NAME
    CGI::Application::Plugin::AnyTemplate - Use any templating system from
    within CGI::Application using a unified interface

VERSION
    Version 0.06

SYNOPSIS
    In your CGI::Application-based webapp:

        use base 'CGI::Application';
        use CGI::Application::Plugin::AnyTemplate;

        sub cgiapp_init {
            my $self = shift;

            # Set template options
            $self->template->config(
                default_type => 'TemplateToolkit',
            );
        }

    Later on, in a runmode:

        sub my_runmode {
            my $self = shift;

            my %template_params = (
                name     => 'Winston Churchill',
                age      => 7,
            );

            $self->template->fill('some_template', \%template_params);
        }

DESCRIPTION
  Template-Independence
    "CGI::Application::Plugin::AnyTemplate" allows you to use any supported
    Perl templating system using a single consistent interface.

    Currently supported templating systems include HTML::Template,
    HTML::Template::Expr, Template::Toolkit and Petal.

    You can access any of these templating systems using the same interface.
    In this way, you can use the same code and switch templating systems on
    the fly.

    This approach has many uses. For instance, it can be useful in migrating
    your application from one templating system to another.

  Embedded Components
    In addition to template abstraction, "AnyTemplate" also provides a
    *embedded component mechanism*. For instance, you might include a
    *header* component at the top of every page and a *footer* component at
    the bottom of every page.

    These components are actually full CGI::Application run modes, and can
    do anything normal run mode can do, including processing form parameters
    and filling in their own templates. See below under "EMBEDDED
    COMPONENTS" for details.

  Multiple Named Template Configurations
    You can set up multiple named template configurations and select between
    them at run time.

        sub cgiapp_init {
            my $self = shift;

            # Can't use Template::Toolkit any more -
            # The boss wants everything has to be XML,
            # so we switch to Petal

            # Set old-style template options (legacy scripts)
            $self->template('oldstyle')->config(
                default_type => 'TemplateToolkit',
                TemplateToolkit => {
                    POST_CHOMP => 1,
                }
            );
            # Set new-style template options as default
            $self->template->config(
                default_type => 'Petal',
                auto_add_template_extension => 0,
            );
        }

        sub old_style_runmode {
            my $self = shift;

            # ...

            # use TemplateToolkit to fill template edit_user.tmpl
            $self->template('oldstyle')->fill('edit_user', \%params);

        }

        sub new_style_runmode {
            my $self = shift;

            # ...

            # use Petal to fill template edit_user.xhml
            $self->template->fill('edit_user.xhtml', \%params);

        }

  Flexible Syntax
    The syntax is pretty flexible. Pick a style that's most comfortable for
    you.

   CGI::Application::Plugin::TT style syntax
        $self->template->process('edit_user', \%params);

    or (with slightly less typing):

        $self->template->fill('edit_user', \%params);

   CGI::Application load_tmpl style syntax
        my $template = $self->template->load('edit_user');
        $template->param('foo' => 'bar');
        $template->output;

   Verbose syntax (for complete control)
        my $template = $self->template('named_config')->load(
            file             => 'edit_user'
            type             => 'TemplateToolkit'
            add_include_path => '.',
        );

        $template->param('foo' => 'bar');
        $template->output;

    See also below under "CHANGING THE NAME OF THE 'template' METHOD".

METHODS
  config
    Initialize the "AnyTemplate" system and provide the default
    configuration.

        $self->template->config(
            default_type => 'HTMLTemplate',
        );

    You can keep multiple configurations handy at the same time by passing a
    value to "template":

        $self->template('oldstyle')->config(
            default_type => 'HTML::Template',
        );
        $self->template('newstyle')->config(
            default_type => 'HTML::Template::Expr',
        );

    Then in a runmode you can mix and match configurations:

        $self->template('oldstyle')->load  # loads an HTML::Template driver object
        $self->template('newstyle')->load  # loads an HTML::Template::Expr driver object

    The configuration passed to "config" is divided into three areas:
    *plugin configuration*, *driver configuration*, and *native
    configuration*:

        Config Type       What it Configures
        -----------       ------------------
        Plugin Config     AnyTemplate itself
        Driver Config     AnyTemplate Driver (e.g. HTMLTemplate)
        Native Config     Actual template module (e.g. HTML::Template)

    These are described in more detail below.

