groundtruth/restful_geof

module RestfulGeof
  module SQL
    class Query

      def initialize
        @parts = {
          :selects => [],
          :from => nil,
          :wheres => [],
          :order_bys => [],
          :limit => nil
        }
      end

      def select(*expressions)
        @parts[:selects] += [expressions].flatten
        self
      end

      def from(table)
        raise "Already specified table" if @parts[:from]
        @parts[:from] = table
        self
      end

      def where(*expressions)
        @parts[:wheres] += [expressions].flatten
        self
      end

      alias_method :and, :where

      def order_by(*expressions)
        @parts[:order_bys] += [expressions].flatten
        self
      end

      def limit(number)
        @parts[:limit] = number
        self
      end

      def to_sql
        raise "Need to specify table" unless @parts[:from]
        [
          select_clause,
          from_clause,
          where_clause,
          order_by_clause,
          limit_clause
        ].compact.join("\n") + "\n;\n"
      end

      private

      def select_clause
        if @parts[:selects].empty?
          "SELECT *"
        else
          "SELECT " + @parts[:selects].join(", ")
        end
      end

      def from_clause
        "FROM #{ @parts[:from] }"
      end

      def where_clause
        "WHERE " + @parts[:wheres].join(" AND ") unless @parts[:wheres].empty?
      end

      def order_by_clause
        "ORDER BY " + @parts[:order_bys].join(", ") unless @parts[:order_bys].empty?
      end

      def limit_clause
        "LIMIT #{ Integer(@parts[:limit]).to_s }" unless @parts[:limit].to_s.empty?
      end

    end
  end
end