//! Companion UI container lifecycle, entirely Quadlet-managed.
//!
//! A "companion" is a small nginx-based container that exposes a
//! browser-friendly UI on top of a headless backend service:
//!
//! | Backend          | Companion          | Purpose                  |
//! |------------------|--------------------|--------------------------|
//! | bitcoin-knots    | archy-bitcoin-ui   | RPC viewer               |
//! | bitcoin-core     | archy-bitcoin-ui   | RPC viewer               |
//! | lnd              | archy-lnd-ui       | wallet/channel UI        |
//! | electrumx        | archy-electrs-ui   | indexer status UI        |
//!
//! Lifecycle: `install` writes a Quadlet `.container` unit to
//! `~/.config/containers/systemd/`, daemon-reloads, then starts the
//! generated `.service`. systemd owns supervision from that point on
//! — archipelago can crash, restart, or be uninstalled without
//! touching the companion.
//!
//! This replaces the old `tokio::spawn { podman run }` block in
//! `install.rs` (~165 lines of fire-and-forget shellouts) with a
//! single declarative call.

use anyhow::{Context, Result};
use std::path::PathBuf;
use tokio::fs;
use tokio::process::Command;
use tracing::{info, warn};

use crate::container::quadlet::{self, BindMount, NetworkMode, QuadletUnit};
use archipelago_container::image_uses_insecure_registry;

const COMPANION_REGISTRY: &str = "146.59.87.168:3000/lfg2025";

/// Static description of one companion. The full list per backend
/// app_id lives in `companions_for`.
#[derive(Debug, Clone)]
pub struct CompanionSpec {
    /// Container + unit name (e.g. "archy-bitcoin-ui").
    pub name: &'static str,
    /// Image base name in the lfg2025 registry namespace
    /// (e.g. "bitcoin-ui" → "146.59.87.168:3000/lfg2025/bitcoin-ui:latest").
    pub image_base: &'static str,
    /// Filesystem locations to look for a local Dockerfile (build wins
    /// over registry pull). Searched in order; first hit wins.
    pub build_dir_candidates: &'static [&'static str],
    /// Optional pre-start hook that renders config files referenced
    /// by `bind_mounts`. Returns Ok(()) on success; bind-mount must
    /// be present at start time or the companion will 502.
    pub pre_start: Option<PreStartHook>,
    /// Bind mounts. Always read-only — companions don't write to
    /// host paths.
    pub bind_mounts: &'static [(&'static str, &'static str)],
}

pub type PreStartHook = fn() -> futures_util::future::BoxFuture<'static, Result<()>>;

/// Companions to install when `package_id` lands. Empty for apps
/// without a companion UI.
pub fn companions_for(package_id: &str) -> &'static [CompanionSpec] {
    match package_id {
        "bitcoin" | "bitcoin-core" | "bitcoin-knots" => BITCOIN_UI,
        "lnd" => LND_UI,
        "electrumx" | "electrs" | "mempool-electrs" => ELECTRS_UI,
        _ => &[],
    }
}

const BITCOIN_UI: &[CompanionSpec] = &[CompanionSpec {
    name: "archy-bitcoin-ui",
    image_base: "bitcoin-ui",
    build_dir_candidates: &[
        "/opt/archipelago/docker/bitcoin-ui",
        "/home/archipelago/archy/docker/bitcoin-ui",
        "/home/archipelago/Projects/archy/docker/bitcoin-ui",
    ],
    pre_start: Some(render_bitcoin_ui),
    bind_mounts: &[(
        "/var/lib/archipelago/bitcoin-ui/nginx.conf",
        "/etc/nginx/conf.d/default.conf",
    )],
}];

const LND_UI: &[CompanionSpec] = &[CompanionSpec {
    name: "archy-lnd-ui",
    image_base: "lnd-ui",
    build_dir_candidates: &[
        "/opt/archipelago/docker/lnd-ui",
        "/home/archipelago/archy/docker/lnd-ui",
        "/home/archipelago/Projects/archy/docker/lnd-ui",
    ],
    pre_start: None,
    bind_mounts: &[],
}];

const ELECTRS_UI: &[CompanionSpec] = &[CompanionSpec {
    name: "archy-electrs-ui",
    image_base: "electrs-ui",
    build_dir_candidates: &[
        "/opt/archipelago/docker/electrs-ui",
        "/home/archipelago/archy/docker/electrs-ui",
        "/home/archipelago/Projects/archy/docker/electrs-ui",
    ],
    pre_start: None,
    bind_mounts: &[],
}];

fn render_bitcoin_ui() -> futures_util::future::BoxFuture<'static, Result<()>> {
    Box::pin(async {
        let paths = crate::container::bitcoin_ui::RenderPaths::default();
        crate::container::bitcoin_ui::render(&paths)
            .await
            .map(|_| ())
            .context("render bitcoin-ui nginx.conf")
    })
}

