mini-static 0.14.5

use std::collections::{HashMap, HashSet};
use std::path::{Path, PathBuf};
use std::sync::{Arc, Mutex};
use std::time::SystemTime;

use bytes::Bytes;

use crate::minify::MinifyError;
use crate::reload::ChangeType;
use crate::watcher::Broadcaster;

/// Default cap on the number of distinct paths [`MinifyCache`] holds minified bytes
/// for. An unbounded cache would grow without limit for a server with enough distinct
/// CSS/JS files — this is a stated ceiling (per architecture principle A2), not
/// "as much as fits."
pub(crate) const DEFAULT_MINIFY_CACHE_CAPACITY: usize = 256;

struct CacheEntry {
    /// (path, mtime) pairs for all files this entry's bytes depend on.
    /// For a single-file minify, this is just one entry (the file itself).
    /// For a bundled file, this includes the entry file and all transitively imported files.
    dependencies: Vec<(PathBuf, SystemTime)>,
    bytes: Bytes,
}

/// An in-memory cache of minified (and optionally bundled) file bytes, keyed by path and
/// valid only if all its dependencies match their stored mtimes.
///
/// A cache hit requires both the path to be present *and* every dependency's current mtime
/// to match what's cached — a stale entry (any dependency changed) is treated as a miss
/// and overwritten, not served. Bounded to `capacity` entries: once full, inserting a new
/// path evicts an arbitrary existing entry (not true LRU — see `DEV_PLAN.md`, deferred
/// until a real embedder hits the cap).
///
/// # Bundling and reverse dependencies
///
/// When a CSS file `index.css` imports `base.css`, `index.css`'s cache entry lists both
/// files' mtimes. To detect staleness immediately (not just on the next request for
/// `index.css`), the cache maintains a reverse-dependency index: if `base.css` changes,
/// the watcher broadcasts a `ChangeEvent`, and `MinifyCache::invalidate(&base_path)` looks
/// up which entries import it (via the reverse-dep index) and evicts all of them.
pub(crate) struct MinifyCache {
    entries: Mutex<HashMap<PathBuf, CacheEntry>>,
    /// dependency_path -> set of entry_paths whose cached bytes depend on it.
    /// Lazily pruned: stale rows for already-evicted entries are acceptable and will be
    /// no-ops on next invalidate. This keeps the reverse-index bounded by the same
    /// `capacity × MAX_IMPORTED_FILES` limit as the entries themselves.
    reverse_deps: Mutex<HashMap<PathBuf, HashSet<PathBuf>>>,
    capacity: usize,
}

impl MinifyCache {
    pub(crate) fn new(capacity: usize) -> Self {
        MinifyCache {
            entries: Mutex::new(HashMap::new()),
            reverse_deps: Mutex::new(HashMap::new()),
            capacity,
        }
    }

    /// Return minified bytes for `path`, using `minify_fn` to produce them on a cache
    /// miss or a stale entry (any dependency's mtime doesn't match what's cached).
    ///
    /// `minify_fn` is a parameter (rather than always calling [`crate::minify::minify`]
    /// directly) so tests can wrap it with a call counter and assert the minifier ran
    /// only on genuine misses — the same "inject the thing you want to observe" shape
    /// as `accept_tests`' fake `TcpAccept` listener elsewhere in this crate.
    ///
    /// # Errors
    ///
    /// Returns `Err` if reading `path` fails, or if `minify_fn` rejects the source
    /// bytes as malformed.
    pub(crate) async fn get_or_minify<F>(
        &self,
        path: &Path,
        mtime: SystemTime,
        change_type: ChangeType,
        minify_fn: F,
    ) -> Result<Bytes, MinifyError>
    where
        F: FnOnce(&[u8], ChangeType) -> Result<Bytes, MinifyError>,
    {
        if let Some(bytes) = self.hit(path, &[(path.to_path_buf(), mtime)]) {
            return Ok(bytes);
        }

        let source = tokio::fs::read(path).await.map_err(MinifyError::Io)?;
        let minified = minify_fn(&source, change_type)?;
        self.insert(path.to_path_buf(), vec![(path.to_path_buf(), mtime)], minified.clone());
        Ok(minified)
    }

