lean-ctx-engine 3.12.3

use std::collections::HashMap;
use std::sync::{Mutex, OnceLock};

const BOUNCE_WINDOW: u64 = 5;
const BOUNCE_RATE_THRESHOLD: f64 = 0.30;
/// Seq-tick window during which a full read is treated as *edit-forced* rather
/// than a compression bounce. Must match the window `should_force_full` uses to
/// escalate post-edit reads to `full`, so the read we forced is never blamed on
/// the compression arm (GL #622).
const EDIT_FORCE_WINDOW: u64 = 10;
/// Outer-map retention: a path whose newest activity is older than this many seq ticks
/// can no longer satisfy BOUNCE_WINDOW (5) or the edit-force window (10), so it is inert
/// and safe to evict. Kept well above both windows to never change detection outcomes.
const TRACKED_PATH_TTL_SEQ: u64 = 64;

#[derive(Debug, Clone)]
struct ReadEvent {
    _mode: String,
    tokens_sent: usize,
    _original_tokens: usize,
    seq: u64,
    view: ReadView,
    /// File mtime when a compressed view was served. A later full read of a
    /// file whose mtime moved re-reads *changed* content — an edit (a host's
    /// native Edit/Write included, which never reaches `record_edit`), not a
    /// compression failure.
    mtime: Option<std::time::SystemTime>,
    /// Scope and task the read ran under; a bounce is that task's signal.
    origin: Option<crate::core::context_store::task_signals::Origin>,
}

fn file_mtime(path: &str) -> Option<std::time::SystemTime> {
    std::fs::metadata(path).and_then(|m| m.modified()).ok()
}

/// What a read showed of the file, for correction (bounce) accounting.
///
/// A correction is a lossy [`Compressed`](ReadView::Compressed) view
/// followed by the [`Full`](ReadView::Full) content. A
/// [`Partial`](ReadView::Partial) read — a line window, `head`/`tail`, a
/// `sed -n` range, a `diff` delta — is precise reading: it neither starts nor
/// completes a correction, and it ends the one a preceding compressed view
/// could have started (that view did its job: it pointed at the window).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ReadView {
    Compressed,
    Full,
    Partial,
}

impl ReadView {
    /// Classify a resolved `ctx_read` mode string.
    ///
    /// `anchored` (whole file) is verbatim plus per-line anchors, so it is
    /// full content like `full`/`raw`/`full-compact`; `anchored:N-M` is a
    /// window. Unknown strings are `Partial`: an unrecognised mode must never
    /// fabricate a correction.
    #[must_use]
    pub fn of_mode(mode: &str) -> Self {
        use crate::core::read_mode::ReadMode;
        match mode.parse::<ReadMode>() {
            Ok(
                ReadMode::Full | ReadMode::FullCompact | ReadMode::Raw | ReadMode::Anchored(None),
            ) => ReadView::Full,
            Ok(
                ReadMode::Anchored(Some(_))
                | ReadMode::Lines(_)
                | ReadMode::LinesMulti(_)
                | ReadMode::LinesTail(_)
                | ReadMode::Diff,
            )
            | Err(_) => ReadView::Partial,
            Ok(
                ReadMode::Signatures
                | ReadMode::Map
                | ReadMode::Aggressive
                | ReadMode::Entropy
                | ReadMode::Cognitive
                | ReadMode::Mdl
                | ReadMode::Task
                | ReadMode::Reference
                | ReadMode::Auto
                | ReadMode::Density(_),
            ) => ReadView::Compressed,
        }
    }
}

#[derive(Debug, Default)]
struct BounceStats {
    total_reads: u64,
    bounces: u64,
    wasted_tokens: usize,
}

/// A detected compressed→full re-read that is not yet booked as a bounce.
///
/// Reading a file compressed for orientation, then in full, then editing it is
/// the normal edit flow (map to orient, full to edit), not a compression
/// failure. A bounce therefore stays provisional for `EDIT_FORCE_WINDOW` seq
/// ticks: an edit of the path inside that window cancels it, otherwise it is
/// committed (ledger entry, path memory, quality signal, scent).
#[derive(Debug, Clone)]
struct PendingBounce {
    path: String,
    /// Seq tick of the full read that triggered the detection.
    seq: u64,
    wasted: usize,
    origin: Option<crate::core::context_store::task_signals::Origin>,
    /// Wall-clock detection time, compared against host edits other
    /// processes report through the edit beacon.
    detected_unix_ms: u64,
    /// The request project at detection. The bounce is booked later (after
    /// the edit window, or by the shutdown flush) outside that request.
    project_root: Option<String>,
    /// The read mode of the compressed view the full read corrected.
    mode: String,
}

#[derive(Debug, Default)]
pub struct BounceTracker {
    recent_reads: HashMap<String, Vec<ReadEvent>>,
    per_extension: HashMap<String, BounceStats>,
    recently_edited: HashMap<String, u64>,
    pending: Vec<PendingBounce>,
    seq_counter: u64,
    total_bounces: u64,
    total_wasted_tokens: usize,
    /// When true (only for the process-global tracker), detected bounces are appended to
    /// the persistent savings ledger so a fresh `gain` process sees historical bounce.
    /// Local trackers in unit tests leave this `false` to avoid touching the real ledger.
    persist: bool,
}

