module RBHive
  class TableSchema
    attr_accessor :name
    attr_reader :columns, :partitions
    def initialize(name, comment=nil, options={}, &blk)
      @name, @comment = name, comment
      @location = options[:location] || nil
      @field_sep = options[:field_sep] || "\t"
      @line_sep = options[:line_sep] || "\n"
      @collection_sep = options[:collection_sep] || "|"
      @columns = []
      @partitions = []
      instance_eval(&blk) if blk
    end
  
    def column(name, type, comment=nil)
      @columns << Column.new(name, type, comment)
    end
  
    def partition(name, type, comment=nil)
      @partitions << Column.new(name, type, comment)
    end
  
    def create_table_statement()
      %[CREATE #{external}TABLE #{table_statement}
  ROW FORMAT DELIMITED
  FIELDS TERMINATED BY '#{@field_sep}'
  COLLECTION ITEMS TERMINATED BY '#{@collection_sep}'
  LINES TERMINATED BY '#{@line_sep}'
  STORED AS TEXTFILE
  #{location}]
    end
  
    def replace_columns_statement
      alter_columns_statement("REPLACE")
    end
  
    def add_columns_statement
      alter_columns_statement("ADD")
    end
  
    def to_s
      table_statement
    end
  
    private

    def external
      @location.nil? ? '' : 'EXTERNAL '
    end
  
    def table_statement
      comment_string = (@comment.nil? ? '' : " COMMENT '#{@comment}'")
      %[`#{@name}` #{column_statement}#{comment_string}\n#{partition_statement}]
    end

    def location
      @location.nil? ? '' : "LOCATION '#{@location}'"
    end
  
    def alter_columns_statement(add_or_replace)
      %[ALTER TABLE `#{name}` #{add_or_replace} COLUMNS #{column_statement}]
    end
  
    def column_statement
      cols = @columns.join(",\n")
      "(\n#{cols}\n)"
    end
  
    def partition_statement
      return "" if @partitions.nil? || @partitions.empty?
      cols = @partitions.join(",\n")
      "PARTITIONED BY (\n#{cols}\n)"
    end
  
    class Column
      attr_reader :name, :type, :comment
      def initialize(name, type, comment=nil)
        @name, @type, @comment = name, type, comment
      end
    
      def to_s
        comment_string = @comment.nil? ? '' : " COMMENT '#{@comment}'"
        "`#{@name}` #{@type.to_s.upcase}#{comment_string}"
      end
    end
  end
end