NAME
     Plugins::Style1 - Generic plugins framework with linear config files

SYNOPSIS
     use Plugins::Style1;

     $plugins = Plugins::Style1->new([context => $context])
     $plugins->readconfig($config_file, self => $self)
     $plugins->initialize()

     $plugins->invoke($method, @args);

     $plugins->invoke_until($method, sub { scalar(@_) }, @args);

     my $iterator = $plugins->iterator();
     while (@results = &$iterator(@args)) {
     }

     for my $plugin ($plugins->plugins()) {
            $plugin->invoke($method);
     }

DESCRIPTION
    Plugins::Style1 is a generic plugins framwork with a simple linear-style
    configuration file that can support plugins of plugins in the same
    configuration file.

    It is based on Plugins.

EXAMPLE CONFIG FILE (SIMPLE)
     sleeptime      1

     plugin SyslogScan::Daemon::BlacklistDetector as bld_

     bld_debug      0

     bld_plugin SyslogScan::Daemon::BlacklistDetector::Postfix
             rx_ourIP       127\.0\.0\.1
             logpath        /var/log/mail.log
             debug          0

     bld_plugin SyslogScan::Daemon::BlacklistDetector::EmailNotify
             debug          1
             notify         "John <root@localhost>"
             renotify_time  7200
             forget_time    3600
             sendfrom       root
             clean_time     1800
             maxkeep        100

CONSTRUCTION AND INITIALIAZATION
    In addition to the parameters for "new()" and "readconfig()" documented
    for Plugins, the following additional parameters may be given...

  %args for new()
    parse_config_line => \&func
        The unknown line parser can be specified here or in "readconfig()"'s
        %args.

  %args for readconfig()
    self => $self
        Set "self" to let "readconfig()" know who called it. With that
        information, "readconfig()" can make callbacks for the other
        parameters. Without a $self "readconfig()" uses "caller()" to and
        uses class methods instead of object methods.

    config_prefix => "prefix_"
        Since the configuration file can support multiple plugins at the
        same time, we need to distinquish what goes with what plugin. This
        is done by setting a configuration prefix here or when calling
        "new()". Only config lines that start with the prefix will be
        parsed: everything else will be ignored. The root/parent program
        should have an empty string as its prefix.

        If this is unspecified, "$self->config_prefix()" will be called. If
        that doesn't exist then an empty-string prefix will be assumed.

        For configuration file readability, your prefix should probably end
        with an underscore ("_").

    parse_config_line => \&func
        "readconfig()" knows about lines that start "${prefix}plugin", but
        for everything else it needs help. The "parse_config_line" parameter
        should be a reference to a function to be called when there is a
        configuration line other than "${prefix}plugin".

        If no "parse_config_line" parameter is specified then
        "$self->parse_config_line()" will be tried. If that doesn't exist
        either then an unknown configuration line is a fatal error.

        The arguments passed to the "&$parse_config_line()" function are:

        $self/$pkg
            The object or package of the caller.

        $config_prefix
            The configuration prefix for the plugin being invoked.

        $configfile
            The filename of the configuration file

        $line
            The configuration line. The prefix has not been removed.

        $line_number
            The line number of the line in the configuration file (for
            generating nice error messages).

        $seqno
            An integer that increments each time the same configuration file
            is read.

CONFIGURATION FILE FORMAT
    The configuration file parser knows about four types of lines:

    Comments
        The hash character ("#") denotes a comment and except for within
        quotes a hash character will end parsing for that line.

    Plugin requests
        <prefix>plugin </file/name<gt [as <prefix_override>]>

        <prefix>plugin <module_name> [as <prefix_override>]

         plugin Foobar::Baz     # defaults to prefix "fb_"
         plugin /some/file      # defaults to no prefix
         plugin a_file          # defaults to no prefix

         fb_plugin Foobar2::Baz as fb2_

        The basic part of a configuation file is a line that starts with the
        word "plugin". What follows on the same line is the name of a perl
        module. The word "plugin" may be preceeded by a prefix. The prefix
        disambiguates whose plugin it is when multiple plugins are sharing a
        configuration file.

        The prefix is normally given by the "config_prefix()" class method
        in the plugin module, but it can be overridden (in order) by (1) the
        config file; or (2) by an argument to readconfig
        ("readconfig($configfile, config_prefix => 'foobar_')") or (3) as by
        member data of the caller to readconfig():

         $self->{config_prefix} = "bar_";
         my $plugins = new Plugins;
         $plugins->readconfig($configfile, self => $self);

        To override the prefix in the config file, add "as prefix-name" the
        end of a plugin line.

        Plugins that are fully-fledged perl modules should be named as such.
        Plugins that are not, (named as files) will be wrapped by Plugins
        into a perl module. Plugins::Style1 dis-ambiguates between files and
        modules by looking for the string "::" in module names.

    Plugin search directory directive
        Plugins that are plain filenames that are not absolute paths are
        searched for with their own search path. The The directive to add to
        that path is "plugin_directory".

         plugin_directory /some/path
         plugin_directory /another/path

        Directory names may not have whitespace in them. Directories that do
        not exist will be silently ignored.

    Arguments to new()
        Any indented lines that follow a plugin request will set what
        arguments are passed to the "new()" when the module is initialized.

        The indented lines a broken up on word boundries except that what is
        between double-quotes or single-quotes counts as a single word.

         bld_plugin SyslogScan::Daemon::BlacklistDetector::EmailNotify
                notify          '"David Sharnoff" <muir@idiom.com>'
                from            root@my.poor.system

        Will produce a call like:

         SyslogScan::Daemon::BlacklistDetector::EmailNotify->new(
                'notify', 
                '"David Sharnoff" <muir@idiom.com>', 
                'from', 
                'root@my.poor.system');

    Freestanding configuration lines.
        Lines that that begin in column one that aren't plugin requests, are
        regular configuration lines. By default they are parsed by the
        "parse_config_line()" method of the plugin that has called
        "readconfig()". The function called can be overridden with the %args
        to "readconfig()". The function will be called as a object method if
        a $self was provided to "readconfig()". It will be called as a class
        method otherwise.