/// Upper bound on provisional bounces kept in memory; the oldest is committed
/// early when a burst exceeds it, so the queue can never grow without limit.
const MAX_PENDING_BOUNCES: usize = 256;

fn extension_of(path: &str) -> String {
    path.rsplit('.')
        .next()
        .map(|e| format!(".{}", e.to_ascii_lowercase()))
        .unwrap_or_default()
}

impl BounceTracker {
    pub fn new() -> Self {
        Self::default()
    }

    pub fn next_seq(&mut self) -> u64 {
        self.seq_counter += 1;
        self.commit_due();
        self.seq_counter
    }

    pub fn set_seq(&mut self, seq: u64) {
        self.seq_counter = seq;
        self.commit_due();
    }

    pub fn record_read(
        &mut self,
        path: &str,
        mode: &str,
        tokens_sent: usize,
        original_tokens: usize,
    ) {
        let norm = crate::core::pathutil::normalize_tool_path(path);
        self.commit_due();
        let seq = self.seq_counter;
        let view = ReadView::of_mode(mode);
        let compressed = view == ReadView::Compressed;

        if view == ReadView::Full {
            self.detect_bounce(&norm, path, seq);
        }
        if self.persist && compressed {
            // K10: a compressed view is a truncated output of its read mode.
            {
                use crate::core::hive_signals as signals;
                signals::truncated(&signals::read_mode_filter(mode));
            }
            // Keep the long-term majority rule honest: compressed reads that
            // did not bounce dilute historical bounces (#496). Full and
            // partial reads — the bounce re-read itself included — are not
            // compression attempts and stay out of the denominator.
            crate::core::path_mode_memory::record_compressed_read_if_tracked(&norm);
        }

        let current = if self.persist {
            crate::core::context_store::task_signals::current_origin()
        } else {
            None
        };
        if let Some(current) = &current {
            // Bounces are seen only by the process that served the read: a
            // task served by several processes is not fully observed.
            crate::core::context_store::task_signals::observe(current);
        }
        let origin = current.filter(|_| compressed);
        self.push_event(
            norm,
            ReadEvent {
                _mode: mode.to_string(),
                tokens_sent,
                _original_tokens: original_tokens,
                seq,
                view,
                mtime: if compressed { file_mtime(path) } else { None },
                origin,
            },
        );

        let ext = extension_of(path);
        if !ext.is_empty() {
            let stats = self.per_extension.entry(ext).or_default();
            stats.total_reads += 1;
        }

        self.prune_stale_paths();
    }

    fn push_event(&mut self, norm: String, event: ReadEvent) {
        let events = self.recent_reads.entry(norm).or_default();
        events.push(event);
        if events.len() > 10 {
            events.drain(..events.len() - 10);
        }
    }

    /// Detect the correction a full read completes: only a full read whose
    /// immediately preceding read of the path was a compressed view within
    /// `BOUNCE_WINDOW`. A partial or full read in between ends the chain.
    fn detect_bounce(&mut self, norm_path: &str, fs_path: &str, full_seq: u64) {
        // A full re-read the system itself forced after an edit is not a
        // compression failure (GL #622): `should_force_full` returns `full` for
        // EDIT_FORCE_WINDOW ticks post-edit, so the agent had no choice. Counting
        // it as a bounce would penalize the compression arm for the edit and
        // inflate the per-extension bounce rate until `should_force_full` pins the
        // whole extension to `full` — a self-reinforcing loss of compression.
        if let Some(&edit_seq) = self.recently_edited.get(norm_path)
            && full_seq.saturating_sub(edit_seq) <= EDIT_FORCE_WINDOW
        {
            return;
        }

        let Some(events) = self.recent_reads.get(norm_path) else {
            return;
        };

        if let Some(ev) = events.iter().next_back()
            && ev.view == ReadView::Compressed
            && full_seq.saturating_sub(ev.seq) <= BOUNCE_WINDOW
            // The file changed since the view was served: the full re-read
            // fetches new content after an edit. A host's native Edit/Write
            // in another process may reach neither `record_edit` nor the
            // edit beacon in time; the moved mtime is direct evidence of it.
            && (ev.mtime.is_none() || file_mtime(fs_path) == ev.mtime)
        {
            // Provisional until EDIT_FORCE_WINDOW passes without an edit of
            // this path (see `PendingBounce`).
            let pending = PendingBounce {
                path: norm_path.to_string(),
                seq: full_seq,
                wasted: ev.tokens_sent,
                origin: ev.origin.clone(),
                detected_unix_ms: now_unix_ms(),
                project_root: crate::core::scent_field::current_project(),
                mode: ev._mode.clone(),
            };
            self.pending.push(pending);
            if self.pending.len() > MAX_PENDING_BOUNCES {
                let oldest = self.pending.remove(0);
                self.commit(oldest);
            }
        }
    }

