CLI::Framework::Application - CLIF Application superclass

CLI-Framework documentation Contained in the CLI-Framework distribution.

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NAME

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CLI::Framework::Application - CLIF Application superclass

SYNOPSIS

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    # The code below shows a few of the methods your application class is likely
    # to override...

    package My::Journal;
    use base qw( CLI::Framework );

    sub usage_text { q{
        $0 [--verbose|v]

        OPTIONS
            --db [path]  : path to SQLite database file
            -v --verbose : be verbose
            -h --help    : show help

        COMMANDS
            help        - show application or command-specific help
            menu        - print command menu
            entry       - work with journal entries
            publish     - publish a journal
            console     - start a command console for the application
    } }

    sub option_spec {
        [ 'help|h'      => 'show help' ],
        [ 'verbose|v'   => 'be verbose' ],
        [ 'db=s'        => 'path to SQLite database file' ],
    }

    sub command_map {
        help    => 'CLI::Framework::Command::Help',
        menu    => 'My::Journal::Command::Menu',
        entry   => 'My::Journal::Command::Entry',
        publish => 'My::Journal::Command::Publish',
        console => 'CLI::Framework::Command::Console',
    }

    sub command_alias {
        h   => 'help',
        m   => 'menu',
        e   => 'entry',
        p   => 'publish',
        sh  => 'console',
        c   => 'console',
    }

    sub init {
        my ($self, $opts) = @_;
        my $db = DBI->connect( ... );
        $self->cache->set( db => $db );
        return 1;
    }
    1;

OBJECT CONSTRUCTION

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new( [interactive => 1] )

    $app = My::Application->new( interactive => 1 );

interactive: Optional parameter. Set this to a true value if the application is to be run interactively (or call set_interactivity_mode later)

Constructs and returns a new CLIF Application object. As part of this process, some validation is performed on SUBCLASS HOOKS defined in the application class. If validation fails, an exception is thrown.

COMMAND INTROSPECTION & REGISTRATION

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The methods in this section are responsible for providing access to the commands in an application.

command_map_hashref()

    $h = $app->command_map_hashref();

Returns a HASH ref built from the command_map for an Application (by direct conversion from the command map array).

If the list returned by the definition of command_map in the application is not hash-worthy, an exception is thrown.

is_valid_command_pkg( $package_name )

    $app->is_valid_command_pkg( 'My::Command::Swim' );

Returns a true value if the specified command class (package name) is valid within the application. Returns a false value otherwise.

A command class is "valid" if it is included in command_map or if it is a built-in command that was included automatically in the application.

is_valid_command_name( $command_name )

    $app->is_valid_command_name( 'swim' );

Returns a true value if the specified command name is valid within the application. Returns a false value otherwise.

A command name is "valid" if it is included in command_map or if it is a built-in command that was included automatically in the application.

registered_command_names()

    @registered_commands = $app->registered_command_names();

Returns a list of the names of all registered commands. These are the names that each command was given in command_map (plus any auto-registered built-ins).

registered_command_object( $command_name )

    $command_object = $app->registered_command_object( 'fly' );

Given the name of a registered command, returns the CLI::Framework::Command object that is registered in the application under that name. If the command is not registered, returns undef.

register_command( $cmd )

    # Register by name...
    $command_object = $app->register_command( $command_name );

    # ...or register by object reference...
    $command_object = CLI::Framework::Command->new( ... );
    $app->register_command( $command_object );

Register a command to be recognized by the application. This method accepts either the name of a command or a reference to a CLI::Framework::Command object.

If $cmd is a CLI::Framework::Command object and it is one of the command types specified in command_map to be valid, the command object is registered and returned.

If $cmd is the name of a valid command specified in command_map, an object of the corresponding command class is registered and returned.

If $cmd is not recognized, an exception is thrown.

get_default_command() / set_default_command( $default_cmd )

get_defualt_command() retrieves the name of the command that is currently set as the default command for the application.

    my $default_command = $app->get_default_command();

Given a command name, set_default_command makes it the default command for the application.

    $app->set_default_command( 'jump' );

get_current_command() / set_current_command( $current )

get_current_command returns the name of the current command (or the one that was most recently run).

    $status = $app->run();
    print 'The command named: ', $app->get_current_command(), ' was just run';

Given a command name, set_current_command forwards execution to that command. This might be useful (for instance) to "redirect" to another command.

    $app->set_current_command( 'fly' );

get_default_usage() / set_default_usage( $default_usage )

The "default usage" message is used as a last resort when usage information is unavailable by other means. See usage.

get_default_usage gets the default usage message for the application.

    $usage_msg = $app->get_default_usage();

set_default_usage sets the default usage message for the application.

    $app->set_default_usage( $usage_message );

PARSING & RUNNING COMMANDS

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usage( $command_name, @subcommand_chain )

    # Application usage...
    print $app->usage();

    # Command-specific usage...
    $command_name = 'task';
    @subcommand_chain = qw( list completed );
    print $app->usage( $command_name, @subcommand_chain );

Returns a usage message for the application or a specific (sub)command.

