Merge pull request #308 from belligerentbeagle/246-dg-command-history…

…-retrieval-implementation

Improve Command History implementation

docs/DeveloperGuide.md

@@ -362,6 +362,18 @@ The <span class="badge bg-light text-dark"><i class="fa-regular fa-square-caret-
 retrieves the last command from the `CommandHistory` Singleton object.
 <puml src="diagrams/CommandHistorySequenceDiagram.puml" alt="Command History Sequence Diagram" />
 
+<box type="info" light>
+
+**Note:** The `CommandHistory` Singleton object is used to store the command history. It is a Singleton object to ensure that there is only one instance of the `CommandHistory` object throughout the application.
+
+</box>
+
+Below is the activity diagram that shows how the process of a user interacting with the input field to retrieve the 
+last command executed.
+
+<puml src="diagrams/CommandHistoryActivityDiagram.puml" width="400" />
+
+
 {{ newPage }}
 
 ### \[Proposed\] Undo/Redo Feature

docs/diagrams/CommandHistoryActivityDiagram.puml

@@ -0,0 +1,29 @@
+@startuml
+skin rose
+skinparam ActivityFontSize 15
+skinparam ArrowFontSize 12
+start
+
+
+:Input field is empty;
+
+if () then ([up or down arrow key pressed])
+    :Retrieves previousCommand
+    from CommandHistory
+    if available;
+    note
+      previousCommand is a generic variable
+      representing a command from CommandHistory.
+      Therefore it can contain an older or nere
+      command depending on the current command
+    end note
+    :previousCommand fills Input field;
+else ([else])
+    :User enters command in Input field;
+endif
+:User executes command;
+:Command saved in CommandHistory;
+:Input field is cleared;
+
+stop
+@enduml