duvis 0.1.3

use anyhow::Result;
use rayon::prelude::*;
use std::collections::HashSet;
use std::fs;
use std::path::Path;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Mutex;
use std::time::SystemTime;

use crate::category::{self, Category};
use crate::entry::Entry;

/// How to attribute bytes when the same inode is reachable via multiple
/// hardlinked paths. Default matches `du` — each inode counts once. Unix
/// only; on Windows this knob has no effect because the std `Metadata`
/// API can't surface a portable file id.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, clap::ValueEnum)]
pub enum HardlinkPolicy {
    /// Each (dev, inode) is counted once. Subsequent links to the same
    /// inode contribute 0 bytes. Matches `du`'s default behavior.
    #[default]
    CountOnce,
    /// Each link contributes its full disk usage, even when the underlying
    /// inode is shared. Inflates totals on trees with many hardlinks
    /// (e.g. content-addressable stores like pnpm).
    CountEach,
}

/// Above this depth, fall back to sequential to avoid task-spawn overhead
/// dominating tiny leaf directories. Empirically, raising it from 3 to a
/// large value cut warm-cache scan time on a deeply-nested ghq tree
/// (lots of node_modules) roughly in half — a directory walk is I/O-bound,
/// so issuing more concurrent metadata calls lets the kernel overlap them.
/// Shallow / wide trees (e.g. ~/Library) see negligible change.
const PARALLEL_DEPTH: usize = 16;

/// Live counters shared between the scanner and any observer. `items_scanned`
/// drives the "12,345 items…" progress UI; `items_skipped` reports filesystem
/// entries we could not read (permission denied, races against deletion, …)
/// so the user can tell that the reported total is incomplete.
#[derive(Default, Debug)]
pub struct ScanCounts {
    pub items_scanned: AtomicU64,
    pub items_skipped: AtomicU64,
}

impl ScanCounts {
    pub fn scanned(&self) -> u64 {
        self.items_scanned.load(Ordering::Relaxed)
    }

    pub fn skipped(&self) -> u64 {
        self.items_skipped.load(Ordering::Relaxed)
    }
}

/// Per-scan state that has to be shared across the rayon workers but
/// isn't part of the public progress signal. `seen_inodes` is what makes
/// hardlink dedup work: the first worker to see a multi-link inode wins
/// the bytes, others report 0.
struct ScanCtx<'a> {
    counts: &'a ScanCounts,
    // Only the Unix `file_disk_usage` reads these — Windows can't surface
    // a portable file id, so dedup is a no-op there. Suppress the
    // dead_code warning rather than splitting the struct by cfg.
    #[cfg_attr(not(unix), allow(dead_code))]
    hardlinks: HardlinkPolicy,
    #[cfg_attr(not(unix), allow(dead_code))]
    seen_inodes: Mutex<HashSet<(u64, u64)>>,
}

impl<'a> ScanCtx<'a> {
    fn new(counts: &'a ScanCounts, hardlinks: HardlinkPolicy) -> Self {
        Self {
            counts,
            hardlinks,
            seen_inodes: Mutex::new(HashSet::new()),
        }
    }
}

/// Scan `path` to completion, returning the tree and the final counters
/// (visited / skipped). Callers that need live progress should use
/// [`scan_with_progress`] and observe a shared [`ScanCounts`] from another
/// thread.
pub fn scan(path: &Path, hardlinks: HardlinkPolicy) -> Result<(Entry, ScanCounts)> {
    let counts = ScanCounts::default();
    let ctx = ScanCtx::new(&counts, hardlinks);
    let entry = scan_recursive(path, 0, Category::Other, &ctx)?;
    Ok((entry, counts))
}

/// Same as [`scan`] but writes progress into `counts` so a UI thread can poll
/// the running totals while the scan is in flight.
pub fn scan_with_progress(
    path: &Path,
    counts: &ScanCounts,
    hardlinks: HardlinkPolicy,
) -> Result<Entry> {
    let ctx = ScanCtx::new(counts, hardlinks);
    scan_recursive(path, 0, Category::Other, &ctx)
}