If a command name is given (optionally with subcommands), returns a usage message string for that (sub)command. If no command name is given or if no usage message is defined for the specified (sub)command, returns a general usage message for the application.

Here is how the usage message is produced:

cache()

CLIF Applications may have the need to share data between individual CLIF Commands and the Application object itself. cache() provides a way for this data to be stored, retrieved, and shared between components.

    $cache_object = $app->cache();

cache() returns a cache object. The following methods demonstrate usage of the resulting object:

    $cache_object->get( 'key' );
    $cache_object->set( 'key' => $value );

Note: The underlying cache class is currently limited to these rudimentary features. In the future, the object returned by cache() may be changed to an instance of a real caching class, such as CHI (which would maintain backwards compatibility but offer expiration, serialization, multiple caching backends, etc.).

run()

    # as class method:
    My::App->run();

    # as object method (when having an object reference to call other methods
    # is desirable):
    my $app = My::App->new();
    $app->run();

    ...

    # Explicitly specify whether or not initialization should be done:
    $app->run( initialize => 0 );

This method controls the request processing and dispatching of a single command. It takes its input from @ARGV (which may be populated by a script running non-interactively on the command line) and dispatches the indicated command, capturing its return value. The command's return value represents the output produced by the command. This value is passed to render for final display.

If errors occur, they result in exceptions that are handled by handle_exception.

The following parameters are accepted:

initialize: This controls whether or not application initialization (via init) should be performed. If not specified, initialization is performed upon the first call to run. Should there be subsequent calls, initialization is not repeated. Passing initialize explicitly can modify this behavior.

INTERACTIVITY

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get_interactivity_mode() / set_interactivity_mode( $is_interactive )

get_interactivity_mode returns a true value if the application is in an interactive state and a false value otherwise.

    print "running interactively" if $app->get_interactivity_mode();

set_interactivity_mode sets the interactivity state of the application. One parameter is recognized: a true or false value to indicate whether the application state should be interactive or non-interactive, respectively.

    $app->set_interactivity_mode(1);

is_interactive_command( $command_name )

    $help_command_is_interactive = $app->is_interactive_command( 'help' );

Returns a true value if there is a valid command with the specified name that is an interactive command (i.e. a command that is enabled for this application in interactive mode). Returns a false value otherwise.

get_interactive_commands()

    my @interactive_commands = $app->get_interactive_commands();

Return a list of all commands that are to be available in interactive mode ("interactive commands").

run_interactive( [%param] )

    MyApp->run_interactive();

    # ...or as an object method:
    $app->run_interactive();

Start an event processing loop to prompt for and run commands in sequence. The menu command is used to display available command selections (the built-in menu command, CLI::Framework::Command::Menu, will be used unless the application defines its own menu command).

Within this loop, valid input is the same as in non-interactive mode except that application options are not accepted (any application options should be handled upon application initialization and before the interactive command loop is entered -- see the description of the initialize parameter below).

The following parameters are recognized:

initialize: causes any application options that are present in @ARGV to be procesed/validated and causes init to be invoked prior to entering the interactive event loop to recognize commands. If run_interactive() is called after application options have already been handled, this parameter can be omitted.

invalid_request_threshold: the number of unrecognized command requests the user can enter before the menu is re-displayed.

read_cmd()

    $app->read_cmd();

This method is responsible for retrieving a command request and placing the user input into @ARGV. It is called in void context.

The default implementation uses Term::ReadLine to prompt the user and read a command request, supporting command history.

Subclasses are free to override this method if a different means of accepting user input is desired. This makes it possible to read command selections without assuming that the console is being used for I/O.

is_quit_signal()

    until( $app->is_quit_signal(read_string_from_user()) ) { ... }

Given a string, return a true value if it is a quit signal (indicating that the application should exit) and a false value otherwise. quit_signals is an application subclass hook that defines what strings signify that the interactive session should exit.

SUBCLASS HOOKS

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There are several hooks that allow CLIF applications to influence the command execution process. This makes customizing the critical aspects of an application as easy as overriding methods.

Except where noted, all hooks are optional -- subclasses may choose not to override them (in fact, runnable CLIF applications can be created with very minimal subclasses).

init( $options_hash )

This hook is called in void context with one parameter:

$options_hash is a hash of pre-validated application options received and parsed from the command line. The options hash has already been checked against the options defined to be accepted by the application in option_spec.

