=encoding utf8

=head1 NAME

Mail::Reporter - base-class and error reporter for Mail::Box

=head1 INHERITANCE

 Mail::Reporter is extended by
   Mail::Box
   Mail::Box::Collection
   Mail::Box::Identity
   Mail::Box::Locker
   Mail::Box::MH::Index
   Mail::Box::MH::Labels
   Mail::Box::Manager
   Mail::Box::Parser
   Mail::Box::Search
   Mail::Box::Thread::Manager
   Mail::Box::Thread::Node
   Mail::Message
   Mail::Message::Body
   Mail::Message::Body::Delayed
   Mail::Message::Convert
   Mail::Message::Field
   Mail::Message::Field::Attribute
   Mail::Message::Head
   Mail::Message::Head::FieldGroup
   Mail::Message::TransferEnc
   Mail::Server
   Mail::Transport

=head1 SYNOPSIS

 $folder->log(WARNING => 'go away');
 print $folder->trace;        # current level
 $folder->trace('PROGRESS');  # set level
 print $folder->errors;
 print $folder->report('PROGRESS');

=head1 DESCRIPTION

The C<Mail::Reporter> class is the base class for all classes, except
L<Mail::Message::Field::Fast|Mail::Message::Field::Fast> because it would become slow...  This
base class is used during initiation of the objects, and for configuring
and logging error messages.

=head1 METHODS

The C<Mail::Reporter> class is the base for nearly all other
objects.  It can store and report problems, and contains the general
constructor L<new()|Mail::Reporter/"Constructors">.

=head2 Constructors

=over 4

=item Mail::Reporter-E<gt>B<new>(%options)

This error container is also the base constructor for all modules, (as long
as there is no need for another base object)  The constructor always accepts
the following %options related to error reports.

 -Option--Default
  log     'WARNINGS'
  trace   'WARNINGS'

=over 2

=item log => LEVEL

Log messages which have a priority higher or equal to the specified
level are stored internally and can be retrieved later.  The global
default for this option can be changed with L<defaultTrace()|Mail::Reporter/"Error handling">.

Known levels are C<INTERNAL>, C<ERRORS>, C<WARNINGS>, C<PROGRESS>,
C<NOTICES> C<DEBUG>, and C<NONE>.  The C<PROGRESS> level relates to
the reading and writing of folders.  C<NONE> will cause only C<INTERNAL>
errors to be logged.
By the way: C<ERROR> is an alias for C<ERRORS>, as C<WARNING> is an alias
for C<WARNINGS>, and C<NOTICE> for C<NOTICES>.

=item trace => LEVEL

Trace messages which have a level higher or equal to the specified level
are directly printed using warn.  The global default for this option can
be changed with L<defaultTrace()|Mail::Reporter/"Error handling">.

=back

=back

=head2 Error handling

=over 4

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

By default, produce a nice warning if the sub-classes cannot resolve
a method.

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

Add the report from other $object to the report of this object. This is
useful when complex actions use temporary objects which are not returned
to the main application but where the main application would like to know
about any problems.

=item $obj-E<gt>B<defaultTrace>( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )

=item Mail::Reporter-E<gt>B<defaultTrace>( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )

Reports the default log and trace level which is used for object as list
of two elements.  When not explicitly set, both are set to C<WARNINGS>.

This method has three different uses. When one argument is specified, that
$level is set for both loglevel as tracelevel.

With two arguments, the second determines which configuration you like.  If
the second argument is a CODE reference, you install a $callback.  The loglevel
will be set to NONE, and all warnings produced in your program will get
passed to the $callback function.  That function will get the problem level,
the object or class which reports the problem, and the problem text passed
as arguments.

In any case two values are returned: the first is the log level, the
second represents the trace level.  Both are special variables: in numeric
context they deliver a value (the internally used value), and in string
context the string name.  Be warned that the string is always in singular
form!

example: setting loglevels

 my ($loglevel, $tracelevel) = Mail::Reporter->defaultTrace;
 Mail::Reporter->defaultTrace('NOTICES');

 my ($l, $t) = Mail::Reporter->defaultTrace('WARNINGS', 'DEBUG');
 print $l;     # prints "WARNING"  (no S!)
 print $l+0;   # prints "4"
 print "Auch" if $l >= $self->logPriority('ERROR');

 Mail::Reporter->defaultTrace('NONE');  # silence all reports

 $folder->defaultTrace('DEBUG');   # Still set as global default!
 $folder->trace('DEBUG');          # local default

example: installing a callback

 Mail::Reporter->defaultTrace

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

Equivalent to

 $folder->report('ERRORS')

=item $obj-E<gt>B<log>( [$level, [$strings]] )

=item Mail::Reporter-E<gt>B<log>( [$level, [$strings]] )

As instance method, this function has three different purposes.  Without
any argument, it returns one scalar containing the number which is internally
used to represent the current log level, and the textual representation of
the string at the same time. See Scalar::Util method C<dualvar> for
an explanation.

