From 89ff0709f5f40f290167839e26d36ea81a60869b Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 12:28:35 +0200
Subject: [PATCH 01/11] Encapsulate state

---
 ecommerce/ordering/lib/ordering/order.rb | 44 +++++++++++++++++-------
 1 file changed, 32 insertions(+), 12 deletions(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index bd8244bb..01bd76fe 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -9,13 +9,13 @@ class Order
 
     def initialize(id)
       @id = id
-      @state = :draft
+      @state = State.new(:draft)
       @basket = Basket.new
     end
 
     def submit(order_number)
-      raise OrderHasExpired if @state.equal?(:expired)
-      raise AlreadySubmitted unless @state.equal?(:draft)
+      raise OrderHasExpired if @state.expired?
+      raise AlreadySubmitted unless @state.draft?
       apply OrderSubmitted.new(
         data: {
           order_id: @id,
@@ -26,7 +26,7 @@ def submit(order_number)
     end
 
     def accept
-      raise InvalidState unless @state.equal?(:submitted)
+      raise InvalidState unless @state.submitted?
       apply OrderPlaced.new(
         data: {
           order_id: @id,
@@ -37,7 +37,7 @@ def accept
     end
 
     def reject
-      raise InvalidState unless @state.equal?(:submitted)
+      raise InvalidState unless @state.submitted?
       apply OrderRejected.new(
         data: {
           order_id: @id
@@ -46,12 +46,12 @@ def reject
     end
 
     def expire
-      raise AlreadySubmitted unless @state.equal?(:draft)
+      raise AlreadySubmitted unless @state.draft?
       apply OrderExpired.new(data: { order_id: @id })
     end
 
     def add_item(product_id)
-      raise AlreadySubmitted unless @state.equal?(:draft)
+      raise AlreadySubmitted unless @state.draft?
       apply ItemAddedToBasket.new(
         data: {
           order_id: @id,
@@ -61,16 +61,16 @@ def add_item(product_id)
     end
 
     def remove_item(product_id)
-      raise AlreadySubmitted unless @state.equal?(:draft)
+      raise AlreadySubmitted unless @state.draft?
       apply ItemRemovedFromBasket.new(data: { order_id: @id, product_id: product_id })
     end
 
     on OrderPlaced do |event|
-      @state = :accepted
+      @state = State.new(:accepted)
     end
 
     on OrderExpired do |event|
-      @state = :expired
+      @state = State.new(:expired)
     end
 
     on ItemAddedToBasket do |event|
@@ -83,11 +83,11 @@ def remove_item(product_id)
 
     on OrderSubmitted do |event|
       @order_number = event.data[:order_number]
-      @state = :submitted
+      @state = State.new(:submitted)
     end
 
     on OrderRejected do |event|
-      @state = :draft
+      @state = State.new(:draft)
     end
 
     class Basket
@@ -113,4 +113,24 @@ def quantity(product_id)
       end
     end
   end
+
+  class State
+    ALLOWED_STATES = %i(draft submitted expired accepted)
+
+    def initialize(state = :draft)
+      @state = state
+    end
+
+    def draft?
+      @state.equal?(:draft)
+    end
+
+    def submitted?
+      @state.equal?(:submitted)
+    end
+
+    def expired?
+      @state.equal?(:expired)
+    end
+  end
 end

From 438b224eb88a30cfbda97443f887551fdfee81a6 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 12:30:27 +0200
Subject: [PATCH 02/11] Refactor

---
 ecommerce/ordering/lib/ordering/order.rb | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index 01bd76fe..7b60611f 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -66,11 +66,11 @@ def remove_item(product_id)
     end
 
     on OrderPlaced do |event|
-      @state = State.new(:accepted)
+      @state = @state.transition_to(:accepted)
     end
 
     on OrderExpired do |event|
-      @state = State.new(:expired)
+      @state = @state.transition_to(:expired)
     end
 
     on ItemAddedToBasket do |event|
@@ -83,11 +83,11 @@ def remove_item(product_id)
 
     on OrderSubmitted do |event|
       @order_number = event.data[:order_number]
-      @state = State.new(:submitted)
+      @state = @state.transition_to(:submitted)
     end
 
     on OrderRejected do |event|
-      @state = State.new(:draft)
+      @state = State.new
     end
 
     class Basket
@@ -132,5 +132,10 @@ def submitted?
     def expired?
       @state.equal?(:expired)
     end
+
+    def transition_to(state)
+      raise InvalidState unless ALLOWED_STATES.include?(state)
+      State.new(state)
+    end
   end
 end

From 1f64ccd00fb0565f038ef2f10f64bf8398ba83c8 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 12:31:09 +0200
Subject: [PATCH 03/11] Allowed transitions

