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Template.pm

#============================================================= -*-perl-*-
#
# Template
#
# DESCRIPTION
#   Module implementing a simple, user-oriented front-end to the Template
#   Toolkit.
#
# AUTHOR
#   Andy Wardley   <abw@wardley.org>
#
# COPYRIGHT
#   Copyright (C) 1996-2022 Andy Wardley.  All Rights Reserved.
#
#   This module is free software; you can redistribute it and/or
#   modify it under the same terms as Perl itself.
#
#========================================================================

package Template;

use strict;
use warnings;
use 5.006;
use base 'Template::Base';

use Template::Config;
use Template::Constants;
use Template::Provider;
use Template::Service;
use File::Basename;
use File::Path;
use Scalar::Util qw(blessed);

our $VERSION = '3.101';
our $ERROR   = '';
our $DEBUG   = 0;
our $BINMODE = 0 unless defined $BINMODE;
our $AUTOLOAD;

# preload all modules if we're running under mod_perl
Template::Config->preload() if $ENV{ MOD_PERL };

#------------------------------------------------------------------------
# process($input, \%replace, $output)
#
# Main entry point for the Template Toolkit.  The Template module
# delegates most of the processing effort to the underlying SERVICE
# object, an instance of the Template::Service class.
#------------------------------------------------------------------------

sub process {
    my ($self, $template, $vars, $outstream, @opts) = @_;
    my ($output, $error);
    my $options = (@opts == 1) && ref($opts[0]) eq 'HASH'
        ? shift(@opts) : { @opts };

$options->{ binmode } = $BINMODE
        unless defined $options->{ binmode };

# we're using this for testing in t/output.t and t/filter.t so
    # don't remove it if you don't want tests to fail...
    $self->DEBUG("set binmode\n") if $DEBUG && $options->{ binmode };

$output = $self->{ SERVICE }->process($template, $vars);

if (defined $output) {
        $outstream ||= $self->{ OUTPUT };
        unless (ref $outstream) {
            my $outpath = $self->{ OUTPUT_PATH };
            $outstream = "$outpath/$outstream" if $outpath;
        }

# send processed template to output stream, checking for error
        return ($self->error($error))
            if ($error = &_output($outstream, \$output, $options));

return 1;
    }
    else {
        return $self->error($self->{ SERVICE }->error);
    }
}

#------------------------------------------------------------------------
# service()
#
# Returns a reference to the internal SERVICE object which handles
# all requests for this Template object
#------------------------------------------------------------------------

sub service {
    my $self = shift;
    return $self->{ SERVICE };
}

#------------------------------------------------------------------------
# context()
#
# Returns a reference to the CONTEXT object within the SERVICE
# object.
#------------------------------------------------------------------------

sub context {
    my $self = shift;
    return $self->{ SERVICE }->{ CONTEXT };
}

sub template {
    shift->context->template(@_);
}

#========================================================================
#                     -- PRIVATE METHODS --
#========================================================================

#------------------------------------------------------------------------
# _init(\%config)
#------------------------------------------------------------------------
sub _init {
    my ($self, $config) = @_;

# convert any textual DEBUG args to numerical form
    my $debug = $config->{ DEBUG };
    $config->{ DEBUG } = Template::Constants::debug_flags($self, $debug)
        || return if defined $debug && $debug !~ /^\d+$/;

# prepare a namespace handler for any CONSTANTS definition
    if (my $constants = $config->{ CONSTANTS }) {
        my $ns  = $config->{ NAMESPACE } ||= { };
        my $cns = $config->{ CONSTANTS_NAMESPACE } || 'constants';
        $constants = Template::Config->constants($constants)
            || return $self->error(Template::Config->error);
        $ns->{ $cns } = $constants;
    }

$self->{ SERVICE } = $config->{ SERVICE }
        || Template::Config->service($config)
        || return $self->error(Template::Config->error);

$self->{ OUTPUT      } = $config->{ OUTPUT } || \*STDOUT;
    $self->{ OUTPUT_PATH } = $config->{ OUTPUT_PATH };

return $self;
}

#------------------------------------------------------------------------
# _output($where, $text)
#------------------------------------------------------------------------

sub _output {
    my ($where, $textref, $options) = @_;
    my $reftype;
    my $error = 0;