    /// Commit every provisional bounce whose edit window has passed. Called
    /// whenever the seq clock moves or a read/edit is recorded.
    fn commit_due(&mut self) {
        if self.pending.is_empty() {
            return;
        }
        let now = self.seq_counter;
        let (due, keep): (Vec<_>, Vec<_>) = std::mem::take(&mut self.pending)
            .into_iter()
            .partition(|p| now.saturating_sub(p.seq) > EDIT_FORCE_WINDOW);
        self.pending = keep;
        for pending in due {
            self.commit(pending);
        }
    }

    /// Commit every provisional bounce now, regardless of its window. Used at
    /// process shutdown so a bounce detected shortly before exit is not lost.
    pub fn flush_pending(&mut self) {
        for pending in std::mem::take(&mut self.pending) {
            self.commit(pending);
        }
    }

    /// Provisional bounces still waiting for their edit window to pass.
    pub fn pending_bounces(&self) -> usize {
        self.pending.len()
    }

    /// Book one bounce: counters, per-extension stats and, for the
    /// process-global tracker, the ledger entry, path memory, quality signal
    /// and scent. A host edit another process reported for the path after the
    /// detection (edit beacon) cancels it instead.
    fn commit(&mut self, pending: PendingBounce) {
        if self.persist && host_edited_since(&pending.path, pending.detected_unix_ms) {
            return;
        }
        let PendingBounce {
            path: norm_path,
            wasted,
            origin,
            project_root,
            mode,
            ..
        } = pending;
        self.total_bounces += 1;
        self.total_wasted_tokens += wasted;

        let ext = extension_of(&norm_path);
        if !ext.is_empty() {
            let stats = self.per_extension.entry(ext).or_default();
            stats.bounces += 1;
            stats.wasted_tokens += wasted;
        }

        if self.persist {
            if let Some(origin) = origin {
                // Off this tracker's lock: recording waits on a file lock.
                std::thread::spawn(move || {
                    crate::core::context_store::task_signals::record(
                        &origin,
                        crate::core::context_store::task_signals::Signal::Bounce,
                    );
                });
            }
            crate::core::savings_ledger::record_bounce_event(wasted);
            // K10: the compressed view was fetched back in full.
            {
                use crate::core::hive_signals as signals;
                signals::refetched(&signals::read_mode_filter(&mode));
            }
            // Long-term per-path memory (#496): remember which exact
            // files keep bouncing so auto-mode learns across restarts.
            crate::core::path_mode_memory::record_bounce(&norm_path);
            // Stigmergy (#540): a bounce marks this path as Stuck so
            // other agents see friction here. Background: lock may block.
            // The project was resolved at detection, inside the request.
            if let Some(project_root) = project_root {
                std::thread::spawn(move || {
                    crate::core::scent_field::deposit_for(
                        &project_root,
                        crate::core::scent_field::scent_agent_id(),
                        crate::core::scent_field::ScentKind::Stuck,
                        &norm_path,
                        0.5,
                    );
                });
            }
        }
    }

    /// A shell read of `path` (`cat`, `head`, `sed -n`, …). A full read can
    /// complete a correction of a preceding compressed view; a partial one
    /// never does. Either way it becomes the path's newest read, so a second
    /// `cat` cannot book the same correction twice.
    pub fn record_shell_read(&mut self, path: &str, view: ReadView) {
        let norm = crate::core::pathutil::normalize_tool_path(path);
        self.commit_due();
        let seq = self.seq_counter;
        if view == ReadView::Full {
            self.detect_bounce(&norm, path, seq);
        }
        self.push_event(
            norm,
            ReadEvent {
                _mode: "shell".to_string(),
                tokens_sent: 0,
                _original_tokens: 0,
                seq,
                // A shell read is never the compressed view of a correction.
                view: if view == ReadView::Compressed {
                    ReadView::Partial
                } else {
                    view
                },
                mtime: None,
                origin: None,
            },
        );
        self.prune_stale_paths();
    }

    /// Records an explicit archive/context expansion as a quality bounce.
    ///
    /// Unlike a full file re-read, `ctx_expand` may address a content handle
    /// rather than a path, so it cannot always be inferred by `detect_bounce`.
    /// Benchmark replay uses this method to keep the quality proxy on the same
    /// tracker as ordinary compressed-then-full bounces.
    pub fn record_expansion(&mut self, source: Option<&str>, wasted_tokens: usize) {
        self.total_bounces = self.total_bounces.saturating_add(1);
        self.total_wasted_tokens = self.total_wasted_tokens.saturating_add(wasted_tokens);

        if let Some(path) = source {
            let ext = extension_of(path);
            if !ext.is_empty() {
                let stats = self.per_extension.entry(ext).or_default();
                stats.bounces = stats.bounces.saturating_add(1);
                stats.wasted_tokens = stats.wasted_tokens.saturating_add(wasted_tokens);
            }
        }
    }

