=encoding utf8

=head1 NAME

Log::Report::Dispatcher - manage message dispatching, display or logging

=head1 INHERITANCE

 Log::Report::Dispatcher is extended by
   Log::Report::Dispatcher::Callback
   Log::Report::Dispatcher::File
   Log::Report::Dispatcher::Log4perl
   Log::Report::Dispatcher::LogDispatch
   Log::Report::Dispatcher::Perl
   Log::Report::Dispatcher::Syslog
   Log::Report::Dispatcher::Try

=head1 SYNOPSIS

 use Log::Report;

 # The following will be created for you automatically
 dispatcher 'PERL', 'default', accept => 'NOTICE-';
 dispatcher close => 'default';  # after deamonize

 dispatcher 'FILE', 'log'
   , mode => 'DEBUG', to => '/var/log/mydir/myfile';

 # Full package name is used, same as 'FILE'
 dispatcher Log::Report::Dispatch::File => 'stderr'
   , to => \*STDERR, accept => 'NOTICE-';

=head1 DESCRIPTION

In L<Log::Report|Log::Report>, dispatchers are used to handle (exception) messages
which are created somewhere else.  Those message were produced (thrown)
by L<Log::Report::error()|Log::Report/"Abbreviations for report()"> and friends.

This base-class handles the creation of dispatchers, plus the common
filtering rules.  See the L</DETAILS> section, below.

=head1 METHODS

=head2 Constructors

=over 4

=item $obj-E<gt>B<close>()

Terminate the dispatcher activities.  The dispatcher gets disabled,
to avoid the case that it is accidentally used.  Returns C<undef> (false)
if the dispatcher was already closed.

=item Log::Report::Dispatcher-E<gt>B<new>($type, $name, %options)

Create a dispatcher.  The $type of back-end to start is required, and listed
in the L</DESCRIPTION> part of this manual-page. For various external
back-ends, special wrappers are created.

The $name must be uniquely identifying this dispatcher.  When a second
dispatcher is created (via L<Log::Report::dispatcher()|Log::Report/"Report Production and Configuration">) with the name
of an existing dispatcher, the existing one will get replaced.

All %options which are not consumed by this base constructor are passed
to the wrapped back-end.  Some of them will check whether all %options
are understood, other ignore unknown %options.

 -Option       --Default
  accept         depend on mode
  charset        <undef>
  format_reason  'LOWERCASE'
  locale         <system locale>
  mode           'NORMAL'

=over 2

=item accept => REASONS

See L<Log::Report::Util::expand_reasons()|Log::Report::Util/"Reasons"> for possible values.  If
the initial mode for this dispatcher does not need verbose or debug
information, then those levels will not be accepted.

When the mode equals "NORMAL" (the default) then C<accept>'s default
is C<NOTICE->.  In case of "VERBOSE" it will be C<INFO->, C<ASSERT>
results in C<ASSERT->, and "DEBUG" in C<ALL>.

=item charset => CHARSET

Convert the messages in the specified character-set (codeset).  By
default, no conversion will take place, because the right choice cannot
be determined automatically.

=item format_reason => 'UPPERCASE'|'LOWERCASE'|'UCFIRST'|'IGNORE'|CODE

How to show the reason text which is printed before the message. When
a CODE is specified, it will be called with a translated text and the
returned text is used.

=item locale => LOCALE

Overrules the global setting.  Can be overruled by
L<Log::Report::report(locale)|Log::Report/"Report Production and Configuration">.

=item mode => 'NORMAL'|'VERBOSE'|'ASSERT'|'DEBUG'|0..3

Possible values are C<NORMAL> (or C<0> or C<undef>), which will not show
C<INFO> or debug messages, C<VERBOSE> (C<1>; shows C<INFO> not debug),
C<ASSERT> (C<2>; only ignores C<TRACE> messages), or C<DEBUG> (C<3>)
which shows everything.  See section L<Log::Report/Run modes>.

You are advised to use the symbolic mode names when the mode is
changed within your program: the numerical values are available
for smooth Getopt::Long integration.

=back

=back

=head2 Accessors

=over 4

=item $obj-E<gt>B<isDisabled>()

=item $obj-E<gt>B<mode>()

Returns the mode in use for the dispatcher as number.  See L<new(mode)|Log::Report::Dispatcher/"Constructors">
and L<Log::Report/Run modes>.

=item $obj-E<gt>B<name>()

Returns the unique name of this dispatcher.