# call a CODE reference
    if (($reftype = ref($where)) eq 'CODE') {
        &$where($$textref);
    }
    # print to a glob (such as \*STDOUT)
    elsif ($reftype eq 'GLOB') {
        print $where $$textref;
    }
    # append output to a SCALAR ref
    elsif ($reftype eq 'SCALAR') {
        $$where .= $$textref;
    }
    # push onto ARRAY ref
    elsif ($reftype eq 'ARRAY') {
        push @$where, $$textref;
    }
    # call the print() method on an object that implements the method
    # (e.g. IO::Handle, Apache::Request, etc)
    elsif (blessed($where) && $where->can('print')) {
        $where->print($$textref);
    }
    # a simple string is taken as a filename
    elsif (! $reftype) {
        local *FP;
        # make destination directory if it doesn't exist
        my $dir = dirname($where);
        eval { mkpath($dir) unless -d $dir; };
        if ($@) {
            # strip file name and line number from error raised by die()
            ($error = $@) =~ s/ at \S+ line \d+\n?$//;
        }
        elsif (open(FP, '>', $where)) {
            # binmode option can be 1 or a specific layer, e.g. :utf8
            my $bm = $options->{ binmode  };
            if (not(defined $bm)) {
              $bm = $BINMODE;
            }
            if ($bm && $bm eq 1) {
                binmode FP;
            }
            elsif ($bm){
                binmode FP, $bm;
            }
            print FP $$textref;
            close FP;
        }
        else {
            $error  = "$where: $!";
        }
    }
    # give up, we've done our best
    else {
        $error = "output_handler() cannot determine target type ($where)\n";
    }

return $error;
}

__END__

=head1 NAME

Template - Front-end module to the Template Toolkit

=head1 SYNOPSIS

use Template;

# some useful options (see below for full list)
    my $config = {
        INCLUDE_PATH => '/search/path',  # or list ref
        INTERPOLATE  => 1,               # expand "$var" in plain text
        POST_CHOMP   => 1,               # cleanup whitespace
        PRE_PROCESS  => 'header',        # prefix each template
        EVAL_PERL    => 1,               # evaluate Perl code blocks
    };

# create Template object
    my $template = Template->new($config);

# define template variables for replacement
    my $vars = {
        var1  => $value,
        var2  => \%hash,
        var3  => \@list,
        var4  => \&code,
        var5  => $object,
    };

# specify input filename, or file handle, text reference, etc.
    my $input = 'myfile.html';

# process input template, substituting variables
    $template->process($input, $vars)
        || die $template->error();

=head1 DESCRIPTION

This documentation describes the Template module which is the direct
Perl interface into the Template Toolkit.  It covers the use of the
module and gives a brief summary of configuration options and template
directives.  Please see L<Template::Manual> for the complete reference
manual which goes into much greater depth about the features and use
of the Template Toolkit.  The L<Template::Tutorial> is also available
as an introductory guide to using the Template Toolkit.

=head1 METHODS

=head2 new(\%config)

The C<new()> constructor method (implemented by the
L<Template::Base|Template::Base#new()> base class) instantiates a new
C<Template> object. A reference to a hash array of configuration items may be
passed as a parameter.

my $tt = Template->new({
        INCLUDE_PATH => '/usr/local/templates',
        EVAL_PERL    => 1,
    }) || die $Template::ERROR, "\n";

A reference to a new C<Template> object is returned, or undef on error. In the
latter case, the error message can be retrieved by calling L<error()> as a
class method or by examining the C<$Template::ERROR> package variable
directly.

my $tt = Template->new(\%config)
        || die Template->error(), "\n";

my $tt = Template->new(\%config)
        || die $Template::ERROR, "\n";

For convenience, configuration items may also be specified as a list
of items instead of a hash array reference.  These are automatically
folded into a hash array by the constructor.

my $tt = Template->new(INCLUDE_PATH => '/tmp', POST_CHOMP => 1)
        || die $Template::ERROR, "\n";

=head2 process($template, \%vars, $output, %options)

The C<process()> method is called to process a template. The first parameter
indicates the input template as one of:

=over 4

=item *

a filename relative to C<INCLUDE_PATH>, if defined

=item *

a reference to a text string containing the template text

=item *

a file handle reference (e.g. C<IO::Handle> or sub-class) or C<GLOB>
(e.g. C<\*STDIN>), from which the template can be read.

