Add the refactoring video's.

Note that the video's themselves aren't included yet, because I still
have to make them web-ready (and cut a little in them).

README.md

@@ -81,6 +81,7 @@ Maintainable software allows __us__ to __quickly__:
 * Ask an extra opinion if needed
 * Don't only give negative feedback
 * Automate automatable stuff
+* Always review your own code
 
 ???
 
@@ -90,6 +91,120 @@ This will make it easier for you to get different insights in your code.
 
 ---
 
+# Refactoring
+
+* Should be an integrated part of your workflow
+* Automated tests can help you validate refactorings
+* Look out for duplication (phpcpd)
+* Static analysis can help you here
+
+---
+
+# Setup
+
+* Make your project easy to set up (locally)
+  * use vagrant/docker
+  * add a setup guide if needed (README)
+  * make code (without interface) "runnable" through tests
+* Make your project easy to deploy
+  * automate deployment
+  * keep your master/default branch stable
+
+---
+
+# SOLID
+
+Keep the SOLID rules in mind.
+
+<https://leanpub.com/principles-of-package-design>
+
+---
+
+<video controls>
+    <source src="video/step1-SRP.mov"/>
+</video>
+
+???
+
+Our library has one entry point: the Converter class. This class has two
+responsibilities: converting from html to json and the other way around.
+
+We'll split the two classes to make sure each class does one thing and one
+thing only.
+
+---
+
+<video>
+    <source src="video/step2-make-dependencies-explicit-take-2.mov"/>
+</video>
+
+???
+
+Note that I've removed the "Converter" suffix from the two main classes. The
+small "type" classes that convert one small item are also called converters.
+The names "HtmlToJson" and "JsonToHtml" are explicit enough.
+
+This refactoring will remove the "ToHtmlContext" and "ToJsonContext". These
+classes were only used from the main entry points. They are instantiated
+in there so they are coupled. All the small type converters are thus also
+coupled. This refactoring makes this more explicit making it easier to
+move to more decoupled code later.
+
+---
+
+<video>
+    <source src="video/step3-split-interface.mov"/>
+</video>
+
+???
+
+We see that our classes always only use one method of our interface. We'll
+split the interface into a ToJson and ToHtml version to follow the
+Interface Segregation Principle.
+
+---
+
+<video>
+    <source src="video/step4-open-closed-part1.mov"/>
+</video>
+
+???
+
+I've already done some refactoring before we'll go to this step. I've
+split the implementation of all converters to a toJson and toHtml version.
+
+I've also gave them a "match" method, so the main entry point classes don't
+have to decide which class to use anymore. This gives it one less responsibility.
+
+In this refactoring, we're going to introduce an "addConverter" method
+which makes our class open for extension. This way, other persons can add
+extra custom converters.
+
+Note that we're not following the open closed principle yet. It's open for
+extension, but not closed to modification, since we'll need to access the class
+to change the order of converters or to remove a default one.
+
+---
+
+<video>
+    <source src="video/step4-open-closed-part2.mov"/>
+</video>
+
+???
+
+In this refactoring, we'll fully remove the dependencies on implementations.
+We're now following the dependency inversion principle: we're depending on
+abstractions, not on implementation.
+
+Our class is also closed for modification. We don't need to enter the class to
+get the behaviour we want.
+
+Note that I've made all classes final later, to avoid extending them. If
+classes can be extended, they can still be modified. I want my class to be
+closed to modifications, since it already has an extension point.
+
+---
+
 # Object calisthenics
 
 * Programming exercises

styles/swag.css

@@ -392,3 +392,10 @@ blockquote p:last-child {
   margin-left: -33%;
   top: 30%;
 }
+video {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+}