Support selecting multiple cards by using a list of numbers (separated by comma, or space)

https://3.basecamp.com/2914079/buckets/37331921/todos/8620236700#__recording_8620273944

app/models/command/parser.rb

@@ -11,14 +11,14 @@ class Command::Parser
     command_name, *command_arguments = string.strip.split(" ")
 
     case command_name
-    when "/assign", "/assignto"
-      Command::Assign.new(assignee_ids: assignees_from(command_arguments).collect(&:id), card_ids: cards.ids)
-    when "/close"
-      Command::Close.new(card_ids: cards.ids, reason: command_arguments.join(" "))
-    when /^@/
-      Command::GoToUser.new(user_id: assignee_from(command_name)&.id)
-    else
-      search(string)
+      when "/assign", "/assignto"
+        Command::Assign.new(assignee_ids: assignees_from(command_arguments).collect(&:id), card_ids: cards.ids)
+      when "/close"
+        Command::Close.new(card_ids: cards.ids, reason: command_arguments.join(" "))
+      when /^@/
+        Command::GoToUser.new(user_id: assignee_from(command_name)&.id)
+      else
+        search(string)
     end
   end
 
@@ -37,10 +37,21 @@ class Command::Parser
     end
 
     def search(string)
-      if card = user.accessible_cards.find_by_id(string)
+      if cards = multiple_cards_from(string)
+        Command::FilterCards.new(card_ids: cards.ids, params: filter.as_params)
+      elsif card = user.accessible_cards.find_by_id(string)
         Command::GoToCard.new(card_id: card.id)
       else
         Command::Search.new(query: string, params: filter.as_params)
       end
     end
+
+    def multiple_cards_from(string)
+      if tokens = string.split(/[\s,]+/).filter { it =~ /\A\d+\z/ }.presence
+        if tokens.many?
+          cards = user.accessible_cards.where(id: tokens)
+          cards.any? ? cards : nil
+        end
+      end
+    end
 end