---
 ecommerce/ordering/lib/ordering/order.rb | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index 7b60611f..6986b5a2 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -116,6 +116,12 @@ def quantity(product_id)
 
   class State
     ALLOWED_STATES = %i(draft submitted expired accepted)
+    ALLOWED_TRANSITIONS = {
+      draft: %i(submitted expired),
+      submitted: %i(accepted rejected),
+      expired: %i(draft)
+    }
+
 
     def initialize(state = :draft)
       @state = state
@@ -135,6 +141,7 @@ def expired?
 
     def transition_to(state)
       raise InvalidState unless ALLOWED_STATES.include?(state)
+      raise InvalidState unless ALLOWED_TRANSITIONS[@state].include?(state)
       State.new(state)
     end
   end

From 4070fc96f66218d249b8dc12572a2467918e584f Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 12:33:03 +0200
Subject: [PATCH 04/11] Remove empty line

---
 ecommerce/ordering/lib/ordering/order.rb | 1 -
 1 file changed, 1 deletion(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index 6986b5a2..bdc1b949 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -122,7 +122,6 @@ class State
       expired: %i(draft)
     }
 
-
     def initialize(state = :draft)
       @state = state
     end

From 58344906295a537162c3f7d0d143bc9f15c2a446 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 12:57:53 +0200
Subject: [PATCH 05/11] add eql? and hash methods

---
 ecommerce/ordering/lib/ordering/order.rb | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index bdc1b949..1d29024f 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -143,5 +143,15 @@ def transition_to(state)
       raise InvalidState unless ALLOWED_TRANSITIONS[@state].include?(state)
       State.new(state)
     end
+
+    def eql?(other)
+      other.instance_of?(State) && other.state.equal?(@state)
+    end
+
+    def hash
+      State.hash ^ @state.hash
+    end
+
+    alias == eql?
   end
 end

From 217a506c257a86cfc71a2b4061886760c0565f33 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 13:07:48 +0200
Subject: [PATCH 06/11] refactor

---
 ecommerce/ordering/lib/ordering/order.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index 1d29024f..f0223491 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -9,7 +9,7 @@ class Order
 
     def initialize(id)
       @id = id
-      @state = State.new(:draft)
+      @state = State.new
       @basket = Basket.new
     end
 

From 4164face5d35f00e043c9bd902eaf7cd0dfd2e04 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 17:07:49 +0200
Subject: [PATCH 07/11] Move State class into Order

---
 ecommerce/ordering/lib/ordering/order.rb | 64 ++++++++++++------------
 1 file changed, 32 insertions(+), 32 deletions(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index f0223491..171def6b 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -112,46 +112,46 @@ def quantity(product_id)
         order_lines[product_id]
       end
     end
-  end
 
-  class State
-    ALLOWED_STATES = %i(draft submitted expired accepted)
-    ALLOWED_TRANSITIONS = {
-      draft: %i(submitted expired),
-      submitted: %i(accepted rejected),
-      expired: %i(draft)
-    }
+    class State
+      ALLOWED_STATES = %i(draft submitted expired accepted)
+      ALLOWED_TRANSITIONS = {
+        draft: %i(submitted expired),
+        submitted: %i(accepted rejected),
+        expired: %i(draft)
+      }
 
-    def initialize(state = :draft)
-      @state = state
-    end
+      def initialize(state = :draft)
+        @state = state
+      end
 
-    def draft?
-      @state.equal?(:draft)
-    end
+      def draft?
+        @state.equal?(:draft)
+      end
 
-    def submitted?
-      @state.equal?(:submitted)
-    end
+      def submitted?
+        @state.equal?(:submitted)
+      end
 
-    def expired?
-      @state.equal?(:expired)
-    end
+      def expired?
+        @state.equal?(:expired)
+      end
 
-    def transition_to(state)
-      raise InvalidState unless ALLOWED_STATES.include?(state)
-      raise InvalidState unless ALLOWED_TRANSITIONS[@state].include?(state)
-      State.new(state)
-    end
+      def transition_to(state)
+        raise InvalidState unless ALLOWED_STATES.include?(state)
+        raise InvalidState unless ALLOWED_TRANSITIONS[@state].include?(state)
+        State.new(state)
+      end
 
-    def eql?(other)
-      other.instance_of?(State) && other.state.equal?(@state)
-    end
+      def eql?(other)
+        other.instance_of?(State) && other.state.equal?(@state)
+      end
 
-    def hash
-      State.hash ^ @state.hash
-    end
+      def hash
+        State.hash ^ @state.hash
+      end
 
