dupes-core 0.2.0

Core library for detecting duplicate and near-duplicate code blocks
Documentation 
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use std::collections::hash_map::DefaultHasher;
use std::fmt;
use std::hash::{Hash, Hasher};

use crate::node::NormalizedNode;

/// A fingerprint of a normalized AST node, wrapping a u64 hash.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct Fingerprint(u64);

impl Fingerprint {
    /// Compute a fingerprint from a normalized node.
    #[must_use]
    pub fn from_node(node: &NormalizedNode) -> Self {
        let mut hasher = DefaultHasher::new();
        node.hash(&mut hasher);
        Self(hasher.finish())
    }

    /// Compute a fingerprint from a signature + body pair.
    #[must_use]
    pub fn from_sig_and_body(sig: &NormalizedNode, body: &NormalizedNode) -> Self {
        let mut hasher = DefaultHasher::new();
        sig.hash(&mut hasher);
        body.hash(&mut hasher);
        Self(hasher.finish())
    }

    /// Compute a composite fingerprint from a set of fingerprints.
    /// Sorts by u64 value for order-independence, then hashes the sorted sequence.
    #[must_use]
    pub fn from_fingerprints(fps: &[Self]) -> Self {
        let mut sorted: Vec<u64> = fps.iter().map(|fp| fp.0).collect();
        sorted.sort_unstable();
        let mut hasher = DefaultHasher::new();
        for v in &sorted {
            v.hash(&mut hasher);
        }
        Self(hasher.finish())
    }

    /// Get the raw u64 value.
    #[must_use]
    pub const fn value(self) -> u64 {
        self.0
    }

    /// Convert to hex string.
    #[must_use]
    pub fn to_hex(self) -> String {
        format!("{:016x}", self.0)
    }

    /// Parse from hex string.
    pub fn from_hex(s: &str) -> Option<Self> {
        u64::from_str_radix(s, 16).ok().map(Fingerprint)
    }
}

impl fmt::Display for Fingerprint {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{:016x}", self.0)
    }
}

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

    #[test]
    fn hex_roundtrip() {
        let fp = Fingerprint(0xdeadbeef12345678);
        let hex = fp.to_hex();
        assert_eq!(hex, "deadbeef12345678");
        let fp2 = Fingerprint::from_hex(&hex).unwrap();
        assert_eq!(fp, fp2);
    }

    #[test]
    fn display_format() {
        let fp = Fingerprint(0x0000000000000042);
        assert_eq!(format!("{fp}"), "0000000000000042");
    }

    #[test]
    fn from_hex_invalid() {
        assert!(Fingerprint::from_hex("not_hex").is_none());
    }

    #[test]
    fn composite_fingerprint_order_independent() {
        let fp1 = Fingerprint(1);
        let fp2 = Fingerprint(2);
        let fp3 = Fingerprint(3);
        assert_eq!(
            Fingerprint::from_fingerprints(&[fp1, fp2, fp3]),
            Fingerprint::from_fingerprints(&[fp3, fp1, fp2])
        );
    }

    #[test]
    fn composite_fingerprint_different_sets_differ() {
        let fp1 = Fingerprint(1);
        let fp2 = Fingerprint(2);
        let fp3 = Fingerprint(3);
        assert_ne!(
            Fingerprint::from_fingerprints(&[fp1, fp2]),
            Fingerprint::from_fingerprints(&[fp2, fp3])
        );
    }

    #[test]
    fn composite_fingerprint_deterministic() {
        let fp1 = Fingerprint(42);
        let fp2 = Fingerprint(99);
        let a = Fingerprint::from_fingerprints(&[fp1, fp2]);
        let b = Fingerprint::from_fingerprints(&[fp1, fp2]);
        assert_eq!(a, b);
    }
}