/// Walk one entry. The outermost ancestor with an explicit (non-Other) category
/// owns its whole subtree, so we pass that category down via `inherited`.
fn scan_recursive(
    path: &Path,
    depth: usize,
    inherited: Category,
    ctx: &ScanCtx<'_>,
) -> Result<Entry> {
    ctx.counts.items_scanned.fetch_add(1, Ordering::Relaxed);
    let name = path
        .file_name()
        .map(|n| n.to_string_lossy().to_string())
        .unwrap_or_else(|| path.to_string_lossy().to_string());

    let metadata = fs::symlink_metadata(path)?;
    let modified_days_ago = days_since_modified(&metadata);

    if metadata.is_dir() {
        let own = category::classify_dir(&name);
        let effective = if inherited != Category::Other {
            inherited
        } else {
            own
        };
        let children = scan_children(path, depth, effective, ctx);
        Ok(Entry::dir(name, effective, modified_days_ago, children))
    } else {
        let effective = if inherited != Category::Other {
            inherited
        } else {
            category::classify_file(&name)
        };
        Ok(Entry::file(
            name,
            file_disk_usage(&metadata, ctx),
            effective,
            modified_days_ago,
        ))
    }
}

/// Bytes a regular file actually occupies on disk. On Unix we use
/// `st_blocks * 512` (matching what `du` reports by default) so that sparse
/// files such as VM disk images (OrbStack `data.img.raw`, `Docker.raw`, ...)
/// don't appear hundreds of times bigger than they really are. APFS/NTFS
/// transparent compression is reflected for the same reason. Windows lacks
/// a portable per-file allocated-bytes API, so we fall back to apparent size.
///
/// When `ctx.hardlinks == CountOnce` we dedupe regular files with
/// `nlink > 1`: the first walker to claim a (dev, ino) reports the bytes,
/// later walkers see 0. Only regular files participate — hardlinks to
/// symlinks/FIFOs/sockets are rare and their footprint is negligible, so
/// counting them every time is simpler than risking surprising "0 B"
/// rows for those types.
///
/// Note: because the walk is parallel via rayon, *which* path among
/// several hardlinks ends up holding the bytes is not deterministic
/// across runs. Totals are stable; per-path attribution and per-category
/// attribution (when the same inode lives under directories of different
/// categories) can shuffle. Use `count-each` if you need every path to
/// report its raw size.
#[cfg(unix)]
fn file_disk_usage(metadata: &fs::Metadata, ctx: &ScanCtx<'_>) -> u64 {
    use std::os::unix::fs::MetadataExt;
    let bytes = metadata.blocks() * 512;
    if ctx.hardlinks == HardlinkPolicy::CountEach {
        return bytes;
    }
    if !metadata.file_type().is_file() || metadata.nlink() <= 1 {
        return bytes;
    }
    let key = (metadata.dev(), metadata.ino());
    let mut seen = ctx.seen_inodes.lock().unwrap();
    if seen.insert(key) {
        bytes
    } else {
        0
    }
}

#[cfg(not(unix))]
fn file_disk_usage(metadata: &fs::Metadata, _ctx: &ScanCtx<'_>) -> u64 {
    metadata.len()
}

fn scan_children(path: &Path, depth: usize, inherited: Category, ctx: &ScanCtx<'_>) -> Vec<Entry> {
    let entries: Vec<_> = match fs::read_dir(path) {
        Ok(rd) => rd
            .filter_map(|e| match e {
                Ok(entry) => Some(entry),
                Err(_) => {
                    ctx.counts.items_skipped.fetch_add(1, Ordering::Relaxed);
                    None
                }
            })
            .collect(),
        Err(_) => {
            // Couldn't open the directory at all (permission denied, vanished,
            // …). Count one skipped entry and bail; the parent dir size will
            // simply be the sum of whatever we managed to read elsewhere.
            ctx.counts.items_skipped.fetch_add(1, Ordering::Relaxed);
            return Vec::new();
        }
    };

    if depth < PARALLEL_DEPTH {
        entries
            .par_iter()
            .filter_map(
                |entry| match scan_recursive(&entry.path(), depth + 1, inherited, ctx) {
                    Ok(e) => Some(e),
                    Err(_) => {
                        ctx.counts.items_skipped.fetch_add(1, Ordering::Relaxed);
                        None
                    }
                },
            )
            .collect()
    } else {
        entries
            .iter()
            .filter_map(
                |entry| match scan_recursive(&entry.path(), depth + 1, inherited, ctx) {
                    Ok(e) => Some(e),
                    Err(_) => {
                        ctx.counts.items_skipped.fetch_add(1, Ordering::Relaxed);
                        None
                    }
                },
            )
            .collect()
    }
}

fn days_since_modified(metadata: &fs::Metadata) -> Option<u64> {
    let modified = metadata.modified().ok()?;
    let duration = SystemTime::now().duration_since(modified).ok()?;
    Some(duration.as_secs() / 86400)
}