    /// The newest read of `path` this process still remembers: whether it
    /// was compressed and the scope and task it ran under, so a later event
    /// is charged to the read that caused it. `None`: no read is known here
    /// (another process, or before a restart). A partial read (line window)
    /// is precise, not lossy, so it reports `false` like a full read.
    pub fn last_read(
        &self,
        path: &str,
    ) -> Option<(
        bool,
        Option<crate::core::context_store::task_signals::Origin>,
    )> {
        let norm = crate::core::pathutil::normalize_tool_path(path);
        let event = self.recent_reads.get(&norm)?.last()?;
        Some((event.view == ReadView::Compressed, event.origin.clone()))
    }

    /// An edit of `path`. Besides exempting the full re-reads it forces, it
    /// cancels any provisional bounce of the path still inside its edit
    /// window: the compressed→full re-read was the read-before-edit, not a
    /// compression failure.
    pub fn record_edit(&mut self, path: &str) {
        let norm = crate::core::pathutil::normalize_tool_path(path);
        self.commit_due();
        self.pending.retain(|p| p.path != norm);
        self.recently_edited.insert(norm, self.seq_counter);
        self.prune_stale_paths();
    }

    /// Evict outer-map entries whose newest seq is older than the detection windows —
    /// they can no longer affect bounce detection or `should_force_full`. Bounds the
    /// `recent_reads` / `recently_edited` maps on a long-lived process.
    fn prune_stale_paths(&mut self) {
        let seq = self.seq_counter;
        self.recent_reads.retain(|_, events| {
            events
                .last()
                .is_some_and(|e| seq.saturating_sub(e.seq) <= TRACKED_PATH_TTL_SEQ)
        });
        self.recently_edited
            .retain(|_, &mut edit_seq| seq.saturating_sub(edit_seq) <= TRACKED_PATH_TTL_SEQ);
    }

    pub fn should_force_full(&self, path: &str) -> bool {
        let norm = crate::core::pathutil::normalize_tool_path(path);

        if let Some(&edit_seq) = self.recently_edited.get(&norm)
            && self.seq_counter.saturating_sub(edit_seq) <= EDIT_FORCE_WINDOW
        {
            return true;
        }

        let ext = extension_of(path);
        if !ext.is_empty()
            && let Some(stats) = self.per_extension.get(&ext)
            && stats.total_reads >= 3
        {
            let rate = stats.bounces as f64 / stats.total_reads as f64;
            if rate >= BOUNCE_RATE_THRESHOLD {
                return true;
            }
        }

        false
    }

    pub fn bounce_rate_for_extension(&self, path: &str) -> Option<f64> {
        let ext = extension_of(path);
        self.per_extension.get(&ext).and_then(|s| {
            if s.total_reads >= 3 {
                Some(s.bounces as f64 / s.total_reads as f64)
            } else {
                None
            }
        })
    }

    pub fn total_bounces(&self) -> u64 {
        self.total_bounces
    }

    pub fn total_wasted_tokens(&self) -> usize {
        self.total_wasted_tokens
    }

    pub fn adjusted_savings(&self, raw_savings: usize) -> isize {
        raw_savings as isize - self.total_wasted_tokens as isize
    }

    pub fn per_extension_json(&self) -> Vec<serde_json::Value> {
        let mut exts: Vec<_> = self
            .per_extension
            .iter()
            .filter(|(_, s)| s.total_reads > 0)
            .collect();
        exts.sort_by_key(|a| std::cmp::Reverse(a.1.bounces));
        exts.iter()
            .take(10)
            .map(|(ext, stats)| {
                let rate = if stats.total_reads > 0 {
                    stats.bounces as f64 / stats.total_reads as f64
                } else {
                    0.0
                };
                serde_json::json!({
                    "ext": ext,
                    "reads": stats.total_reads,
                    "bounces": stats.bounces,
                    "wasted_tokens": stats.wasted_tokens,
                    "rate": (rate * 1000.0).round() / 1000.0,
                })
            })
            .collect()
    }

    pub fn format_summary(&self) -> String {
        if self.total_bounces == 0 {
            return "Bounces: 0".to_string();
        }
        let mut lines = vec![format!(
            "Bounces: {} ({} wasted tokens)",
            self.total_bounces, self.total_wasted_tokens
        )];
        let mut exts: Vec<_> = self
            .per_extension
            .iter()
            .filter(|(_, s)| s.bounces > 0)
            .collect();
        exts.sort_by_key(|a| std::cmp::Reverse(a.1.bounces));
        for (ext, stats) in exts.iter().take(5) {
            let rate = if stats.total_reads > 0 {
                stats.bounces as f64 / stats.total_reads as f64 * 100.0
            } else {
                0.0
            };
            lines.push(format!(
                "  {ext}: {}/{} reads bounced ({rate:.0}%), {} tok wasted",
                stats.bounces, stats.total_reads, stats.wasted_tokens,
            ));
        }
        lines.join("\n")
    }
}

static GLOBAL_TRACKER: OnceLock<Mutex<BounceTracker>> = OnceLock::new();

pub fn global() -> &'static Mutex<BounceTracker> {
    GLOBAL_TRACKER.get_or_init(|| {
        // Seed from the persistent ledger so every process (including a fresh `gain`)
        // accounts for historical bounce, then mark this tracker as the persisting one.
        let summary = crate::core::savings_ledger::summary();
        let mut bt = BounceTracker::new();
        bt.total_wasted_tokens = summary.bounce_tokens as usize;
        bt.total_bounces = summary.bounce_events as u64;
        bt.persist = true;
        Mutex::new(bt)
    })
}

