.Dd Jan 6, 2023
.Dt IMAPFILTER_CONFIG 5
.Os
.Sh NAME
.Nm imapfilter_config
.Nd imapfilter configuration file
.Sh SYNOPSIS
.Pa $HOME/.imapfilter/config.lua
.Sh DESCRIPTION
.Xr imapfilter 1
uses the Lua programming language as a configuration and extension language,
therefore, the configuration file is a Lua script.
.Pp
Although knowledge of Lua is not required to use
.Xr imapfilter 1 ,
it is nonetheless recommended, especially if one wants to extend it. For more
information on Lua see
.Ad http://www.lua.org/docs.html .
.Sh CONVENTIONS
.Pp
A brief description of the Lua values and types mentioned hereafter in the
manual page follows:
.Bl -item -offset 4n
.It
The
.Vt nil
is the type of the value
.Dq nil ,
whose main property is to be different from any other value; usually it
represents the absence of a useful value.
.It
The
.Vt boolean
is the type of the values
.Dq true
and
.Dq false .
Both
.Dq nil
and
.Dq false
make a condition false; any other value makes it true.
.It
The type
.Vt number
represents real numbers.
.It
The type
.Vt string
represents a sequence of characters and can be defined using single quotes,
double quotes or double square brackets.
.It
The type
.Vt table
implements associative arrays, that is, arrays that can be indexed not only
with numbers, but with any value.
.It
A
.Vt function
is a first-class value; it can be stored in variables, passed as argument to
other functions, and returned as a result.
.El
.Sh OPTIONS
Program's options are set using an already initialised
.Vt table
named
.Dq options ,
in the following manner:
.Bd -literal -offset 4n
options.timeout = 120
options.namespace = false
options.charset = 'ISO-8859-1'
.Ed
.Pp
Available options are:
.Bl -tag -width Ds
.It Va cache
When this option is enabled, parts of messages are cached locally in memory to
avoid being downloaded more than once.  The cache is preserved for the current
session only. This variable takes a
.Vt boolean
as a value. Default is
.Dq true .
.It Va certificates
When this option is enabled, the server certificate can be accepted and stored,
to validate the authenticity of the server in future connections. This
variable takes a
.Vt boolean
as a value. Default is
.Dq true .
.It Va charset
Indicates to the server the character set of the strings for the searching
methods.  This variable takes a
.Vt string
as a value.  By default, no character set is set, and thus plain ASCII should be
assumed by the server.
.It Va create
According to the IMAP specification, when trying to write a message to a
non-existent mailbox, the server must send a hint to the client, whether it
should create the mailbox and try again or not. However, some IMAP servers don't
follow the specification and don't send the correct response code to the
client. By enabling this option the client tries to create the mailbox, despite
of the server's response. This variable takes a
.Vt boolean
as a value.  Default is
.Dq false .
.It Va close
This option controls whether the currently selected mailbox is implicitly
closed at the end of each performed operation, thus removing all messages that
are marked deleted. This variable takes a
.Vt boolean
as a value.  Default is
.Dq false .
.It Va expunge
Normally, messages are marked for deletion and are actually deleted when the
mailbox is closed.  When this option is enabled, messages are expunged
immediately after being marked deleted.  This variable takes a
.Vt boolean
as a value.  Default is
.Dq true .
.It Va hostnames
When this option is enabled, the server hostname is validated, in
order to verify the client is talking to the correct server. This variable
takes a
.Vt boolean
as a value. Default is
.Dq true .
.It Va info
When this option is enabled, a summary of the program's actions is printed,
while processing mailboxes.  This variable takes a
.Vt boolean
as a value.  Default is
.Dq true .
.It Va keepalive
The time in minutes before terminating and re-issuing the IDLE command, in
order to keep alive the connection, by resetting the inactivity timeout of the
server.  A standards compliant server must have an inactivity timeout of at
least 30 minutes.  But some IMAP servers might not respect that,
or some intermediary network device has a shorter timeout.  By setting this
option the above problem can be worked around. This variable takes a
.Vt number
as a value. Default is
.Dq 29
minutes.
.It Va limit
Some servers have problems handling very long requests, but some of the
requests that need to be sent can become quite long because they apply an
action for many messages at once.  When this option is set, the client will try
to break up these requests into smaller requests, that each operates on fewer
messages at a time.  A good value for this would be
.Dq 50 .
This variable takes a
.Vt number
as a value.  Default is
.Dq 0 .
See also the
.Va range
option which is related.
