Allows easy patching and editing of files with strings

patch.rb

# Allows easy patching and editing of files with strings
# 
# Extracted from methods seen in adva cms setup.rb 
# See http://github.com/svenfuchs/adva_cms
# Thought it would be useful to extend the String and File classes to include this functionality. 
# I find it useful when running install hooks for plugins.


module Patch
  module InstanceMethods
    module StringMethods 
       def patch(insert, mode = :insert_after)
        case mode
        when :change
          "#{insert}"
        when :insert_after
          "#{self}\n#{insert}"
        when :insert_before
          "#{insert}\n#{self}"
        else
          self.patch(insert, :insert_after)
        end
      end
    end
  end
  
  module ClassMethods
    module FileMethods
      # == Parameters
      # *path* - the path to the file to patch
      # *current* - the string to look for in the file.
      # *insert* - the string to patch into the file.
      # *options* - only options is :patch_mode which determines the way to patch the file. 
      #
      # Valid patch modes:
      #
      # :insert_after - this will add the insert text into the file on the line after current.  
      #
      # :insert_before - This will add the insert text into the file on the line before current.  
      #
      # :change - This will replace the current text with insert text
      # 
      # == Examples 
      # * The following will find the line "{ config: { a: 1, b: 2 } }" in the the file public/javascripts/file_to_patch.js and change it to "{ config: { a: 3, b: 4} }"  
      # the_file = File.join("public", "javascripts", "file_to_patch.js")
      #	File.patch(the_file, "{ config: { a: 1, b: 2 } }", "{ config: { a: 3, b: 4} }", :patch_mode => :change)
       def patch(path, current, insert, options = {})
        options = {
          :patch_mode => :insert_after
        }.merge(options)

        old_text = current
        new_text = current.patch(insert, options[:patch_mode])

        content = self.open(path) { |f| f.read }
        content.gsub!(old_text, new_text) unless content =~ /#{Regexp.escape(insert)}/mi
        self.open(path, 'w') { |f| f.write(content) }
      end
    end
  end
end

String.send(:include, Patch::InstanceMethods::StringMethods)
File.send(:extend, Patch::ClassMethods::FileMethods)