=back

A reference to
a hash array may be passed as the second parameter, containing definitions of
template variables.

# filename
    $tt->process('welcome.tt2')
        || die $tt->error(), "\n";

# text reference
    $text = "[% INCLUDE header %]\nHello world!\n[% INCLUDE footer %]";
    $tt->process(\$text)
        || die $tt->error(), "\n";

# file handle (GLOB)
    $tt->process(\*DATA)
        || die $tt->error(), "\n";

__END__
    [% INCLUDE header %]
    This is a template defined in the __END__ section which is
    accessible via the DATA "file handle".
    [% INCLUDE footer %]

By default, the processed template output is printed to C<STDOUT>. The
C<process()> method then returns C<1> to indicate success. A third parameter
may be passed to the C<process()> method to specify a different output location.
This value may be one of:

=over 4

=item *

a plain string indicating a filename which will be opened (relative to
C<OUTPUT_PATH>, if defined) and the output written to

=item *

a file GLOB opened ready for output

=item *

a reference to a scalar (e.g. a text string) to which output/error is appended

=item *

a reference to a subroutine which is called, passing the output as a parameter

=item *

any object reference which implements a C<print()> method (e.g. C<IO::Handle>,
C<Apache::Request>, etc.) which will be called, passing the generated output
as a parameter.

=back

Examples:

# output filename
    $tt->process('welcome.tt2', $vars, 'welcome.html')
        || die $tt->error(), "\n";

# reference to output subroutine
    sub myout {
        my $output = shift;
        ...
    }
    $tt->process('welcome.tt2', $vars, \&myout)
        || die $tt->error(), "\n";

# reference to output text string
    my $output = '';
    $tt->process('welcome.tt2', $vars, \$output)
        || die $tt->error(), "\n";

print "output: $output\n";

In an Apache/mod_perl handler:

sub handler {
        my $req = shift;

# ...your code here...

# direct output to Apache::Request via $req->print($output)
        $tt->process($file, $vars, $req) || do {
            $req->log_reason($tt->error());
            return SERVER_ERROR;
        };
        return OK;
    }

After the optional third output argument can come an optional
reference to a hash or a list of C<(name, value)> pairs providing further
options for the output.  The only option currently supported is
C<binmode> which, when set to any true value will ensure that files
created (but not any existing file handles passed) will be set to
binary mode.

# either: hash reference of options
    $tt->process($infile, $vars, $outfile, { binmode => 1 })
        || die $tt->error(), "\n";

# or: list of name, value pairs
    $tt->process($infile, $vars, $outfile, binmode => 1)
        || die $tt->error(), "\n";

Alternately, the C<binmode> argument can specify a particular IO layer such
as C<:utf8>.

$tt->process($infile, $vars, $outfile, binmode => ':utf8')
        || die $tt->error(), "\n";

The C<OUTPUT> configuration item can be used to specify a default output
location other than C<\*STDOUT>.  The C<OUTPUT_PATH> specifies a directory
which should be prefixed to all output locations specified as filenames.

my $tt = Template->new({
        OUTPUT      => sub { ... },       # default
        OUTPUT_PATH => '/tmp',
    ...
    }) || die Template->error(), "\n";

# use default OUTPUT (sub is called)
    $tt->process('welcome.tt2', $vars)
        || die $tt->error(), "\n";

# write file to '/tmp/welcome.html'
    $tt->process('welcome.tt2', $vars, 'welcome.html')
        || die $tt->error(), "\n";

The C<process()> method returns C<1> on success or C<undef> on error. The
error message generated in the latter case can be retrieved by calling the
L<error()> method. See also L<CONFIGURATION SUMMARY> which describes how error
handling may be further customised.