/// Provision and start every companion for `package_id`. Each
/// companion is independent — a failure in one is logged but does
/// not abort the others.
pub async fn install_for(package_id: &str) -> Vec<(String, anyhow::Error)> {
    let mut failures = Vec::new();
    for spec in companions_for(package_id) {
        if let Err(e) = install_one(spec).await {
            warn!(companion = spec.name, error = %e, "companion install failed");
            failures.push((spec.name.to_string(), e));
        }
    }
    failures
}

/// Stop and remove every companion for `package_id`. Best effort:
/// errors are logged but do not abort the sequence.
pub async fn remove_for(package_id: &str) {
    let dir = match quadlet::unit_dir().await {
        Ok(d) => d,
        Err(e) => {
            warn!("companion remove: cannot resolve quadlet dir: {e:#}");
            return;
        }
    };
    for spec in companions_for(package_id) {
        if let Err(e) = quadlet::disable_remove(spec.name, &dir).await {
            warn!(companion = spec.name, error = %e, "companion remove failed");
        }
    }
}

/// Provision one companion: pre-start hook → image present → write
/// quadlet → daemon-reload → start.
pub async fn install_one(spec: &CompanionSpec) -> Result<()> {
    if let Some(hook) = spec.pre_start {
        hook().await.with_context(|| {
            format!(
                "pre-start hook failed for {} — companion will not start",
                spec.name
            )
        })?;
    }
    let image = ensure_image_present(spec).await?;
    let unit = build_unit(spec, &image);
    let dir = quadlet::unit_dir().await?;
    let changed = quadlet::write_if_changed(&unit, &dir).await?;
    if changed {
        info!(companion = spec.name, "wrote quadlet unit");
        quadlet::daemon_reload_user().await?;
    }
    // Start is idempotent — if already running, systemctl returns 0.
    quadlet::enable_now(&unit.service_name()).await?;
    info!(companion = spec.name, "companion started");
    Ok(())
}

/// Build companion image locally if a Dockerfile exists, otherwise
/// pull from the lfg2025 registry. Returns the image ref the quadlet
/// should reference (`localhost/<base>:latest` for build, registry
/// URL for pull).
async fn ensure_image_present(spec: &CompanionSpec) -> Result<String> {
    let local_image = format!("localhost/{}:latest", spec.image_base);
    let registry_image = format!("{}/{}:latest", COMPANION_REGISTRY, spec.image_base);

    // Prefer local build — companions can carry build-time customizations
    // (e.g. nginx.conf templates baked in). Search known candidates.
    for dir in spec.build_dir_candidates {
        let dockerfile = PathBuf::from(dir).join("Dockerfile");
        if fs::try_exists(&dockerfile).await.unwrap_or(false) {
            info!(companion = spec.name, "building locally from {dir}");
            let out = Command::new("podman")
                .args(["build", "--no-cache", "-t", &local_image, dir])
                .output()
                .await
                .context("spawn podman build")?;
            if out.status.success() {
                return Ok(local_image);
            }
            warn!(
                companion = spec.name,
                "local build failed: {}",
                String::from_utf8_lossy(&out.stderr).trim()
            );
            // Fall through to registry pull rather than fail outright.
            break;
        }
    }

    // Registry pull. Use insecure flag only for whitelisted hosts.
    let mut cmd = Command::new("podman");
    cmd.arg("pull");
    if image_uses_insecure_registry(&registry_image) {
        cmd.arg("--tls-verify=false");
    }
    cmd.arg(&registry_image);
    let out = cmd.output().await.context("spawn podman pull")?;
    if !out.status.success() {
        anyhow::bail!(
            "no local Dockerfile and registry pull failed for {}: {}",
            spec.name,
            String::from_utf8_lossy(&out.stderr).trim()
        );
    }
    Ok(registry_image)
}