-    alias == eql?
+      alias == eql?
+    end
   end
 end

From b7dc1f5df3d6fb54f9a7bbffe63195be864adb79 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 17:09:09 +0200
Subject: [PATCH 08/11] Currently this VO is not used for any comparison

---
 ecommerce/ordering/lib/ordering/order.rb | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index 171def6b..a3313e02 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -142,16 +142,6 @@ def transition_to(state)
         raise InvalidState unless ALLOWED_TRANSITIONS[@state].include?(state)
         State.new(state)
       end
-
-      def eql?(other)
-        other.instance_of?(State) && other.state.equal?(@state)
-      end
-
-      def hash
-        State.hash ^ @state.hash
-      end
-
-      alias == eql?
     end
   end
 end

From 73adf444c708ca22e9afff2531ca5530c7683749 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 17:10:40 +0200
Subject: [PATCH 09/11] Remove transition_to method

The `transition_to` method was only called in the `on` DSL. The problem
is that the transition_to method raises the exception when state is
either not allowed or it is not valid transition. Exceptions shouldn't
be raised when building state of the aggregate. Past is past.
---
 ecommerce/ordering/lib/ordering/order.rb | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index a3313e02..37221c71 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -66,11 +66,11 @@ def remove_item(product_id)
     end
 
     on OrderPlaced do |event|
-      @state = @state.transition_to(:accepted)
+      @state = State.new(:accepted)
     end
 
     on OrderExpired do |event|
-      @state = @state.transition_to(:expired)
+      @state = State.new(:expired)
     end
 
     on ItemAddedToBasket do |event|
@@ -83,7 +83,7 @@ def remove_item(product_id)
 
     on OrderSubmitted do |event|
       @order_number = event.data[:order_number]
-      @state = @state.transition_to(:submitted)
+      @state = State.new(:submitted)
     end
 
     on OrderRejected do |event|
@@ -136,12 +136,6 @@ def submitted?
       def expired?
         @state.equal?(:expired)
       end
-
-      def transition_to(state)
-        raise InvalidState unless ALLOWED_STATES.include?(state)
-        raise InvalidState unless ALLOWED_TRANSITIONS[@state].include?(state)
-        State.new(state)
-      end
     end
   end
 end

From 3077db02e049ccec4a018c7e718905ac8a038269 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 17:12:49 +0200
Subject: [PATCH 10/11] Remove unused

---
 ecommerce/ordering/lib/ordering/order.rb | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index 37221c71..ea8b7ab0 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -114,13 +114,6 @@ def quantity(product_id)
     end
 
     class State
-      ALLOWED_STATES = %i(draft submitted expired accepted)
-      ALLOWED_TRANSITIONS = {
-        draft: %i(submitted expired),
-        submitted: %i(accepted rejected),
-        expired: %i(draft)
-      }
-
       def initialize(state = :draft)
         @state = state
       end

From d844c35f629f87435b2ce63dabab1558e8b2ab41 Mon Sep 17 00:00:00 2001
From: lukaszreszke <lukaszreszke93@gmail.com>
Date: Tue, 6 Aug 2024 17:23:51 +0200
Subject: [PATCH 11/11] States as methods

Accepted didn't get it's own method as it doesn't seem like this
"accepted" information is used in any way
---
 ecommerce/ordering/lib/ordering/order.rb | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/ecommerce/ordering/lib/ordering/order.rb b/ecommerce/ordering/lib/ordering/order.rb
index ea8b7ab0..48c5b364 100644
--- a/ecommerce/ordering/lib/ordering/order.rb
+++ b/ecommerce/ordering/lib/ordering/order.rb
@@ -9,7 +9,7 @@ class Order
 
     def initialize(id)
       @id = id
-      @state = State.new
+      @state = State.draft
       @basket = Basket.new
     end
 
@@ -70,7 +70,7 @@ def remove_item(product_id)
     end
 
     on OrderExpired do |event|
-      @state = State.new(:expired)
+      @state = State.expired
     end
 
     on ItemAddedToBasket do |event|
@@ -83,11 +83,11 @@ def remove_item(product_id)
 
     on OrderSubmitted do |event|
       @order_number = event.data[:order_number]
-      @state = State.new(:submitted)
+      @state = State.submitted
     end
 
     on OrderRejected do |event|
-      @state = State.new
+      @state = State.draft
     end
 
     class Basket
@@ -114,7 +114,19 @@ def quantity(product_id)
     end
 
     class State
-      def initialize(state = :draft)
+      def self.draft
+        new(:draft)
+      end
+
+      def self.submitted
+        new(:submitted)
+      end
+
+      def self.expired
+        new(:expired)
+      end
+
+      def initialize(state)
         @state = state
       end