        Lines in the configuratin file that being with a plugin prefix will
        be parsed by that plugin's "parse_config_line()" method (if it has
        one). This will happen after "new()" is called so
        "parse_config_line()" will be called as a class method.

        The function to call for these lines defaults to
        "parse_config_line()" but it can be overridden by passing a function
        to the call to readconfig:

         my $plugins = new Plugins;
         $plugins->readconfig($configfile, parse_config_line => \&some_function);

        Or it can be overridden with member data of the caller:

         $self->{parse_config_line} = \&some_parse_function;
         my $plugins = new Plugins;
         $plugins->readconfig($configfile, self => $self);

        If no parse_config_line() function is provided, the parser will die
        on any lines that aren't recognized.

    The same configuration file is potentially re-read for each plugin.
    Generally plugins that have plugins will need to be calling
    "readconfig()".

EXAMPLE CONFIG FILE (NOT SO SIMPLE)
     sleeptime      10

     plugin SyslogScan::Daemon::BlacklistDetector
            debug           1

     bld_plugin SyslogScan::Daemon::BlacklistDetector::Postfix
            debug           1
            rx_ourIP        216\.240\.47\.\d+
            logpath         /var/log/mail.log

     bld_plugin SyslogScan::Daemon::BlacklistDetector::EmailNotify
            debug           1
            notify          you@yourhost.
            renotify_time   7200
            forget_time     3600
            sendfrom        root    # comments are allowed here
            clean_time      1800
            maxkeep         100

     bld_plugin SyslogScan::Daemon::BlacklistDetector::KeepTrack
            # indented comments are allowed here
            debug           1
            dbi_dsn         DBI:mysql:database=quarentene;host=localhost 
            username        quarentene 
            password        bloorf 
            table_prefix    kt_
            # comments can go nearly anywhere
            postcommand     "(cd /etc/postfix; make)"
            postfile        /etc/postfix/outbound-problems
            pool            /etc/postfix/outbound-list
            latency         10
            decay_day       3600
            decay_rate      0.98
            decay_done      0.2

     # of course, comments are allowed in column 1.

     plugin SyslogScan::Daemon::BlacklistDetector as bld2_
            debug           1

     bld2_plugin SyslogScan::Daemon::BlacklistDetector::Postfix as x1_
            debug           1

     x1_rx_ourIP    216\.240\.47\.\d+
     x1_logpath     /tmp/mail.log

     bld2_plugin SyslogScan::Daemon::BlacklistDetector::EmailNotify as x2_
            debug           1

     x2_notify      you@yourhost
     x2_renotify_time       7200
     x2_forget_time 3600
     x2_sendfrom    root
     x2_clean_time  1800
     x2_maxkeep     100

     bld2_plugin SyslogScan::Daemon::BlacklistDetector::KeepTrack as x3_
            debug           1
            postcommand     ''

     x3_dbi_dsn     DBI:mysql:database=quarentene;host=localhost 
     x3_username    quarentene 
     x3_password    ''
     x3_table_prefix        kt2_
     x3_postfile    /etc/postfix/outbound-problems2
     x3_pool        /etc/postfix/outbound-list
     x3_latency     10
     x3_decay_day   3600
     x3_decay_rate  0.98
     x3_decay_done  0.2

WRITING PLUGINS
  Plugin-defined methods
    Plugins should be subclasses of "Plugins::Style1".

    config_prefix()
        This method is used to determine the default configuration-line
        prefix for the plugin. Defining this method is manditory.

    parse_config_line($prefix, $configfile, $line, $lineno, $seqno)
        If your want to be able to have configuration directives other than
        what is passed to "new()", then you'll need to define a
        "parse_config_line()" method. Eg:

         my $bar = 7;

         sub config_prefix { 'foo_' }

         sub parse_config_line
         {
                my ($self, $prefix, $configfile, $line, $lineno, $seqno) = @_;
                if ($line =~ /^${prefix}bar\s*=\*(\d+)) { 
                        $bar = $1;
                } else {
                        die "illegal config at $configfile line $lineno\n";
                }
         }

        One way to get a simple parser like this and also something to
        handle arguments to "new()" is to use Plugins::SimpleConfig.

  Plugins with plugins
    One subtle aspect of sharing configuration files is that plugin prefix
    may be overridden. This is done on a per-configuration file basis. If
    for some reason you want to un-override your configuration prefix then
    don't pass that part of the $context:

     $self->{plugins} = new Plugins context => $self->{context}, config_prefix => 'something_else_';

    Since the *child requestors*'s configuration file may get read twice,
    the "parse_config_line" method may get called twice. To avoid this, pass
    in a null function for "parse_config_line":

     $self->{plugins} = new Plugins context => $self->{context}, parse_config_line => sub {}

    Or

     $self->{plugins}->readconfig($config, self => $self, parse_config_line => sub {});

    In most cases there probably isn't any harm in this double parsing.

SEE ALSO
    Plugins

THANK THE AUTHOR
    If you find this module useful and wish to show your appreciation to the
    author, please give me a Request-For-Quote on your next high-speed
    internet pipe order. I have good pricing for T1s, T3s, OC3s etc.

LICENSE
    Copyright (C) 2006-2007, David Muir Sharnoff <muir@idiom.com>. This
    module may be used and redistributed on the same terms as Perl itself.