.It Va namespace
When enabled, the program gets the namespace of the user's personal mailboxes,
and applies automatically the prefix and hierarchy delimiter to any mailboxes
residing on the mail server; the user must use the
.Sq /
character as the delimiter and
.Dq
(i.e.  nothing) as the prefix, regardless of the folder
format of the mail server.  This must be disabled, if the user wants to
manually specify mailbox names (e.g. because they are not part of the user's
personal namespace mailboxes).  This variable takes a
.Vt boolean
as a value.  Default is
.Dq true .
.It Va range
Some servers have problems handling long sequence number ranges, and by setting
this option, the number of messages included in each range can be limited.  A
good value for this would be
.Dq 50 .
This variable takes a
.Vt number
as a value.  By default, no such limit is imposed.  See also the
.Va limit
option which is related.
.It Va starttls
When this option is enabled and the server supports the IMAP STARTTLS
extension, a TLS connection will be negotiated with the mail server in the
beginning of the session.  This variable takes a
.Vt boolean
as value.  Default is
.Dq true .
.It Va subscribe
By enabling this option new mailboxes that were automatically created, get also
subscribed; they are set active in order for IMAP clients to recognize them.
This variable takes a
.Vt boolean
as a value.  Default is
.Dq false .
.It Va timeout
The time in seconds for the program to wait for a mail server's response.  If
set to 0, the client will block indefinitely.  This variable takes a
.Vt number
as a value.  Default is
.Dq 60
seconds.
.It Va wakeonany
By enabling this option, the IDLE command will return on any event that is
received from the server, and not just on the
.Dq RECENT
and
.Dq EXISTS
events, that normally indicate the arrival of a new message.  Examples of other
events are
.Dq FETCH ,
which indicates that the details of a message (e.g. its flags) have been
modified, or
.Dq EXPUNGE ,
which indicates that a message has been deleted.  This variable takes a
.Vt boolean
as a value.  Default is
.Dq false .
.El
.Sh ACCOUNTS
Accounts are initialized using the
.Fn IMAP
function, and the details of the connection are defined using an account
.Vt table :
.Bd -literal -offset 4n
myaccount = IMAP {
    server = 'imap.mail.server',
    username = 'me',
    password = 'secret',
    ssl = 'auto'
}
.Ed
.Pp
An account
.Vt table
must have the following elements:
.Bl -tag -width Ds
.It Va server
The hostname of the IMAP server to connect to.  It takes a
.Vt string
as a value.
.It Va username
User's name.  It takes a
.Vt string
as a value.
.El
.Pp
An account
.Vt table
can also have the following optional elements:
.Bl -tag -width Ds
.It Va password
User's secret keyword.  If a password wasn't supplied, the user will be asked to
enter one interactively the first time it will be needed (unless
.Vt oauth2
has been set).  It takes a
.Vt string
as a value.
.Pp
Passwords can also be extracted during execution time from an encrypted
password vault.  The
.Pa samples/extend.lua
file contains such an example.
.Pp
Note that due to Lua using backslash
.Sq \e
as an escape character for its strings, one has to use double backslashes in
order to insert a single backslash, and thus a backslash
character inside a password might require four backslashes.
.It Va oauth2
The OAuth2 string to use to authenticate if the server supports the XOAUTH2
authentication mechanism.  If the server does not support it and a
.Vt password
has also been set, authentication will be attempted using the
.Vt password .
It takes a
.Vt string
as a value.
.Pp
Note that this requires that an OAuth client ID and client secret have been
obtained, an OAuth2 token has been generated and authorized, a new access token
has been generated using the refresh token if the last access token has
expired, and an OAuth2 string has been generated from the access token.  The
aforementioned OAuth2 string is a Base64 encoded string that should be set
here.  For more information, see
.Ad https://developers.google.com/gmail/xoauth2_protocol .
.Pp
The
.Pa samples/extend.lua
file contains an example of authentication using OAuth2.
.It Va port
The port to connect to.  It takes a
.Vt number
as a value.  Default is
.Dq 143
for imap and
.Dq 993
for imaps.
.It Va ssl
Forces an imaps connection and specifies the SSL/TLS protocol/version to be
used.  It takes a
.Vt string
as a value, specifically one of:
.Dq auto ,
.Dq tls1.2 ,
.Dq tls1.1 ,
.Dq tls1 ,
.Dq ssl3 .
.Pp
Note that the latest versions of the OpenSSL library have deprecated
version specific methods, and the actual protocol version used, will be
negotiated to be the highest version mutually supported by the client
and the server.  This is also what the
.Dq auto
value does.
.El
.Pp
.Ss LISTING
The following methods can be used on an account to list mailboxes in a folder
of an account:
.Pp
.Bl -tag -width Ds -compact
.It Fn list_all folder
Lists all the available mailboxes in the
.Fa folder
.Pq Vt string ,
and returns a
.Vt table
that contains
.Vt strings ,
the available mailboxes,
and a
.Vt table
that contains
.Vt strings ,
the available folders.