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

    fn unique_tmp(label: &str) -> std::path::PathBuf {
        std::env::temp_dir().join(format!(
            "duvis_test_{}_{}_{}",
            label,
            std::process::id(),
            std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .map(|d| d.as_nanos())
                .unwrap_or(0)
        ))
    }

    fn find<'a>(entry: &'a Entry, name: &str) -> Option<&'a Entry> {
        entry.children()?.iter().find(|c| c.name == name)
    }

    #[test]
    fn scan_walks_a_real_directory() {
        let tmp = unique_tmp("walk");
        let _ = fs::remove_dir_all(&tmp);
        fs::create_dir_all(tmp.join("sub")).unwrap();
        fs::write(tmp.join("a.txt"), b"hello").unwrap();
        fs::write(tmp.join("sub/b.txt"), b"world!").unwrap();

        let (entry, _counts) = scan(&tmp, HardlinkPolicy::CountOnce).unwrap();
        assert!(entry.is_dir());
        // Sizes use disk allocation now (st_blocks * 512 on Unix), so the
        // exact byte count depends on the filesystem block size. We just
        // assert the size is at least the apparent total.
        assert!(entry.size >= 5 + 6);

        let children = entry.children().unwrap();
        assert_eq!(children.len(), 2);

        fs::remove_dir_all(&tmp).unwrap();
    }

    /// Files inside a Cache directory inherit Cache, regardless of their own
    /// extension-based classification.
    #[test]
    fn category_propagates_into_node_modules() {
        let tmp = unique_tmp("nm");
        let _ = fs::remove_dir_all(&tmp);
        fs::create_dir_all(tmp.join("node_modules/some-pkg")).unwrap();
        fs::write(tmp.join("node_modules/some-pkg/preview.png"), b"x").unwrap();
        fs::write(tmp.join("node_modules/some-pkg/debug.log"), b"x").unwrap();

        let (root, _counts) = scan(&tmp, HardlinkPolicy::CountOnce).unwrap();
        let nm = find(&root, "node_modules").unwrap();
        assert_eq!(nm.category, Category::Cache);
        let pkg = find(nm, "some-pkg").unwrap();
        assert_eq!(pkg.category, Category::Cache);
        // .png would normally be Media, but inherits Cache from node_modules.
        let png = find(pkg, "preview.png").unwrap();
        assert_eq!(png.category, Category::Cache);
        // .log would normally be Log, but inherits Cache.
        let log = find(pkg, "debug.log").unwrap();
        assert_eq!(log.category, Category::Cache);

        fs::remove_dir_all(&tmp).unwrap();
    }

    /// The outermost explicit-category ancestor wins; nested classifications
    /// are ignored once we are already inside one.
    #[test]
    fn outermost_ancestor_wins() {
        let tmp = unique_tmp("nest");
        let _ = fs::remove_dir_all(&tmp);
        // node_modules (Cache) > target (would be Build, but stays Cache)
        fs::create_dir_all(tmp.join("node_modules/inner/target")).unwrap();
        fs::write(tmp.join("node_modules/inner/target/main.o"), b"x").unwrap();

        let (root, _counts) = scan(&tmp, HardlinkPolicy::CountOnce).unwrap();
        let nm = find(&root, "node_modules").unwrap();
        let inner = find(nm, "inner").unwrap();
        let target = find(inner, "target").unwrap();
        assert_eq!(target.category, Category::Cache);
        assert_eq!(find(target, "main.o").unwrap().category, Category::Cache);

        fs::remove_dir_all(&tmp).unwrap();
    }

    /// Without an explicit-category ancestor, leaves keep their own
    /// classification.
    #[test]
    fn leaves_keep_own_category_outside_named_dirs() {
        let tmp = unique_tmp("free");
        let _ = fs::remove_dir_all(&tmp);
        fs::create_dir_all(tmp.join("Movies")).unwrap();
        fs::write(tmp.join("Movies/clip.mp4"), b"x").unwrap();
        fs::write(tmp.join("Movies/notes.txt"), b"x").unwrap();

        let (root, _counts) = scan(&tmp, HardlinkPolicy::CountOnce).unwrap();
        let movies = find(&root, "Movies").unwrap();
        // The dir name "Movies" is not in classify_dir, so dir is Other.
        assert_eq!(movies.category, Category::Other);
        // Inside Other, the file's own classification stands.
        assert_eq!(find(movies, "clip.mp4").unwrap().category, Category::Media);
        assert_eq!(find(movies, "notes.txt").unwrap().category, Category::Other);

