pub type DesiredCapabilities = FireFox | Edge

struct FireFox {
    browser_name          string = 'firefox'
    accept_insecure_certs bool   = true
    moz_debugger_address  bool   = true
}

struct Edge {
    browser_name string = 'MicrosoftEdge'
}

fn struct_values[T](s T) map[string]string {
    mut res := map[string]string{}
    $if T is $struct {
        $for field in T.fields {
            res[field.name] = s.$(field.name).str()
        }
    }
    return res
}

fn useit(dc DesiredCapabilities) string {
    $for v in dc.variants {
        if dc is v {
            $if v is $struct {
                result := struct_values(dc)
                return result.str()
            }
        }
    }
    return ''
}

fn test_main() {
    assert useit(Edge{}) == "{'browser_name': 'MicrosoftEdge'}"
    assert useit(FireFox{}) == "{'browser_name': 'firefox', 'accept_insecure_certs': 'true', 'moz_debugger_address': 'true'}"
}