/// Process shutdown: commit the global tracker's provisional bounces. A no-op
/// when this process never created the tracker (no read was served).
pub fn flush_pending() {
    if let Some(tracker) = GLOBAL_TRACKER.get()
        && let Ok(mut bt) = tracker.lock()
    {
        bt.flush_pending();
    }
}

fn now_unix_ms() -> u64 {
    std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map_or(0, |d| u64::try_from(d.as_millis()).unwrap_or(u64::MAX))
}

// ── Edit beacon ─────────────────────────────────────────────────────────────
//
// Native host edits (Claude Code `Edit`/`Write`, Cursor `StrReplace`, …) are
// observed by short-lived hook processes, not by the MCP server that holds the
// in-memory tracker. They append `<unix_ms>\t<normalized path>` to a small
// append-only file; a provisional bounce consults it once, at commit time, and
// is cancelled when its path was edited after the detection. Lines are written
// with one `O_APPEND` write each, so concurrent hook processes do not
// interleave; the file rotates to `.1` above `EDIT_BEACON_MAX_BYTES`, and the
// reader scans both generations.

const EDIT_BEACON_FILE: &str = "edit_beacon.log";
const EDIT_BEACON_MAX_BYTES: u64 = 128 * 1024;

fn edit_beacon_path() -> Option<std::path::PathBuf> {
    crate::core::data_dir::lean_ctx_data_dir()
        .ok()
        .map(|dir| dir.join(EDIT_BEACON_FILE))
}

fn rotated_beacon_path(path: &std::path::Path) -> std::path::PathBuf {
    path.with_extension("log.1")
}

/// Hook processes: report a native host edit of `path` (best-effort).
pub fn note_host_edit(path: &str) {
    let Some(beacon) = edit_beacon_path() else {
        return;
    };
    append_edit_beacon(&beacon, path, now_unix_ms());
}

/// Hook processes: report the files a native shell command rewrites
/// (`sed -i`, `>`, `tee`, `cp`/`mv`, `apply_patch` bodies), relative paths
/// resolved against `cwd`. Best-effort, like [`note_host_edit`].
pub fn note_host_shell_edits(command: &str, cwd: &str) {
    for path in crate::core::shell_file_effects::analyze(command).edits {
        note_host_edit(&resolve_against(cwd, &path));
    }
}

/// Hook processes: report the files of a Codex `apply_patch` patch body.
pub fn note_host_patch_edits(patch: &str, cwd: &str) {
    for path in crate::core::shell_file_effects::apply_patch_targets(patch) {
        note_host_edit(&resolve_against(cwd, &path));
    }
}

/// `path` made absolute against `cwd` (the hook payload's), falling back to
/// the hook process's own working directory.
fn resolve_against(cwd: &str, path: &str) -> String {
    if std::path::Path::new(path).is_absolute() {
        return path.to_string();
    }
    let base = if cwd.trim().is_empty() {
        std::env::current_dir().ok()
    } else {
        Some(std::path::PathBuf::from(cwd))
    };
    base.map_or_else(
        || path.to_string(),
        |dir| dir.join(path).to_string_lossy().into_owned(),
    )
}

fn append_edit_beacon(beacon: &std::path::Path, path: &str, unix_ms: u64) {
    use std::io::Write;
    let norm = crate::core::pathutil::normalize_tool_path(path);
    if norm.is_empty() || norm.contains('\n') {
        return;
    }
    if std::fs::metadata(beacon).is_ok_and(|m| m.len() > EDIT_BEACON_MAX_BYTES) {
        let _ = std::fs::rename(beacon, rotated_beacon_path(beacon));
    }
    if let Some(parent) = beacon.parent() {
        let _ = std::fs::create_dir_all(parent);
    }
    if let Ok(mut file) = std::fs::OpenOptions::new()
        .create(true)
        .append(true)
        .open(beacon)
    {
        let _ = file.write_all(format!("{unix_ms}\t{norm}\n").as_bytes());
    }
}

fn host_edited_since(norm_path: &str, since_unix_ms: u64) -> bool {
    edit_beacon_path().is_some_and(|beacon| beacon_has_edit(&beacon, norm_path, since_unix_ms))
}

fn beacon_has_edit(beacon: &std::path::Path, norm_path: &str, since_unix_ms: u64) -> bool {
    use std::io::Read;
    [rotated_beacon_path(beacon), beacon.to_path_buf()]
        .iter()
        .any(|file| {
            let Ok(handle) = std::fs::File::open(file) else {
                return false;
            };
            let mut raw = String::new();
            // Bounded: rotation keeps each generation near EDIT_BEACON_MAX_BYTES.
            if handle
                .take(EDIT_BEACON_MAX_BYTES * 2)
                .read_to_string(&mut raw)
                .is_err()
            {
                return false;
            }
            raw.lines().any(|line| {
                line.split_once('\t').is_some_and(|(ts, path)| {
                    path == norm_path && ts.parse::<u64>().is_ok_and(|ts| ts >= since_unix_ms)
                })
            })
        })
}