   Plugin Configuration
    These configuration params are specific to the
    "CGI::Application::Plugin::AnyTemplate" itself. They are included at the
    top level of the configuration hash passed to "config". For instance:

        $self->template->config(
            default_type                => 'HTMLTemplate',
            auto_add_template_extension => 0,
        );

    The *plugin configuration* parameters and their defaults are as follows:

    default_type
    type
        The default type of template for this named configuration. Should be
        the name of a driver in the
        "CGI::Application::Plugin::AnyTemplate::Driver" namespace:

            Type                Driver
            ----                ------
            HTMLTemplate        CGI::Application::Plugin::AnyTemplate::Driver::HTMLTemplate
            HTMLTemplateExpr    CGI::Application::Plugin::AnyTemplate::Driver::HTMLTemplateExpr
            TemplateToolkit     CGI::Application::Plugin::AnyTemplate::Driver::TemplateToolkit
            Petal               CGI::Application::Plugin::AnyTemplate::Driver::Petal

    include_paths
        Include Paths (sometimes called search paths) are used by the
        various template backends to find filenames that aren't fully
        qualified by an absolute path. Each directory is searched in turn
        until the template file is found.

        Can be a single string or a reference to a list.

    auto_add_template_extension
        Add a template-system specific extension to template filenames.

        So, if this feature is enabled and you provide the filename
        "myfile", then the actual filename will depend on the current
        template driver:

            Driver                 Template
            ------                 --------
            HTMLTemplate           myfile.html
            HTMLTemplateExpr       myfile.html
            TemplateToolkit        myfile.tmpl
            Petal                  myfile.xhtml

        The per-type extension is controlled by the driver config for each
        "AnyTemplate" driver (see below under "Driver and Native
        Configuration" for how to set this).

        The "auto_add_template_extension" feature is on by default. To
        disable it, pass a value of zero:

            $self->template->config(
                auto_add_template_extension => 0,
            );

    component_handler_class
        Normally, component embedding is handled by
        CGI::Application::Plugin::AnyTemplate::ComponentHandler. If you want
        to use a different class for this purpose, specify the class name as
        the value of this paramter.

        It still has to provide the same interface as
        CGI::Application::Plugin::AnyTemplate::ComponentHandler. See the
        source code of that module for details.

   Driver and Native Configuration
    You can configure all the drivers at once with a single call to
    "config", by including subsections for each driver type:

        $self->template->config(
            default_type => 'HTMLTemplate',
            HTMLTemplate => {
                cache              => 1,
                global_vars        => 1,
                die_on_bad_params  => 0,
                template_extension => '.html',
            },
            HTMLTemplateExpr => {
                cache              => 1,
                global_vars        => 1,
                die_on_bad_params  => 0,
                template_extension => '.html',
            },
            TemplateToolkit => {
                POST_CHOMP         => 1,
                template_extension => '.tmpl',
            },
            Petal => {
                error_on_undef     => 0,
                template_extension => '.xhtml',
            },
        );

    Each driver knows how to separate its own configuration from the
    configuration belonging to the underlying template system.

    For instance in the example above, the "HTMLTemplate" driver knows that
    "template_extension" is a driver config parameter, but
    "cache_global_vars" and "die_on_bad_params" are all HTML::Template
    configuration parameters.

    Similarly, The "TemplateToolkit" driver knows that template_extension is
    a driver config parameter, but "POST_CHOMP" is a "Template::Toolkit"
    configuration parameter.

    For details on driver configuration, see the docs for the individual
    drivers:

    CGI::Application::Plugin::AnyTemplate::Driver::HTMLTemplate
    CGI::Application::Plugin::AnyTemplate::Driver::HTMLTemplateExpr
    CGI::Application::Plugin::AnyTemplate::Driver::TemplateToolkit
    CGI::Application::Plugin::AnyTemplate::Driver::Petal

   Copying Query data into Templates
    By default, all data in "$self->query" are copied into the template
    object before the template is processed.

    For the "HTMLTemplate" and "HTMLTemplateExpr" drivers this is done with
    the "associate" feature of HTML::Template and HTML::Template::Expr,
    respectively:

        my $template = HTML::Template->new(
            associate => $self->query,
        );

    For the other systems, this feature is emulated, by copying the query
    params into the template params before the template is processed.

    To disable this feature, pass a false value to "associate_query" or
    "emulate_associate_query" (depending on the template system):

        $self->template->config(
            default_type => 'HTMLTemplate',
            HTMLTemplate => {
                associate_query => 0,
            },
            HTMLTemplateExpr => {
                associate_query => 0,
            },
            TemplateToolkit => {
                emulate_associate_query => 0,
            },
            Petal => {
                emulate_associate_query => 0,
            },
        );

  load
    Create a new template object and configure it.

    This can be as simple (and magical) as:

        my $template = $self->template->load;

    When you call "load" with no parameters, it uses the default template
    type, the default template configuration, and it determines the name of
    the template based on the name of the current run mode.

