use axum::extract::State;
use axum::http::StatusCode;
use axum::response::IntoResponse;
use axum::routing::get;
use axum::Router;

pub use metrics_exporter_prometheus::PrometheusHandle;

use metrics_exporter_prometheus::PrometheusBuilder;

/// Initialize the global metrics recorder and return a handle for rendering.
pub fn init() -> Result<PrometheusHandle, metrics_exporter_prometheus::BuildError> {
    PrometheusBuilder::new().install_recorder()
}

/// Axum handler that renders all registered metrics in Prometheus exposition format.
pub async fn metrics_handler(State(handle): State<PrometheusHandle>) -> impl IntoResponse {
    (
        StatusCode::OK,
        [("content-type", "text/plain; version=0.0.4; charset=utf-8")],
        handle.render(),
    )
}

/// Returns a minimal axum router with just `GET /metrics`.
pub fn router(handle: PrometheusHandle) -> Router {
    Router::new()
        .route("/metrics", get(metrics_handler))
        .with_state(handle)
}