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

    #[test]
    fn no_bounce_when_first_read_is_full() {
        let mut bt = BounceTracker::new();
        bt.seq_counter = 1;
        bt.record_read("src/main.rs", "full", 500, 500);
        assert_eq!(bt.total_bounces(), 0);
        assert_eq!(bt.total_wasted_tokens(), 0);
    }

    #[test]
    fn bounce_detected_on_compressed_then_full() {
        let mut bt = BounceTracker::new();
        bt.seq_counter = 1;
        bt.record_read("src/main.rs", "map", 50, 500);
        bt.seq_counter = 2;
        bt.record_read("src/main.rs", "full", 500, 500);
        assert_eq!(
            bt.pending_bounces(),
            1,
            "provisional until the edit window passes"
        );
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 1);
        assert_eq!(bt.total_wasted_tokens(), 50);
    }

    #[test]
    fn full_reread_of_externally_edited_file_is_not_a_bounce() {
        // A host's native Edit/Write runs in another process and never calls
        // `record_edit`; the moved mtime is what exempts the re-read.
        let dir = tempfile::tempdir().unwrap();
        let file = dir.path().join("edited.rs");
        std::fs::write(&file, "fn a() {}\n").unwrap();
        let path = file.to_str().unwrap();
        let old = std::time::SystemTime::now() - std::time::Duration::from_mins(2);
        std::fs::File::options()
            .write(true)
            .open(&file)
            .unwrap()
            .set_times(std::fs::FileTimes::new().set_modified(old))
            .unwrap();

        let mut bt = BounceTracker::new();
        bt.seq_counter = 1;
        bt.record_read(path, "map", 40, 500);
        std::fs::write(&file, "fn a() { changed() }\n").unwrap();
        bt.seq_counter = 2;
        bt.record_read(path, "full", 500, 500);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 0, "re-read after an edit is no bounce");

        // Unchanged file: the same pattern is still a real bounce.
        bt.seq_counter = 10;
        bt.record_read(path, "map", 40, 500);
        bt.seq_counter = 11;
        bt.record_read(path, "full", 500, 500);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 1);
    }

    #[test]
    fn no_bounce_outside_window() {
        let mut bt = BounceTracker::new();
        bt.seq_counter = 1;
        bt.record_read("src/main.rs", "map", 50, 500);
        bt.seq_counter = 10;
        bt.record_read("src/main.rs", "full", 500, 500);
        assert_eq!(bt.total_bounces(), 0);
    }

    #[test]
    fn shell_access_triggers_bounce() {
        let mut bt = BounceTracker::new();
        bt.seq_counter = 1;
        bt.record_read("config.yml", "signatures", 30, 400);
        bt.seq_counter = 3;
        bt.record_shell_read("config.yml", ReadView::Full);
        // A second `cat` does not book the same correction again.
        bt.seq_counter = 4;
        bt.record_shell_read("config.yml", ReadView::Full);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 1);
        assert_eq!(bt.total_wasted_tokens(), 30);
    }

    #[test]
    fn read_view_classification() {
        for mode in ["full", "full-compact", "raw", "anchored"] {
            assert_eq!(ReadView::of_mode(mode), ReadView::Full, "{mode}");
        }
        for mode in [
            "lines:10-40",
            "lines:5,10-20",
            "lines:-30",
            "anchored:10-20",
            "diff",
            "bogus",
        ] {
            assert_eq!(ReadView::of_mode(mode), ReadView::Partial, "{mode}");
        }
        for mode in [
            "map",
            "signatures",
            "aggressive",
            "entropy",
            "task",
            "reference",
            "cognitive",
            "mdl",
            "auto",
            "density:0.40",
        ] {
            assert_eq!(ReadView::of_mode(mode), ReadView::Compressed, "{mode}");
        }
    }

    /// Reading a file window by window, then in full, is no correction:
    /// windows are precise reads, not lossy views.
    #[test]
    fn lines_then_full_is_not_a_bounce() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("docs/guide.md", "lines:1-80", 300, 2000);
        bt.next_seq();
        bt.record_read("docs/guide.md", "lines:81-160", 300, 2000);
        bt.next_seq();
        bt.record_read("docs/guide.md", "full", 2000, 2000);
        bt.next_seq();
        bt.record_shell_read("docs/guide.md", ReadView::Full);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 0);
    }

    #[test]
    fn map_then_head_is_not_a_bounce() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/a.rs", "map", 40, 500);
        bt.next_seq();
        bt.record_shell_read("src/a.rs", ReadView::Partial);
        assert_eq!(bt.pending_bounces(), 0);
        // The window ended the chain: a later full read is not the map's fault.
        bt.next_seq();
        bt.record_shell_read("src/a.rs", ReadView::Full);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 0);
    }

