use axum::{extract::State, http::header, response::IntoResponse};
use sqlx::SqlitePool;

use crate::error::Result;

/// Exposition des métriques au format Prometheus text (scraping Grafana/Prometheus).
///
/// Endpoint : GET /metrics
/// Compatible avec prometheus.yml :
///   scrape_configs:
///     - job_name: sentinelmesh
///       static_configs:
///         - targets: ['sentinelmesh:8080']
pub async fn metrics(State(db): State<SqlitePool>) -> Result<impl IntoResponse> {
    let rows = sqlx::query_as::<_, (
        String, String,
        Option<f64>, Option<f64>, Option<f64>, Option<f64>,
        Option<i64>, Option<i64>,
    )>(
        "SELECT a.hostname, m.agent_id,
                m.cpu_percent, m.ram_percent, m.disk_percent, m.temperature_c,
                m.net_rx_bps, m.net_tx_bps
         FROM metrics m JOIN agents a ON a.id = m.agent_id",
    )
    .fetch_all(&db)
    .await?;

    let mut out = String::with_capacity(2048);

    macro_rules! gauge {
        ($name:expr, $help:expr, $type:expr) => {
            out.push_str(&format!(
                "# HELP sentinelmesh_{} {}\n# TYPE sentinelmesh_{} {}\n",
                $name, $help, $name, $type
            ));
        };
    }

    gauge!("cpu_percent",   "Utilisation CPU en pourcentage",        "gauge");
    gauge!("ram_percent",   "Utilisation RAM en pourcentage",        "gauge");
    gauge!("disk_percent",  "Utilisation disque en pourcentage",     "gauge");
    gauge!("temperature_c", "Température CPU/système en Celsius",    "gauge");
    gauge!("net_rx_bps",    "Débit réseau entrant en octets/s",      "gauge");
    gauge!("net_tx_bps",    "Débit réseau sortant en octets/s",      "gauge");

    for (hostname, agent_id, cpu, ram, disk, temp, rx, tx) in &rows {
        let lbl = format!("agent=\"{agent_id}\",hostname=\"{hostname}\"");
        let push = |name: &str, val: f64| format!("sentinelmesh_{name}{{{lbl}}} {val:.2}\n");

        if let Some(v) = cpu  { out.push_str(&push("cpu_percent",   *v)); }
        if let Some(v) = ram  { out.push_str(&push("ram_percent",   *v)); }
        if let Some(v) = disk { out.push_str(&push("disk_percent",  *v)); }
        if let Some(v) = temp { out.push_str(&push("temperature_c", *v)); }
        if let Some(v) = rx   { out.push_str(&push("net_rx_bps",    *v as f64)); }
        if let Some(v) = tx   { out.push_str(&push("net_tx_bps",    *v as f64)); }
    }

    Ok((
        [(header::CONTENT_TYPE, "text/plain; version=0.0.4; charset=utf-8")],
        out,
    ))
}