    If you call "load" with one paramter, it is taken to be either the
    filename or a reference to a string containing the template text:

        my $template = $self->template->load('somefile');
        my $template = $self->template->load(\$some_text);

    If the parameter "auto_add_template_exension" is true, then the
    appropriate extension will be added for this template type.

    If you call "load" with more than one parameter, then you can specify
    filename and configuration paramters directly:

        my $template = $self->template->load(
            file                        => 'some_file.tmpl',
            type                        => 'HTMLTemplate',
            auto_add_template_extension => 0,
            add_inlcude_path            => '..',
            HTMLTemplate => {
                die_on_bad_params => 1,
            },
        );

    To initialize the template from a string rather than a file, use:

        my $template = $self->template->load(
            string =>  \$some_text,
        );

    The configuration parameters you pass to "load" are merged with the
    configuration that was passed to "config".

    You can include any of the configuration parameters that you can pass to
    config, plus the following extra parameters:

    file
        If you are loading the template from a file, then the "file"
        parameter contains the template's filename.

    string
        If you are loading the template from a string, then the "string"
        parameter contains the text of the template. It can be either a
        scalar or a reference to a scalar. Both of the following will work:

            # passing a string
            my $template = $self->template->load(
                string => $some_text,
            );

            # passing a reference to a string
            my $template = $self->template->load(
                string => \$some_text,
            );

    add_include_paths
        Additional include paths. These will be merged with "include_paths"
        before being passed to the template driver.

    The "load" method returns a template driver object. See below under
    "DRIVER METHODS", for how to use this object.

  fill
    Fill is a convenience method which in a single step creates the
    template, fills it with the template paramters and returns its output.

    You can call it with or without a filename.

    The code:

        $self->template->fill('filename', \%params);

    is equivalent to:

        my $template = $self->template->load('filename');
        $template->output(\%params);

    And the code:

        $self->template->fill(\%params);

    is equivalent to:

        my $template = $self->template->load;
        $template->output(\%params);

  process
    "process" is an alias for "fill".

DRIVER METHODS
    These are the most commonly used methods of the "AnyTemplate" driver
    object. The driver is what you get back from calling
    "$self->template->load".

    param
        The "param" method gets and sets values within the template.

            my $template = $self->template->load;

            my @param_names = $template->param();

            my $value = $template->param('name');

            $template->param('name' => 'value');
            $template->param(
                'name1' => 'value1',
                'name2' => 'value2'
            );

        It is designed to behave similarly to the "param" method in other
        modules like CGI and HTML::Template.

    get_param_hash
        Returns the template variables as a hash of names and values.

            my %params     = $self->template->get_param_hash;

        In a scalar context, returns a reference to the hash used internally
        to contain the values:

            my $params_ref = $self->template->get_param_hash;

            $params_ref->{'foo'} = 'bar';  # directly change parameter 'foo'

    output
        Returns the template with all the values filled in.

            return $template->output;

        You can also supply names and values to the template at this stage:

            return $template->output('name' => 'value', 'name2' => 'value2');

PRE- AND POST- PROCESS
    Before the template output is generated, your application's
    "$self->template_pre_process" method is called. This method is passed a
    reference to the $template object.

    It can modify the parameters passed into the template by using the
    "param" method:

        sub template_pre_process {
            my ($self, $template) = @_;

            # Change the internal template parameters by reference
            my $params = $template->get_param_hash;

            foreach my $key (keys %$params) {
                $params{$key} = to_piglatin($params{$key});
            }

            # Can also set values using the param method
            $template->param('foo', 'bar');

        }

    After the template output is generated, your application's
    "$self->template_post_process" method is called. This method is passed a
    reference to the template object and a reference to the output generated
    by the template. You can modify this output:

        sub template_post_process {
            my ($self, $template, $output_ref) = @_;

            $$output_ref =~ s/foo/bar/;
        }

    When you call the "output" method, any components embedded in the
    template are run. See "EMBEDDED COMPONENTS", below.

EMBEDDED COMPONENTS
  Introduction
    "CGI::Application::Plugin::AnyTemplate" allows you to include
    application components within your templates.

    For instance, you might include a *header* component a the top of every
    page and a *footer* component at the bottom of every page.

    These componenets are actually first-class run modes. When the template
    engine finds a special tag marking an embedded component, it passes
    control to the run mode of that name. That run mode can then do whatever
    a normal run mode could do. But typically it will load its own template
    and return the template's output.

    This output returned from the embedded run mode is inserted into the
    containing template.

    The syntax for embed components is specific to each type of template
    driver.