This method allows CLIF applications to perform any common initialization tasks that are necessary regardless of which command is to be run. Some examples of this include connecting to a database and storing a connection handle in the shared cache slot for use by individual commands, setting up a logging facility that can be used by each command by storing a logging object in the cache, or initializing settings from a configuration file.

pre_dispatch( $command_object )

This hook is called in void context. It allows applications to perform actions after each command object has been prepared for dispatch but before the command dispatch actually takes place. Its purpose is to allow applications to do whatever may be necessary to prepare for running the command. For example, a log entry could be inserted in a database to store a record of every command that is run.

option_spec()

An example definition of this hook is as follows:

    sub option_spec {
        [ 'verbose|v'   => 'be verbose'         ],
        [ 'logfile=s'   => 'path to log file'   ],
    }

This method should return an option specification as expected by Getopt::Long::Descriptive. The option specification defines what options are allowed and recognized by the application.

validate_options( $options_hash )

This hook is called in void context. It is provided so that applications can perform validation of received options.

$options_hash is an options hash parsed from the command-line.

This method should throw an exception if the options are invalid (throwing the exception using die() is sufficient).

Note that Getopt::Long::Descriptive, which is used internally for part of the options processing, will perform some validation of its own based on the option_spec. However, the validate_options hook allows for additional flexibility in validating application options.

command_map()

Return a mapping between command names and Command classes (classes that inherit from CLI::Framework::Command). The mapping is a list of key-value pairs. The list should be "hash-worthy", meaning that it can be directly converted to a hash.

Note that the order of the commands in this list determines the order that the commands are displayed in the built-in interactive menu.

The keys are names that should be used to install the commands in the application. The values are the names of the packages that implement the corresponding commands, as in this example:

    sub command_map {
        # custom commands:
        fly     => 'My::Command::Fly',
        run     => 'My::Command::Run',

        # overridden built-in commands:
        menu    => 'My::Command::Menu',

        # built-in commands:
        help    => 'CLI::Framework::Command::Help',
        list    => 'CLI::Framework::Command::List',
        tree    => 'CLI::Framework::Command::Tree',
        'dump'  => 'CLI::Framework::Command::Dump',
        console => 'CLI::Framework::Command::Console',
        alias   => 'CLI::Framework::Command::Alias',
    }

command_alias()

This hook allows aliases for commands to be specified. The aliases will be recognized in place of the actual command names. This is useful for setting up shortcuts to longer command names.

command_alias should return a "hash-worthy" list where the keys are aliases and the values are command names.

An example of its definition:

    sub command_alias {
        h   => 'help',
        l   => 'list',
        ls  => 'list',
        sh  => 'console',
        c   => 'console',
    }

noninteractive_commands()

    sub noninteractive_commands { qw( console menu ) }

Certain commands do not make sense to run interactively (e.g. the "console" command, which itself puts the application into interactive mode). This method should return a list of their names. These commands will be disabled during interactive mode. By default, all commands are interactive commands except for console and menu.

quit_signals()

    sub quit_signals { qw( q quit exit ) }

An application can specify exactly what input represents a request to end an interactive session. By default, the example definition above is used.

handle_exception( $e )

    sub handle_exception {
        my ($app, $e) = @_;

        # Handle the exception represented by object $e...
        $app->my_error_logger( error => $e->error, pid => $e->pid, gid => $e->gid, ... );

        warn "caught error ", $e->error, ", continuing...";
        return;
    }

Error conditions are caught by CLIF and forwarded to this exception handler. It receives an exception object (see Exception::Class::Base for methods that can be called on the object).

If not overridden, the default implementation extracts the error message from the exception object and processes it through the render method.

render( $output )

    $app->render( $output );

This method is responsible for presentation of the result from a command. The default implementation simply attempts to print the $output scalar, assuming that it is a string.

Subclasses are free to override this method to provide more sophisticated behavior such as processing the $output scalar through a templating system.

usage_text()

    sub usage_text {
        q{
        OPTIONS
            -v --verbose : be verbose
            -h --help    : show help

        COMMANDS
            tree        - print a tree of only those commands that are currently-registered in your application
            menu        - print command menu
            help        - show application or command-specific help
            console     - start a command console for the application
            list        - list all commands available to the application
        }
    }

To provide application usage information, this method may be overridden. It accepts no parameters and should return a string containing a useful help message for the overall application.

Overriding this method is encouraged in order to provide a better usage message than the default. See usage.

ERROR HANDLING IN CLIF

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Internally, CLIF handles errors by throwing exceptions.

The handle_exception method provides an opportunity for customizing the way errors are treated in a CLIF application.

Application and Command class hooks such as validate_options and validate are expected to indicate success or failure by throwing exceptions (via die() or something more elaborate, such as exception objects).

CONFIGURATION & ENVIRONMENT

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For interactive usage, Term::ReadLine is used by default. Depending on which readline libraries are available on your system, your interactive experience will vary (for example, systems with GNU readline can benefit from a command history buffer).

DEPENDENCIES

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Exception::Class::TryCatch

Getopt::Long::Descriptive

Text::ParseWords (only for interactive use)

Term::ReadLine (only for interactive use)

CLI::Framework::Exceptions

CLI::Framework::Command

DEFECTS AND LIMITATIONS

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No known bugs.