    /// Drop the cached entry for `path` and every entry that depends on `path`.
    ///
    /// For a non-bundled file, this just removes `path` itself. For a bundled file that
    /// imports other files, a watcher event for one of those imports triggers invalidation
    /// of every bundle entry that (transitively) imports it.
    pub(crate) fn invalidate(&self, path: &Path) {
        let mut entries = self.entries.lock().unwrap();
        let mut reverse_deps = self.reverse_deps.lock().unwrap();

        if let Some(dependent_entries) = reverse_deps.remove(path) {
            for entry_path in dependent_entries {
                entries.remove(&entry_path);
            }
        }

        entries.remove(path);
    }

    /// Spawn a background task that invalidates cache entries as CSS/Script change
    /// events arrive from `broadcaster` — reusing the file watcher already started for
    /// live-reload rather than running a second one. Without this, a changed file's
    /// stale entry would only be noticed reactively, on the next request for it (the
    /// mtime check in [`Self::get_or_minify`] still catches it then — this just makes
    /// the eviction immediate instead of deferred to that next request).
    ///
    /// Runs until `broadcaster`'s sender side is dropped (server shutdown).
    pub(crate) fn subscribe_to_invalidation(self: Arc<Self>, broadcaster: &Broadcaster) {
        let mut events = broadcaster.subscribe();
        tokio::spawn(async move {
            while let Some(event) = events.recv().await {
                if matches!(event.change_type, ChangeType::Css | ChangeType::Script) {
                    self.invalidate(&event.path);
                }
            }
        });
    }

    fn hit(&self, path: &Path, dependencies: &[(PathBuf, SystemTime)]) -> Option<Bytes> {
        let entries = self.entries.lock().unwrap();
        let entry = entries.get(path)?;

        if entry.dependencies.len() != dependencies.len() {
            return None;
        }

        for (stored_path, stored_mtime) in &entry.dependencies {
            let current_mtime = dependencies
                .iter()
                .find(|(p, _)| p == stored_path)
                .map(|(_, m)| m)?;

            if stored_mtime != current_mtime {
                return None;
            }
        }

        Some(entry.bytes.clone())
    }

    fn insert(&self, path: PathBuf, dependencies: Vec<(PathBuf, SystemTime)>, bytes: Bytes) {
        self.remove_entry_and_reverse_deps(&path, &dependencies);

        let mut entries = self.entries.lock().unwrap();
        let mut reverse_deps = self.reverse_deps.lock().unwrap();

        if entries.len() >= self.capacity && !entries.contains_key(&path) {
            if let Some(victim) = entries.keys().next().cloned() {
                if let Some(entry) = entries.remove(&victim) {
                    for (dep_path, _) in &entry.dependencies {
                        if let Some(dependents) = reverse_deps.get_mut(dep_path) {
                            dependents.remove(&victim);
                        }
                    }
                }
            }
        }

        for (dep_path, _) in &dependencies {
            reverse_deps.entry(dep_path.clone()).or_default().insert(path.clone());
        }

        entries.insert(path, CacheEntry { dependencies, bytes });
    }

    fn remove_entry_and_reverse_deps(&self, path: &PathBuf, _dependencies: &[(PathBuf, SystemTime)]) {
        let mut entries = self.entries.lock().unwrap();
        let mut reverse_deps = self.reverse_deps.lock().unwrap();

        if let Some(entry) = entries.remove(path) {
            for (dep_path, _) in &entry.dependencies {
                if let Some(dependents) = reverse_deps.get_mut(dep_path) {
                    dependents.remove(path);
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::sync::atomic::{AtomicUsize, Ordering};

    fn counting_minify(counter: &AtomicUsize) -> impl Fn(&[u8], ChangeType) -> Result<Bytes, MinifyError> + '_ {
        move |bytes, change_type| {
            counter.fetch_add(1, Ordering::SeqCst);
            crate::minify::minify(bytes, change_type)
        }
    }

    #[tokio::test]
    async fn minifies_once_per_mtime_then_serves_from_cache() {
        let dir = tempfile::TempDir::new().unwrap();
        let path = dir.path().join("app.css");
        std::fs::write(&path, "body {  color: red;  }").unwrap();
        let mtime = std::fs::metadata(&path).unwrap().modified().unwrap();

        let cache = MinifyCache::new(DEFAULT_MINIFY_CACHE_CAPACITY);
        let calls = AtomicUsize::new(0);

        let first = cache
            .get_or_minify(&path, mtime, ChangeType::Css, counting_minify(&calls))
            .await
            .unwrap();
        let second = cache
            .get_or_minify(&path, mtime, ChangeType::Css, counting_minify(&calls))
            .await
            .unwrap();

        assert_eq!(calls.load(Ordering::SeqCst), 1, "second request with the same mtime should hit the cache");
        assert_eq!(first, second);

