(iter)) != NULL) T_BEGIN {
		mailbox_autoexpunge_set(ns, info->vname, set->autoexpunge,
					set->autoexpunge_max_mails);
	} T_END;
	if (mailbox_list_iter_deinit(&iter) < 0) {
		i_error("Failed to iterate autoexpunge mailboxes '%s': %s",
			iter_name, mailbox_list_get_last_error(ns->list, NULL));
	}
}

static bool
mail_namespace_autoexpunge(struct mail_namespace *ns,
			   struct mailbox_autoexpunge_lock *lock)
{
	struct mailbox_settings *const *box_set;
	const char *vname;

	if (!array_is_created(&ns->set->mailboxes))
		return TRUE;

	array_foreach(&ns->set->mailboxes, box_set) {
		if ((*box_set)->autoexpunge == 0 &&
		    (*box_set)->autoexpunge_max_mails == 0)
			continue;

		if (!mailbox_autoexpunge_lock(ns->user, lock))
			return FALSE;

		if (strpbrk((*box_set)->name, "*?") != NULL)
			mailbox_autoexpunge_wildcards(ns, *box_set);
		else {
			if ((*box_set)->name[0] == '\0' && ns->prefix_len > 0 &&
			    ns->prefix[ns->prefix_len-1] == mail_namespace_get_sep(ns))
				vname = t_strndup(ns->prefix, ns->prefix_len - 1);
			else
				vname = t_strconcat(ns->prefix, (*box_set)->name, NULL);
			mailbox_autoexpunge_set(ns, vname, (*box_set)->autoexpunge,
						(*box_set)->autoexpunge_max_mails);
		}
	}
	return TRUE;
}

void mail_user_autoexpunge(struct mail_user *user)
{
	struct mailbox_autoexpunge_lock lock = { .fd = -1 };
	struct mail_namespace *ns;

	for (ns = user->namespaces; ns != NULL; ns = ns->next) {
		if (ns->alias_for == NULL) {
			if (!mail_namespace_autoexpunge(ns, &lock))
				break;
		}
	}
	if (lock.fd != -1) {
		i_unlink(lock.path);
		i_close_fd(&lock.fd);
		file_lock_free(&lock.lock);
	}
}