spider_network_blocker 0.0.85

use crate::trie::Trie;
use arc_swap::ArcSwap;
use std::sync::Arc;

/// Immutable snapshot of trie layers. Each `extend` adds a layer
/// instead of cloning and rebuilding.
#[derive(Default)]
struct Layers {
    tries: Vec<Arc<Trie>>,
}

impl Layers {
    fn with_trie(mut trie: Trie) -> Self {
        // Freeze here so every layer reader hits the packed fast path and
        // we never hold a Vec-form trie behind an `Arc`.
        trie.shrink_to_fit();
        Self {
            tries: vec![Arc::new(trie)],
        }
    }

    #[inline]
    fn contains_prefix(&self, text: &str) -> bool {
        for trie in &self.tries {
            if trie.contains_prefix(text) {
                return true;
            }
        }
        false
    }

    fn len(&self) -> usize {
        self.tries.len()
    }
}

/// A lock-free, dynamically updatable block list backed by layered [`Trie`]s.
///
/// Can optionally wrap an existing static `&Trie` (e.g. `URL_IGNORE_TRIE`)
/// as a base that is always checked first. Runtime patterns are added as
/// layers on top — `extend` never clones existing data.
///
/// Reads are wait-free (atomic pointer load). Writers build off the hot path
/// and atomically swap in the new layer set.
pub struct DynamicBlockList {
    base: Option<&'static Trie>,
    layers: ArcSwap<Layers>,
}

impl DynamicBlockList {
    /// Create an empty dynamic block list with no base trie.
    pub fn new() -> Self {
        Self {
            base: None,
            layers: ArcSwap::from_pointee(Layers::default()),
        }
    }

    /// Wrap an existing static trie as the base layer.
    ///
    /// The base is always checked first and is never affected by `seed`,
    /// `swap`, `extend`, or `compact` — those only operate on dynamic layers.
    ///
    /// ```rust,ignore
    /// use spider_network_blocker::scripts::URL_IGNORE_TRIE;
    /// use spider_network_blocker::dynamic_blocklist::DynamicBlockList;
    ///
    /// let blocklist = DynamicBlockList::with_base(&URL_IGNORE_TRIE);
    /// blocklist.extend(["https://my-custom-tracker.com/"]);
    ///
    /// // Checks the static trie first, then dynamic layers
    /// blocklist.is_blocked("https://www.google-analytics.com/analytics.js"); // true (from base)
    /// blocklist.is_blocked("https://my-custom-tracker.com/pixel");           // true (from extend)
    /// ```
    pub fn with_base(base: &'static Trie) -> Self {
        Self {
            base: Some(base),
            layers: ArcSwap::from_pointee(Layers::default()),
        }
    }

    /// Create a dynamic block list pre-seeded with `patterns` and no base trie.
    pub fn from_patterns<'a>(patterns: impl IntoIterator<Item = &'a str>) -> Self {
        let mut trie = Trie::new();
        for p in patterns {
            trie.insert(p);
        }
        Self {
            base: None,
            layers: ArcSwap::from_pointee(Layers::with_trie(trie)),
        }
    }

    /// Lock-free check — returns `true` if `url` matches any prefix in the
    /// base trie or any dynamic layer.
    #[inline]
    pub fn is_blocked(&self, url: &str) -> bool {
        if let Some(base) = self.base {
            if base.contains_prefix(url) {
                return true;
            }
        }
        self.layers.load().contains_prefix(url)
    }

    /// Atomically replace all dynamic layers with a single `new_trie`.
    /// The base trie (if any) is unaffected.
    pub fn swap(&self, new_trie: Trie) {
        self.layers.store(Arc::new(Layers::with_trie(new_trie)));
    }

    /// Replace all dynamic layers with a single trie built from `patterns`.
    /// The base trie (if any) is unaffected.
    pub fn seed<'a>(&self, patterns: impl IntoIterator<Item = &'a str>) {
        let mut trie = Trie::new();
        for p in patterns {
            trie.insert(p);
        }
        self.layers.store(Arc::new(Layers::with_trie(trie)));
    }