.Pp
.It Fn list_subscribed folder
Lists all the subscribed mailboxes in the
.Fa folder
.Pq Vt string ,
and returns a
.Vt table
that contains
.Vt strings ,
the subscribed mailboxes,
and a
.Vt table
that contains
.Vt strings ,
the subscribed folders.
.El
.Pp
The following methods can be used on an account to list mailboxes, using
wildcards, in a folder of an account.  The
.Sq *
wildcard, matches any character and the
.Sq %
matches any character except the folder delimiter, i.e.  non-recursively:
.Pp
.Bl -tag -width Ds -compact
.It Fn list_all folder mailbox
Lists all the available mailboxes in the
.Fa folder
.Pq Vt string
with the name
.Fa mailbox
.Pq Vt string ,
and returns a
.Vt table
that contains
.Vt strings ,
the available mailboxes,
and a
.Vt table
that contains
.Vt strings ,
the available folders.  Wildcards may only be used in the
.Fa mailbox
argument.
.Pp
.It Fn list_subscribed folder mailbox
Lists all the subscribed mailboxes in the
.Fa folder
.Pq Vt string
with the name
.Fa mailbox
.Pq Vt string ,
and returns a
.Vt table
that contains
.Vt strings ,
the subscribed mailboxes,
and a
.Vt table
that contains
.Vt strings ,
the subscribed folders.  Wildcards may only be used in the
.Fa mailbox
argument.
.El
.Pp
Examples:
.Bd -literal -offset 4n
mailboxes, folders = myaccount:list_subscribed('myfolder')
mailboxes, folders = myaccount:list_all('myfolder/mysubfolder', '*')
.Ed
.Ss MANIPULATING
The following methods can be used to manipulate mailboxes in an account:
.Pp
.Bl -tag -width Ds -compact
.It Fn create_mailbox name
Creates the
.Fa name
.Pq Vt string
mailbox.
.Pp
.It Fn delete_mailbox name
Deletes the
.Fa name
.Pq Vt string
mailbox.
.Pp
.It Fn rename_mailbox oldname newname
Renames the
.Fa oldname
.Pq Vt string
mailbox to
.Fa newname
.Pq Vt string .
.Pp
.It Fn subscribe_mailbox name
Subscribes the
.Fa name
.Pq Vt string
mailbox.
.Pp
.It Fn unsubscribe_mailbox name
Unsubscribes the
.Fa name
.Pq Vt string
mailbox.
.El
.Pp
Examples:
.Bd -literal -offset 4n
myaccount:create_mailbox('mymailbox')
myaccount:subscribe_mailbox('mymailbox')
myaccount:unsubscribe_mailbox('myfolder/mymailbox')
myaccount:delete_mailbox('myfolder/mymailbox')
.Ed
.Sh MAILBOXES
After an IMAP account has been initialized, mailboxes residing in that account
can be accessed simply as elements of the account
.Vt table :
.Bd -literal -offset 4n
myaccount.mymailbox
.Ed
.Pp
If mailbox names don't only include letters, digits and underscores, or begin
with a digit, an alternative form must be used:
.Bd -literal -offset 4n
myaccount['mymailbox']
.Ed
.Pp
A mailbox inside a folder can be only accessed by using the alternative form:
.Bd -literal -offset 4n
myaccount['myfolder/mymailbox']
.Ed
.Pp
The methods that are available for an account (e.g.
.Fn list_all ,
.Fn create_mailbox ,
etc.) , are considered keywords and must not be used as mailbox names, and the
same also applies for any string starting with an underscore, as they are
considered reserved.
.Ss CHECKING
The following methods can be used to check the status of a mailbox:
.Pp
.Bl -tag -width Ds -compact
.It Fn check_status
.Pp
The
.Fn check_status
method gets the current status of a mailbox, and returns four values of
.Vt number
type: the total number of messages, the number of recent messages, the
number of unseen messages in the mailbox, and the next UID to be assigned to a
new message in the mailbox.
.Pp
.It Fn enter_idle
The
.Fn enter_idle
method implements the IMAP IDLE (RFC 2177) extension.  By using this extension
it's not necessary to poll the server for changes to the selected mailbox (i.e.
using the
.Fn check_status
method), but instead the server sends an update when there is a change
in the mailbox (e.g. in case of new mail).  When the
.Fn enter_idle
method has been called no more commands in the configuration file are executed
until an update is received, at which point the
.Fn enter_idle
method returns.  For the
.Fn enter_idle
to work, the IDLE extension has to be supported by the IMAP server.
