#coding: utf-8
=begin
  字段映射，业务字段-数据库字段对应
=end
require 'fileutils'
module FieldMapping
  def self.included(base)
    base.extend(ClassMethods)
  end

  def as_json(options={})
    self.class.buz_hashize(self.attributes)
  end

  def update_from_buz(params={})
    update_attributes(self.class.db_hashize(params))
  end
  
  module ClassMethods
    #Fix a bug on 20111117 by shang
    def __model_clazz_name
      self.name.underscore
    end
    def model_key
      "#{__model_clazz_name}_fields"
    end

    def mapping
      GlobalConst.send(model_key)
    end

    def get_map_value(k, value)
      #raise "Not implemented!"
      #提供默认处理
      #TODO 根据数据类型做些更好的转换
      case k
      when :created_at, :updated_at
        value.try(:to_s, :db)
      else
        value
      end
    end
    
    def dump_new(force=true)
      if defined?(Rails)
        file = "#{Rails.root}/data/#{model_key}_#{Time.now.to_i}.yml"
        path = File.dirname(file)
        FileUtils.mkpath(path) unless File.directory?(path)
        existed = File.exists?(file)
        if existed
          puts "Warning: #{file} has existed! check it! Default override it!"
        end
        if !existed || force
          File.open(file, 'w+') do |f|
            f.puts YAML.dump(buz_hashize)
          end
        end
      end
    end
    
    #辅助方法
    def new_from_buz(params = {})
      new(db_hashize(params))
    end
    def create_from_buz(params = {})
      create(db_hashize(params))
    end
    
    #生成field mapping，dump到指定的yaml文件中
    def dump_mapping(attr_prefix = nil, force = true)
      if defined?(Rails)
        file = "#{Rails.root}/#{GlobalConst::APP_CODE_HASHES}fields/#{model_key}_#{Time.now.to_i}.yml"
        path = File.dirname(file)
        FileUtils.mkpath(path) unless File.directory?(path)
        existed = File.exists?(file)
        if existed
          puts "Warning: #{file} has existed! check it! Default override it!"
        end
        if !existed || force
          #获取数据库字段列表，屏蔽掉自动维护的created_at/updated_at，也可在生成的文件中配上
          keys = new.attributes.symbolize_keys.keys.delete_if{|k| k =~ /^created_at|updated_at$/}
          h = keys.inject({}) do |r, k|
            #移除掉表前缀
            rm_prefix = attr_prefix.nil? ? "#{__model_clazz_name}_" : attr_prefix
            new_key = k.to_s.sub(rm_prefix, '').to_sym
            r[new_key] = k 
            r
          end
          FileUtils.rm_f(file) if existed
          File.open(file, 'w+') do |f|
            f.puts YAML.dump(model_key.to_sym=>h)
          end
          puts "==>gen new file #{file} ..."
        end
      end
    end

    #TODO
    def dump_field_map(force=true)
      puts "==Warning: please use dump_mapping instead, this will be removed..."
      dump_mapping(nil, true)
    end
   
    #业务层到数据层字段参数转换并做一定值处理
    def db_hashize(params = {})
      new_params = params.symbolize_keys
      common_keys = new_params.keys & mapping.keys
      common_keys.inject({}) do |result, key|
        result[mapping[key]] = get_map_value(key, new_params[key])
        result
      end
    end
 
    #将数据层表示转成业务层表示
    def buz_hashize(attrs = {})
      #return {} if attrs.blank?
      #获取默认初始值
      attrs = new.attributes if attrs.blank?
      new_attrs = attrs.symbolize_keys
      invert_maps = mapping.invert_data
      common_db_attrs = new_attrs.keys & invert_maps.keys
      common_db_attrs.inject({}) do |result, attr| 
        buz_field = invert_maps[attr]
        result[buz_field] = get_map_value(buz_field, new_attrs[attr])
        result
      end
    end
  end
end