use core::ptr::NonNull;
use discreet_metrics::{ encoders::text::TextEncoder, metrics::counter::Counter, MetricDesc, Registry };
use std::sync::Once;

// A registry will be typically declared in a static
static REGISTRY: Registry = Registry::new();

// Then referenced from within a file where it is required
// ```
// extern "Rust" {
//    static REGISTRY: Registry<'static>;
//}

// Declare a metric in a file where it is used, again as a static
static SOME_METRIC: Counter = Counter::new();
static mut SOME_METRIC_DESC: MetricDesc = 
    MetricDesc::new("some-metric", "Some metric", None, &["some-label"], &SOME_METRIC);

// Register the metric descriptor - once, and only once! The following is achieved
// using std::sync::Once, but other methods including the lazy_static library can be
// used. This initialization would also typically appear within the file where the
// metric is used.
static REGISTER_METRICS: Once = Once::new();
    
// later...
REGISTER_METRICS.call_once(|| {
    REGISTRY.register(unsafe { &mut SOME_METRIC_DESC });
});

// Do what we do with metric counters!
SOME_METRIC.inc();

// Elsewhere, establish the encoder and output its bytes somewhere 
// either periodically or on demand.
let mut encoder = TextEncoder;
let _encoder = REGISTRY.encode(&mut encoder);