    /// Extend the block list with additional patterns — lock-free, no cloning.
    ///
    /// Builds a small trie from only the new patterns and appends it as a new
    /// layer. Existing layers are shared via `Arc` — zero copying.
    pub fn extend<'a>(&self, patterns: impl IntoIterator<Item = &'a str>) {
        let mut trie = Trie::new();
        for p in patterns {
            trie.insert(p);
        }
        let current = self.layers.load();
        let mut new_layers = Layers {
            tries: current.tries.clone(), // clones Arc pointers, not trie data
        };
        new_layers.tries.push(Arc::new(trie));
        self.layers.store(Arc::new(new_layers));
    }

    /// Merge all dynamic layers into a single trie.
    /// The base trie (if any) is unaffected.
    pub fn compact(&self) {
        let current = self.layers.load();
        if current.len() <= 1 {
            return;
        }
        let mut merged = Trie::new();
        for trie in &current.tries {
            collect_into(trie, &mut merged);
        }
        self.layers.store(Arc::new(Layers::with_trie(merged)));
    }

    /// Number of dynamic trie layers (excludes the base).
    pub fn layer_count(&self) -> usize {
        self.layers.load().len()
    }
}

impl Default for DynamicBlockList {
    fn default() -> Self {
        Self::new()
    }
}

/// Walk `source` and re-insert every stored word into `dest`.
fn collect_into(source: &Trie, dest: &mut Trie) {
    source.for_each_word(|bytes| {
        if let Ok(word) = std::str::from_utf8(bytes) {
            dest.insert(word);
        }
    });
}

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

    #[test]
    fn test_empty_blocks_nothing() {
        let bl = DynamicBlockList::new();
        assert!(!bl.is_blocked("https://example.com"));
    }

    #[test]
    fn test_from_patterns() {
        let bl = DynamicBlockList::from_patterns([
            "https://ads.example.com/",
            "https://tracker.example.com/",
        ]);
        assert!(bl.is_blocked("https://ads.example.com/banner.js"));
        assert!(bl.is_blocked("https://tracker.example.com/pixel"));
        assert!(!bl.is_blocked("https://cdn.example.com/app.js"));
    }

    #[test]
    fn test_with_base_checks_static_trie() {
        // Simulate a static trie
        static BASE: LazyLock<Trie> = LazyLock::new(|| {
            let mut t = Trie::new();
            t.insert("https://static-blocked.example.com/");
            t
        });

        let bl = DynamicBlockList::with_base(&BASE);

        // Base pattern is blocked
        assert!(bl.is_blocked("https://static-blocked.example.com/x"));
        // Unknown is not
        assert!(!bl.is_blocked("https://cdn.example.com/x"));
    }

    #[test]
    fn test_with_base_plus_extend() {
        static BASE: LazyLock<Trie> = LazyLock::new(|| {
            let mut t = Trie::new();
            t.insert("https://static-blocked.example.com/");
            t
        });

        let bl = DynamicBlockList::with_base(&BASE);
        bl.extend(["https://dynamic-blocked.example.com/"]);

        // Both base and dynamic patterns are blocked
        assert!(bl.is_blocked("https://static-blocked.example.com/x"));
        assert!(bl.is_blocked("https://dynamic-blocked.example.com/x"));
        assert!(!bl.is_blocked("https://cdn.example.com/x"));
    }

    #[test]
    fn test_seed_does_not_affect_base() {
        static BASE: LazyLock<Trie> = LazyLock::new(|| {
            let mut t = Trie::new();
            t.insert("https://static-blocked.example.com/");
            t
        });

        let bl = DynamicBlockList::with_base(&BASE);
        bl.extend(["https://old-dynamic.example.com/"]);

        // Seed replaces dynamic layers but not the base
        bl.seed(["https://new-dynamic.example.com/"]);

        assert!(bl.is_blocked("https://static-blocked.example.com/x")); // base intact
        assert!(bl.is_blocked("https://new-dynamic.example.com/x")); // new seed
        assert!(!bl.is_blocked("https://old-dynamic.example.com/x")); // old dynamic gone
    }

    #[test]
    fn test_with_real_static_trie() {
        use crate::scripts::URL_IGNORE_TRIE;

        let bl = DynamicBlockList::with_base(&URL_IGNORE_TRIE);
        bl.extend(["https://my-custom-tracker.example.com/"]);