=head2 error()

When called as a class method, it returns the value of the C<$ERROR> package
variable.  Thus, the following are equivalent.

my $tt = Template->new()
        || die Template->error(), "\n";

my $tt = Template->new()
        || die $Template::ERROR, "\n";

When called as an object method, it returns the value of the internal
C<_ERROR> variable, as set by an error condition in a previous call to
process().

$tt->process('welcome.tt2')
        || die $tt->error(), "\n";

Errors are represented in the Template Toolkit by objects of the
L<Template::Exception> class. If the L<process()> method returns a false value
then the C<error()> method can be called to return an object of this class.
The L<type()|Template::Exception#type()> and
L<info()|Template::Exception#info()> methods can called on the object to
retrieve the error type and information string, respectively. The
L<as_string()|Template::Exception#as_string()>
method can be called to return a string of the form C<$type - $info>. This
method is also overloaded onto the stringification operator allowing the
object reference itself to be printed to return the formatted error string.

$tt->process('somefile') || do {
        my $error = $tt->error();
        print "error type: ", $error->type(), "\n";
        print "error info: ", $error->info(), "\n";
        print $error, "\n";
    };

=head2 service()

The C<Template> module delegates most of the effort of processing templates
to an underlying L<Template::Service> object.  This method returns a reference
to that object.

=head2 context()

The L<Template::Service> module uses a core L<Template::Context> object for
runtime processing of templates.  This method returns a reference to
that object and is equivalent to C<< $template-E<gt>service-E<gt>context() >>.

=head2 template($name)

This method is a simple wrapper around the L<Template::Context> method of the
same name.  It returns a compiled template for the source provided as an
argument.

=head1 CONFIGURATION SUMMARY

The following list gives a short summary of each Template Toolkit
configuration option.  See L<Template::Manual::Config> for full details.

=head2 Template Style and Parsing Options

=head3 ENCODING

Specifies the character encoding.

=head3 START_TAG, END_TAG

Define tokens that indicate start and end of directives
(default: 'C<[%>' and 'C<%]>').

=head3 TAG_STYLE

Set C<START_TAG> and C<END_TAG> according to a pre-defined style (default:
'C<template>', as above).

=head3 PRE_CHOMP, POST_CHOMP

Removes whitespace before/after directives (default: 0/0).

=head3 TRIM

Remove leading and trailing whitespace from template output (default: 0).

=head3 INTERPOLATE

Interpolate variables embedded like C<$this> or C<${this}> (default: 0).

=head3 ANYCASE

Allow directive keywords in lower case (default: 0 - UPPER only).

=head2 Template Files and Blocks

=head3 INCLUDE_PATH

One or more directories to search for templates.

=head3 DELIMITER

Delimiter for separating paths in C<INCLUDE_PATH> (default: 'C<:>').

=head3 ABSOLUTE

Allow absolute file names, e.g. C</foo/bar.html> (default: 0).

=head3 RELATIVE

Allow relative filenames, e.g. C<../foo/bar.html> (default: 0).

=head3 DEFAULT

Default template to use when another not found.

=head3 BLOCKS

Hash array pre-defining template blocks.

=head3 AUTO_RESET

Enabled by default causing C<BLOCK> definitions to be reset each time a
template is processed.  Disable to allow C<BLOCK> definitions to persist.

=head3 RECURSION

Flag to permit recursion into templates (default: 0).

=head2 Template Variables

=head3 VARIABLES

Hash array of variables and values to pre-define in the stash.

=head2 Runtime Processing Options

=head3 EVAL_PERL

Flag to indicate if C<PERL>/C<RAWPERL> blocks should be processed (default: 0).

=head3 PRE_PROCESS, POST_PROCESS

Name of template(s) to process before/after main template.

=head3 PROCESS

Name of template(s) to process instead of main template.

=head3 ERROR

Name of error template or reference to hash array mapping error types to
templates.

=head3 OUTPUT

Default output location or handler.

=head3 OUTPUT_PATH

Directory into which output files can be written.