PLANS FOR FUTURE VERSIONS

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SEE ALSO

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CLI::Framework

CLI::Framework::Command

CLI::Framework::Tutorial

LICENSE AND COPYRIGHT

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Copyright (c) 2009 Karl Erisman (kerisman@cpan.org). All rights reserved.

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

AUTHOR

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Karl Erisman (kerisman@cpan.org)

CLI-Framework documentation Contained in the CLI-Framework distribution. 
package CLI::Framework::Application;

use strict;
use warnings;

our $VERSION = '0.04';

use Getopt::Long::Descriptive;
use Exception::Class::TryCatch;

use CLI::Framework::Exceptions qw( :all );
use CLI::Framework::Command;

# Certain built-in commands are required:
use constant REQUIRED_BUILTINS_PKGS => qw(
    CLI::Framework::Command::Help
);
use constant REQUIRED_BUILTINS_NAMES => qw(
    help
);
# Certain built-in commands are required only in interactive mode:
use constant REQUIRED_BUILTINS_PKGS_INTERACTIVE => qw(
    CLI::Framework::Command::Menu
);
use constant REQUIRED_BUILTINS_NAMES_INTERACTIVE => qw(
    menu
);

#FIXME-TODO-CLASS_GENERATION:
#sub import {
#    my ($class, $app_pkg, $app_def) = @_;
#
#    # If caller has supplied import args, CLIF's "inline form" is being used.
#    # The application class must be generated dynamically...
#
#}

#-------

sub new {
    my ($class, %args) = @_;

    my $interactive = $args{ interactive };             # boolean: interactive mode?

    my $cache = CLI::Framework::Cache->new();

    my $app = {
        _registered_command_objects => undef,           # (k,v)=(cmd pkg name,cmd obj) for all registered commands
        _default_command            => 'help',          # name of default command
        _current_command            => undef,           # name of current (or last) command to run
        _interactive                => $interactive,    # boolean: interactive state
        _cache                      => $cache,          # storage for data shared between app and cmd
        _initialized                => 0,               # initialization status
    };
    bless $app, $class;

    # Validate some hook methods so we can assume that they behave properly...
    $app->_validate_hooks();

    return $app;
}

sub _validate_hooks {
    my ($app) = @_;

    # Ensure that hook methods return expected data structure types according
    # to their preconditions...

    my $class = ref $app;

    # Ensure that command_map() succeeds...
    eval { $app->command_map() };
    if( catch my $e ) {
        throw_app_hook_exception( error =>
            "method 'command_map' in class '$class' fails" );
    }
    # Ensure that command_map() returns a "hash-worthy" list...
    else {
        eval { $app->_list_to_hashref( 'command_map' ) };
        if( catch my $e ) {
            $e->isa( 'CLI::Framework::Exception' ) && do{ $e->rethrow() };
            throw_app_hook_exception( error => $e );
        }
    }
    # Ensure that command_alias() succeeds...
    eval { $app->command_alias() };
    if( catch my $e ) {
        throw_app_hook_exception(
            error   => "method 'command_alias' in class '$class' fails" );
    }
    # Ensure that commandf_alias() returns a "hash-worthy" list...
    else {
        eval { $app->_list_to_hashref( 'command_alias' ) };
        if( catch my $e ) {
            $e->isa( 'CLI::Framework::Exception' ) && do{ $e->rethrow() };
            throw_app_hook_exception( error => $e );
        }
    }
}

sub cache { $_[0]->{_cache} }

###############################
#
#   COMMAND INTROSPECTION & REGISTRATION
#
###############################

# convert a list to a HASH ref if list is hash-worthy
sub _list_to_hashref {
    my ($app, $method) = @_;

    my $class = ref $app;
    my @map = $app->$method;

    # throw exception if command_map list is of odd length
    if( scalar @map % 2 ) {
        throw_app_hook_exception( error =>
            "odd-length list returned by application hook '$method' in class '$class' is not hash-worthy\n" );
    }
    my %h;
    for my $i (0..$#map-1) {
        if($i % 2 == 0) {
            my ($k,$v) = ( $map[$i], $map[$i+1] );
            # throw exception if command_map list-to-hash conversion would
            # lose data due to duplicate keys
            if( exists $h{$k} ) {
                throw_app_hook_exception( error =>
                    "list returned by application hook '$method' in class '$class' is not hash-worthy (duplicate keys for $i)\n" );
            }
            $h{ $map[$i] } = $map[$i+1];
        }
    }
    return \%h;
}

# Transform command map to hashref
sub command_map_hashref {
    my ($app) = @_;
    return $app->_list_to_hashref('command_map');
}

# Return names of all valid commands in same order as specified by
# command_map()
sub _valid_command_names {
    my ($app) = @_;

