// In-process systemd state for nova-shell.
//
// Lists of units and machines are exposed to QML as JSON-encoded QString props
// (`failedUnitsJson`, `containersJson`) rather than QList<QVariantMap>. cxx-qt
// 0.8.1 does not implement QVariantValue for QVariantMap/QVariantList, and
// cxx-qt main on git regressed qt-build-utils to require QuickControls2.prl
// files that nixpkgs strips. Switch to QList<QVariantMap> when a release ships
// with both fixes.

use core::pin::Pin;
use cxx_qt_lib::QString;
use serde::Serialize;
use std::sync::OnceLock;
use tokio::runtime::Runtime;
use zbus::{Connection, proxy};

#[cxx_qt::bridge]
pub mod qobject {
    unsafe extern "C++" {
        include!("cxx-qt-lib/qstring.h");
        type QString = cxx_qt_lib::QString;
    }

    extern "RustQt" {
        #[qobject]
        #[qml_element]
        #[qml_singleton]
        #[qproperty(QString, hostname)]
        #[qproperty(QString, system_state, cxx_name = "systemState")]
        #[qproperty(QString, user_state, cxx_name = "userState")]
        #[qproperty(i32, failed_count, cxx_name = "failedCount")]
        // JSON array: [{ name, description, subState, scope: "system"|"user", machine: "" | name }]
        #[qproperty(QString, failed_units_json, cxx_name = "failedUnitsJson")]
        // JSON array: [{ name, class, service, systemState, failedUnits: [...] }]
        #[qproperty(QString, containers_json, cxx_name = "containersJson")]
        type SystemdService = super::SystemdServiceRust;

        #[qinvokable]
        fn poll(self: Pin<&mut Self>);

        #[qinvokable]
        #[cxx_name = "restartUnit"]
        fn restart_unit(self: Pin<&mut Self>, name: QString, scope: QString, machine: QString);
    }

    impl cxx_qt::Initialize for SystemdService {}
}

// systemd1.Manager.ListUnitsFiltered returns a(ssssssouso): name, description,
// load_state, active_state, sub_state, follower, unit_path, job_id, job_type, job_path.
type UnitTuple = (
    String,
    String,
    String,
    String,
    String,
    String,
    zbus::zvariant::OwnedObjectPath,
    u32,
    String,
    zbus::zvariant::OwnedObjectPath,
);

#[proxy(
    interface = "org.freedesktop.systemd1.Manager",
    default_service = "org.freedesktop.systemd1",
    default_path = "/org/freedesktop/systemd1"
)]
trait SystemdManager {
    #[zbus(property)]
    fn system_state(&self) -> zbus::Result<String>;

    fn list_units_filtered(&self, states: Vec<&str>) -> zbus::Result<Vec<UnitTuple>>;

    fn restart_unit(&self, name: &str, mode: &str)
    -> zbus::Result<zbus::zvariant::OwnedObjectPath>;
}

#[proxy(
    interface = "org.freedesktop.machine1.Manager",
    default_service = "org.freedesktop.machine1",
    default_path = "/org/freedesktop/machine1"
)]
trait Machined {
    fn list_machines(
        &self,
    ) -> zbus::Result<Vec<(String, String, String, zbus::zvariant::OwnedObjectPath)>>;
}

#[derive(Serialize)]
struct UnitJson<'a> {
    name: &'a str,
    description: &'a str,
    #[serde(rename = "subState")]
    sub_state: &'a str,
    scope: &'a str,
    machine: &'a str,
}

#[derive(Serialize)]
struct ContainerJson<'a> {
    name: &'a str,
    class: &'a str,
    service: &'a str,
    #[serde(rename = "systemState")]
    system_state: &'a str,
    #[serde(rename = "failedUnits")]
    failed_units: Vec<UnitJson<'a>>,
}

pub struct SystemdServiceRust {
    hostname: QString,
    system_state: QString,
    user_state: QString,
    failed_count: i32,
    failed_units_json: QString,
    containers_json: QString,
}

impl Default for SystemdServiceRust {
    fn default() -> Self {
        Self {
            hostname: QString::from(read_hostname()),
            system_state: QString::from("unknown"),
            user_state: QString::from("unknown"),
            failed_count: 0,
            failed_units_json: QString::from("[]"),
            containers_json: QString::from("[]"),
        }
    }
}

fn read_hostname() -> String {
    std::fs::read_to_string("/etc/hostname")
        .map(|s| s.trim().to_string())
        .unwrap_or_else(|_| "localhost".to_string())
}