=item $obj-E<gt>B<needs>( [$reason] )

Returns the list with all REASONS which are needed to fulfill this
dispatcher's needs.  When disabled, the list is empty, but not forgotten.

[0.999] when only one $reason is specified, it is returned if in the
list.

=item $obj-E<gt>B<type>()

The dispatcher $type, which is usually the same as the class of this
object, but not in case of wrappers like for Log::Dispatch.

=back

=head2 Logging

=over 4

=item $obj-E<gt>B<addSkipStack>(@CODE)

=item Log::Report::Dispatcher-E<gt>B<addSkipStack>(@CODE)

[1.13] Add one or more CODE blocks of caller lines which should not be
collected for stack-traces or location display.  A CODE gets
called with an ARRAY of caller information, and returns true
when that line should get skipped.

B<Warning:> this logic is applied globally: on all dispatchers.

example: 

By default, all lines in the Log::Report packages are skipped from
display, with a simple CODE as this:

  sub in_lr { $_[0][0] =~ m/^Log\:\:Report(?:\:\:|$)/ }
  Log::Report::Dispatcher->addSkipStack(\&in_lr);

The only parameter to in_lr is the return of caller().  The first
element of that ARRAY is the package name of a stack line.

=item $obj-E<gt>B<collectLocation>()

=item Log::Report::Dispatcher-E<gt>B<collectLocation>()

Collect the information to be displayed as line where the error occurred.

=item $obj-E<gt>B<collectStack>( [$maxdepth] )

=item Log::Report::Dispatcher-E<gt>B<collectStack>( [$maxdepth] )

Returns an ARRAY of ARRAYs with text, filename, line-number.

=item $obj-E<gt>B<log>(HASH-$of-%options, $reason, $message, $domain)

This method is called by L<Log::Report::report()|Log::Report/"Report Production and Configuration"> and should not be called
directly.  Internally, it will call L<translate()|Log::Report::Dispatcher/"Logging">, which does most $of
the work.

=item $obj-E<gt>B<skipStack>()

[1.13] Returns the number of nestings in the stack which should be skipped
to get outside the Log::Report (and related) modules.  The end-user
does not want to see those internals in stack-traces.

=item $obj-E<gt>B<stackTraceLine>(%options)

=item Log::Report::Dispatcher-E<gt>B<stackTraceLine>(%options)

 -Option    --Default
  abstract    1
  call        <required>
  filename    <required>
  linenr      <required>
  max_line    undef
  max_params  8
  package     <required>
  params      <required>

=over 2

=item abstract => INTEGER

The higher the abstraction value, the less details are given
about the caller.  The minimum abstraction is specified, and
then increased internally to make the line fit within the C<max_line>
margin.

=item call => STRING

=item filename => STRING

=item linenr => INTEGER

=item max_line => INTEGER

=item max_params => INTEGER

=item package => CLASS

=item params => ARRAY

=back

=item $obj-E<gt>B<translate>(HASH-$of-%options, $reason, $message)

See L</Processing the message>, which describes the actions taken by
this method.  A string is returned, which ends on a new-line, and
may be multi-line (in case a stack trace is produced).

=back

=head1 DETAILS

=head2 Available back-ends

When a dispatcher is created (via L<new()|Log::Report::Dispatcher/"Constructors"> or L<Log::Report::dispatcher()|Log::Report/"Report Production and Configuration">),
you must specify the TYPE of the dispatcher.  This can either be a class
name, which extends a L<Log::Report::Dispatcher|Log::Report::Dispatcher>, or a pre-defined
abbreviation of a class name.  Implemented are:

=over 4

=item L<Log::Report::Dispatcher::Perl|Log::Report::Dispatcher::Perl> (abbreviation 'PERL')

Use Perl's own C<print()>, C<warn()> and C<die()> to ventilate
reports.  This is the default dispatcher.

=item L<Log::Report::Dispatcher::File|Log::Report::Dispatcher::File> (abbreviation 'FILE')

Logs the message into a file, which can either be opened by the
class or be opened before the dispatcher is created.

=item L<Log::Report::Dispatcher::Syslog|Log::Report::Dispatcher::Syslog> (abbreviation 'SYSLOG')

Send messages into the system's syslog infrastructure, using
Sys::Syslog.

=item L<Log::Report::Dispatcher::Callback|Log::Report::Dispatcher::Callback> (abbreviation 'CALLBACK')

Calls any CODE reference on receipt of each selected message, for
instance to send important message as email or SMS.

=item C<Log::Dispatch::*>

All of the Log::Dispatch::Output extensions can be used directly.
The L<Log::Report::Dispatcher::LogDispatch|Log::Report::Dispatcher::LogDispatch> will wrap around that
back-end.

