#-- vim:sw=2:et
#++
#
# :title: Alias plugin for rbot
#
# Author:: Yaohan Chen <yaohan.chen@gmail.com>
# Copyright:: (C) 2007 Yaohan Chen
# License:: GPLv2
#
# This plugin allows defining aliases for rbot commands. Aliases are like normal rbot
# commands and can take parameters. When called, they will be substituted into an
# exisitng rbot command and that is run.
#
# == Example Session
#   < alias googlerbot *terms => google site:ruby-rbot.org <terms>
#   > okay
#   < googlerbot plugins
#   > Results for site:ruby-rbot.org plugins: ....
#
# == Security
# By default, only the owner can define and remove aliases, while everyone else can
# use and view them. When a command is executed with an alias, it's mapped normally with
# the alias user appearing to attempt to execute the command. Therefore it should be not
# possible to use aliases to circumvent permission sets. Care should be taken when
# defining aliases, due to these concerns:
# * Defined aliases can potentially override other plugins' maps, if this plugin is
#   loaded first
# * Aliases can cause infinite recursion of aliases and/or commands. The plugin attempts
#   to detect and stop this, but a few recursive calls can still cause spamming

require 'yaml'
require 'set'

class AliasPlugin < Plugin
  # an exception raised when loading or getting input of invalid alias definitions
  class AliasDefinitionError < ArgumentError
  end

  def initialize
    super
    @aliases = @registry[:aliases]
    unless @aliases
      # attempt to load aliases from data file yaml
      filename = File.join(datafile, 'aliases.yaml')
      if File.exists? filename
        begin
          @aliases = {}
          YAML.load_file(filename).each_pair do |a, c|
            add_alias(a, c)
          end
        rescue
          warning _("Data file is not found or corrupt, reinitializing data")
          @aliases = {}
        end
      else
        @aliases = {}
      end
    end
  end

  def save
    @registry[:aliases] = @aliases
    @registry.flush
  end

  def cmd_add(m, params)
    begin
      add_alias(params[:text].to_s, params[:command].to_s)
      m.okay
    rescue AliasDefinitionError
      m.reply _('The definition you provided is invalid: %{reason}') % {:reason => $!}
    end
  end

  def cmd_remove(m, params)
    text = params[:text].to_s
    if @aliases.has_key?(text)
      @aliases.delete(text)
      # TODO when rbot supports it, remove the mapping corresponding to the alias
      m.okay
    else
      m.reply _('No such alias is defined')
    end
  end

  def cmd_list(m, params)
    if @aliases.empty?
      m.reply _('No aliases defined')
    else
      m.reply @aliases.map {|a, c| "#{a} => #{c}"}.join(' | ')
    end
  end

  def cmd_whatis(m, params)
    text = params[:text].to_s
    if @aliases.has_key?(text)
      m.reply _('Alias of %{command}') % {:command => @aliases[text]}
    else
      m.reply _('No such alias is defined')
    end
  end

  def add_alias(text, command)
    # each alias is implemented by adding a message map, whose handler creates a message
    # containing the aliased command

    command.scan(/<(\w+)>/).flatten.to_set ==
      text.split.grep(/\A[:*](\w+)\Z/) {$1}.to_set or
      raise AliasDefinitionError.new(_('The arguments in alias must match the substitutions in command, and vice versa'))

    begin
      map text, :action => :"alias_handle<#{text}>", :auth_path => 'run'
    rescue
      raise AliasDefinitionError.new(_('Error mapping %{text} as command: %{error}') %
                                     {:text => text, :error => $!})
    end
    @aliases[text] = command
  end

  def respond_to?(name, include_private=false)
    name.to_s =~ /\Aalias_handle<.+>\Z/ || super
  end

  def method_missing(name, *args, &block)
    if name.to_s =~ /\Aalias_handle<(.+)>\Z/
      text = $1
      m, params = args

      command = @aliases[text]
      if command
        begin
          # create a fake message containing the intended command
          @bot.plugins.privmsg fake_message(command.gsub(/<(\w+)>/) {|arg| params[:"#{$1}"].to_s}, :from => m, :delegate => false)
        rescue RecurseTooDeep
          m.reply _('The alias seems to have caused infinite recursion. Please examine your alias definitions')
          return
        end
      else
        m.reply(_("Error handling the alias, The alias %{text} is not defined or has beeen removed. I will stop responding to it after rescan,") %
                {:text => text})
      end
    else
      super(name, *args, &block)
    end
  end

  def help(plugin, topic='')
    case topic
    when ''
      if plugin == 'alias' # FIXME find out plugin name programmatically
        _('Create and use aliases for commands. Topics: create, commands')
      else
        # show definition of all aliases whose first word is the parameter of the help
        # command
        @aliases.keys.select {|a| a[/\A(\w+)/, 1] == plugin}.map do |a|
          "#{a} => #{@aliases[a]}"
        end.join ' | '
      end
    when 'create'
      _('"alias <text> => <command>" => add text as an alias of command. Text can contain placeholders marked with : or * for :words and *multiword arguments. The command can contain placeholders enclosed with < > which will be substituded with argument values. For example: alias googlerbot *terms => google site:ruby-rbot.org <terms>')
    when 'commands'
      _('alias list => list defined aliases | alias whatis <alias> => show definition of the alias | alias remove <alias> => remove defined alias | see the "create" topic about adding aliases')
    end
  end
end

plugin = AliasPlugin.new
plugin.default_auth('edit', false)
plugin.default_auth('run', true)
plugin.default_auth('list', true)

plugin.map 'alias list',
           :action => :cmd_list,
           :auth_path => 'view'
plugin.map 'alias whatis *text',
           :action => :cmd_whatis,
           :auth_path => 'view'
plugin.map 'alias remove *text',
           :action => :cmd_remove,
           :auth_path => 'edit'
plugin.map 'alias rm *text',
           :action => :cmd_remove,
           :auth_path => 'edit'
plugin.map 'alias *text => *command',
           :action => :cmd_add,
           :auth_path => 'edit'