    # ordered pairs of (command name, command class)
    my @valid_command_name_class_pairs = $app->command_map();
    
    # unordered command names
    my @command_names = keys %{ { @valid_command_name_class_pairs } };

    my @ordered_command_names;
    for my $c (@valid_command_name_class_pairs) {
        push @ordered_command_names, $c
            if grep {$_ eq $c} @command_names;
    }
    return @ordered_command_names;
}

# Return package names for all valid commands
sub _valid_command_pkgs {
    my ($app) = @_;
    my $valid_commands_hashref = $app->command_map_hashref;
    return values %$valid_commands_hashref;
}

## Given a command name, return its package name
#sub _find_command_pkg_named {
#    my ($app, $cmd_name) = @_;
#    
#    my $valid_commands_hashref = $app->command_map_hashref;
#    return $valid_commands_hashref->{$cmd_name};
#}

sub is_valid_command_pkg {
    my ($app, $cmd_pkg) = @_;
    return unless $cmd_pkg;

    my @valid_pkgs = ( $app->_valid_command_pkgs(), REQUIRED_BUILTINS_PKGS );
    push @valid_pkgs, REQUIRED_BUILTINS_PKGS_INTERACTIVE
        if $app->get_interactivity_mode();

    return grep { $cmd_pkg eq $_ } @valid_pkgs;
}

sub is_valid_command_name {
    my ($app, $cmd_name) = @_;
    return unless $cmd_name;

    my @valid_aliases = ( $app->_valid_command_names() );
    push @valid_aliases, REQUIRED_BUILTINS_NAMES;
    push @valid_aliases, REQUIRED_BUILTINS_NAMES_INTERACTIVE
        if $app->get_interactivity_mode();

    return grep { $cmd_name eq $_ } @valid_aliases;
}

sub registered_command_names {
    my ($app) = @_;

    my @names;

    # For each registered command package (name)...
    for my $cmd_pkg_name (keys %{ $app->{_registered_command_objects} }) {
        # Find command names that this command package was registered under...
        push @names, grep { $_ } map {
            $_ if $app->command_map_hashref->{$_} eq $cmd_pkg_name
        } $app->_valid_command_names
    }
    return @names;
}

sub registered_command_object {
    my ($app, $cmd_name) = @_;
    return unless $cmd_name;

    my $cmd_pkg = $app->command_map_hashref->{$cmd_name};

    return unless $cmd_pkg
        && exists $app->{_registered_command_objects}
        && exists $app->{_registered_command_objects}->{$cmd_pkg};

    return $app->{_registered_command_objects}->{$cmd_pkg};
}

sub register_command {
    my ($app, $cmd) = @_;
    return unless $cmd;

    if( ref $cmd && $app->is_valid_command_pkg(ref $cmd) ) {
        # Register by reference...
        return unless $cmd->isa( 'CLI::Framework::Command' );
        $app->{_registered_command_objects}->{ref $cmd} = $cmd;
    }
    elsif( $app->is_valid_command_pkg($app->command_map_hashref->{$cmd}) ) {
        # Register by command name...
        my $pkg = $app->command_map_hashref->{$cmd};
        $cmd = CLI::Framework::Command->manufacture( $pkg );
        $app->{_registered_command_objects}->{ref $cmd} = $cmd;
    }
#FIXME:use REQUIRED_BUILTINS_PKGS_INTERACTIVE & REQUIRED_BUILTINS_NAMES_INTERACTIVE
    elsif( $cmd eq 'help' ) {
        # Required built-in is always valid...
        $cmd = CLI::Framework::Command->manufacture( 'CLI::Framework::Command::Help' );
        $app->{_registered_command_objects}->{'CLI::Framework::Command::Help'} = $cmd;
    }
    elsif( $app->get_interactivity_mode() && $cmd eq 'menu' ) {
        # Required built-in for interactive usage is always valid...
        $cmd = CLI::Framework::Command->manufacture( 'CLI::Framework::Command::Menu' );
        $app->{_registered_command_objects}->{'CLI::Framework::Command::Menu'} = $cmd;
    }
    else {
        throw_cmd_registration_exception(
            error => "Error: failed attempt to register invalid command '$cmd'" );
    }
    # Metacommands should be app-aware...
    $cmd->set_app( $app ) if $cmd->isa( 'CLI::Framework::Command::Meta' );

    return $cmd;
}

sub get_default_command { $_[0]->{_default_command} }
sub set_default_command { $_[0]->{_default_command} = $_[1] }

sub get_current_command { $_[0]->{_current_command} }
sub set_current_command { $_[0]->{_current_command} = $_[1] }

sub get_default_usage { $_[0]->{_default_usage} }
sub set_default_usage { $_[0]->{_default_usage} = $_[1] }

###############################
#
#   PARSING & RUNNING COMMANDS
#
###############################

sub usage {
    my ($app, $command_name, @args) = @_;

