enum-gui.ts

type KeyEnumOf<T> = {[P in keyof T]: P}

class Enum {
    static make<T>(source: T): Readonly<KeyEnumOf<T>> {
        let result = {} as KeyEnumOf<T>;
        for (const k in source) {
            result[k] = k;
        }
        return Object.freeze(result);
    }

    static allCases<T>(source: T): (keyof T)[] {
        var keys = [] as (keyof T)[];
        for (const k in source) {
            keys.push(k);
        }
        return keys;
    }
}

const RendererType = Enum.make({
    'rasterizer': '',
    'raytracer': '',
});

const RendererTypeDefault = RendererType.rasterizer;

const RendererTypeAllCases = Enum.allCases(RendererType);

class GUI {
    add<T, K extends keyof T>(target: T, key: K, value: T[K] | T[K][]): void {
    }
}

type Params = {
    renderer: keyof typeof RendererType,
    rotateCamera: boolean
}

var params: Params = {renderer: RendererTypeDefault, rotateCamera: true};

var gui: GUI = new GUI();
gui.add(params, 'renderer', RendererTypeAllCases);
gui.add(params, 'rotateCamera', true);