fn rt() -> &'static Runtime {
    static RT: OnceLock<Runtime> = OnceLock::new();
    RT.get_or_init(|| {
        tokio::runtime::Builder::new_current_thread()
            .enable_all()
            .build()
            .expect("tokio runtime")
    })
}

async fn fetch_failed(bus: &Connection) -> (String, Vec<UnitTuple>) {
    let mut state = String::from("unknown");
    let mut units = Vec::new();
    if let Ok(mgr) = SystemdManagerProxy::new(bus).await {
        if let Ok(s) = mgr.system_state().await {
            state = s;
        }
        if let Ok(u) = mgr.list_units_filtered(vec!["failed"]).await {
            units = u;
        }
    }
    (state, units)
}

async fn poll_async() -> (
    String,
    String,
    Vec<UnitTuple>,
    Vec<UnitTuple>,
    Vec<(String, String, String)>,
) {
    let mut sys_state = String::from("unknown");
    let mut sys_units = Vec::new();
    let mut user_state = String::from("unknown");
    let mut user_units = Vec::new();
    let mut machines = Vec::new();

    if let Ok(c) = Connection::system().await {
        let (s, u) = fetch_failed(&c).await;
        sys_state = s;
        sys_units = u;
        if let Ok(m) = MachinedProxy::new(&c).await {
            if let Ok(list) = m.list_machines().await {
                machines = list
                    .into_iter()
                    .filter(|(name, _, _, _)| name != ".host")
                    .map(|(n, c, s, _)| (n, c, s))
                    .collect();
            }
        }
    }
    if let Ok(c) = Connection::session().await {
        let (s, u) = fetch_failed(&c).await;
        user_state = s;
        user_units = u;
    }

    (sys_state, user_state, sys_units, user_units, machines)
}

fn unit_jsons<'a>(units: &'a [UnitTuple], scope: &'a str, machine: &'a str) -> Vec<UnitJson<'a>> {
    units
        .iter()
        .map(|u| UnitJson {
            name: &u.0,
            description: &u.1,
            sub_state: &u.4,
            scope,
            machine,
        })
        .collect()
}

impl cxx_qt::Initialize for qobject::SystemdService {
    fn initialize(self: Pin<&mut Self>) {
        self.poll();
    }
}

impl qobject::SystemdService {
    fn poll(mut self: Pin<&mut Self>) {
        let (sys_state, user_state, sys_units, user_units, machines) = rt().block_on(poll_async());

        let mut all_failed: Vec<UnitJson> = Vec::with_capacity(sys_units.len() + user_units.len());
        all_failed.extend(unit_jsons(&sys_units, "system", ""));
        all_failed.extend(unit_jsons(&user_units, "user", ""));
        let count = all_failed.len() as i32;
        let failed_json = serde_json::to_string(&all_failed).unwrap_or_else(|_| "[]".into());

        let containers: Vec<ContainerJson> = machines
            .iter()
            .map(|(n, c, s)| ContainerJson {
                name: n,
                class: c,
                service: s,
                system_state: "unknown",
                failed_units: Vec::new(),
            })
            .collect();
        let containers_json = serde_json::to_string(&containers).unwrap_or_else(|_| "[]".into());

        self.as_mut().set_system_state(QString::from(sys_state));
        self.as_mut().set_user_state(QString::from(user_state));
        self.as_mut()
            .set_failed_units_json(QString::from(failed_json));
        self.as_mut().set_failed_count(count);
        self.as_mut()
            .set_containers_json(QString::from(containers_json));
    }

    fn restart_unit(self: Pin<&mut Self>, name: QString, scope: QString, machine: QString) {
        let name = name.to_string();
        let scope = scope.to_string();
        let machine = machine.to_string();
        let _ = self;
        rt().block_on(async move {
            // Local-only restart for now. Container/remote restart comes later.
            if !machine.is_empty() {
                tracing::warn!(target: "nova_plugin", machine = %machine, "container restart not yet implemented");
                return;
            }
            let conn = match scope.as_str() {
                "user" => Connection::session().await,
                _ => Connection::system().await,
            };
            let Ok(conn) = conn else { return };
            let Ok(mgr) = SystemdManagerProxy::new(&conn).await else {
                return;
            };
            if let Err(e) = mgr.restart_unit(&name, "replace").await {
                tracing::warn!(target: "nova_plugin", unit = %name, error = %e, "restart_unit failed");
            }
        });
    }
}