Script to convert a properties file in `key=value` form to use confd properties, for use in Docker containers

properties_to_confd.rb

##
## This utility makes it easy to convert a properties file specified in the _file_to_update_ variable to use confd properties.
## Takes a properties file in the form: 
## `key=value`
##
## It reads the file in  and creates a new file with _.new_ extension
## Every property key is converted to a confd path, the property value becomes the default value for the confd parameter
## Optional properties, denoted by being commented out, e.g. `# key=value`, are converted to optional confd properties.
##
## Example:
## `property.key1=foo` => `property.key1={{getv "/property/key1" "foo"}}`
## `#property.optional=foo` 
##    => ```{{if exists "/property/optional" -}}
##       property.optional={{getv "/property/optional" "foo"}}`
##       {{end -}}
##       ```

def isCommentOrBlank?(line) 
  return line.start_with?('#') || line.strip.empty?()
end

file_to_update="path/to/file/to_update.properties"

File.open("#{file_to_update}.new",'w') do |file|
 lines = File.open(file_to_update).read
 lines.each_line do |line|

    optionalProperty=/^#([^=]+)=(.+)$/

    line.match(optionalProperty) do |m|
	name=m[1].strip
	value=m[2].strip
	env_property=name.gsub('.','/').downcase

	file.write("{{if exists \"/#{env_property}\" -}}\n")
        new_line="#{name} = {{getv \"/#{env_property}\" \"#{value}\"}}\n"
	file.write(new_line)
	file.write("{{end -}}\n")
    end

    if ( isCommentOrBlank?(line)  ) then
	# Don't process comments
	file.write(line)
    else

      name_value = line.split('=')
      name=name_value[0].strip
      value=name_value[1].strip

      env_property=name.gsub('.','/').downcase
      new_line="#{name} = {{getv \"/#{env_property}\" \"#{value}\"}}\n"
      file.write(new_line)
    end
  end
end