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#-- vim:sw=2:et
#++
#
# :title: Stream filters
#
# Author:: Giuseppe "Oblomov" Bilotta <giuseppe.bilotta@gmail.com>
# Copyright:: (C) 2008 Giuseppe Bilotta
# License:: GPL v2
#
# This file collects methods to handle 'stream filters', a generic mechanism
# to transform text+attributes into other text+attributes
module ::Irc
class Bot
# The DataStream class. A DataStream is just a Hash. The :text key has
# a special meaning because it's the value that will be used when
# converting to String
class DataStream < Hash
def initialize(hsh={})
self.replace(hsh)
end
# Returns the :text key
def to_s
return self[:text]
end
end
# The DataFilter class. A DataFilter is a wrapper around a block
# that can be run on a DataStream to process it. The block is supposed to
# return another DataStream object
class DataFilter
def initialize(&block)
raise "No block provided" unless block_given?
@block = block
end
def call(stream)
@block.call(stream)
end
alias :run :call
alias :filter :call
end
# This method processes the DataStream _stream_ with the filters _name_.
# _name_ can be either a single Symbol (filter name), or an Array of
# Symbols, in which case the output of each filter will be used as input
# for the next
#
def filter(name, stream={})
@filters ||= {}
names = (Symbol === name ? [name] : name.dup)
ds = (DataStream === stream ? stream : DataStream.new(stream))
return ds if names.empty?
# check if filters exist
missing = names - @filters.keys
raise "Missing filters: #{missing.join(', ')}" unless missing.empty?
fs = @filters.values_at(*names)
fs.inject(ds) { |mid, f| mid = f.call(mid) }
end
# This method is used to register a new filter
def register_filter(name, &block)
raise "No block provided" unless block_given?
@filters ||= {}
@filters[name.to_sym] = DataFilter.new &block
end
# This method clears the filter list and installs the identity filter
def clear_filters
@filters ||= {}
@filters.clear
register_filter(:identity) { |stream| stream }
end
end
end
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