=head3 DEBUG

Enable debugging messages.

=head2 Caching and Compiling Options

=head3 CACHE_SIZE

Maximum number of compiled templates to cache in memory (default:
undef - cache all)

=head3 COMPILE_EXT

Filename extension for compiled template files (default: undef - don't
compile).

=head3 COMPILE_DIR

Root of directory in which compiled template files should be written
(default: undef - don't compile).

=head2 Plugins and Filters

=head3 PLUGINS

Reference to a hash array mapping plugin names to Perl packages.

=head3 PLUGIN_BASE

One or more base classes under which plugins may be found.

=head3 LOAD_PERL

Flag to indicate regular Perl modules should be loaded if a named plugin
can't be found  (default: 0).

=head3 FILTERS

Hash array mapping filter names to filter subroutines or factories.

=head2 Customisation and Extension

=head3 LOAD_TEMPLATES

List of template providers.

=head3 LOAD_PLUGINS

List of plugin providers.

=head3 LOAD_FILTERS

List of filter providers.

=head3 TOLERANT

Set providers to tolerate errors as declinations (default: 0).

=head3 SERVICE

Reference to a custom service object (default: L<Template::Service>).

=head3 CONTEXT

Reference to a custom context object (default: L<Template::Context>).

=head3 STASH

Reference to a custom stash object (default: L<Template::Stash>).

=head3 PARSER

Reference to a custom parser object (default: L<Template::Parser>).

=head3 GRAMMAR

Reference to a custom grammar object (default: L<Template::Grammar>).

=head1 DIRECTIVE SUMMARY

The following list gives a short summary of each Template Toolkit directive.
See L<Template::Manual::Directives> for full details.

=head2 GET

Evaluate and print a variable or value.

[%   GET variable %]    # 'GET' keyword is optional
    [%       variable %]
    [%       hash.key %]
    [%         list.n %]
    [%     code(args) %]
    [% obj.meth(args) %]
    [%  "value: $var" %]

=head2 CALL

As per L<GET> but without printing result (e.g. call code)

[%  CALL variable %]

=head2 SET

Assign a values to variables.

[% SET variable = value %]    # 'SET' also optional
    [%     variable = other_variable
           variable = 'literal text @ $100'
           variable = "interpolated text: $var"
           list     = [ val, val, val, val, ... ]
           list     = [ val..val ]
           hash     = { var => val, var => val, ... }
    %]

=head2 DEFAULT

Like L<SET>, but variables are only set if currently unset (i.e. have no
true value).

[% DEFAULT variable = value %]

=head2 INSERT

Insert a file without any processing performed on the contents.

[% INSERT legalese.txt %]

=head2 PROCESS

Process another template file or block and insert the generated output.
Any template L<BLOCK>s or variables defined or updated in the C<PROCESS>ed
template will thereafter be defined in the calling template.

[% PROCESS template %]
    [% PROCESS template  var = val, ... %]

=head2 INCLUDE

Similar to C<PROCESS>, but using a local copy of the current variables.
Any template C<BLOCK>s or variables defined in the C<INCLUDE>d template
remain local to it.

[% INCLUDE template %]
    [% INCLUDE template  var = val, ... %]

=head2 WRAPPER

The content between the C<WRAPPER> and corresponding C<END> directives is first
evaluated, with the output generated being stored in the C<content> variable.
The named template is then process as per C<INCLUDE>.

[% WRAPPER layout %]
       Some template markup [% blah %]...
    [% END %]

A simple F<layout> template might look something like this:

Your header here...
    [% content %]
    Your footer here...

=head2 BLOCK

Define a named template block for L<INCLUDE>, L<PROCESS> and L<WRAPPER>
to use.

[% BLOCK hello %]
       Hello World
    [% END %]

[% INCLUDE hello %]

=head2 FOREACH

Repeat the enclosed C<FOREACH> ... C<END> block for each value in the list.

[% FOREACH variable IN [ val, val, val ] %]    # either
    [% FOREACH variable IN list %]                 # or
       The variable is set to [% variable %]
    [% END %]

=head2 WHILE

The block enclosed between C<WHILE> and C<END> block is processed while
the specified condition is true.