    # Allow aliases in place of command name...
    $app->_canonicalize_cmd( $command_name );

    my $usage_text;
    if( $command_name && $app->is_valid_command_name($command_name) ) {
        # Get usage from Command object...
        my $cmd = $app->registered_command_object( $command_name )
            || $app->register_command( $command_name );
        $usage_text = $cmd->usage(@args);
    }
    else {
        # Get usage from Application object...
        $usage_text = $app->usage_text();
    }
    # Finally, fall back to default application usage message...
    $usage_text ||= $app->get_default_usage();

    return $usage_text;
}

sub _canonicalize_cmd {
    my ($self, $input) = @_;

    # Translate shorthand aliases for commands to full names...

    return unless $input;

    my $command_name;
        my %aliases = $self->command_alias();
        return unless %aliases;
        $command_name = $aliases{$input} || $input;
    $_[1] = $command_name;
}

sub _handle_global_app_options {
    my ($app) = @_;

    # Process the [app-opts] prefix of the command request...

    # preconditions:
    #   - tail of @ARGV has been parsed and removed, leaving only the
    #   [app-opts] portion of the request
    # postconditions:
    #   - application options have been parsed and any application-specific
    #     validation and initialization that is defined has been performed
    #   - invalid tokens after [app-opts] and before <cmd> are detected and
    #     handled

    # Parse [app-opts], consuming them from @ARGV...
    my ($app_options, $app_usage);
    eval { ($app_options, $app_usage) = describe_options( '%c %o ...', $app->option_spec ) };
    if( catch my $e ) { # (failed application options parsing)
        throw_app_opts_parse_exception( error => $e );
    }
    $app->set_default_usage( $app_usage->text );

    # Detect invalid tokens in the [app-opts] part of the request
    # (@ARGV should be empty unless such invalid tokens exist because <cmd> has
    # been removed and any valid options have been processed)...
    if( @ARGV ) {
        my $err = @ARGV > 1 ? 'Unrecognized options: ' : 'Unrecognized option: ';
        $err .= join(' ', @ARGV ) . "\n";
        throw_app_opts_parse_exception( error => $err );
    }
    # --- VALIDATE APP OPTIONS ---
    eval { $app->validate_options($app_options) };
    if( catch my $e ) { # (failed application options validation)
        $e->isa( 'CLI::Framework::Exception' ) && do{ $e->rethrow() };
        throw_app_opts_validation_exception( error => $e . "\n" . $app->usage );
    }
    # --- INITIALIZE APP ---
    eval{ $app->init($app_options) };
    if( catch my $e ) { # (application failed initialization)
        $e->isa( 'CLI::Framework::Exception' ) && do{ $e->rethrow() };
        throw_app_init_exception( error => $e );
    }
    $app->{_initialized} = 1;

    return 1;
}

sub _parse_request {
    my ($app, %param) = @_;

    # Parse options/arguments from a command request and set the name of the
    # current command...

    # If requested, perform validation and initialization of the application.
    # NOTE: Application validation/initialization should NOT be performed here
    # in interactive mode for each command request because it should only be
    # done once for the application, not every time a command is run.

    #~~~~~~~~~~~~~~~~~~~~~~~
    # ARGV_Format
    #
    # non-interactive case:     @ARGV:      [app-opts]  <cmd> [cmd-opts] [cmd-args]
    # interactive case:         @ARGV:                  <cmd> [cmd-opts] [cmd-args]
    #~~~~~~~~~~~~~~~~~~~~~~~

    my $initialize_app = $param{initialize};

    # Parse options/arguments for the application and the command from @ARGV...
    my ($command_name, @command_opts_and_args);
    for my $i ( 0..$#ARGV ) {
        # Find first valid command name in @ARGV...
        $app->_canonicalize_cmd( $ARGV[$i] );
        if( $app->is_valid_command_name($ARGV[$i]) ) {
            # Extract and store '<cmd> [cmd-opts] [cmd-args]', leaving
            # preceding contents (potentially '[app-opts]') in @ARGV...
            ($command_name, @command_opts_and_args) = @ARGV[$i..@ARGV-1];
            splice @ARGV, $i;
            last;
        }
    }
    unless( defined $command_name ) {
        # If no valid command, fall back to default, ignoring any args...
        $command_name = $app->get_default_command();
        @command_opts_and_args = ();

        # If no valid command then any non-option tokens are invalid args...
        my @invalid_args = grep { substr($_, 0, 1) ne '-' } @ARGV;
        if( @invalid_args ) {
            my $err = @invalid_args > 1 ? 'Invalid arguments: ' : 'Invalid argument: ';
            $err .= join(' ', @invalid_args );
            throw_invalid_cmd_exception( error => $err );
        }
    }
    # Set internal current command name...
    $app->set_current_command( $command_name );

    # If requested, parse [app-opts] and initialize application...
    # (this is an optional step because in interactive mode, it should not be
    # done for every request)
    $app->_handle_global_app_options() if $initialize_app;

