//! Startup auto-update: on `hive-c0re serve` boot, rebuild any sub-agent
//! container whose recorded "hyperhive rev" differs from the current one,
//! then write the new rev as the marker. Skips rebuild when nothing changed
//! so warm restarts are near-free.
//!
//! "Rev" is the canonical filesystem path of the configured hyperhive flake
//! (e.g. `/nix/store/<hash>-source` when `/etc/hyperhive` is a symlink the
//! NixOS module wires up). For non-path flake URLs we don't have a cheap rev
//! signal, so auto-update is a no-op — operators rebuild manually.

use std::path::{Path, PathBuf};
use std::sync::Arc;

use anyhow::{Context, Result};

use crate::coordinator::Coordinator;
use crate::lifecycle::{self, AGENT_PREFIX, MANAGER_NAME};

/// Marker file recording the hyperhive rev a sub-agent's container was last
/// built against. Sibling of `applied/<name>/` (rather than inside it) to
/// keep it out of the applied repo's git history. Uses a leading dot so a
/// glob over `applied/*` doesn't include it.
pub fn rev_marker_path(name: &str) -> PathBuf {
    PathBuf::from(format!("/var/lib/hyperhive/applied/.{name}.hyperhive-rev"))
}

/// Resolve the current rev of `hyperhive_flake`. For a path on disk we
/// canonicalize (following symlinks) so a /etc/hyperhive → /nix/store/...
/// update yields a different string. For anything else we return None.
#[must_use]
pub fn current_flake_rev(hyperhive_flake: &str) -> Option<String> {
    let path = Path::new(hyperhive_flake);
    if !path.exists() {
        return None;
    }
    std::fs::canonicalize(path)
        .ok()
        .map(|p| p.display().to_string())
}

/// Read the marker for `name` and return whether the recorded rev matches
/// `current_rev`. Missing/unreadable marker counts as out-of-date.
#[must_use]
pub fn agent_needs_update(name: &str, current_rev: &str) -> bool {
    let prev = std::fs::read_to_string(rev_marker_path(name))
        .ok()
        .map(|s| s.trim().to_owned());
    prev.as_deref() != Some(current_rev)
}

/// Rebuild one sub-agent and refresh its marker. Used by both the startup
/// scanner and the dashboard's manual "update" button so the two paths
/// can't diverge.
pub async fn rebuild_agent(coord: &Arc<Coordinator>, name: &str, current_rev: &str) -> Result<()> {
    tracing::info!(%name, rev = %current_rev, "rebuild agent");
    let agent_dir = coord
        .ensure_runtime(name)
        .with_context(|| format!("ensure_runtime {name}"))?;
    let applied_dir = Coordinator::agent_applied_dir(name);
    let claude_dir = Coordinator::agent_claude_dir(name);
    let notes_dir = Coordinator::agent_notes_dir(name);
    // Suppress crash_watch during the stop+start window inside
    // lifecycle::rebuild. Dashboard rebuilds already do this via
    // lifecycle_action; this catches the auto-update scan + any
    // other direct caller.
    coord.set_transient(name, crate::coordinator::TransientKind::Rebuilding);
    let result = lifecycle::rebuild(
        name,
        &coord.hyperhive_flake,
        &agent_dir,
        &applied_dir,
        &claude_dir,
        &notes_dir,
        coord.dashboard_port,
        &coord.operator_pronouns,
    )
    .await;
    coord.clear_transient(name);
    match &result {
        Ok(()) => {
            if let Err(e) = std::fs::write(rev_marker_path(name), current_rev) {
                tracing::warn!(%name, error = ?e, "write rev marker failed");
            }
            coord.notify_manager(&hive_sh4re::HelperEvent::Rebuilt {
                agent: name.to_owned(),
                ok: true,
                note: None,
                sha: None,
                tag: None,
            });
            // Wake the agent on its next turn so claude sees a
            // "you were rebuilt — check /state/ for notes, --continue
            // session intact" hint. Covers dashboard rebuild, admin
            // CLI rebuild, auto-update startup scan, and the
            // dashboard's meta-input update path — all of which
            // route through rebuild_agent.
            coord.kick_agent(name, "container rebuilt");
        }
        Err(e) => {
            coord.notify_manager(&hive_sh4re::HelperEvent::Rebuilt {
                agent: name.to_owned(),
                ok: false,
                note: Some(format!("{e:#}")),
                sha: None,
                tag: None,
            });
        }
    }
    result
}