        fs::remove_dir_all(&tmp).unwrap();
    }

    /// A clean scan reports zero skipped entries and a non-zero scanned count.
    #[test]
    fn counts_are_populated_on_clean_scan() {
        let tmp = unique_tmp("counts");
        let _ = fs::remove_dir_all(&tmp);
        fs::create_dir_all(tmp.join("a")).unwrap();
        fs::write(tmp.join("a/x.txt"), b"x").unwrap();
        fs::write(tmp.join("y.txt"), b"y").unwrap();

        let (_, counts) = scan(&tmp, HardlinkPolicy::CountOnce).unwrap();
        // root + "a" + "x.txt" + "y.txt" = 4 visited.
        assert_eq!(counts.scanned(), 4);
        assert_eq!(counts.skipped(), 0);

        fs::remove_dir_all(&tmp).unwrap();
    }

    /// On Unix we can mode 000 a directory and confirm scan_children records a
    /// skip instead of pretending the directory is empty. Skipped on Windows
    /// where chmod semantics differ.
    #[cfg(unix)]
    #[test]
    fn unreadable_directory_is_counted_as_skipped() {
        use std::os::unix::fs::PermissionsExt;

        let tmp = unique_tmp("noperm");
        let _ = fs::remove_dir_all(&tmp);
        fs::create_dir_all(tmp.join("locked")).unwrap();
        fs::write(tmp.join("locked/secret"), b"x").unwrap();
        fs::write(tmp.join("readable"), b"y").unwrap();

        // Strip read+execute on the inner dir so read_dir refuses.
        let mut perms = fs::metadata(tmp.join("locked")).unwrap().permissions();
        perms.set_mode(0o000);
        fs::set_permissions(tmp.join("locked"), perms).unwrap();

        let (_, counts) = scan(&tmp, HardlinkPolicy::CountOnce).unwrap();
        // We tried to walk into "locked" → +1 skip when read_dir failed.
        assert!(
            counts.skipped() >= 1,
            "expected ≥1 skip, got {}",
            counts.skipped(),
        );

        // Restore perms so the cleanup can proceed.
        let mut perms = fs::metadata(tmp.join("locked")).unwrap().permissions();
        perms.set_mode(0o755);
        fs::set_permissions(tmp.join("locked"), perms).unwrap();
        fs::remove_dir_all(&tmp).unwrap();
    }

    /// A hardlinked file should contribute its bytes once under CountOnce
    /// (matching `du`) and twice under CountEach. This is the v0.1.3 fix:
    /// before, the dedup didn't exist and totals were inflated by every
    /// extra link.
    #[cfg(unix)]
    #[test]
    fn hardlink_dedup_obeys_policy() {
        let tmp = unique_tmp("hardlink");
        let _ = fs::remove_dir_all(&tmp);
        fs::create_dir_all(&tmp).unwrap();
        // 4 KiB of payload — comfortably bigger than one block on any
        // sensible filesystem so the size diff is obvious.
        fs::write(tmp.join("original.bin"), vec![b'x'; 4096]).unwrap();
        fs::hard_link(tmp.join("original.bin"), tmp.join("alias.bin")).unwrap();

        let (once, _) = scan(&tmp, HardlinkPolicy::CountOnce).unwrap();
        let (each, _) = scan(&tmp, HardlinkPolicy::CountEach).unwrap();

        // Same inode reachable from two paths: CountEach must report 2x
        // CountOnce because both links contribute their full disk usage.
        assert!(once.size > 0);
        assert_eq!(each.size, once.size * 2);

        // Per-child accounting: under CountOnce one of the links holds
        // the bytes and the other reports 0 (which one wins is rayon-
        // order-dependent). Under CountEach both report the full size.
        let once_children = once.children().unwrap();
        let once_sizes: Vec<u64> = once_children.iter().map(|c| c.size).collect();
        assert_eq!(once_sizes.iter().filter(|s| **s == 0).count(), 1);
        assert_eq!(once_sizes.iter().filter(|s| **s > 0).count(), 1);

        for c in each.children().unwrap() {
            assert!(c.size > 0, "{} reported 0 under CountEach", c.name);
        }

        fs::remove_dir_all(&tmp).unwrap();
    }
}