    # Leave '[cmd-opts] [cmd-args]' in @ARGV...
    @ARGV = @command_opts_and_args;

    return 1;
}

sub run {
    my ($app, %param) = @_;

    # Auto-instantiate if necessary...
    unless( ref $app ) {
        my $class = $app;
        $app = $class->new();
    }
    # Determine whether to do initialization -- if not explicitly indicated,
    # default to doing initialization only if it has not yet been done...
    my $initialize = $param{initialize};
    $initialize = not $app->{_initialized} unless defined $initialize;

    # Parse request; perform initialization...
    eval { $app->_parse_request( initialize => $initialize ) };
    if( catch my $e ) { $app->handle_exception($e); return }

    my $command_name = $app->get_current_command();

    # Lazy registration of commands...
    my $command = $app->registered_command_object( $command_name )
        || $app->register_command( $command_name );

    # Parse command options and auto-generate minimal usage message...
    my ($cmd_options, $cmd_usage);
    my $currently_interactive = $app->get_interactivity_mode();
    my $format = "$command_name %o ...";                            # Getopt::Long::Descriptive format string
    $format = '%c '.$format unless $currently_interactive;          # (%c is command name -- irrelevant in interactive mode)

    # (configure Getopt::Long to stop consuming tokens when first non-option is
    # encountered on input stream)
    my $getopt_configuration = { getopt_conf => [qw(require_order)] };
    eval { ($cmd_options, $cmd_usage) =
        describe_options( $format, $command->option_spec, $getopt_configuration )
    };
    # (handle failed command options parsing)
    if( catch my $e ) {
        if( $e->isa('CLI::Framework::Exception') ) {
            $app->handle_exception($e);
            return;
        }
        eval{ throw_cmd_opts_parse_exception( error => $e ) };
        if( catch my $e ) { $app->handle_exception( $e ); return }
    }
    $command->set_default_usage( $cmd_usage->text );

    # Share session data with command...
    # (init() method may have populated shared session data in cache for use by all commands)
    $command->set_cache( $app->cache );

    # --- APP HOOK: COMMAND PRE-DISPATCH ---
    $app->pre_dispatch( $command );

    # --- RUN COMMAND ---
    my $output;
    eval { $output = $command->dispatch( $cmd_options, @ARGV ) };
    if( catch my $e ) { $app->handle_exception($e); return }

    # Display output of command, if any...
    $app->render( $output ) if defined $output;

    return 1;
}

###############################
#
#   INTERACTIVITY
#
###############################

sub get_interactivity_mode { $_[0]->{_interactive} }
sub set_interactivity_mode { $_[0]->{_interactive} = $_[1] }

sub is_interactive_command {
    my ($app, $command_name) = @_;

    my @noninteractive_commands = $app->noninteractive_commands();

    # Command must be valid...
    return 0 unless $app->is_valid_command_name( $command_name );

    # Command must NOT be non-interactive...
    return 1 unless grep { $command_name eq $_ } @noninteractive_commands;

    return 0;
}

sub get_interactive_commands {
    my ($app) = @_;

    my @valid_commands = $app->_valid_command_names;

    # All valid commands are enabled in non-interactive mode...
    return @valid_commands unless( $app->get_interactivity_mode() );

    # ...otherwise, in interactive mode, include only interactive commands...
    my @command_names;
    for my $c ( @valid_commands ) {
        push @command_names, $c if $app->is_interactive_command( $c );
    }
    return @command_names;
}

sub run_interactive {
    my ($app, %param) = @_;

    # Auto-instantiate if necessary...
    unless( ref $app ) {
        my $class = $app;
        $app = $class->new();
    }
    $app->set_interactivity_mode(1);

    # If default command is non-interactive, reset it, remembering default...
    my $orig_default_command = $app->get_default_command();
    if( grep { $orig_default_command eq $_ } $app->noninteractive_commands() ) {
        $app->set_default_command( 'help' );
    }
    # If initialization indicated, run init() and handle existing input...
    eval { $app->_parse_request( initialize => $param{initialize} )
        if $param{initialize}
    };
    if( catch my $e ) { $app->handle_exception($e); return }

    # Find how many prompts to display in sequence between displaying menu...
    my $menu_cmd = $app->registered_command_object('menu')
        || $app->register_command( 'menu' );
    $menu_cmd->isa( 'CLI::Framework::Command::Menu' )
        or throw_type_exception(
            error => "Menu command must be a subtype of " .
                     "CLI::Framework::Command::Menu" );

    my $invalid_request_threshold = $param{invalid_request_threshold}
        || $menu_cmd->line_count(); # num empty prompts b4 re-displaying menu

    $app->_run_cmd_processing_loop(
        menu_cmd                    => $menu_cmd,
        invalid_request_threshold   => $invalid_request_threshold
    );
    # Restore original default command...
    $app->set_default_command( $orig_default_command );
}

sub _run_cmd_processing_loop {
    my ($app, %param) = @_;

    my $menu_cmd                    = $param{menu_cmd};
    my $invalid_request_threshold   = $param{invalid_request_threshold};

