C4::Letters - Give functions for Letters management
use C4::Letters;
"Letters" is the tool used in Koha to manage informations sent to the patrons and/or the library. This include some cron jobs like late issues, as well as other tasks like sending a mail to users that have subscribed to a "serial issue alert" (= being warned every time a new issue has arrived at the library) Letters are managed through "alerts" sent by Koha on some events. All "alert" related functions are in this module too.
$letters = &GetLetters($module); returns informations about letters. if needed, $module filters for letters given module
    my $letter_templates = GetLetterTemplates(
        {
            module => 'circulation',
            code => 'my code',
            branchcode => 'CPL', # '' for default,
        }
    );
    Return a hashref of letter templates.
    The key will be the message transport type.
    my $letters = GetLettersAvailableForALibrary(
        {
            branchcode => 'CPL', # '' for default
            module => 'circulation',
        }
    );
    Return an arrayref of letters, sorted by name.
    If a specific letter exist for the given branchcode, it will be retrieve.
    Otherwise the default letter will be.
    DelLetter(
        {
            branchcode => 'CPL',
            module => 'circulation',
            code => 'my code',
            [ mtt => 'email', ]
        }
    );
    Delete the letter. The mtt parameter is facultative.
    If not given, all templates mathing the other parameters will be removed.
    parameters : 
    - $borrowernumber : the number of the borrower subscribing to the alert
    - $type : the type of alert.
    - $externalid : the primary key of the object to put alert on. For issues, the alert is made on subscriptionid.
    
    create an alert and return the alertid (primary key)
    parameters :
    - alertid : the alert id
    deletes the alert
    parameters :
    - $borrowernumber : the number of the borrower subscribing to the alert
    - $type : the type of alert.
    - $externalid : the primary key of the object to put alert on. For issues, the alert is made on subscriptionid.
    all parameters NON mandatory. If a parameter is omitted, the query is done without the corresponding parameter. For example, without $externalid, returns all alerts for a borrower on a topic.
    parameters :
    - $type : the type of alert
    - $externalid : the id of the "object" to query
    In the table alert, a "id" is stored in the externalid field. This "id" is related to another table, depending on the type of the alert.
    When type=issue, the id is related to a subscriptionid and this sub returns the name of the biblio.
    my $err = &SendAlerts($type, $externalid, $letter_code);
    Parameters:
      - $type : the type of alert
      - $externalid : the id of the "object" to query
      - $letter_code : the notice template to use
    C<&SendAlerts> sends an email notice directly to a patron or a vendor.
    Currently it supports ($type):
      - claim serial issues (claimissues)
      - claim acquisition orders (claimacquisition)
      - send acquisition orders to the vendor (orderacquisition)
      - notify patrons about newly received serial issues (issue)
      - notify patrons when their account is created (members)
    Returns undef or { error => 'message } on failure.
    Returns true on success.
    %params hash:
      module => letter module, mandatory
      letter_code => letter code, mandatory
      branchcode => for letter selection, if missing default system letter taken
      tables => a hashref with table names as keys. Values are either:
        - a scalar - primary key value
        - an arrayref - primary key values
        - a hashref - full record
      substitute => custom substitution key/value pairs
      repeat => records to be substituted on consecutive lines:
        - an arrayref - tries to guess what needs substituting by
          taking remaining << >> tokensr; not recommended
        - a hashref token => @tables - replaces <token> << >> << >> </token>
          subtemplate for each @tables row; table is a hashref as above
      want_librarian => boolean,  if set to true triggers librarian details
        substitution from the userenv
    Return value:
      letter fields hashref (title & content useful)
    parameters :
    - $letter : a hash to letter fields (title & content useful)
    - $table : the Koha table to parse.
    - $values_in : table record hashref
    parse all fields from a table, and replace values in title & content with the appropriate value
    (not exported sub, used only internally)
  my $success = EnqueueLetter( { letter => $letter, 
        borrowernumber => '12', message_transport_type => 'email' } )
places a letter in the message_queue database table, which will eventually get processed (sent) by the process_message_queue.pl cronjob when it calls SendQueuedMessages.
return message_id on success
  my $sent = SendQueuedMessages( { verbose => 1 } );
sends all of the 'pending' items in the message queue.
returns number of messages sent.
  my $message_list = GetRSSMessages( { limit => 10, borrowernumber => '14' } )
returns a listref of all queued RSS messages for a particular person.
  my $message_list = GetPrintMessages( { borrowernumber => $borrowernumber } )
Returns a arrayref of all queued print messages (optionally, for a particular person).
  my $messages = GetQueuedMessage( { borrowernumber => '123', limit => 20 } );
fetches messages out of the message queue.
returns: list of hashes, each has represents a message in the message queue.
my @mtt = GetMessageTransportTypes(); returns an arrayref of transport types
my $message = C4::Letters::Message($message_id);
Attempt to resend a message which has failed previously. my $has_been_resent = C4::Letters::ResendMessage($message_id); Updates the message to 'pending' status so that it will be resent later on. returns 1 on success, 0 on failure, undef if no message was found
named parameters: letter - the standard letter hashref attachments - listref of attachments. each attachment is a hashref of: type - the mime type, like 'text/plain' content - the actual attachment filename - the name of the attachment. message - a MIME::Lite object to attach these to.
returns your letter object, with the content updated.