        // Touch the file (new mtime) and request again: must re-minify.
        std::thread::sleep(std::time::Duration::from_millis(10));
        std::fs::write(&path, "body {  color: blue;  }").unwrap();
        let new_mtime = std::fs::metadata(&path).unwrap().modified().unwrap();
        assert_ne!(mtime, new_mtime, "test fixture must actually produce a new mtime");

        let third = cache
            .get_or_minify(&path, new_mtime, ChangeType::Css, counting_minify(&calls))
            .await
            .unwrap();

        assert_eq!(calls.load(Ordering::SeqCst), 2, "a changed mtime must be treated as a miss");
        assert_ne!(first, third, "content changed, so minified bytes must differ");
    }

    #[tokio::test]
    async fn invalidate_forces_a_reminify_even_with_an_unchanged_mtime() {
        let dir = tempfile::TempDir::new().unwrap();
        let path = dir.path().join("app.css");
        std::fs::write(&path, "body { color: red; }").unwrap();
        let mtime = std::fs::metadata(&path).unwrap().modified().unwrap();

        let cache = MinifyCache::new(DEFAULT_MINIFY_CACHE_CAPACITY);
        let calls = AtomicUsize::new(0);

        cache
            .get_or_minify(&path, mtime, ChangeType::Css, counting_minify(&calls))
            .await
            .unwrap();
        cache.invalidate(&path);
        cache
            .get_or_minify(&path, mtime, ChangeType::Css, counting_minify(&calls))
            .await
            .unwrap();

        assert_eq!(calls.load(Ordering::SeqCst), 2, "invalidate() must force a re-minify on the next request");
    }

    #[tokio::test]
    async fn capacity_is_enforced() {
        let dir = tempfile::TempDir::new().unwrap();
        let cache = MinifyCache::new(2);
        let calls = AtomicUsize::new(0);

        for i in 0..5 {
            let path = dir.path().join(format!("f{i}.css"));
            std::fs::write(&path, format!("body {{ color: red{i}; }}")).unwrap();
            let mtime = std::fs::metadata(&path).unwrap().modified().unwrap();
            cache
                .get_or_minify(&path, mtime, ChangeType::Css, counting_minify(&calls))
                .await
                .unwrap();
        }

        assert!(
            cache.entries.lock().unwrap().len() <= 2,
            "cache must never exceed its stated capacity"
        );
    }

    #[tokio::test]
    async fn broadcaster_change_event_invalidates_before_the_next_request() {
        let dir = tempfile::TempDir::new().unwrap();
        let path = dir.path().join("app.css");
        std::fs::write(&path, "body { color: red; }").unwrap();
        let mtime = std::fs::metadata(&path).unwrap().modified().unwrap();

        let cache = Arc::new(MinifyCache::new(DEFAULT_MINIFY_CACHE_CAPACITY));
        let calls = AtomicUsize::new(0);

        // Populate the cache.
        cache
            .get_or_minify(&path, mtime, ChangeType::Css, counting_minify(&calls))
            .await
            .unwrap();
        assert_eq!(calls.load(Ordering::SeqCst), 1);

        // Reuse the same broadcaster live-reload's watcher already runs — not a
        // second watcher — and subscribe the cache to it.
        let broadcaster = Broadcaster::new();
        Arc::clone(&cache).subscribe_to_invalidation(&broadcaster);

        broadcaster.broadcast(crate::watcher::ChangeEvent {
            path: path.clone(),
            change_type: ChangeType::Css,
        });

        // Give the spawned subscriber task a moment to process the event before the
        // "next request" arrives — matching the DEV_PLAN spec: the entry must be gone
        // *before* that next request, not just eventually consistent by the one after.
        tokio::time::sleep(std::time::Duration::from_millis(50)).await;

        // Same mtime as before: if the entry were still cached, this would be a hit
        // and the minifier would NOT run again. A second call proves invalidation.
        cache
            .get_or_minify(&path, mtime, ChangeType::Css, counting_minify(&calls))
            .await
            .unwrap();
        assert_eq!(
            calls.load(Ordering::SeqCst),
            2,
            "the broadcaster's change event must have evicted the entry before this request"
        );
    }

    #[tokio::test]
    async fn bundle_cache_hit_requires_every_dependency_mtime_unchanged() {
        let dir = tempfile::TempDir::new().unwrap();
        let base_path = dir.path().join("base.css");
        let entry_path = dir.path().join("entry.css");

        std::fs::write(&base_path, "body { margin: 0; }").unwrap();
        std::fs::write(&entry_path, "@import \"base.css\";").unwrap();

        let base_mtime = std::fs::metadata(&base_path).unwrap().modified().unwrap();
        let entry_mtime = std::fs::metadata(&entry_path).unwrap().modified().unwrap();

        let cache = MinifyCache::new(DEFAULT_MINIFY_CACHE_CAPACITY);
        let deps = vec![(base_path.clone(), base_mtime), (entry_path.clone(), entry_mtime)];

