Add ColorCommand to change text and background colors using color

See #13

Author: nihaltp

src/main/java/com/mycmd/App.java

@@ -51,5 +51,6 @@ private static void registerCommands(Map<String, Command> commands) {
         commands.put("help", new HelpCommand(commands));
         commands.put("exit", new ExitCommand());
         commands.put("ver", new VersionCommand());
+        commands.put("color", new ColorCommand());
     }
 }

src/main/java/com/mycmd/commands/ColorCommand.java

@@ -0,0 +1,35 @@
+package com.mycmd.commands;
+
+import com.mycmd.Command;
+import com.mycmd.ShellContext;
+
+public class ColorCommand implements Command {
+    @Override
+    public void execute(String[] args, ShellContext context) {
+        if (args.length == 1) {
+            String color = args[0];
+            String background = String.valueOf(color.charAt(0));
+            String text = String.valueOf(color.charAt(1));
+
+            if (background == text) {
+                return;
+            }
+
+            int bgIndex = Integer.parseInt(background,16);
+            int fgIndex = Integer.parseInt(text,16);
+
+            String[] ansiForeground = {"30","34","32","36","31","35","33","37","90","94","92","96","91","95","93","97"};
+            String[] ansiBackground = {"40","44","42","46","41","45","43","47","100","104","102","106","101","105","103","107"};
+
+            String bg = "\033[" + ansiBackground[bgIndex] + "m";
+            String fg = "\033[" + ansiForeground[fgIndex] + "m";
+
+            System.out.println(bg + fg);
+        }
+
+        else {
+            // set default color
+            System.out.println("\033[0m");
+        }
+    }
+}