use hyper::{
    service::{make_service_fn, service_fn},
    Body, Request, Response, Server,
};
use prometheus_client::{encoding::text::encode, metrics::counter::Counter, registry::Registry};
use std::{future::Future, io, net::SocketAddr, pin::Pin, sync::Arc};
use tokio::signal::unix::{signal, SignalKind};

#[derive(Debug, Clone)]
pub struct Metrics {
    pub existing_or_updated_bridges: Counter,
    pub new_bridges: Counter,
    pub removed_bridges: Counter,
    pub blocked_bridges: Counter,
    pub open_inv_count: Counter,
    pub trust_promo_count: Counter,
    pub trust_mig_count: Counter,
    pub level_up_count: Counter,
    pub issue_invite_count: Counter,
    pub redeem_invite_count: Counter,
    pub check_blockage_count: Counter,
    pub blockage_migration_count: Counter,
    pub k_reset_count: Counter,
    pub invites_requested: Counter,
}

impl Default for Metrics {
    fn default() -> Self {
        // Create counters.
        let existing_or_updated_bridges = Counter::default();
        let new_bridges = Counter::default();
        let removed_bridges = Counter::default();
        let blocked_bridges = Counter::default();
        let open_inv_count = Counter::default();
        let trust_promo_count = Counter::default();
        let trust_mig_count = Counter::default();
        let level_up_count = Counter::default();
        let issue_invite_count = Counter::default();
        let redeem_invite_count = Counter::default();
        let check_blockage_count = Counter::default();
        let blockage_migration_count = Counter::default();
        let k_reset_count = Counter::default();
        let invites_requested = Counter::default();

        Metrics {
            existing_or_updated_bridges,
            new_bridges,
            removed_bridges,
            blocked_bridges,
            open_inv_count,
            trust_promo_count,
            trust_mig_count,
            level_up_count,
            issue_invite_count,
            redeem_invite_count,
            check_blockage_count,
            blockage_migration_count,
            k_reset_count,
            invites_requested,
        }
    }
}

impl Metrics {
    pub fn register(&self) -> Registry {
        // Create a Registry and register Counter.
        let mut r = <Registry>::with_prefix("lox-metrics");
        r.register(
            "existing_or_updated_bridges",
            "number of existing or updated bridges recorded at rdsys sync",
            self.existing_or_updated_bridges.clone(),
        );
        r.register(
            "new_bridges",
            "number of new bridges added to bridge table",
            self.new_bridges.clone(),
        );
        r.register(
            "removed_bridges",
            "number of bridges removed from the bridgetable",
            self.removed_bridges.clone(),
        );
        r.register(
            "blocked_bridges",
            "number of bridges blocked",
            self.blocked_bridges.clone(),
        );
        r.register(
            "open_inv_counter",
            "number of open invitations distributed",
            self.open_inv_count.clone(),
        );
        r.register(
            "trust_promo_counter",
            "number of trust promotions requests",
            self.trust_promo_count.clone(),
        );
        r.register(
            "trust_mig_counter",
            "number of trust migrations requests",
            self.trust_mig_count.clone(),
        );
        r.register(
            "level_up_counter",
            "number of level up requests",
            self.level_up_count.clone(),
        );
        r.register(
            "issue_invite_counter",
            "number of issue invite requests",
            self.issue_invite_count.clone(),
        );
        r.register(
            "redeem_invite_counter",
            "number of level up requests",
            self.redeem_invite_count.clone(),
        );
        r.register(
            "check_blockage_counter",
            "number of check blockage requests",
            self.check_blockage_count.clone(),
        );
        r.register(
            "blockage_migration_counter",
            "number of blockage migration requests",
            self.blockage_migration_count.clone(),
        );
        r.register(
            "k_reset_counter",
            "number of times k has reset to 0",
            self.k_reset_count.clone(),
        );
        r.register(
            "invites_requested",
            "number of invites requested",
            self.invites_requested.clone(),
        );
        r
    }
}

/// Start a HTTP server to report metrics.
pub async fn start_metrics_server(metrics_addr: SocketAddr, registry: Registry) {
    let mut shutdown_stream = signal(SignalKind::terminate()).unwrap();

    eprintln!("Starting metrics server on {metrics_addr}");

    let registry = Arc::new(registry);
    Server::bind(&metrics_addr)
        .serve(make_service_fn(move |_conn| {
            let registry = registry.clone();
            async move {
                let handler = make_handler(registry);
                Ok::<_, io::Error>(service_fn(handler))
            }
        }))
        .with_graceful_shutdown(async move {
            shutdown_stream.recv().await;
        })
        .await
        .unwrap();
}

/// This function returns an HTTP handler (i.e. another function)
pub fn make_handler(
    registry: Arc<Registry>,
) -> impl Fn(Request<Body>) -> Pin<Box<dyn Future<Output = io::Result<Response<Body>>> + Send>> {
    // This closure accepts a request and responds with the OpenMetrics encoding of our metrics.
    move |_req: Request<Body>| {
        let reg = registry.clone();
        Box::pin(async move {
            let mut buf = String::new();
            encode(&mut buf, &reg.clone())
                .map_err(|e| std::io::Error::new(std::io::ErrorKind::Other, e))
                .map(|_| {
                    let body = Body::from(buf);
                    Response::builder()
                        .header(
                            hyper::header::CONTENT_TYPE,
                            "application/openmetrics-text; version=1.0.0; charset=utf-8",
                        )
                        .body(body)
                        .unwrap()
                })
        })
    }
}