.Pp
The
.Fn enter_idle
method returns a value of type
.Vt boolean :
.Dq true
if the IDLE extension is supported and there was an update in the mailbox, and
.Dq false
if the IDLE extension is not supported, in which case the method returns
immediately.  When the aforementioned return value was
.Dq true ,
an additional second value of type
.Vt string
is also returned, indicating the event received from the server, which is
useful when the
.Va wakeonany
option has been enabled.
.Pp
Apart from an event received by the server, the SIGUSR1 or SIGUSR2 signals can
also interrupt the IDLE mode at any time, and the execution of the
configuration file will then continue from the next line after the
.Fn enter_idle .
In this case, only the value
.Dq true
is returned.
.El
.Pp
Examples:
.Bd -literal -offset 4n
exist, unread, unseen, uidnext = myaccount.mymailbox:check_status()
update = myaccount.mymailbox:enter_idle()
update, event = myaccount.mymailbox:enter_idle()
.Ed
.Ss SEARCHING
.Pp
The searching methods in this subsection can be applied to any mailbox.
They return a special form of
.Vt table ,
that contains the messages that match the searching method.  This
.Vt table
can be combined with other
.Vt tables
using logic theory. There are three available operations, that implement
logical
.Dq or ,
logical
.Dq and
and logical
.Dq not .
.Pp
The logical
.Dq or
is implemented using the
.Sq +
operator:
.Bd -literal -offset 4n
results = myaccount.mymailbox:is_unseen() +
          myaccount.mymailbox:is_larger(100000)
.Ed
.Pp
The logical
.Dq and
is implemented using the
.Sq *
operator:
.Bd -literal -offset 4n
results = myaccount.mymailbox:is_unseen() *
          myaccount.mymailbox:is_larger(100000)
.Ed
.Pp
The logical
.Dq not
is implemented using the
.Sq -
operator:
.Bd -literal -offset 4n
results = myaccount.mymailbox:is_unseen() -
          myaccount.mymailbox:is_larger(100000)
.Ed
.Pp
The three logical operators can be combined in the same expression. The logical
.Dq and
has higher precedence than the logical
.Dq or
and the logical
.Dq not ,
with the latter two having the same precedence, and parentheses may be used to
change this behaviour:
.Bd -literal -offset 4n
results = myaccount.mymailbox:is_unseen() +
          myaccount.mymailbox:is_larger(100000) *
          myaccount.mymailbox:contain_subject('test')

results = ( myaccount.mymailbox:is_unseen() +
            myaccount.mymailbox:is_larger(100000) ) *
            myaccount.mymailbox:contain_subject('test')
.Ed
.Pp
The returned
.Vt tables
of the searching methods can also be stored in variables and then further
processed:
.Bd -literal -offset 4n
unseen = myaccount.mymailbox:is_unseen()
larger = myaccount.mymailbox:is_larger(100000)
subject = myaccount.mymailbox:contain_subject('test')
results = unseen + larger * subject
.Ed
.Pp
A composite filter that includes one or more simple rules can be defined:
.Bd -literal -offset 4n
myfilter = function ()
	       return myaccount.mymailbox:is_unseen() +
	              myaccount.mymailbox:is_larger(100000) *
                      myaccount.mymailbox:contain_subject('test')
           end

results = myfilter()
.Ed
.Pp
Composite filters can may be more dynamic by adding arguments:
.Bd -literal -offset 4n
myfilter = function (mailbox, size, subject)
	       return mailbox:is_unseen() +
                      mailbox:is_larger(size) *
                      mailbox:contain_subject(subject)
           end

results = myfilter(myaccount.mailbox, 100000, 'test')
.Ed
.Pp
It is also possible to combine the searching methods in different mailboxes,
either at the same or different accounts, for example when the same actions
will be executed on messages residing in different mailboxes or accounts.
.Bd -literal -offset 4n
results = myaccount.mymailbox:is_unseen() +
	  myaccount.myothermailbox:is_larger(100000) +
	  myotheraccount.myothermailbox:contain_subject('test')
.Ed
.Pp
And for those that want to know more about the return values of the following
methods, it is a
.Vt table
which contains
.Vt tables
with two values: the mailbox
.Pq Vt table
the message belongs to, and the message UID
.Pq Vt number
which points to the matching message.  For examples on iterating these
returned tables, or creating new tables of this format (they are actually
metatables implementing sets), see the
.Va samples/extend.lua
file.
.Bd -literal -offset 4n
{
    { <myaccount.mymailbox>, 1 },
    { <myaccount.mymailbox>, 3 },
    { <myaccount.myothermailbox>, 5 },
    { <myothermailbox.myothermailbox>, 7},
    { ... },
    ...