    $app->render( $menu_cmd->run() );

    my ($cmd_succeeded, $invalid_request_count, $done) = (0,0,0);
    until( $done ) {
        if( $invalid_request_count >= $invalid_request_threshold ) {
            # Reached threshold for invalid cmd requests => re-display menu...
            $invalid_request_count = 0;
            $app->render( $menu_cmd->run() );
        }
        elsif( $cmd_succeeded ) {
            # Last command request was successful => re-display menu...
            $app->render( $menu_cmd->run() );
            $cmd_succeeded = $invalid_request_count = 0;
        }
        # Read a command request...
        $app->read_cmd();

        if( @ARGV ) {
            # Recognize quit requests...
            if( $app->is_quit_signal($ARGV[0]) ) {
                undef @ARGV;
                last;
            }
            $app->_canonicalize_cmd($ARGV[0]); # translate cmd aliases

            if( $app->is_interactive_command($ARGV[0]) ) {
                if( $app->run() ) {
                    $cmd_succeeded = 1;
                }
                else { $invalid_request_count++ }
            }
            else {
                $app->render( 'unrecognized command request: ' . join(' ',@ARGV) . "\n");
                $invalid_request_count++;
            }
        }
        else { $invalid_request_count++ }
    }
}

sub read_cmd {
    my ($app) = @_;

    require Text::ParseWords;

    # Retrieve or cache Term::ReadLine object (this is necessary to save
    # command-line history in persistent object)...
    my $term = $app->{_readline};
    unless( $term ) {
        require Term::ReadLine;
        $term = Term::ReadLine->new('CLIF Application');
        select $term->OUT;
        $app->{_readline} = $term;

#FIXME-TODO-CMDLINE_COMPLETION:
#        # Arrange for command-line completion...
#        my $attribs = $term->Attribs;
#        $attribs->{completion_function} = $app->_cmd_request_completions();
    }
    # Prompt for the name of a command and read input from STDIN.
    # Store the individual tokens that are read in @ARGV.
    my $command_request = $term->readline('> ');
    if(! defined $command_request ) {
        # Interpret CTRL-D (EOF) as a quit signal...
        @ARGV = $app->quit_signals();
        print "\n"; # since EOF character is rendered as ''
    }
    else {
        # Prepare command for usual parsing...
        @ARGV = Text::ParseWords::shellwords( $command_request );
        $term->addhistory($command_request)
            if $command_request =~ /\S/ and !$term->Features->{autohistory};
    }
    return 1;
}

##FIXME-TODO-CMDLINE_COMPLETION:this should only return interactive commands; it should pay attention
##to its text/line/start args, ...; also: make it work with subcommands
##  --see Term::Readline::Gnu
#sub _cmd_request_completions {
#    my ($app) = @_;
#    return sub {
#        my ($text, $line, $start) = @_;
#        return $app->_valid_command_names;
#    }
#}

sub is_quit_signal {
    my ($app, $command_name) = @_;

    my @quit_signals = $app->quit_signals();
    return grep { $command_name eq  $_ } @quit_signals;
}

###############################
#
#   APPLICATION SUBCLASS HOOKS
#
###############################

#XXX-CONSIDER: consider making default implementation of init():
#       $app->set_current_command('help') if $opts->{help}
sub init { 1 }

sub pre_dispatch { }

sub usage_text { }

sub option_spec { }

sub validate_options { 1 }

sub command_map {
    help        => 'CLI::Framework::Command::Help',
    console     => 'CLI::Framework::Command::Console',
    menu        => 'CLI::Framework::Command::Menu',
    list        => 'CLI::Framework::Command::List',
    'dump'      => 'CLI::Framework::Command::Dump',
    tree        => 'CLI::Framework::Command::Tree',
    alias       => 'CLI::Framework::Command::Alias',
}

sub command_alias { }

sub noninteractive_commands { qw( console menu ) }

sub quit_signals { qw( q quit exit ) }

sub handle_exception {
    my ($app, $e) = @_;
    $app->render( $e->description . "\n\n" . $e->error );
    return;
}

sub render {
    my ($app, $output) = @_;

#XXX-CONSIDER: consider built-in features to help simplify associating templates
#with commands (each command would probably have its own template for its
#output)
    print $output;
}

###############################
#
#   CACHING
#
###############################

package CLI::Framework::Cache;

use strict;
use warnings;

sub new {
    my ($class) = @_;

    bless { _cache => { } }, $class;
}

sub get {
    my ($self, $k) = @_;

    my $v = $self->{_cache}->{$k};
    return $v;
}

sub set {
    my ($self, $k, $v) = @_;

    $self->{_cache}->{$k} = $v;
    return $v;
}

#-------
1;

__END__