module CassandraObject
  module Persistence
    extend ActiveSupport::Concern

    module ClassMethods
      def remove(id)
        execute_cql "DELETE FROM #{column_family} WHERE KEY = ?", id
      end

      def delete_all
        execute_cql "TRUNCATE #{column_family}"
      end

      def create(attributes = {})
        new(attributes).tap do |object|
          object.save
        end
      end

      def write(id, attributes)
        if (encoded = encode_attributes(attributes)).any?
          insert_attributes = {'KEY' => id}.update encode_attributes(attributes)
          statement = "INSERT INTO #{column_family} (#{insert_attributes.keys * ','}) VALUES (#{Array.new(insert_attributes.size, '?') * ','})"
          execute_cql statement, *insert_attributes.values
        end

        if (nil_attributes = attributes.select { |key, value| value.nil? }).any?
          execute_cql "DELETE #{nil_attributes.keys * ','} FROM #{column_family} WHERE KEY = ?", id
        end
      end

      def instantiate(id, attributes)
        allocate.tap do |object|
          object.instance_variable_set("@id", id) if id
          object.instance_variable_set("@new_record", false)
          object.instance_variable_set("@destroyed", false)
          object.instance_variable_set("@attributes", typecast_attributes(object, attributes))
        end
      end

      def encode_attributes(attributes)
        encoded = {}
        attributes.each do |column_name, value|
          # The ruby thrift gem expects all strings to be encoded as ascii-8bit.
          unless value.nil?
            encoded[column_name.to_s] = attribute_definitions[column_name.to_sym].coder.encode(value)
          end
        end
        encoded
      end

      def typecast_attributes(object, attributes)
        attributes = attributes.symbolize_keys
        Hash[attribute_definitions.map { |k, attribute_definition| [k.to_s, attribute_definition.instantiate(object, attributes[k])] }]
      end
    end

    def new_record?
      @new_record
    end

    def destroyed?
      @destroyed
    end

    def persisted?
      !(new_record? || destroyed?)
    end

    def save(*)
      new_record? ? create : update
    end

    def destroy
      self.class.remove(id)
      @destroyed = true
      freeze
    end

    def update_attribute(name, value)
      name = name.to_s
      send("#{name}=", value)
      save(validate: false)
    end

    def update_attributes(attributes)
      self.attributes = attributes
      save
    end

    def update_attributes!(attributes)
      self.attributes = attributes
      save!
    end

    def reload
      @attributes.update(self.class.find(id).instance_variable_get('@attributes'))
    end

    private
      def update
        write
      end

      def create
        @new_record = false
        write
      end

      def write
        changed_attributes = Hash[changed.map { |attr| [attr, read_attribute(attr)] }]
        self.class.write(id, changed_attributes)
      end
  end
end