}
.Ed
.Pp
The following method can be used to get all messages in a mailbox:
.Pp
.Bl -tag -width Ds -compact
.It Fn select_all
All messages.
.El
.Pp
The following methods can be used to search for messages that are in a specific
state:
.Pp
.Bl -tag -width Ds -compact
.It Fn is_answered
Messages that have been answered.
.Pp
.It Fn is_deleted
Messages that are marked for later removal.
.Pp
.It Fn is_draft
Messages that have not completed composition.
.Pp
.It Fn is_flagged
Messages that are flagged for urgent/special attention.
.Pp
.It Fn is_new
Messages that are recently arrived (this session is the first to have been
notified about these messages) and have not been read.
.Pp
.It Fn is_old
Messages that are not recently arrived (this session is not the first to have
been notified about these messages) and have not been read.
.Pp
.It Fn is_recent
Messages that are recently arrived (this session is the first to have been
notified about these messages).
.Pp
.It Fn is_seen
Messages that have been read.
.Pp
.It Fn is_unanswered
Messages that have not been answered.
.Pp
.It Fn is_undeleted
Messages that are not marked for later removal.
.Pp
.It Fn is_undraft
Messages that have completed composition.
.Pp
.It Fn is_unflagged
Messages that are not flagged for urgent/special attention.
.Pp
.It Fn is_unseen
Messages that have not been read.
.El
.Pp
The following method can be used to search for messages that have a specific
keyword flag set:
.Pp
.Bl -tag -width Ds -compact
.It Fn has_keyword flag
Messages with the specified keyword flag
.Pq Vt string
set.
.It Fn has_unkeyword flag
Messages without the specified keyword flag
.Pq Vt string
set.
.El
.Pp
The following methods can be used to search for messages based on their size:
.Pp
.Bl -tag -width Ds -compact
.It Fn is_larger size
Messages that are larger than the size
.Pq Vt number
in octets (bytes).
.Pp
.It Fn is_smaller size
Messages that are smaller than the size
.Pq Vt number
in octets (bytes).
.El
.Pp
The following methods can be used to search for messages based on their age:
.Pp
.Bl -tag -width Ds -compact
.It Fn is_newer age
Messages that are newer than the
.Fa age
.Pq Vt number
in days.
.Pp
.It Fn is_older age
Messages that are older than the
.Fa age
.Pq Vt number
in days.
.El
.Pp
The following methods can be used to search for messages based on their arrival
or sent date, in the
.Dq day-month-year
form, where day is the day of the month as a decimal number (01-31), month is
the abbreviated month (
.Dq Jan ,
.Dq Feb ,
.Dq Mar ,
.Dq Apr ,
.Dq May ,
.Dq Jun ,
.Dq Jul ,
.Dq Aug ,
.Dq Sep ,
.Dq Oct ,
.Dq Nov ,
.Dq Dec )
and year is the year as decimal number including the century (e.g. 2007):
.Pp
.Bl -tag -width Ds -compact
.It Fn arrived_before date
messages that have arrived earlier than the
.Fa date
.Pq Vt string ,
where
.Fa date
is in the
.Dq day-month-year
form.
.Pp
.It Fn arrived_on date
Messages that have arrived within the
.Fa date
.Pq Vt string ,
where
.Fa date
is in the
.Dq day-month-year
form.
.Pp
.It Fn arrived_since date
Messages that have arrived within or later than the
.Fa date
.Pq Vt string ,
where
.Fa date
is in the
.Dq day-month-year
form.
.Pp
.It Fn sent_before date
Messages that have been sent earlier than the
.Fa date
.Pq Vt string ,
where
.Fa date
is in the
.Dq day-month-year
form.
.Pp
.It Fn sent_on date
Messages that have been sent within the
.Fa date
.Pq Vt string ,
where
.Fa date
is in the
.Dq day-month-year
form.
.Pp
.It Fn sent_since date
Messages that have been sent within or later than the
.Fa date
.Pq Vt string ,
where
.Fa date
is in the
.Dq day-month-year
form.
.El
.Pp
The following methods can be used to do case-insensitive searching, for
messages that contain a specific word or phrase:
.Pp
.Bl -tag -width Ds -compact
.It Fn contain_bcc string
Messages that contain the
.Fa string
.Pq Vt string
in the
.Dq Bcc
header field.
.Pp
.It Fn contain_cc string
Messages that contain the
.Fa string
.Pq Vt string
in the
.Dq Cc
header field.
.Pp
.It Fn contain_from string
Messages that contain the
.Fa string
.Pq Vt string
in the
.Dq From
header field.
