# String#to_proc
#
# See http://weblog.raganwald.com/2007/10/stringtoproc.html
#
# Ported from the String Lambdas in Oliver Steele's Functional Javascript
# http://osteele.com/sources/javascript/functional/
#
# This work is licensed under the MIT License:
#
# (c) 2007 Reginald Braithwaite
# Portions Copyright (c) 2006 Oliver Steele
# 
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
# 
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

class String
  unless public_method_defined? :to_proc
    def to_proc &block
      params = []
      expr = self
      sections = expr.split(/\s*->\s*/m)
      if sections.length > 1 then
          eval_block(sections.reverse!.inject { |e, p| "(Proc.new { |#{p.split(/\s/).join(', ')}| #{e} })" }, block)
      elsif expr.match(/\b_\b/)
          eval_block("Proc.new { |_| #{expr} }", block)
      else
          leftSection = expr.match(/^\s*(?:[+*\/%&|\^\.=<>\[]|!=)/m)
          rightSection = expr.match(/[+\-*\/%&|\^\.=<>!]\s*$/m)
          if leftSection || rightSection then
              if (leftSection) then
                  params.push('$left')
                  expr = '$left' + expr
              end
              if (rightSection) then
                  params.push('$right')
                  expr = expr + '$right'
              end
          else
              self.gsub(
                  /(?:\b[A-Z]|\.[a-zA-Z_$])[a-zA-Z_$\d]*|[a-zA-Z_$][a-zA-Z_$\d]*:|self|arguments|'(?:[^'\\]|\\.)*'|"(?:[^"\\]|\\.)*"/, ''
              ).scan(
                /([a-z_$][a-z_$\d]*)/i
              ) do |v|  
                params.push(v) unless params.include?(v)
              end
          end
          eval_block("Proc.new { |#{params.join(', ')}| #{expr} }", block)
      end
    end
    private
    def eval_block(code, block)
      eval code, block && block.binding
    end
  end
end