Add theme switcher command

assets/ts/terminal/Terminal.ts

@@ -6,6 +6,7 @@ import { Help } from "./commands/Help";
 import { Kitties } from "./commands/Kitties";
 import { List } from "./commands/List";
 import { AutocompletingCommand } from "./AutocompletingCommand";
+import { Theme } from "./commands/Theme";
 
 export class Terminal {
   private inputElement = document.getElementById("prompt-input") as HTMLSpanElement;
@@ -20,6 +21,7 @@ export class Terminal {
     new Help(),
     new Kitties(),
     new List(),
+    new Theme(),
   ];
 
   public initialise(): void {

assets/ts/terminal/commands/Theme.ts

@@ -0,0 +1,37 @@
+import { Command } from "../Command";
+import { Terminal } from "../Terminal";
+import { setDarkMode } from "../../darkMode";
+import { Theme as ThemeType } from "../../types/main";
+import { AutocompletingCommand } from "../AutocompletingCommand";
+
+export class Theme extends AutocompletingCommand {
+  public readonly name: string = "theme";
+  public readonly description: string =
+    "Set the theme of the website. Available themes: light, dark, system";
+  private readonly validThemes = ["light", "dark", "system"];
+
+  public execute(terminal: Terminal, args: string[]): void {
+    if (args.length < 1) {
+      terminal.print("theme: missing arguments");
+      return;
+    }
+
+    if (args.length > 1) {
+      terminal.print("theme: too many arguments");
+      return;
+    }
+
+    const theme = args[0];
+
+    if (!this.validThemes.includes(theme)) {
+      terminal.print("theme: unknown theme");
+      return;
+    }
+
+    setDarkMode(theme as ThemeType);
+  }
+
+  suggestAutocompletions(arg: string): string[] {
+    return this.validThemes.filter((name: string) => name.startsWith(arg));
+  }
+}