.Pp
.It Fn contain_subject string
Messages that contain the
.Fa string
.Pq Vt string
in the
.Dq Subject
header field.
.Pp
.It Fn contain_to string
Messages that contain the
.Fa string
.Pq Vt string
in the
.Dq To
header field.
.Pp
.It Fn contain_field field string
Messages that contain the
.Fa string
.Pq Vt string
in the
.Fa field
.Pq Vt string
header field.
.Pp
.It Fn contain_body string
Messages that contain the
.Fa string
.Pq Vt string
in the message body.
.Pp
.It Fn contain_message string
Messages that contain the
.Fa string
.Pq Vt string
in the message.
.El
.Pp
The following methods can be used to do case-sensitive searching, for messages
that match a specific regular expression pattern. The matching mechanism that
is used to support this is based on the Perl-compatible regular expressions
(PCRE), and more information about the patterns and modifiers that can be used,
is available in the relevant documentation at
.Ad http://pcre.org/original/doc/html/ .
.Pp
This way of searching is not supported by the IMAP protocol, and this means
that what actually happens under the hood, is that the relevant parts of all
the messages are downloaded and matched locally.  It is therefore recommended
to use these methods with meta-searching (see following section), in order to
narrow down the set of messages that should be searched, and thus minimize what
will be downloaded.
.Pp
Note that due to Lua using backslash
.Sq \e
as an escape character for its strings, one has to use double backslashes in
order to insert a single backslash inside a regular expression pattern:
.Pp
.Bl -tag -width Ds -compact
.It Fn match_bcc pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the
.Dq Bcc
header field.
.Pp
.It Fn match_cc pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the
.Dq Cc
header field.
.Pp
.It Fn match_from pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the
.Dq From
header field.
.Pp
.It Fn match_subject pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the
.Dq Subject
header field.
.Pp
.It Fn match_to pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the
.Dq To
header field.
.Pp
.It Fn match_field field pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the
.Fa field
.Pq Vt string
header field.
.Pp
.It Fn match_header pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the message header.
.Pp
.It Fn match_body pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the message body.
.Pp
.It Fn match_message pattern
Messages that match the regular expression
.Fa pattern
.Pq Vt string
in the message.
.El
.Pp
The following method can be used to search for messages using user queries
based on the IMAP specification (RFC 3501 Section 6.4.4):
.Pp
.Bl -tag -width Ds -compact
.It Fn send_query criteria
Searches messages by sending an IMAP search query as described in the
search
.Fa criteria
.Pq Vt string .
.El
.Pp
Examples:
.Bd -literal -offset 4n
results = myaccount.mymailbox:select_all()
results = myaccount.mymailbox:is_new()
results = myaccount.mymailbox:is_recent()
results = myaccount.mymailbox:is_larger(100000)
results = myaccount.mymailbox:is_older(10)
results = myaccount.mymailbox:has_keyword('MyFlag')
results = myaccount.mymailbox:arrived_before('01-Jan-2007')
results = myaccount.mymailbox:sent_since('01-Jan-2007')
results = myaccount.mymailbox:contain_subject('test')
results = myaccount.mymailbox:contain_field('Sender', 'user@host')
results = myaccount.mymailbox:contain_body('hello world')
results = myaccount.mymailbox:match_from('.*(user1|user2)@host')
results = myaccount.mymailbox:send_query('ALL')

results = myaccount['mymailbox']:is_new()
results = myaccount['myfolder/mymailbox']:is_recent()
.Ed
.Sh RESULTS
After one of more searching methods have been applied to one or more mailboxes,
the result contains all the necessary information, such as which messages
matched in which mailboxes.  Using this result these messages can be either
searched further or processed in various way.
.Ss META-SEARCHING
The results of the searching methods can be searched further on in the same way
as searching is done in mailboxes.  The difference is that instead of doing the
search in the whole mailbox, ie. in all the messages, it is instead done only
to those messages that were returned in a previous search.
.Pp
Examples:
.Bd -literal -offset 4n
results:match_message('^[Hh]ello world!?$')
myaccount.mymailbox:is_new():match_body('^[Ww]orld, hello!?$')
.Ed
.Ss PROCESSING
The processing methods are applied to the results that searching returned.
.Pp
The following method can be used to delete messages in a mailbox:
.Pp
.Bl -tag -width Ds -compact
.It Fn delete_messages
Deletes the messages that matched.
.El
.Pp
The following methods can be used to copy and move messages in a mailbox at the
same or different accounts.  If the destination mailbox is in a different
account than the source mailbox, then the messages are downloaded and then
uploaded to the destination:
.Pp
.Bl -tag -width Ds -compact
.It Fn copy_messages destination
Copies the messages to the
.Fa destination ,
which is a mailbox at an account.
