moeix 0.5.0

//! ix background daemon — ixd.
//!
//! Safety guarantees (v0.1.2+):
//! - `SIGTERM`/`SIGINT` → clean shutdown (beacon removed, watcher joined, no zombies)
//! - `Builder::new` returns `Result` — no panics on unwritable `.ix` dir
//! - RSS ceiling in builder (512MB) — OOM protection
//! - TOCTOU guards in `process_file` — skips vanished/permission-denied files

#![warn(clippy::pedantic)]
#![allow(clippy::cast_possible_truncation)] // u16/u32→u64 widenings and entropy values bounded

use clap::Parser;
use ix::builder::Builder;
use ix::format::Beacon;
use ix::idle::IdleTracker;
use ix::watcher::Watcher;
use llmosafe::{EscalationPolicy, ResourceGuard, SafetyDecision};
use std::fs;
use std::path::PathBuf;
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::time::Duration;

// Safety policy constants — explicit timing for backpressure mechanisms
// ENTROPY thresholds are load-bearing (safety depends on them)
const ENTROPY_SAFE_THRESHOLD: u16 = 800; // Skip updates above 80% ceiling
const ENTROPY_CRITICAL: u16 = 1000; // Treat as escalation on check error
const PRE_BUILD_WAIT_SECS: u64 = 5; // Wait for memory to stabilize before build
const WARN_COOLDOWN_MS: u64 = 300; // Warning pause

#[derive(Parser)]
#[command(
    name = "ixd",
    version = env!("CARGO_PKG_VERSION"),
    about = "Background daemon for automatic indexing with safety monitoring."
)]
struct Cli {
    #[arg(default_value = ".", value_name = "PATH")]
    path: PathBuf,
}

fn main() -> ix::error::Result<()> {
    let cli = Cli::parse();
    let root = cli.path.canonicalize().map_err(ix::error::Error::Io)?;

    println!("ixd: watching {}...", root.display());

    // Shutdown flag shared with signal handlers
    let running = Arc::new(AtomicBool::new(true));

    // Install SIGTERM + SIGINT via sigaction — reliable, handler persists across deliveries
    {
        use nix::sys::signal::{SaFlags, SigAction, SigHandler, SigSet, Signal, sigaction};
        let action = SigAction::new(
            SigHandler::Handler(handle_signal),
            SaFlags::empty(),
            SigSet::empty(),
        );
        // SAFETY: handler only stores to an atomic bool — async-signal-safe.
        unsafe {
            sigaction(Signal::SIGTERM, &action).expect("failed to install SIGTERM handler");
            sigaction(Signal::SIGINT, &action).expect("failed to install SIGINT handler");
        }
    }
    // Concurrent instance guard — refuse to start if another ixd owns this root.
    let ix_dir_early = root.join(".ix");
    let beacon_path = ix_dir_early.join("beacon.json");
    if beacon_path.exists()
        && let Ok(existing) = ix::format::Beacon::read_from(&ix_dir_early)
    {
        let pid = nix::unistd::Pid::from_raw(existing.pid);
        if nix::sys::signal::kill(pid, None).is_ok() {
            eprintln!(
                "ixd: another instance is already watching {} (PID {}). \
                 Stop it first or remove {}/beacon.json.",
                root.display(),
                existing.pid,
                ix_dir_early.display()
            );
            std::process::exit(1);
        }
        // Dead PID — stale beacon, safe to continue
        eprintln!("ixd: removing stale beacon from PID {}", existing.pid);
        let _ = std::fs::remove_file(&beacon_path);
    }

    let guard = ResourceGuard::auto(0.6); // 60% system memory ceiling

    let mut builder = match Builder::new(&root) {
        Ok(b) => b.with_resource_guard(guard.clone()),
        Err(e) => {
            eprintln!("ixd: cannot create index in {}: {}", root.display(), e);
            return Err(e);
        }
    };

    // Pre-check memory before initial build — prevents OOM on large repos
    // Loop until safe or timeout (30s max)
    let pre_build_timeout = Duration::from_secs(30);
    let pre_build_start = std::time::Instant::now();
    while pre_build_start.elapsed() < pre_build_timeout {
        match guard.check_blocking() {
            Ok(_) => break, // Safe to proceed
            Err(e) => {
                eprintln!("ixd: memory pressure before initial build: {e:?} — waiting...");
                std::thread::sleep(Duration::from_secs(PRE_BUILD_WAIT_SECS));
            }
        }
    }

    if let Err(e) = builder.build() {
        eprintln!("ixd: initial build failed: {e} — will watch for changes anyway");
    } else {
        println!(
            "ixd: initial build complete ({} files, {} trigrams)",
            builder.files_len(),
            builder.trigrams_len()
        );
    }

    let mut watcher = Watcher::new(&root);
    let rx = watcher.start()?;

    let ix_dir = root.join(".ix");
    if !ix_dir.exists() {
        fs::create_dir_all(&ix_dir)?;
    }
    let mut beacon = Beacon::new(&root);
    beacon.write_to(&ix_dir)?;

    let mut idle = IdleTracker::new();

    run_main_loop(
        &mut builder,
        &rx,
        &ix_dir,
        &mut beacon,
        &mut idle,
        &guard,
        &running,
    );