With one argument, a new level of logging detail is set (specify a number
of one of the predefined strings).  With more arguments, it is a report
which may need to be logged or traced.

As class method, only a message can be passed.  The global configuration
value set with L<defaultTrace()|Mail::Reporter/"Error handling"> is used to decide whether the message is
shown or ignored.

Each log-entry has a $level and a text string which will
be constructed by joining the $strings.  If there is no newline, it will
be added.

example: 

 print $message->log;      # may print "NOTICE"
 print $message->log +0;   # may print "3"
 $message->log('ERRORS');  # sets a new level, returns the numeric value

 $message->log(WARNING => "This message is too large.");
 $folder ->log(NOTICE  => "Cannot read from file $filename.");
 $manager->log(DEBUG   => "Hi there!", reverse sort @l);

 Mail::Message->log(ERROR => 'Unknown');

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

=item Mail::Reporter-E<gt>B<logPriority>($level)

One error level (log or trace) has more than one representation: a
numeric value and one or more strings.  For instance, C<4>, C<'WARNING'>,
and C<'WARNINGS'> are all the same.  You can specify any of these,
and in return you get a dualvar (see Scalar::Util method C<dualvar>)
back, which contains the number and the singular form.

The higher the number, the more important the message.
Only messages about C<INTERNAL> problems are more important than C<NONE>.

example: 

 my $r = Mail::Reporter->logPriority('WARNINGS');
 my $r = Mail::Reporter->logPriority('WARNING');    # same
 my $r = Mail::Reporter->logPriority(4);            # same, deprecated
 print $r;      # prints 'WARNING'  (no S!)
 print $r + 0;  # prints 4
 if($r < Mail::Reporter->logPriority('ERROR')) {..} # true

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

Returns a list of C<(key => value)> pairs which can be used to initiate
a new object with the same log-settings as this one.

example: 

 $head->new($folder->logSettings);

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

A special case of L<log()|Mail::Reporter/"Error handling">, which logs a C<INTERNAL>-error
and then croaks.  This is used by extension writers.

=item $obj-E<gt>B<report>( [$level] )

Get logged reports, as list of strings.  If a $level is specified, the log
for that level is returned.

In case no $level is specified, you get all messages each as reference
to a tuple with level and message.

example: 

 my @warns = $message->report('WARNINGS');
   # previous indirectly callable with
   my @warns = $msg->warnings;

 print $folder->report('ERRORS');

 if($folder->report('DEBUG')) {...}

 my @reports = $folder->report;
 foreach (@reports) {
    my ($level, $text) = @$_;
    print "$level report: $text";
 }

=item $obj-E<gt>B<reportAll>( [$level] )

Report all messages which were produced by this object and all the objects
which are maintained by this object.  This will return a list of triplets,
each containing a reference to the object which caught the report, the
level of the report, and the message.

example: 

 my $folder = Mail::Box::Manager->new->open(folder => 'inbox');
 my @reports = $folder->reportAll;
 foreach (@reports) {
    my ($object, $level, $text) = @$_;

    if($object->isa('Mail::Box')) {
       print "Folder $object: $level: $message";
    } elsif($object->isa('Mail::Message') {
       print "Message ".$object->seqnr.": $level: $message";
    }
 }

=item $obj-E<gt>B<trace>( [$level] )

Change the trace $level of the object. When no arguments are specified, the
current level is returned only.  It will be returned in one scalar which
contains both the number which is internally used to represent the level,
and the string which represents it.  See L<logPriority()|Mail::Reporter/"Error handling">.

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

Equivalent to

 $folder->report('WARNINGS')

=back

=head2 Cleanup

=over 4

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

Cleanup the object.

=back

=head1 DIAGNOSTICS

=over 4

=item Error: Package $package does not implement $method.

Fatal error: the specific package (or one of its superclasses) does not
implement this method where it should. This message means that some other
related classes do implement this method however the class at hand does
not.  Probably you should investigate this and probably inform the author
of the package.

=back

=head1 SEE ALSO

This module is part of Mail-Message distribution version 3.008,
built on February 11, 2019. Website: F<http://perl.overmeer.net/CPAN/>

=head1 LICENSE

Copyrights 2001-2019 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/>