.Pp
.It Fn move_messages destination
Moves the messages to the
.Fa destination ,
which is a mailbox at an account.
.El
.Pp
The following methods can be used to mark messages in a mailbox:
.Pp
.Bl -tag -width Ds -compact
.It Fn mark_answered
Marks the messages as answered.
.Pp
.It Fn mark_deleted
Marks the messages for later removal.
.Pp
.It Fn mark_draft
Marks the messages as draft.
.Pp
.It Fn mark_flagged
Marks the messages for urgent/special attention.
.Pp
.It Fn mark_seen
Marks the messages as read.
.Pp
.It Fn unmark_answered
Unmarks the messages that have been marked as answered.
.Pp
.It Fn unmark_deleted
Unmarks the messages that have been marked for later removal.
.Pp
.It Fn unmark_draft
Unmarks the messages that have been marked as draft.
.Pp
.It Fn unmark_flagged
Unmarks the messages that have been marked for urgent/special attention.
.Pp
.It Fn unmark_seen
Unmarks the messages that have been marked as read.
.Pp
.El
.Pp
The following methods can be used to flag messages in a mailbox. The standard
system flags are
.Dq \eAnswered ,
.Dq \eDeleted ,
.Dq \eDraft ,
.Dq \eFlagged ,
.Dq \eSeen ,
while, if the server supports it, new user keywords may be defined:
.Pp
.Bl -tag -width Ds -compact
.It Fn add_flags flags
Adds the
.Fa flags
.Po
.Vt table
that contains
.Vt strings
.Pc
to the messages.
.Pp
.It Fn remove_flags flags
Removes the
.Fa flags
.Po
.Vt table
that contains
.Vt strings
.Pc
from the messages.
.Pp
.It Fn replace_flags flags
Replaces the
.Fa flags
.Po
.Vt table
that contains
.Vt strings
.Pc
of the messages.
.El
.Pp
Examples:
.Bd -literal -offset 4n
results:delete_messages()
results:copy_messages(myaccount.myothermailbox)
results:move_messages(myotheraccount.mymailbox)
results:mark_seen()
results:unmark_flagged()
results:add_flags({ 'MyFlag', '\e\eSeen' })
results:remove_flags({ '\e\eSeen' })

results:move_messages(myotheraccount['myfolder/mymailbox'])
.Ed
.Sh MESSAGES
The messages that are residing in any mailbox can also be accessed, as a whole
or in parts.  Messages can be accessed using their unique identifier (UID):
.Bd -literal -offset 4n
myaccount.mymailbox[22]
.Ed
.Pp
The UIDs of messages the user is interested in, are gained from the results of
searching:
.Bd -literal -offset 4n
results = account.INBOX:is_unseen()
for _, message in ipairs(results) do
    mailbox, uid = table.unpack(message)
    header = mailbox[uid]:fetch_header()
end
.Ed
.Ss FETCHING
.Pp
The following methods can be used to fetch parts of messages.  The methods
return a
.Vt string .
The downloaded message parts are cached locally, so they can be reused inside
the same program session:
.Pp
.Bl -tag -width Ds -compact
.It Fn fetch_message
Fetches the header and body of the message.
.Pp
.It Fn fetch_header
Fetches the header of the message.
.Pp
.It Fn fetch_body
Fetches the body of the messages.
.Pp
.It Fn fetch_field field
Fetches the specified header
.Fa field
.Pq Vt string
of the message.
.Pp
.It Fn fetch_part part
Fetches the specified
.Fa part
.Pq Vt string
of the message.
.El
.Pp
The following methods can be used to fetch details about the state of a
message:
.Pp
.Bl -tag -width Ds -compact
.It Fn fetch_flags
Fetches the flags of the message.  Returns a
.Vt table
of
.Vt strings .
.Pp
.It Fn fetch_date
Fetches the internal date of the message.  Returns a
.Vt string .
.Pp
.It Fn fetch_size
Fetches the size of the message.  Returns a
.Vt number .
.Pp
.It Fn fetch_structure
Fetches the body structure of the message. Returns a
.Vt table
that has as keys the parts of the message, and as values a
.Vt table
that has one mandatory element, the type
.Pq Vt string
of the part, and two optional elements, the size
.Pq Vt number
and name
.Pq Vt string
of the part.
.El
.Ss APPENDING
.Pp
The following methods can be used to append a message to a mailbox:
.Pp
.Bl -tag -width Ds -compact
.It Fn append_message message
Appends the
.Fa message
.Pq Vt string
to the mailbox.
