code-kb-core 1.0.3

use ignore::WalkBuilder;
use notify::RecursiveMode;
use notify_debouncer_full::{DebouncedEvent, Debouncer, RecommendedCache, new_debouncer};
use std::path::{Path, PathBuf};
use std::time::Duration;
use thiserror::Error;
use tracing::{info, warn};

use crate::sync::{delete_file, ensure_fresh_file, scan_workspace, update_file};
use crate::workspace::{Workspace, is_hard_excluded, to_forward_slash};

#[derive(Debug, Error)]
pub enum WatcherError {
    #[error("Failed to initialize notify watcher: {0}")]
    Notify(#[from] notify::Error),
    #[error("Failed to build gitignore filters: {0}")]
    Ignore(#[from] ignore::Error),
}

/// Active background file watcher handle.
pub struct WatcherHandle {
    // Retaining debouncer keeps the background notify thread running
    _debouncer: Debouncer<notify::RecommendedWatcher, RecommendedCache>,
}

/// Starts debounced background file watcher with git storm circuit breaker.
pub fn start_watcher(
    workspace: Workspace,
    db_path: PathBuf,
) -> Result<WatcherHandle, WatcherError> {
    let ws_clone = workspace.clone();
    let db_clone = db_path.clone();

    // 150ms debounce window
    let mut debouncer = new_debouncer(
        Duration::from_millis(150),
        None,
        move |res: Result<Vec<DebouncedEvent>, _>| {
            let events = match res {
                Ok(evts) => evts,
                Err(err) => {
                    warn!("File watcher error: {:?}", err);
                    return;
                }
            };

            if events.is_empty() {
                return;
            }

            let mut ignore_builder = WalkBuilder::new(&ws_clone.canonical_root);
            ignore_builder
                .standard_filters(true)
                .hidden(false)
                .add_custom_ignore_filename(".julieignore")
                .add_custom_ignore_filename(".code-kb-ignore")
                .add_custom_ignore_filename(".codekbignore");
            let mut ignore_matcher = match ignore_builder.build_matchers().pop() {
                Some(m) => m,
                None => {
                    warn!("Failed to initialize ignore matcher for workspace root; skipping tick");
                    return;
                }
            };

            let mut relevant_files = Vec::new();
            for event in &events {
                // Ignore read/access events (e.g. inotify IN_OPEN / IN_ACCESS)
                if event.kind.is_access() {
                    continue;
                }

                for path in &event.paths {
                    let norm_path = dunce::simplified(path);
                    if let Some(rel) =
                        crate::workspace::strip_prefix_lossy(norm_path, &ws_clone.canonical_root)
                    {
                        let rel_str = to_forward_slash(rel);
                        let rel_str = rel_str.trim_start_matches('/').to_string();
                        if rel_str.is_empty() || is_hard_excluded(&rel_str) {
                            continue;
                        }
                        let is_dir = norm_path.is_dir();
                        let (matched, error) =
                            ignore_matcher.matched_with_errors(Path::new(&rel_str), is_dir);
                        if let Some(error) = error {
                            warn!("Failed to load ignore rule: {error}");
                        }
                        if matched.is_ignore() {
                            continue;
                        }
                        relevant_files.push((norm_path.to_path_buf(), rel_str));
                    }
                }
            }

            if relevant_files.is_empty() {
                return;
            }

            // Deduplicate paths in this window
            relevant_files.sort_by(|a, b| a.1.cmp(&b.1));
            relevant_files.dedup_by(|a, b| a.1 == b.1);

            // Git checkout storm circuit-breaker:
            // If more than 50 files changed within the debounce window,
            // cancel micro-updates and run a single bulk scan.
            if relevant_files.len() > 50 {
                tracing::debug!(
                    "Git storm detected ({} files changed in window). Running bulk scan...",
                    relevant_files.len()
                );
                if let Err(e) = scan_workspace(&ws_clone, &db_clone, false) {
                    warn!("Bulk scan failed during git storm: {e}");
                }
                return;
            }

            // Otherwise, process incremental updates in lock-free WAL mode
            let conn_opt = crate::db::open_read_only(&db_clone).ok();
            for (abs, rel) in relevant_files {
                if abs.exists() && abs.is_file() {
                    let mut handled = false;
                    if let Some(ref conn) = conn_opt
                        && let Ok(_fresh) = ensure_fresh_file(&ws_clone, &db_clone, conn, &rel)
                    {
                        handled = true;
                    }
                    if !handled {
                        let _ = update_file(&ws_clone, &db_clone, &rel);
                    }
                } else if !abs.exists() {
                    let mut child_paths = Vec::new();
                    let local_conn;
                    let conn_ref = match conn_opt.as_ref() {
                        Some(c) => Some(c),
                        None => {
                            local_conn = crate::db::open_read_only(&db_clone).ok();
                            local_conn.as_ref()
                        }
                    };
                    if let Some(conn) = conn_ref {
                        let escaped = crate::queries::escape_like(&rel);
                        let pattern = format!("{escaped}/%");
                        if let Ok(mut stmt) = conn.prepare(
                            "SELECT path FROM files WHERE path LIKE ?1 ESCAPE '\\' LIMIT 51",
                        ) && let Ok(rows) = stmt.query_map([&pattern], |r| r.get::<_, String>(0))
                        {
                            for child in rows.flatten() {
                                child_paths.push(child);
                            }
                        }
                    }
                    if child_paths.len() > 50 {
                        let _ = scan_workspace(&ws_clone, &db_clone, false);
                    } else {
                        for child in child_paths {
                            let _ = delete_file(&ws_clone, &db_clone, &child);
                        }
                        let _ = delete_file(&ws_clone, &db_clone, &rel);
                    }
                }
            }
        },
    )?;

    // Watch workspace root recursively
    debouncer.watch(&workspace.canonical_root, RecursiveMode::Recursive)?;

    info!(
        "Tier 3 file watcher active on '{}' (150ms debounce)",
        workspace.canonical_root.display()
    );

    Ok(WatcherHandle {
        _debouncer: debouncer,
    })
}

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

    #[test]
    fn test_drive_root_leading_slash_trimmed() {
        let raw_rel = Path::new("/src/components/button.rs");
        let rel_str = to_forward_slash(raw_rel);
        let trimmed = rel_str.trim_start_matches('/').to_string();
        assert_eq!(trimmed, "src/components/button.rs");
        assert!(!trimmed.starts_with('/'));

        let raw_rel_win = Path::new("\\src\\components\\button.rs");
        let rel_str_win = to_forward_slash(raw_rel_win);
        let trimmed_win = rel_str_win.trim_start_matches('/').to_string();
        assert_eq!(trimmed_win, "src/components/button.rs");
        assert!(!trimmed_win.starts_with('/'));
    }

    #[test]
    fn test_child_files_query_pattern_escaped() {
        let dir_rel = "src/components";
        let escaped = dir_rel
            .replace('\\', "\\\\")
            .replace('%', "\\%")
            .replace('_', "\\_");
        let pattern = format!("{escaped}/%");
        assert_eq!(pattern, "src/components/%");

        let dir_with_wildcards = "src/foo_bar%baz";
        let escaped2 = dir_with_wildcards
            .replace('\\', "\\\\")
            .replace('%', "\\%")
            .replace('_', "\\_");
        let pattern2 = format!("{escaped2}/%");
        assert_eq!(pattern2, "src/foo\\_bar\\%baz/%");
    }
}