fix: deep copy settings when duplicating an engine (#907)

src/utils/engines.ts

@@ -69,6 +69,14 @@ export type RemoteEngine = z.output<typeof remoteEngineSchema>;
 export const engineSchema = z.union([localEngineSchema, remoteEngineSchema]);
 export type Engine = z.output<typeof engineSchema>;
 
+export function duplicateEngine(engine: LocalEngine): LocalEngine {
+    return {
+        ...structuredClone(engine),
+        id: crypto.randomUUID(),
+        name: `${engine.name} (Copy)`,
+    };
+}
+
 export function stopEngine(engine: LocalEngine, tab: string): Promise<void> {
     return commands.stopEngine(engine.id, tab).then((r) => {
         unwrap(r);

src/utils/tests/engines.test.ts

@@ -0,0 +1,49 @@
+import { expect, test } from "vitest";
+import { duplicateEngine, type LocalEngine } from "../engines";
+
+const stockfish: () => LocalEngine = () => ({
+    type: "local",
+    id: "stockfish",
+    name: "Stockfish",
+    version: "17",
+    path: "/usr/bin/stockfish",
+    go: { t: "Depth", c: 20 },
+    settings: [
+        { name: "MultiPV", value: 1 },
+        { name: "Threads", value: 4 },
+        { name: "Hash", value: 16 },
+    ],
+});
+
+test("duplicateEngine gives the copy a new id and name", () => {
+    const original = stockfish();
+    const copy = duplicateEngine(original);
+
+    expect(copy.id).not.toBe(original.id);
+    expect(copy.name).toBe("Stockfish (Copy)");
+    expect(copy.settings).toEqual(original.settings);
+    expect(copy.go).toEqual(original.go);
+});
+
+test("duplicateEngine does not share settings with the original", () => {
+    const original = stockfish();
+    const copy = duplicateEngine(original);
+
+    copy.settings!.find((s) => s.name === "Threads")!.value = 8;
+    copy.settings!.push({ name: "Ponder", value: true });
+
+    expect(original.settings).toEqual([
+        { name: "MultiPV", value: 1 },
+        { name: "Threads", value: 4 },
+        { name: "Hash", value: 16 },
+    ]);
+});
+
+test("duplicateEngine does not share the go mode with the original", () => {
+    const original = stockfish();
+    const copy = duplicateEngine(original);
+
+    (copy.go as { c: number }).c = 30;
+
+    expect(original.go).toEqual({ t: "Depth", c: 20 });
+});