Merge pull request #292 from belligerentbeagle/246-dg-command-history…

…-retrieval-implementation

Add PUML Implementation Diagram for Command History

docs/DeveloperGuide.md

@@ -221,7 +221,13 @@ This section describes some noteworthy details on how certain features are imple
 
 ### Command History Retrieval
 
-**TODO**
+Let's consider the scenario where the user wants to retrieve the last command executed. The user can do this by 
+pressing the <span class="badge bg-light text-dark"><i class="fa-regular fa-square-caret-up"></i> UP</span> key on 
+the keyboard. 
+
+The <span class="badge bg-light text-dark"><i class="fa-regular fa-square-caret-up"></i> UP</span> key press event is captured by the `CommandBox` class, which then 
+retrieves the last command from the `CommandHistory` Singleton object.
+<puml src="diagrams/CommandHistorySequenceDiagram.puml" alt="Command History Sequence Diagram" />
 
 {{ newPage }}
 

docs/diagrams/CommandHistorySequenceDiagram.puml

@@ -0,0 +1,32 @@
+@startuml
+!include style.puml
+skinparam ArrowFontStyle plain
+
+box Command History UI_COLOR_T2
+participant ":CommandBox" as Model UI_COLOR_T3
+participant ":CommandHistory" as ModelCH UI_COLOR_T3
+end box
+
+[-> Model : keyPress(e)
+activate Model
+
+Model -> Model : handleKeyPressEvent(e)
+Model -> Model : handleArrowKeyPress(e)
+activate Model
+Model -> ModelCH : getInstance()
+activate ModelCH
+ModelCH --> Model :
+deactivate ModelCH
+
+Model -> ModelCH : getCommandHistory(direction)
+activate ModelCH
+
+ModelCH --> Model : previousCommand
+deactivate ModelCH
+
+Model -> Model : setText(previousCommand)
+
+[<-- Model
+deactivate Model
+
+@enduml