Storable Types for Kemal-Session

storable_types.cr

require "json"

STORABLE_TYPES = [] of Nil

class StorageInstance
  macro finished
    alias StorableObjects = Union({{ *STORABLE_TYPES }})
  end

  JSON.mapping({
    objects: Hash(String, StorableObjects)
  })

  def initialize
    @objects = {} of String => StorableObjects
  end

  def object(key : String, val : StorableObjects)
    objects[key] = val
  end

  def object(key : String)
    objects[key]
  end
end

module StorableObject
  class NotImplementedException < Exception; end

  macro included
    {% STORABLE_TYPES << @type %}

    macro finished
      {% if !@type.class.overrides?(Object, "from_json") %}
        {{ raise("StorableObject #{@type} needs to define `from_json`") }}
      {% end %}

      {% if !@type.overrides?(Object, "to_json") %}
        {{ raise("StoraableObject #{@type} needs to define `to_json`") }}
      {% end %}
    end
  end
end

class Whatever
  JSON.mapping({
    doit: String
  })
  include StorableObject
end

class Something
  JSON.mapping({
    blah: String
  })
  include StorableObject

  def self.something; end

  def doit
    1
  end
end

store = StorageInstance.new
store.object("first", Whatever.from_json("{\"doit\":\"something\"}"))
store.object("second", Something.from_json("{\"blah\":\"so yeah\"}"))
string = store.to_json
new_store = StorageInstance.from_json(string)
puts new_store.object("first").doit