Proposal for Sandthorn 2.0

proposal.rb

# = Example Sandthorn setup

Sandthorn.config do |sand|
  sand.snapshot_store = SnapshotStore.new
  sand.event_stores = {
    default:      SequelStore.new(url: "sqlite://my_db", snapshot_store: sand.snapshot_store)
    alternative:  MongoStore.new(url: "some_url", snapshot_store: sand.snapshot_store)
    aux:          InMemoryStore.new
  }
  # This maps aggregates to event stores.
  # Aggregates that aren't exlicitly mapped will be stored in the default store.
  # I see the need to be able to define either concrete classes or patterns.
  sand.aggregate_mappings = {
    alternative: [StoreAggregates::Foo, StoreAggregates::Bar]
    aux: /LogAggregates/
  }
end

# Example aggregate

class MyAggregate
  include AggregateRoot

  attr_reader :name

  def initialize(name: nil)
    @name = name
  end

  def change_name(name)
    @name = name
    name_changed
  end

  def name_changed
    commit
  end
end

# = Committing
# When commit is called, we just construct the appropriate event and save it in the aggregate.
# The events should be in the agreed-upon event format.

# = Saving an aggregate
# Saving means finding the appropriate event store for the aggregate type, and then calling `save_events` on the event store with any unsaved events.
# Example:
#   1. my_aggregate.save calls Sandthorn.event_store_for(my_aggregate) and gets an event_store
#   2. Call event_store.save_events(my_aggregate, my_aggregate.unsaved_events)

# Here's an incomplete implementation of AggregateRoot

module Sandthorn
  module AggregateRoot

    attr_reader :unsaved_events

    def self.included(base)
      base.extend(ClassMethods)
    end

    module ClassMethods
      def event_store
        Sandthorn.event_store_for(self)
      end
    end

    def save
      if unsaved_events.any?
        save_events(unsaved_events)
      end
    end

    private

    def save_events(events)
      event_store.save_events(self, events)
    end

    def event_store
      self.class.event_store
    end

  end
end

Very nice indeed! I concur.