class Card
  class Query
    class SqlStatement
      def initialize query=nil
        @query = query
        @mods = query && query.mods
      end

      def build
        @fields = fields
        @tables = tables
        @joins  = joins @query.all_joins
        @where  = where
        @group  = group
        @order  = order
        @limit_and_offset = limit_and_offset
        self
      end

      def to_s
        [comment,
         "SELECT DISTINCT #{@fields}",
         "FROM #{@tables}",
         @joins,
         @where,
         @group,
         @order,
         @limit_and_offset
        ].compact * "\n"
      end

      def comment
        return nil unless Card.config.sql_comments && @query.comment
        "/* #{@query.comment} */"
      end

      def tables
        "cards #{@query.table_alias}"
      end

      def fields
        table = @query.table_alias
        field = @mods[:return] unless @mods[:return] =~ /_\w+/
        field = field.blank? ? :card : field.to_sym
        field = full_field(table, field)
        [field, @mods[:sort_join_field]].compact * ", "
      end

      def full_field table, field
        case field
        when :raw      then "#{table}.*"
        when :card     then "#{table}.*"
        when :content  then "#{table}.db_content"
        when :count
          "coalesce(count( distinct #{table}.id),0) as count"
        else
          if ATTRIBUTES[field.to_sym] == :basic
            "#{table}.#{field}"
          else
            safe_sql field
          end
        end
      end

      def joins join_list
        clauses = []
        join_list.each do |join|
          clauses << join_on_clause(join)
          clauses << joins(deeper_joins join) unless join.left?
        end
        clauses.flatten * "\n"
      end

      def join_on_clause join
        [join_clause(join), "ON", on_clause(join)].join " "
      end

      def deeper_joins join
        deeper_joins = join.subjoins
        deeper_joins += join.to.all_joins if join.to.is_a? Card::Query
        deeper_joins
      end

      def join_clause join
        to_table = join.to_table
        to_table = "(#{to_table.sql})" if to_table.is_a? Card::Query
        table_segment = [to_table, join.to_alias].join " "

        if join.left?
          djoins = deeper_joins(join)
          unless djoins.empty?
            table_segment = "(#{table_segment} #{joins djoins})"
          end
        end
        [join.side, "JOIN", table_segment].compact.join " "
      end

      def on_clause join
        on_conditions = join.conditions
        on_ids = [
          "#{join.from_alias}.#{join.from_field}",
          "#{join.to_alias}.#{join.to_field}"
        ].join " = "
        on_conditions.unshift on_ids
        if join.to.is_a? Card::Query
          if join.to.conditions_on_join == join
            on_conditions.push query_conditions(join.to)
          end
          on_conditions.push standard_conditions(join.to)
        end
        basic_conditions(on_conditions) * " AND "
      end

      def where
        conditions = [query_conditions(@query), standard_conditions(@query)]
        conditions = conditions.reject(&:blank?).join "\nAND "
        "WHERE #{conditions}" unless conditions.blank?
      end

      def query_conditions query
        cond_list = basic_conditions query.conditions
        cond_list +=
          query.subqueries.map do |subquery|
            next if subquery.conditions_on_join
            query_conditions subquery
          end
        cond_list.reject!(&:blank?)

        if cond_list.size > 1
          cond_list = cond_list.join "\n#{query.current_conjunction.upcase} "
          "(#{cond_list})"
        else
          cond_list.join
        end
      end

      def basic_conditions conditions
        conditions.map do |condition|
          if condition.is_a? String
            condition
          else
            field, val = condition
            val.to_sql field
          end
        end
      end

      def standard_conditions query
        table = query.table_alias
        [trash_condition(table), permission_conditions(table)].compact * " AND "
      end

      def trash_condition table
        "#{table}.trash is false"
      end

      def permission_conditions table
        return if Auth.always_ok?
        read_rules = Auth.as_card.read_rules
        read_rule_list = read_rules.present? ? read_rules.join(",") : 1
        "#{table}.read_rule_id IN (#{read_rule_list})"
      end

      def group
        group = @mods[:group]
        "GROUP BY #{safe_sql group}" if group.present?
      end

      def limit_and_offset
        full_syntax do
          limit = @mods[:limit]
          offset = @mods[:offset]
          if limit.to_i > 0
            string =  "LIMIT  #{limit.to_i} "
            string += "OFFSET #{offset.to_i} " if offset.present?
            string
          end
        end
      end

      def full_syntax
        @query.full? ? yield : return
      end

      def order
        full_syntax do
          order_key ||= @mods[:sort].blank? ? "update" : @mods[:sort]

          order_directives = [order_key].flatten.map do |key|
            dir = if @mods[:dir].blank?
                    DEFAULT_ORDER_DIRS[key.to_sym] || "asc"
                  else
                    safe_sql @mods[:dir]
                  end
            sort_field key, @mods[:sort_as], dir
          end.join ", "
          "ORDER BY #{order_directives}"
        end
      end

      def sort_field key, as, dir
        table = @query.table_alias
        order_field =
          case key
          when "id"             then "#{table}.id"
          when "update"         then "#{table}.updated_at"
          when "create"         then "#{table}.created_at"
          when /^(name|alpha)$/ then "#{table}.key"
          when "content"        then "#{table}.db_content"
          when "relevance"      then "#{table}.updated_at" # deprecated
          else
            safe_sql(key)
          end
        order_field = "CAST(#{order_field} AS #{cast_type(safe_sql as)})" if as
        @fields += ", #{order_field}"
        "#{order_field} #{dir}"
      end

      def safe_sql txt
        txt = txt.to_s
        if txt =~ /[^\w\*\(\)\s\.\,]/
          raise "WQL contains disallowed characters: #{txt}"
        else
          txt
        end
      end

      def cast_type type
        cxn ||= ActiveRecord::Base.connection
        (val = cxn.cast_types[type.to_sym]) ? val[:name] : safe_sql(type)
      end
    end
  end
end