.Dd December 8, 2011
.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.
.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,
in order 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 crammd5
When this option is enabled and the server supports the Challenge-Response
Authentication Mechanism (specifically CRAM-MD5), this method will be used for
user authentication instead of a plaintext password LOGIN.  This variable
takes a 
.Vt boolean
as a value.  Default is
.Dq true .
.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 info
When this options 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 it may happen that some IMAP servers don't 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 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
(ie.  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 (eg. because they are not part of the user's
personal namespace mailboxes).  This variable takes
.Vt boolean
as a value.  Default is
.Dq true .
.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
not set, the client will block indefinitely.  This variable takes a
.Vt number
as a value.  By default no value is set.
.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 = 'ssl3'
}
.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.  It takes a
.Vt string
as a value.
.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 to be used.  It
takes a
.Vt string
as a value, specifically one of:
.Dq ssl2 ,
.Dq ssl3 ,
.Dq tls1 .
.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, ie.  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 (eg.
.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 (ie.
using the
.Fn check_status
method), but instead the server sends an update when there is a change
in the mailbox (eg. 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.  The
.Fn enter_idle
method returns one value of type
.Vt boolean :
.Dq true
if the IDLE extension is supported and there was a update in the mailbox, and
.Dq false
if the IDLE extension is not supported, in which case the method returns
immediately.
.El
.Pp
Examples:
.Bd -literal -offset 4n
exist, unread, unseen, uidnext = myaccount.mymailbox:check_status()
update = 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.myaccount: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
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
flag set:
.Pp
.Bl -tag -width Ds -compact
.It Fn has_flag keyword
Messages with 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 (eg. 2007):
.Pp
.Bl -tag -width Ds -compact
.It Fn arrived_before date
messages that have arrived before 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 on 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 after 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 before 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 on 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 after 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 search 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 search for messages that match a specific
regular expression pattern.
.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 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_flag('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 be also 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
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
.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 / .
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 double backslashes in order
to insert a single backslash inside a regular expression pattern:
.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('^[PpCcRrEe]: (\e\ew)$', 'mystring')
.Ed
.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
.Sh BUGS
.Pp
Since version 2.2, a different format is used for the returned structures of
the searching methods, due to the introduction of multiple mailbox searching
and meta-searching, and thus any configuration files that rely on them should
be updated.  Consequently, the processing and fetching methods have been also
enhanced and the relevant documentation modified, and while these changes are
backwards compatible, an update of the configuration file is still recommended.
.Pp
Since version 2.0, the configuration file format has changed.  The new format
is not backwards compatible, and thus it should not be mixed with the old
format. Nevertheless, configuration files that employ the old, and now
deprecated, format can still be read and executed as before.