json_to_java.rb

require 'json'
require 'active_support/inflector'
require 'digest'
require 'fileutils'

PACKAGE_PATH = "com.mbildner.domain"

class JavaClass
  attr_accessor :name, :body

  def initialize(name, body)
    @name = name
    @body = body
  end

  def package_file_path
    @_package_file_path ||= File.join(*PACKAGE_PATH.split("."))
  end

  def file_name
    "#{name}.java"
  end

  def path
    File.join(package_file_path, file_name)
  end
end

class Parser
  def initialize(finalize)
    @finalize = finalize
    @classes = []
  end

  attr_reader :classes

  def parse(source_hash, base_class_name)
    if source_hash.class == Array
      collection_name = "#{base_class_name.capitalize}".pluralize
      base_class_name = base_class_name + "Collection"
      source_hash = {
        collection_name => source_hash
      }
    end

    js_to_java(source_hash, base_class_name)
  end

  private

  def java_class(name, members=nil)
    throw Exception.new("java class must have a name") if name == nil
    java_class = <<-JAVA_CODE
package #{PACKAGE_PATH}

public class #{name} {
    #{members}
}

    JAVA_CODE

    JavaClass.new(name, java_class)
  end

  def js_to_java(js, class_name=nil, root=false)
    case(js)
    when TrueClass
      'boolean'
    when FalseClass
      'boolean'
    when NilClass
      'null'
    when String
      'String'
    when Fixnum
      'Number'
    when Float
      'Number'
    when Array
      types = js.map { |element| js_to_java(element, class_name) }
      type = types.uniq.size == 1 ? types.first : "Object"
      "List<#{type.singularize}>"
    when Hash
      members = js.map do |(key, value)|
        "\t #{optional_final_keyword} #{js_to_java(value, key.capitalize)} #{root ? key.downcase : key};"
      end.join("\n")

      @classes << java_class(class_name, members)

      class_name
    else
      throw Exception.new("Not clear what type this is, failing to build")
    end
  end

  def optional_final_keyword
    "final" if @finalize
  end
end

finalize = ARGV.include? "--finalize"

source_json_file = ARGV[0]
source_string = File.read(source_json_file)
source_json = JSON.parse(source_string)

parser = Parser.new(finalize=finalize)

base_name = source_json_file.gsub(/\.json$/, "").capitalize

parser.parse(source_json, base_name)

parser.classes.uniq do |java_class|
  java_class.name
end.map do |java_class|
  FileUtils.mkdir_p(java_class.package_file_path)

  File.open(java_class.path, 'w') { |f| f.write(java_class.body) }
end