module ETL #:nodoc:
  module Control #:nodoc:
    # Base class for destinations.
    class Destination
      # Read-only accessor for the ETL::Control::Control instance
      attr_reader :control
      
      # Read-only accessor for the configuration Hash
      attr_reader :configuration
      
      # Read-only accessor for the destination mapping Hash
      attr_reader :mapping
      
      # Accessor to the buffer size
      attr_accessor :buffer_size
      
      # Unique flag.
      attr_accessor :unique
      
      class << self
        # Get the destination class for the specified name.
        # 
        # For example if name is :database or 'database' then the DatabaseDestination class 
        # is returned
        def class_for_name(name)
          ETL::Control.const_get("#{name.to_s.classify}Destination")
        end
      end
      
      # Initialize the destination
      #
      # Arguments:
      # * <tt>control</tt>: The ETL::Control::Control instance
      # * <tt>configuration</tt>: The configuration Hash
      # * <tt>mapping</tt>: The mapping Hash
      #
      # Options:
      # * <tt>:buffer_size</tt>: The output buffer size (default 1000 records)
      def initialize(control, configuration, mapping)
        @control = control
        @configuration = configuration
        @mapping = mapping
        @buffer_size = configuration[:buffer_size] ||= 1000
      end
      
      # Get the current row number
      def current_row
        @current_row ||= 1
      end
      
      # Write the given row
      def write(row)
        buffer << row
        flush if buffer.length >= buffer_size
      end
      
      # Abstract method
      def flush
        raise NotImplementedError, "flush method must be implemented by subclasses"
      end
      
      # Abstract method
      def close
        raise NotImplementedError, "close method must be implemented by subclasses"
      end
      
      def errors
        @errors ||= []
      end
      
      protected
      # Access the buffer
      def buffer
        @buffer ||= []
      end
      
      # Access the generators map
      def generators
        @generators ||= {}
      end
      
      # Get the order of elements from the source order
      def order_from_source
        order = []
        control.sources.first.definition.each do |item|
          case item
          when Hash
            order << item[:name]
          else
            order << item
          end
        end
        order
      end
      
      # Return true if the row is allowed. The row will not be allowed if the :unique option is specified
      # in the configuration and the compound key already exists
      def row_allowed?(row)
        if unique
          key = (unique.collect { |k| row[k] }).join('|')
          return false if compound_key_constraints[key]
          compound_key_constraints[key] = 1
        end
        return true
      end
      
      # Get a hash of compound key contraints. This is used to determine if a row can be written when the
      # unique option is specified
      def compound_key_constraints
        @compound_key_constraints ||= {}
      end
      
      # Add any virtual fields to the row. Virtual rows will get their value from one of the following:
      # * If the mapping is a Class, then an object which implements the next method
      # * If the mapping is a Symbol, then the XGenerator where X is the classified symbol
      # * If the mapping is a Proc, then it will be called with the row
      # * Otherwise the value itself will be assigned to the field
      def add_virtuals!(row)
        if mapping[:virtual]
          mapping[:virtual].each do |key,value|
            # Engine.logger.debug "Mapping virtual #{key}/#{value} for row #{row}"
            case value
            when Class
              generator = generators[key] ||= value.new
              row[key] = generator.next
            when Symbol
              generator = generators[key] ||= ETL::Generator::Generator.class_for_name(value).new
              row[key] = generator.next
            when Proc
              row[key] = value.call(row)
            else
              row[key] = value
            end
          end
        end
      end
    end
  end
end

Dir[File.dirname(__FILE__) + "/destination/*.rb"].each { |file| require(file) }