    // Clean shutdown — guaranteed to run on SIGTERM or SIGINT
    eprintln!("ixd: shutting down...");
    watcher.stop();
    let _ = fs::remove_file(ix_dir.join("beacon.json"));

    Ok(())
}

fn run_main_loop(
    builder: &mut Builder,
    rx: &crossbeam_channel::Receiver<Vec<PathBuf>>,
    ix_dir: &std::path::Path,
    beacon: &mut Beacon,
    idle: &mut IdleTracker,
    guard: &ResourceGuard,
    running: &Arc<AtomicBool>,
) {
    loop {
        if SHUTDOWN.load(Ordering::SeqCst) {
            running.store(false, Ordering::SeqCst);
            break;
        }

        match rx.recv_timeout(Duration::from_millis(500)) {
            Ok(changed_files) => {
                handle_changes(builder, &changed_files, ix_dir, beacon, idle, guard);
            }
            Err(crossbeam_channel::RecvTimeoutError::Timeout) => {}
            Err(crossbeam_channel::RecvTimeoutError::Disconnected) => break,
        }
    }
}

fn handle_changes(
    builder: &mut Builder,
    changed_files: &[PathBuf],
    ix_dir: &std::path::Path,
    beacon: &mut Beacon,
    idle: &mut IdleTracker,
    guard: &ResourceGuard,
) {
    let check_result = guard.check_blocking();

    let (entropy, safety_decision) = match check_result {
        Ok(synapse) => {
            let raw = synapse.raw_entropy();
            let policy = EscalationPolicy::default();
            let decision = policy.decide(raw, 0, false);
            (raw, decision)
        }
        Err(e) => {
            eprintln!("ixd: resource check error: {e:?} — proceeding with elevated caution");
            (
                ENTROPY_CRITICAL,
                SafetyDecision::Escalate {
                    entropy: ENTROPY_CRITICAL,
                    reason: llmosafe::llmosafe_integration::EscalationReason::ResourcePressure,
                    cooldown_ms: u32::from(ENTROPY_CRITICAL),
                },
            )
        }
    };

    // Act on safety decision
    match &safety_decision {
        SafetyDecision::Halt(err, cooldown) => {
            eprintln!("ixd: critical safety decision (Halt: {err:?}) — pausing operations");
            beacon.status = "safety halt".to_string();
            let _ = beacon.write_to(ix_dir);
            std::thread::sleep(Duration::from_millis(u64::from(*cooldown)));
            return;
        }
        SafetyDecision::Exit(err) => {
            eprintln!("ixd: SAFETY EXIT (unrecoverable: {err:?}) — terminating");
            beacon.status = "safety exit".to_string();
            let _ = beacon.write_to(ix_dir);
            std::process::exit(1);
        }
        SafetyDecision::Escalate {
            entropy: esc_entropy,
            reason,
            cooldown_ms,
        } => {
            eprintln!(
                "ixd: safety escalation (entropy: {esc_entropy}, reason: {reason:?}) — throttling"
            );
            beacon.status = format!("escalated (entropy: {esc_entropy})");
            let _ = beacon.write_to(ix_dir);
            std::thread::sleep(Duration::from_millis(u64::from(*cooldown_ms)));
            return;
        }
        SafetyDecision::Warn(reason) => {
            if safety_decision.severity() >= 2 {
                eprintln!(
                    "ixd: safety warning (severity {}): {reason}",
                    safety_decision.severity()
                );
                beacon.status = format!("warned: {reason}");
                let _ = beacon.write_to(ix_dir);
                std::thread::sleep(Duration::from_millis(WARN_COOLDOWN_MS));
            }
        }
        SafetyDecision::Proceed => {}
    }

    println!(
        "ixd: {} files changed, updating index... (Entropy: {entropy}, Decision: {safety_decision:?})",
        changed_files.len(),
    );

    beacon.status = format!("indexing (entropy: {entropy})");
    beacon.last_event_at = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap_or_default()
        .as_secs();
    let _ = beacon.write_to(ix_dir);

    idle.record_change();

    if entropy > ENTROPY_SAFE_THRESHOLD {
        eprintln!("ixd: entropy too high ({entropy}), deferring update");
        beacon.status = format!("deferred (entropy: {entropy})");
        let _ = beacon.write_to(ix_dir);
        return;
    }

    if let Err(e) = builder.update(changed_files) {
        eprintln!("ixd: update failed: {e} — retrying on next change");
    } else {
        tracing::debug!("ixd: index updated — caches will self-invalidate on next query");
    }

    beacon.status = "idle".to_string();
    let _ = beacon.write_to(ix_dir);
}

/// Global shutdown flag set by the raw signal handler.
static SHUTDOWN: std::sync::atomic::AtomicBool = std::sync::atomic::AtomicBool::new(false);

/// Raw signal handler — only touches the atomic flag (async-signal-safe).
extern "C" fn handle_signal(_: libc::c_int) {
    SHUTDOWN.store(true, Ordering::SeqCst);
}