  Syntax
    HTML::Template syntax:

        <TMPL_VAR NAME="CGIAPP_embed('some_run_mode')">

    HTML::Template::Expr syntax:

        <TMPL_VAR EXPR="CGIAPP_embed('some_run_mode')">

    Template::Toolkit syntax:

        [% CGIAPP.embed("some_run_mode") %]

    Petal syntax:

        <span tal:replace="structure CGIAPP/embed 'some_run_mode'">
            this text gets replaced by the output of some_run_mode
        </span>

  Getting Template Variables from the Containing Template
    The component run mode is passed a reference to the template object that
    contained the component. The component run mode can use this object to
    access the params that were passed to the containing template.

    For instance:

        sub header {
            my ($self, $containing_template, @other_params) = @_;

            my %tmplvars = (
                'title' => 'My glorious home page',
            );

            my $template = $self->template->load;

            $template->param(%tmplvars, $containing_template->get_param_hash);
            return $template->output;
        }

    In this example, the template values of the enclosing template would
    override any values set by the embedded component.

  Passing Parameters
    The template can pass parameters to the target run mode. These are
    passed in after the reference to the containing template object.

    Parameters can either be literal strings, specified within the template
    text, or they can be keys that will be looked up in the template's
    params.

    Literal strings are enclosed in double or single quotes. Param keys are
    barewords.

    HTML::Template syntax:

        <TMPL_VAR NAME="CGIAPP_embed('some_run_mode', param1, 'literal string2')">

    *Note that HTML::Template doesn't support this type of callback
    natively* *and that this behaviour is emulated by the HTMLTemplate
    driver* *see the docs to*
    CGI::Application::Plugin::AnyTemplate::Driver::HTMLTemplate *for
    limitations to the emulation*.

    HTML::Template::Expr syntax:

        <TMPL_VAR EXPR="CGIAPP_embed('some_run_mode', param1, 'literal string2')">

    Template::Toolkit syntax:

        [% CGIAPP.embed("some_run_mode", param1, 'literal string2' ) %]

    Petal syntax:

        <span tal:replace="structure CGIAPP/embed 'some_run_mode' param1 'literal string2' ">
            this text gets replaced by the output of some_run_mode
        </span>

CHANGING THE NAME OF THE 'template' METHOD
    If you want to access the features of this module using a method other
    than "template", you can do so via Anno Siegel's Exporter::Renaming
    module (available on CPAN).

    For instance, to use syntax similar to CGI::Application::Plugin::TT:

        use Exporter::Renaming;
        use CGI::Application::Plugin::AnyTemplate Renaming => [ template => tt];

        sub cgiapp_init {
            my $self = shift;

            my %params = ( ... );

            # Set config file and other options
            $self->tt->config(
                default_type => 'TemplateToolkit',
            );

        }

        sub my_runmode {
            my $self = shift;
            $self->tt->process('file', \%params);
        }

    And to use syntax similar to CGI::Application's "load_tmpl" mechanism:

        use Exporter::Renaming;
        use CGI::Application::Plugin::AnyTemplate Renaming => [ template => tmpl];

        sub cgiapp_init {
            my $self = shift;

            # Set config file and other options
            $self->tmpl->config(
                default_type => 'HTMLTemplate',
            );

        }

        sub my_runmode {
            my $self = shift;

            my %params = ( ... );

            my $template = $self->tmpl->load('file');
            $template->param(\%params);
            $template->output;
        }

AUTHOR
    Michael Graham, "<mag-perl@occamstoothbrush.com>"

ACKNOWLEDGEMENTS
    I originally wrote this to be a subsystem in Richard Dice's
    CGI::Application-based framework, before I moved it into its own module.

    Various ideas taken from CGI::Application (Jesse Erlbaum),
    CGI::Application::Plugin::TT (Cees Hek) and "Text::Boilerplate" (Stephen
    Nelson).

    "Template::Toolkit" singleton support code stolen from
    CGI::Application::Plugin::TT.

BUGS
    Please report any bugs or feature requests to
    "bug-cgi-application-plugin-anytemplate@rt.cpan.org", or through the web
    interface at <http://rt.cpan.org>. I will be notified, and then you'll
    automatically be notified of progress on your bug as I make changes.

SEE ALSO
        CGI::Application::Plugin::AnyTemplate::Base
        CGI::Application::Plugin::AnyTemplate::ComponentHandler
        CGI::Application::Plugin::AnyTemplate::Driver::HTMLTemplate
        CGI::Application::Plugin::AnyTemplate::Driver::HTMLTemplateExpr
        CGI::Application::Plugin::AnyTemplate::Driver::TemplateToolkit
        CGI::Application::Plugin::AnyTemplate::Driver::Petal

        CGI::Application

        Template::Toolkit
        HTML::Template
        Petal

        Exporter::Renaming

        CGI::Application::Plugin::TT

COPYRIGHT & LICENSE
    Copyright 2005 Michael Graham, All Rights Reserved.

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