[% WHILE condition %]
       content
    [% END %]

=head2 IF / UNLESS / ELSIF / ELSE

The enclosed block is processed if the condition is true / false.

[% IF condition %]
       content
    [% ELSIF condition %]
     content
    [% ELSE %]
     content
    [% END %]

[% UNLESS condition %]
       content
    [% # ELSIF/ELSE as per IF, above %]
       content
    [% END %]

=head2 SWITCH / CASE

Multi-way switch/case statement.

[% SWITCH variable %]
    [%   CASE val1 %]
           content
    [%   CASE [ val2, val3 ] %]
           content
    [%   CASE %]         # or [% CASE DEFAULT %]
           content
    [% END %]

=head2 MACRO

Define a named macro.

[% MACRO name <directive> %]
    [% MACRO name(arg1, arg2) <directive> %]
    ...
    [% name %]
    [% name(val1, val2) %]

=head2 FILTER

Process enclosed C<FILTER> ... C<END> block then pipe through a filter.

[% FILTER name %]                       # either
    [% FILTER name( params ) %]             # or
    [% FILTER alias = name( params ) %]     # or
       content
    [% END %]

=head2 USE

Load a plugin module (see C<Template::<Manual::Plugins>), or any regular Perl
module when the C<LOAD_PERL> option is set.

[% USE name %]                      # either
    [% USE name( params ) %]            # or
    [% USE var = name( params ) %]      # or
    ...
    [% name.method %]
    [% var.method %]

=head2 PERL / RAWPERL

Evaluate enclosed blocks as Perl code (requires the C<EVAL_PERL> option to be
set).

[% PERL %]
     # perl code goes here
     $stash->set('foo', 10);
     print "set 'foo' to ", $stash->get('foo'), "\n";
     print $context->include('footer', { var => $val });
    [% END %]

[% RAWPERL %]
       # raw perl code goes here, no magic but fast.
       $output .= 'some output';
    [% END %]

=head2 TRY / THROW / CATCH / FINAL

Exception handling.

[% TRY %]
     content
       [% THROW type info %]
    [% CATCH type %]
     catch content
       [% error.type %] [% error.info %]
    [% CATCH %] # or [% CATCH DEFAULT %]
     content
    [% FINAL %]
       this block is always processed
    [% END %]

=head2 NEXT

Jump straight to the next item in a C<FOREACH> or C<WHILE> loop.

[% NEXT %]

=head2 LAST

Break out of C<FOREACH> or C<WHILE> loop.

[% LAST %]

=head2 RETURN

Stop processing current template and return to including templates.

[% RETURN %]

=head2 STOP

Stop processing all templates and return to caller.

[% STOP %]

=head2 TAGS

Define new tag style or characters (default: C<[%> C<%]>).

[% TAGS html %]
    [% TAGS  %]

=head2 COMMENTS

Ignored and deleted.

[% # this is a comment to the end of line
       foo = 'bar'
    %]

[%# placing the '#' immediately inside the directive
        tag comments out the entire directive
    %]

=head1 SOURCE CODE REPOSITORY

The source code for the Template Toolkit is held in a public git repository
on Github: L<https://github.com/abw/Template2>

=head1 AUTHOR

Andy Wardley E<lt>abw@wardley.orgE<gt> L<http://wardley.org/>

=head1 VERSION

Template Toolkit version 3.100, released on July 13 2020.

=head1 SUPPORT

The Template Toolkit mailing list provides a forum for discussing
issues relating to the use and abuse of the Template Toolkit.  There
are a number of knowledgeable and helpful individuals who frequent the
list (including the author) who can often offer help or suggestions.
Please respect their time and patience by checking the documentation
and/or mailing list archives before asking questions that may already
have been answered.

To subscribe to the mailing list, send an email to:

template-toolkit+subscribe@groups.io

You can also use the web interface:

https://groups.io/g/template-toolkit

For information about commercial support and consultancy for the Template
Toolkit, please contact the author.

=head1 COPYRIGHT

This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

=cut

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