    #[test]
    fn map_then_lines_window_is_not_a_bounce() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/a.rs", "map", 40, 500);
        bt.next_seq();
        bt.record_read("src/a.rs", "lines:20-60", 120, 500);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 0);
    }

    #[test]
    fn map_then_cat_is_a_bounce_unless_edited() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/a.rs", "map", 40, 500);
        bt.next_seq();
        bt.record_shell_read("src/a.rs", ReadView::Full);
        assert_eq!(bt.pending_bounces(), 1);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 1);
        assert_eq!(bt.total_wasted_tokens(), 40);

        let mut edited = BounceTracker::new();
        edited.next_seq();
        edited.record_read("src/b.rs", "map", 40, 500);
        edited.next_seq();
        edited.record_shell_read("src/b.rs", ReadView::Full);
        edited.next_seq();
        // e.g. `sed -i` through ctx_shell
        edited.record_edit("src/b.rs");
        edited.flush_pending();
        assert_eq!(edited.total_bounces(), 0);
    }

    /// `anchored` is verbatim: it never starts a correction, and as full
    /// content it completes one (cancelled by the `ctx_patch` that follows).
    #[test]
    fn anchored_is_full_content() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/a.rs", "anchored", 500, 500);
        bt.next_seq();
        bt.record_read("src/a.rs", "full", 500, 500);
        assert_eq!(bt.pending_bounces(), 0, "anchored→full is no correction");

        bt.next_seq();
        bt.record_read("src/a.rs", "map", 40, 500);
        bt.next_seq();
        bt.record_read("src/a.rs", "anchored", 500, 500);
        assert_eq!(bt.pending_bounces(), 1);
        bt.next_seq();
        bt.record_edit("src/a.rs");
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 0);
    }

    #[test]
    fn diff_never_completes_a_correction() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/a.rs", "map", 40, 500);
        bt.next_seq();
        bt.record_read("src/a.rs", "diff", 20, 500);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 0);
    }

    #[test]
    fn partial_read_is_not_charged_as_compressed() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/a.rs", "lines:1-20", 100, 500);
        assert_eq!(bt.last_read("src/a.rs").map(|(c, _)| c), Some(false));
        bt.next_seq();
        bt.record_read("src/a.rs", "map", 40, 500);
        assert_eq!(bt.last_read("src/a.rs").map(|(c, _)| c), Some(true));
    }

    #[test]
    fn explicit_expansion_tracks_quality_and_waste() {
        let mut bt = BounceTracker::new();
        bt.record_expansion(Some("src/main.rs"), 125);
        assert_eq!(bt.total_bounces(), 1);
        assert_eq!(bt.total_wasted_tokens(), 125);
    }

    #[test]
    fn edit_forced_full_read_is_not_a_bounce() {
        // GL #622: a compressed overview read, then an edit, then the `full`
        // re-read that `should_force_full` mandates must NOT register as a bounce
        // — the edit forced it, the compression did not fail.
        let mut bt = BounceTracker::new();
        bt.seq_counter = 1;
        bt.record_read("src/lib.rs", "map", 40, 500);
        bt.seq_counter = 2;
        bt.record_edit("src/lib.rs");
        bt.seq_counter = 4;
        bt.record_read("src/lib.rs", "full", 500, 500);
        assert_eq!(
            bt.total_bounces(),
            0,
            "edit-forced full read must not count as a compression bounce"
        );
    }

    #[test]
    fn full_read_without_edit_still_bounces() {
        // The guard is scoped to edit-forced reads only: an unprompted full
        // re-read after a compressed read is still a real bounce.
        let mut bt = BounceTracker::new();
        bt.seq_counter = 1;
        bt.record_read("src/lib.rs", "map", 40, 500);
        bt.seq_counter = 3;
        bt.record_read("src/lib.rs", "full", 500, 500);
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 1);
    }

    #[test]
    fn should_force_full_after_edit() {
        let mut bt = BounceTracker::new();
        bt.seq_counter = 5;
        bt.record_edit("src/lib.rs");
        bt.seq_counter = 8;
        assert!(bt.should_force_full("src/lib.rs"));
        bt.seq_counter = 20;
        assert!(!bt.should_force_full("src/lib.rs"));
    }

    #[test]
    fn should_force_full_by_extension_bounce_rate() {
        let mut bt = BounceTracker::new();
        for i in 1..=6 {
            bt.seq_counter = i * 2 - 1;
            bt.record_read(&format!("f{i}.yml"), "map", 30, 400);
            bt.seq_counter = i * 2;
            bt.record_read(&format!("f{i}.yml"), "full", 400, 400);
        }
        bt.flush_pending();
        assert!(bt.should_force_full("new.yml"));
    }

    #[test]
    fn adjusted_savings_subtracts_waste() {
        let mut bt = BounceTracker::new();
        bt.seq_counter = 1;
        bt.record_read("a.rs", "map", 50, 500);
        bt.seq_counter = 2;
        bt.record_read("a.rs", "full", 500, 500);
        bt.flush_pending();
        assert_eq!(bt.adjusted_savings(1000), 950);
    }