        // Static patterns still work
        assert!(bl.is_blocked("https://www.google-analytics.com/analytics.js"));
        // Dynamic extension works
        assert!(bl.is_blocked("https://my-custom-tracker.example.com/pixel"));
        // Legitimate URLs still pass
        assert!(!bl.is_blocked("https://cdn.example.com/app.js"));
    }

    #[test]
    fn test_seed_replaces() {
        let bl = DynamicBlockList::from_patterns(["https://old.example.com/"]);
        assert!(bl.is_blocked("https://old.example.com/x"));

        bl.seed(["https://new.example.com/"]);
        assert!(!bl.is_blocked("https://old.example.com/x"));
        assert!(bl.is_blocked("https://new.example.com/y"));
    }

    #[test]
    fn test_extend_adds_without_cloning_tries() {
        let bl = DynamicBlockList::from_patterns(["https://ads.example.com/"]);
        assert_eq!(bl.layer_count(), 1);

        bl.extend(["https://tracker.example.com/"]);
        assert_eq!(bl.layer_count(), 2);

        assert!(bl.is_blocked("https://ads.example.com/banner.js"));
        assert!(bl.is_blocked("https://tracker.example.com/pixel"));
        assert!(!bl.is_blocked("https://cdn.example.com/app.js"));
    }

    #[test]
    fn test_multiple_extends() {
        let bl = DynamicBlockList::from_patterns(["https://ads.example.com/"]);
        bl.extend(["https://tracker.example.com/"]);
        bl.extend(["https://analytics.example.com/"]);
        bl.extend(["https://pixel.example.com/"]);

        assert_eq!(bl.layer_count(), 4);
        assert!(bl.is_blocked("https://ads.example.com/x"));
        assert!(bl.is_blocked("https://tracker.example.com/x"));
        assert!(bl.is_blocked("https://analytics.example.com/x"));
        assert!(bl.is_blocked("https://pixel.example.com/x"));
    }

    #[test]
    fn test_compact_merges_layers() {
        let bl = DynamicBlockList::from_patterns(["https://ads.example.com/"]);
        bl.extend(["https://tracker.example.com/"]);
        bl.extend(["https://analytics.example.com/"]);
        assert_eq!(bl.layer_count(), 3);

        bl.compact();
        assert_eq!(bl.layer_count(), 1);

        assert!(bl.is_blocked("https://ads.example.com/x"));
        assert!(bl.is_blocked("https://tracker.example.com/x"));
        assert!(bl.is_blocked("https://analytics.example.com/x"));
        assert!(!bl.is_blocked("https://cdn.example.com/x"));
    }

    #[test]
    fn test_compact_noop_single_layer() {
        let bl = DynamicBlockList::from_patterns(["https://ads.example.com/"]);
        bl.compact();
        assert_eq!(bl.layer_count(), 1);
        assert!(bl.is_blocked("https://ads.example.com/x"));
    }

    #[test]
    fn test_swap() {
        let bl = DynamicBlockList::from_patterns(["https://old.example.com/"]);
        let mut new_trie = Trie::new();
        new_trie.insert("https://new.example.com/");
        bl.swap(new_trie);

        assert!(!bl.is_blocked("https://old.example.com/x"));
        assert!(bl.is_blocked("https://new.example.com/y"));
    }

    #[test]
    fn test_concurrent_reads_during_extend() {
        use std::sync::Arc;

        let bl = Arc::new(DynamicBlockList::from_patterns([
            "https://ads.example.com/",
        ]));

        let handles: Vec<_> = (0..8)
            .map(|_| {
                let bl = Arc::clone(&bl);
                std::thread::spawn(move || bl.is_blocked("https://ads.example.com/banner.js"))
            })
            .collect();

        bl.extend(["https://new.example.com/"]);

        for h in handles {
            let _ = h.join().unwrap();
        }

        assert!(bl.is_blocked("https://ads.example.com/x"));
        assert!(bl.is_blocked("https://new.example.com/x"));
    }

    use std::sync::LazyLock;
}