initial commit (it all starts here...)

src/cli/types.ts

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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+/**
+ * CLI command representing an action that the CLI program supports.
+ */
+export interface Command {
+    /**
+     * Execute the command with the specified arguments.
+     *
+     * @param args List of CLI arguments to pass to the command.
+     */
+    execute(args: string[]): Promise<void>;
+    /**
+     * Help text for this command.
+     */
+    helpText: string;
+}
+
+/**
+ * Error that commands can issue to indicate incorrect usage along with help
+ * text to guide the user to correct their mistake.
+ */
+export class UsageError extends Error {
+    public readonly helpText: string;
+
+    public constructor(message: string, helpText: string) {
+        super(message);
+
+        this.helpText = helpText;
+    }
+}