=item C<Log::Log4perl>

Use the Log::Log4perl main object to write to dispatchers.  This
infrastructure uses a configuration file.

=item L<Log::Report::Dispatcher::Try|Log::Report::Dispatcher::Try> (abbreviation 'TRY')

Used by function L<Log::Report::try()|Log::Report/"Report Production and Configuration">.  It collects the exceptions
and can produce them on request.

=back

=head2 Processing the message

=head3 Addition information

The modules which use C<Log::Report> will only specify the base of
the message string.  The base dispatcher and the back-ends will extend
this message with additional information:

=over 4

=item . the reason

=item . the filename/line-number where the problem appeared

=item . the filename/line-number where it problem was reported

=item . the error text in C<$!>

=item . a stack-trace

=item . a trailing new-line

=back

When the message is a translatable object (L<Log::Report::Message|Log::Report::Message>, for
instance created with L<Log::Report::__()|Log::Report/"Messages (optionally translatable)">), then the added components
will get translated as well.  Otherwise, all will be in English.

Exactly what will be added depends on the actual mode of the dispatcher
(change it with L<mode()|Log::Report::Dispatcher/"Accessors">, initiate it with L<new(mode)|Log::Report::Dispatcher/"Constructors">).

                        mode mode mode mode
 REASON   SOURCE   TE!  NORM VERB ASSE DEBUG
 trace    program  ...                 S
 assert   program  ...            SL   SL
 info     program  T..       S    S    S
 notice   program  T..  S    S    S    S
 mistake  user     T..  S    S    S    SL
 warning  program  T..  S    S    SL   SL
 error    user     TE.  S    S    SL   SC
 fault    system   TE!  S    S    SL   SC
 alert    system   T.!  SL   SL   SC   SC
 failure  system   TE!  SL   SL   SC   SC
 panic    program  .E.  SC   SC   SC   SC

 T - usually translated
 E - exception (execution interrupted)
 ! - will include $! text at display
 L - include filename and linenumber
 S - show/print when accepted
 C - stack trace (like Carp::confess())

=head3 Filters

With a filter, you can block or modify specific messages before
translation.  There may be a wish to change the REASON of a report
or its content.  It is not possible to avoid the exit which is
related to the original message, because a module's flow depends
on it to happen.

When there are filters defined, they will be called in order of
definition.  For each of the dispatchers which are called for a
certain REASON (which C<accept> that REASON), it is checked whether
its name is listed for the filter (when no names where specified,
then the filter is applied to all dispatchers).

When selected, the filter's CODE reference is called with four arguments:
the dispatcher object (a L<Log::Report::Dispatcher|Log::Report::Dispatcher>), the HASH-of-OPTIONS
passed as optional first argument to L<Log::Report::report()|Log::Report/"Report Production and Configuration">, the
REASON, and the MESSAGE.  Returned is the new REASON and MESSAGE.
When the returned REASON is C<undef>, then the message will be ignored
for that dispatcher.

Be warned about processing the MESSAGE: it is a L<Log::Report::Message|Log::Report::Message>
object which may have a C<prepend> string and C<append> string or
object.  When the call to L<Log::Report::report()|Log::Report/"Report Production and Configuration"> contained multiple
comma-separated components, these will already have been joined together
using concatenation (see L<Log::Report::Message::concat()|Log::Report::Message/"Processing">.

B<. Example: a filter on syslog>

 dispatcher filter => \&myfilter, 'syslog';

 # ignore all translatable and non-translatable messages containing
 # the word "skip"
 sub myfilter($$$$)
 {   my ($disp, $opts, $reason, $message) = @_;
     return () if $message->untranslated =~ m/\bskip\b/;
     ($reason, $message);
 }

B<. Example: take all mistakes and warnings serious>

 dispatch filter => \&take_warns_seriously;
 sub take_warns_seriously($$$$)
 {   my ($disp, $opts, $reason, $message) = @_;
       $reason eq 'MISTAKE' ? (ERROR   => $message)
     : $reason eq 'WARNING' ? (FAULT   => $message)
     :                        ($reason => $message);
 }

=head1 SEE ALSO

This module is part of Log-Report distribution version 1.31,
built on January 15, 2021. Website: F<http://perl.overmeer.net/CPAN/>

=head1 LICENSE

Copyrights 2007-2021 by [Mark Overmeer <markov@cpan.org>]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See F<http://dev.perl.org/licenses/>