        // Simulate a bundled entry: entry depends on both itself and base.css
        cache.insert(entry_path.clone(), deps.clone(), Bytes::from("body{margin:0}"));

        // Hit with unchanged mtimes.
        assert!(cache.hit(&entry_path, &deps).is_some());

        // Touch base.css (mtime changes).
        std::thread::sleep(std::time::Duration::from_millis(10));
        std::fs::write(&base_path, "body { margin: 1px; }").unwrap();
        let new_base_mtime = std::fs::metadata(&base_path).unwrap().modified().unwrap();
        assert_ne!(base_mtime, new_base_mtime);

        let stale_deps = vec![(base_path.clone(), new_base_mtime), (entry_path.clone(), entry_mtime)];
        // Miss because base.css's mtime changed.
        assert!(cache.hit(&entry_path, &stale_deps).is_none());
    }

    #[tokio::test]
    async fn changed_leaf_dependency_invalidates_all_bundles_that_import_it() {
        let dir = tempfile::TempDir::new().unwrap();
        let shared_path = dir.path().join("shared.css");
        let entry1_path = dir.path().join("entry1.css");
        let entry2_path = dir.path().join("entry2.css");

        std::fs::write(&shared_path, "body { padding: 0; }").unwrap();
        std::fs::write(&entry1_path, "@import \"shared.css\";").unwrap();
        std::fs::write(&entry2_path, "@import \"shared.css\";").unwrap();

        let shared_mtime = std::fs::metadata(&shared_path).unwrap().modified().unwrap();
        let entry1_mtime = std::fs::metadata(&entry1_path).unwrap().modified().unwrap();
        let entry2_mtime = std::fs::metadata(&entry2_path).unwrap().modified().unwrap();

        let cache = Arc::new(MinifyCache::new(DEFAULT_MINIFY_CACHE_CAPACITY));

        // Both entries depend on shared.css.
        cache.insert(
            entry1_path.clone(),
            vec![(shared_path.clone(), shared_mtime), (entry1_path.clone(), entry1_mtime)],
            Bytes::from("entry1"),
        );
        cache.insert(
            entry2_path.clone(),
            vec![(shared_path.clone(), shared_mtime), (entry2_path.clone(), entry2_mtime)],
            Bytes::from("entry2"),
        );

        assert!(cache.entries.lock().unwrap().contains_key(&entry1_path));
        assert!(cache.entries.lock().unwrap().contains_key(&entry2_path));

        // Invalidate the shared dependency.
        Arc::clone(&cache).invalidate(&shared_path);

        // Both entries should be gone.
        assert!(!cache.entries.lock().unwrap().contains_key(&entry1_path));
        assert!(!cache.entries.lock().unwrap().contains_key(&entry2_path));
    }

    #[tokio::test]
    async fn eviction_cleans_up_reverse_dep_index() {
        let dir = tempfile::TempDir::new().unwrap();
        let dep_path = dir.path().join("dep.css");
        let entry_path = dir.path().join("entry.css");

        std::fs::write(&dep_path, "body { }").unwrap();
        std::fs::write(&entry_path, "@import \"dep.css\";").unwrap();

        let dep_mtime = std::fs::metadata(&dep_path).unwrap().modified().unwrap();
        let entry_mtime = std::fs::metadata(&entry_path).unwrap().modified().unwrap();

        let cache = MinifyCache::new(1);

        cache.insert(
            entry_path.clone(),
            vec![(dep_path.clone(), dep_mtime), (entry_path.clone(), entry_mtime)],
            Bytes::from("bundled"),
        );

        {
            let reverse_deps = cache.reverse_deps.lock().unwrap();
            assert!(reverse_deps.get(&dep_path).is_some());
            assert!(reverse_deps[&dep_path].contains(&entry_path));
        }

        // Insert another entry to trigger eviction of the first.
        let other_dep = dir.path().join("other.css");
        let other_entry = dir.path().join("other.css");
        std::fs::write(&other_dep, "").unwrap();
        cache.insert(
            other_entry.clone(),
            vec![(other_dep.clone(), dep_mtime)],
            Bytes::from("other"),
        );

        // First entry should be evicted.
        assert!(!cache.entries.lock().unwrap().contains_key(&entry_path));

        // Reverse-dep for the evicted entry's dependency should be cleaned up.
        {
            let reverse_deps = cache.reverse_deps.lock().unwrap();
            let dependents = reverse_deps.get(&dep_path);
            assert!(dependents.is_none() || !dependents.unwrap().contains(&entry_path));
        }
    }
}