/// Auto-create the manager container on startup if it isn't already there.
/// hive-c0re manages hm1nd end-to-end (Phase 8 follow-up): operators no
/// longer declare `containers.hm1nd` in their host NixOS config. Bypasses
/// the approval queue — manager is required infrastructure. Idempotent.
pub async fn ensure_manager(coord: &Arc<Coordinator>) -> Result<()> {
    let existing = lifecycle::list().await.unwrap_or_default();
    let current_rev = current_flake_rev(&coord.hyperhive_flake);
    if existing.iter().any(|c| c == MANAGER_NAME) {
        // Container exists already. If it predates the unified lifecycle
        // (no applied flake on disk) we must rebuild — otherwise it's
        // running whatever the host-declarative config was at create
        // time, with a wrong systemd unit and port.
        let applied_flake = Coordinator::agent_applied_dir(MANAGER_NAME).join("flake.nix");
        if !applied_flake.exists()
            && let Some(rev) = current_rev.as_ref()
        {
            tracing::warn!(
                "manager container exists but no applied flake — forcing rebuild to migrate"
            );
            let coord_clone = coord.clone();
            if let Err(e) = rebuild_agent(&coord_clone, MANAGER_NAME, rev).await {
                tracing::warn!(error = ?e, "manager migration rebuild failed");
            }
        } else {
            tracing::debug!("manager container already present");
        }
        return Ok(());
    }
    tracing::info!("manager container missing — spawning");
    let runtime = coord.ensure_runtime(MANAGER_NAME)?;
    let proposed = Coordinator::agent_proposed_dir(MANAGER_NAME);
    let applied = Coordinator::agent_applied_dir(MANAGER_NAME);
    let claude_dir = Coordinator::agent_claude_dir(MANAGER_NAME);
    let notes_dir = Coordinator::agent_notes_dir(MANAGER_NAME);
    lifecycle::spawn(
        MANAGER_NAME,
        &coord.hyperhive_flake,
        &runtime,
        &proposed,
        &applied,
        &claude_dir,
        &notes_dir,
        coord.dashboard_port,
        &coord.operator_pronouns,
    )
    .await?;
    if let Some(rev) = current_rev {
        let _ = std::fs::write(rev_marker_path(MANAGER_NAME), rev);
    }
    Ok(())
}

/// Rebuild every sub-agent whose marker differs from the current rev. Logs
/// per-agent outcomes and continues past failures. Returns Ok even if some
/// rebuilds failed — startup shouldn't be blocked by a broken agent.
pub async fn run(coord: Arc<Coordinator>) -> Result<()> {
    let Some(current_rev) = current_flake_rev(&coord.hyperhive_flake) else {
        tracing::info!(
            flake = %coord.hyperhive_flake,
            "auto-update: hyperhive_flake has no canonical path; skipping",
        );
        return Ok(());
    };
    tracing::info!(rev = %current_rev, "auto-update: scanning agents");

    // Bump meta's hyperhive input up-front so the per-agent rebuilds
    // below build against the new base. Failure here is logged but
    // not fatal — individual rebuilds will surface concrete errors.
    if let Err(e) = crate::meta::lock_update_hyperhive().await {
        tracing::warn!(error = ?e, "auto-update: meta lock_update_hyperhive failed");
    }

    let containers = match lifecycle::list().await {
        Ok(c) => c,
        Err(e) => {
            tracing::warn!(error = ?e, "auto-update: nixos-container list failed");
            return Ok(());
        }
    };

    // Sequential, one agent at a time. Parallel rebuilds collide on
    // nix-store's sqlite cache (the "sqlite db busy, not using
    // cache" warning) and also race the meta-lock mutex; the
    // resulting log interleave was bad enough on its own. Builds
    // serialize on nix-daemon internally anyway, so this isn't a
    // throughput loss in practice.
    for container in containers {
        // Manager and sub-agents share the same lifecycle now; both go
        // through rebuild_agent with name-derived paths.
        let logical = if container == MANAGER_NAME {
            Some(MANAGER_NAME.to_owned())
        } else {
            container.strip_prefix(AGENT_PREFIX).map(str::to_owned)
        };
        let Some(name) = logical else {
            continue;
        };
        if !agent_needs_update(&name, &current_rev) {
            tracing::debug!(%name, "auto-update: up-to-date");
            continue;
        }
        if let Err(e) = rebuild_agent(&coord, &name, &current_rev).await {
            tracing::warn!(%name, error = ?e, "auto-update: rebuild failed");
        }
    }
    Ok(())
}