import { describe, expect, it } from "vitest";
import { SceneStateMachine } from "@/scene/SceneStateMachine";

describe("SceneStateMachine", () => {
  it("starts in idle state for every new instance", () => {
    const machine = new SceneStateMachine();
    const anotherMachine = new SceneStateMachine();

    expect(machine.getState()).toBe("idle");
    expect(anotherMachine.getState()).toBe("idle");
  });

  it("allows legal transitions defined by the state machine", () => {
    const machine = new SceneStateMachine();

    machine.transitionTo("loading");
    expect(machine.getState()).toBe("loading");

    machine.transitionTo("idle");
    expect(machine.getState()).toBe("idle");
  });

  it("throws on illegal transitions and keeps current state", () => {
    const machine = new SceneStateMachine();

    expect(() => machine.transitionTo("idle")).toThrowError(
      'Invalid scene transition: "idle" -> "idle"'
    );
    expect(machine.getState()).toBe("idle");

    machine.transitionTo("loading");
    expect(machine.getState()).toBe("loading");

    expect(() => machine.transitionTo("loading")).toThrowError(
      'Invalid scene transition: "loading" -> "loading"'
    );
    expect(machine.getState()).toBe("loading");
  });
});