use axum::{extract::State, response::IntoResponse};
use metrics::{counter, gauge, histogram};
use metrics_exporter_prometheus::{PrometheusBuilder, PrometheusHandle};

pub fn init() -> PrometheusHandle {
    PrometheusBuilder::new()
        .install_recorder()
        .expect("install prometheus recorder")
}

// --- Emission ---------------------------------------------------------------
// The recorder was installed and `/metrics` served, but nothing was ever
// measured. These are the emit sites the runner calls so an operator scraping
// `/metrics` sees real build activity, not an empty page.

/// A build was accepted and fanned out.
pub fn build_started() {
    counter!("bento_builds_total").increment(1);
}

/// A target run reached a terminal state. `status` is `ok` / `failed` /
/// `aborted`; `secs` is its wall-clock duration.
pub fn target_finished(target: &str, status: &str, secs: f64) {
    counter!("bento_target_runs_total", "target" => target.to_owned(), "status" => status.to_owned())
        .increment(1);
    histogram!("bento_target_run_seconds", "target" => target.to_owned()).record(secs);
}

/// Set the gauge of target tasks currently in flight (the live `active` count).
pub fn set_in_flight(n: usize) {
    gauge!("bento_targets_in_flight").set(n as f64);
}

pub async fn render(State(handle): State<PrometheusHandle>) -> impl IntoResponse {
    handle.render()
}

/// A render handle that does NOT install the global recorder — the global is a
/// process-wide singleton, so tests (many `AppState`s per process) must not
/// call [`init`]. Metrics emitted via the macros are dropped under this handle,
/// which is fine for tests that only exercise routes.
#[cfg(test)]
pub fn test_handle() -> PrometheusHandle {
    PrometheusBuilder::new().build_recorder().handle()
}