ioquatix/mapping

# Copyright, 2016, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
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# of this software and associated documentation files (the "Software"), to deal
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# 
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# THE SOFTWARE.

module Mapping
    class Model
        PREFIX = 'map_'.freeze
        
        # This function generates mapping names like `map_Array` and `map_Hash` which while a bit non-standard are perfectly fine for our purposes and this never really needs to leak.
        def self.method_for_mapping(klass)
            PREFIX + klass.name.gsub(/::/, '_')
        end
        
        # Get the name of the method for mapping the given object.
        def method_for_mapping(object)
            self.class.method_for_mapping(object.class)
        end
        
        # Add a mapping from a given input class to a specific block.
        def self.map(*klasses, &block)
            klasses.each do |klass|
                method_name = self.method_for_mapping(klass)
                define_method(method_name, &block)
            end
        end
        
        # Sometimes you just want to map things to themselves (the identity function). This makes it convenient to specify a lot of identity mappings.
        def self.map_identity(*klasses)
            self.map(*klasses) {|value| value}
        end
        
        # Remove a mapping, usually an inherited one, which you don't want.
        def self.unmap(*klasses)
            klasses.each do |klass|
                method_name = self.method_for_mapping(klass)
                undef_method(method_name)
            end
        end
        
        # The primary function, which maps an input object to an output object.
        def map(root, *args)
            method_name = self.method_for_mapping(root)
            
            self.send(method_name, root, *args)
        end
    end
end