    #[test]
    fn bounce_rate_for_extension_below_minimum() {
        let bt = BounceTracker::new();
        assert!(bt.bounce_rate_for_extension("test.rs").is_none());
    }

    #[test]
    fn format_summary_empty() {
        let bt = BounceTracker::new();
        assert_eq!(bt.format_summary(), "Bounces: 0");
    }

    #[test]
    fn map_full_edit_is_not_a_bounce() {
        // Read-before-edit: orient compressed, read full, edit. The full read
        // was the edit's preparation, not a compression failure.
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/edit_me.rs", "map", 40, 500);
        bt.next_seq();
        bt.record_read("src/edit_me.rs", "full", 500, 500);
        assert_eq!(bt.pending_bounces(), 1);
        for _ in 0..3 {
            bt.next_seq();
        }
        bt.record_edit("src/edit_me.rs");
        assert_eq!(
            bt.pending_bounces(),
            0,
            "the edit cancels the provisional bounce"
        );
        for _ in 0..(EDIT_FORCE_WINDOW + 5) {
            bt.next_seq();
        }
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 0);
        assert_eq!(bt.total_wasted_tokens(), 0);
    }

    #[test]
    fn map_full_without_edit_commits_when_window_passes() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/only_read.rs", "map", 40, 500);
        bt.next_seq();
        bt.record_read("src/only_read.rs", "full", 500, 500);
        for _ in 0..EDIT_FORCE_WINDOW {
            bt.next_seq();
        }
        assert_eq!(bt.total_bounces(), 0, "still inside the edit window");
        bt.next_seq();
        assert_eq!(bt.pending_bounces(), 0);
        assert_eq!(bt.total_bounces(), 1, "committed once the window passed");
        assert_eq!(bt.total_wasted_tokens(), 40);
        // An edit after the window no longer changes the booked bounce.
        bt.record_edit("src/only_read.rs");
        assert_eq!(bt.total_bounces(), 1);
    }

    #[test]
    fn edit_of_another_path_keeps_the_bounce() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/a.rs", "map", 40, 500);
        bt.next_seq();
        bt.record_read("src/a.rs", "full", 500, 500);
        bt.record_edit("src/b.rs");
        bt.flush_pending();
        assert_eq!(bt.total_bounces(), 1);
    }

    #[test]
    fn flush_pending_commits_at_shutdown() {
        let mut bt = BounceTracker::new();
        bt.next_seq();
        bt.record_read("src/late.rs", "signatures", 25, 300);
        bt.next_seq();
        bt.record_read("src/late.rs", "full", 300, 300);
        assert_eq!(bt.total_bounces(), 0);
        bt.flush_pending();
        assert_eq!(bt.pending_bounces(), 0);
        assert_eq!(bt.total_bounces(), 1);
        assert_eq!(bt.total_wasted_tokens(), 25);
    }

    #[test]
    fn pending_queue_is_bounded() {
        let mut bt = BounceTracker::new();
        for i in 0..(MAX_PENDING_BOUNCES + 4) {
            let path = format!("src/burst{i}.rs");
            bt.record_read(&path, "map", 10, 100);
            bt.record_read(&path, "full", 100, 100);
        }
        assert_eq!(bt.pending_bounces(), MAX_PENDING_BOUNCES);
        assert_eq!(bt.total_bounces(), 4, "overflow commits the oldest early");
    }

    #[test]
    fn edit_beacon_reports_host_edits_after_detection() {
        let dir = tempfile::tempdir().unwrap();
        let beacon = dir.path().join(EDIT_BEACON_FILE);
        let file = dir.path().join("edited.rs");
        std::fs::write(&file, "fn main() {}\n").unwrap();
        let path = file.to_string_lossy().to_string();
        let norm = crate::core::pathutil::normalize_tool_path(&path);

        assert!(!beacon_has_edit(&beacon, &norm, 0), "no beacon yet");
        append_edit_beacon(&beacon, &path, 2_000);
        assert!(
            beacon_has_edit(&beacon, &norm, 1_500),
            "edit after detection"
        );
        assert!(
            !beacon_has_edit(&beacon, &norm, 2_500),
            "edit before detection"
        );
        assert!(!beacon_has_edit(&beacon, "/other/path.rs", 0));
    }

    #[test]
    fn edit_beacon_rotation_keeps_the_previous_generation_readable() {
        let dir = tempfile::tempdir().unwrap();
        let beacon = dir.path().join(EDIT_BEACON_FILE);
        append_edit_beacon(&beacon, "/rotated/first.rs", 10);
        let filler = "x".repeat(usize::try_from(EDIT_BEACON_MAX_BYTES).unwrap() + 1);
        std::fs::OpenOptions::new()
            .append(true)
            .open(&beacon)
            .and_then(|mut f| std::io::Write::write_all(&mut f, filler.as_bytes()))
            .unwrap();
        append_edit_beacon(&beacon, "/rotated/second.rs", 20);
        assert!(rotated_beacon_path(&beacon).exists());
        assert!(beacon_has_edit(&beacon, "/rotated/first.rs", 0));
        assert!(beacon_has_edit(&beacon, "/rotated/second.rs", 0));
    }
}