.Pp
.It Fn append_message message flags date
Appends the
.Fa message
.Pq Vt string
to the mailbox, setting the specified
.Fa flags
.Po
.Vt table
of
.Vt strings
.Pc ,
as returned by
.Fn fetch_flags ,
and
.Fa date
.Pq Vt string ,
as returned by
.Fn fetch_date .
.El
.Pp
Examples:
.Bd -literal -offset 4n
myaccount.mymailbox[2]:fetch_message()
myaccount.mymailbox[3]:fetch_field('subject')
myaccount.mymailbox[5]:fetch_part('1.1')

myaccount['mymailbox'][7]:fetch_message()
myaccount['myfolder/mymailbox'][11]:fetch_message()

myaccount.mymailbox:append_message(message)
.Ed
.Sh FUNCTIONS
The following auxiliary functions are also available for convenience:
.Pp
.Bl -tag -width Ds -compact
.It Fn form_date days
Forms a date in
.Dq day-month-year
format that the system had before the number of
.Fa days
.Pq Vt number ,
and returns it as a
.Vt string .
.Pp
.It Fn get_password prompt
Displays the specified
.Fa prompt
.Pq Vt string ,
and reads a password, while character echoing is turned off.  Returns
that password as a
.Vt string .
.Pp
.It Fn become_daemon interval commands
.It Fn become_daemon interval commands nochdir
.It Fn become_daemon interval commands nochdir noclose
Detaches the program from the controlling terminal and runs it in the
background as system daemon. The program will then repeatedly poll at the
specified
.Fa interval
.Pq Vt number
in seconds. Each time the program wakes up, the
.Fa commands
.Pq Vt function
are executed.
.Pp
If
.Fa nochdir
.Pq Vt boolean
is
.Dq true ,
the current working directory is not changed to the root directory
.Pq Pa / .
.Pp
If
.Fa noclose
.Pq Vt boolean
is
.Dq true ,
the standard input, standard output and standard error are not redirected to
.Pa /dev/null .
.Pp
.It Fn pipe_to command data
Executes the system's
.Fa command
.Pq Vt string
and sends the
.Fa data
.Pq Vt string
to the standard input channel of the subprocess. Returns a
.Vt number ,
the exit status of the child process.
.Pp
.It Fn pipe_from command
Executes the system's
.Fa command
.Pq Vt string
and retrieves the data from the standard output channel of the subprocess.
Returns a
.Vt number ,
the exit status of the child process, and a
.Vt string ,
the output of the child process.
.Pp
.It Fn regex_search pattern string
Implements Perl-compatible regular expressions (PCRE). The
.Fa pattern
.Pq Vt string
is a PCRE pattern. The
.Vt string
.Pq Vt string
is the subject string in which the pattern is
matched against. Returns at least a
.Vt boolean ,
that denotes if the match was successful, and any captures which are of
.Vt string
type.  Note that due to Lua using backslash
.Sq \e
as an escape character for its strings, one has to use double backslashes in
order to insert a single backslash inside a regular expression pattern.  For
more information on PCRE see
.Ad http://pcre.org/original/doc/html/ .
.Pp
.It Fn sleep interval
Delay for the specified
.Fa interval
.Pq Vt number
in seconds.
.Pp
.It Fn recover commands
.It Fn recover commands retries
Protects the
.Fa commands
.Pq Vt function
executed from raising an error. Whenever an error is raised, it sleeps for a
few seconds (using exponential backoff up to some upper limit), and then re-executes the
.Fa commands
.Pq Vt function
from start.
.Pp
If the maximum count of
.Fa retries
.Pq Vt number
is specified, it will retry up to the specified number of times, otherwise it will never give up.
.Pp
Returns the status code of the execution as the first result,
.Dq true
if it succeeded or
.Dq false
if it failed. If it succeeded, it returns all values the
.Fa commands
.Pq Vt function
returned as additional results.  If it failed, it returns the error as an additional result.
.El
.Pp
Examples:
.Bd -literal -offset 4n
date = form_date(14)
password = get_password('Enter password: ')
become_daemon(600, myfunction)
status = pipe_to('mycommandline', 'mydata')
status, data = pipe_from('mycommandline')
success, capture = regex_search('^(?i)pcre: (\e\ew)$', 'mystring')
sleep(300)
recover(myfunction, 5)
.Pp
.Ed
For more examples, see the
.Pa samples/extend.lua
file.
.Sh EXAMPLES
See
.Pa samples/config.lua
and
.Pa samples/extend.lua
in the source code distribution.
.Sh ENVIRONMENT
.Bl -tag -width Ds
.It Ev HOME
User's home directory.
.El
.Sh SEE ALSO
.Xr imapfilter 1