fn build_unit(spec: &CompanionSpec, image: &str) -> QuadletUnit {
    QuadletUnit {
        name: spec.name.into(),
        description: format!("Archipelago companion UI: {}", spec.name),
        image: image.into(),
        // Companions proxy to localhost — backend is on :5678, bitcoin
        // RPC on :8332. Host network is the simplest way to reach them
        // without per-app gateway plumbing.
        network: NetworkMode::Host,
        // Run as root inside the container so nginx can chown its
        // worker dirs. Rootless podman maps this to a high host UID,
        // so it is unprivileged on the host.
        user: Some("0:0".into()),
        memory_mb: Some(128),
        cap_drop_all: true,
        cap_add: vec![
            "CHOWN".into(),
            "DAC_OVERRIDE".into(),
            "NET_BIND_SERVICE".into(),
            "SETUID".into(),
            "SETGID".into(),
        ],
        bind_mounts: spec
            .bind_mounts
            .iter()
            .map(|(host, container)| BindMount {
                host: PathBuf::from(*host),
                container: PathBuf::from(*container),
                read_only: true,
            })
            .collect(),
        extra_podman_args: vec![],
        depends_on: vec![],
    }
}

/// Is a user systemd manager reachable? In production archipelago.service
/// inherits XDG_RUNTIME_DIR from systemd; in unit tests / CI sandboxes it
/// is unset, in which case `systemctl --user` would fail and write to
/// HOME would be an unwanted side effect. The reconciler skips its
/// companion stage when this is false.
fn user_systemd_available() -> bool {
    std::env::var_os("XDG_RUNTIME_DIR")
        .map(|v| !v.is_empty())
        .unwrap_or(false)
}

/// Reconcile companion presence: every expected companion for the
/// given installed apps must have its quadlet unit on disk and its
/// service active. Returns a list of (companion, error) for anything
/// that needed correction and failed.
///
/// Called from `boot_reconciler` so a deleted unit file or a stopped
/// service is repaired within one tick. No-ops if the user systemd
/// manager is not reachable (CI / test environments).
pub async fn reconcile(installed_apps: &[String]) -> Vec<(String, anyhow::Error)> {
    if !user_systemd_available() {
        return Vec::new();
    }
    let mut failures = Vec::new();
    for app_id in installed_apps {
        for spec in companions_for(app_id) {
            match needs_repair(spec).await {
                Ok(false) => {}
                Ok(true) => {
                    info!(
                        companion = spec.name,
                        "reconcile: companion not active, repairing"
                    );
                    if let Err(e) = install_one(spec).await {
                        failures.push((spec.name.to_string(), e));
                    }
                }
                Err(e) => {
                    warn!(companion = spec.name, error = %e, "reconcile probe failed");
                    failures.push((spec.name.to_string(), e));
                }
            }
        }
    }
    failures
}

/// Does this companion need install_one to be re-run? Returns true if
/// the unit file is missing OR the service is not active.
async fn needs_repair(spec: &CompanionSpec) -> Result<bool> {
    let dir = quadlet::unit_dir().await?;
    let unit_path = dir.join(format!("{}.container", spec.name));
    if !fs::try_exists(&unit_path).await.unwrap_or(false) {
        return Ok(true);
    }
    let svc = format!("{}.service", spec.name);
    Ok(!quadlet::is_active(&svc).await)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn companions_for_known_apps_returns_expected_set() {
        assert_eq!(companions_for("bitcoin-knots").len(), 1);
        assert_eq!(companions_for("bitcoin-core").len(), 1);
        assert_eq!(companions_for("bitcoin").len(), 1);
        assert_eq!(companions_for("lnd").len(), 1);
        assert_eq!(companions_for("electrumx").len(), 1);
        assert_eq!(companions_for("electrs").len(), 1);
        assert_eq!(companions_for("mempool-electrs").len(), 1);
        assert_eq!(companions_for("nextcloud").len(), 0);
        assert_eq!(companions_for("not-a-real-app").len(), 0);
    }

    #[test]
    fn build_unit_uses_host_network_and_drops_caps() {
        let spec = &BITCOIN_UI[0];
        let u = build_unit(spec, "localhost/bitcoin-ui:latest");
        assert_eq!(u.name, "archy-bitcoin-ui");
        assert!(matches!(u.network, NetworkMode::Host));
        assert!(u.cap_drop_all);
        assert!(u.cap_add.iter().any(|c| c == "NET_BIND_SERVICE"));
        assert_eq!(u.user.as_deref(), Some("0:0"));
        assert_eq!(u.memory_mb, Some(128));
        assert_eq!(u.bind_mounts.len(), 1);
        assert_eq!(
            u.bind_mounts[0].container,
            PathBuf::from("/etc/nginx/conf.d/default.conf")
        );
        assert!(u.bind_mounts[0].read_only);
    }
}