vipune 0.11.0

A minimal memory layer for AI agents
Documentation 
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//! Content hashing for dedup (issue #191).
//!
//! Provides a single shared, dependency-free 64-bit FNV-1a hash over
//! normalised content (lowercased, whitespace-collapsed). Used by:
//! - `Database::insert_with_hash` (the hook insert path)
//! - The dedup migration backfill (issue #191, task-c)
//!
//! The hash function and the normalisation step must remain identical
//! across all call sites or dedup will silently break.

/// Normalise content for hashing: lowercase, collapse all whitespace
/// runs (spaces, tabs, newlines) into single spaces, trim the result.
#[allow(dead_code)] // used by hook path (task-b) and migration backfill (task-c)
pub fn normalize_content(content: &str) -> String {
    let lower = content.to_lowercase();
    let mut out = String::with_capacity(lower.len());
    let mut in_space = false;
    for c in lower.chars() {
        if c.is_whitespace() {
            if !in_space && !out.is_empty() {
                out.push(' ');
                in_space = true;
            }
        } else {
            out.push(c);
            in_space = false;
        }
    }
    out.trim().to_string()
}

/// 64-bit FNV-1a hash of `input`, hex-encoded (16 lowercase chars).
/// No external crate — hand-rolled per project std-first philosophy.
#[allow(dead_code)] // used by content_hash; content_hash used by hook + migration
pub fn fnv1a64_hex(input: &str) -> String {
    let mut hash: u64 = 0xcbf2_9ce4_8422_2325; // FNV offset basis
    for byte in input.as_bytes() {
        hash ^= *byte as u64;
        hash = hash.wrapping_mul(0x0000_0100_0000_01b3); // FNV prime
    }
    format!("{:016x}", hash)
}

/// Compute the dedup hash for a content string:
/// normalise (lowercase + collapse whitespace) then FNV-1a 64-bit hex.
#[allow(dead_code)] // used by hook insert path (task-b) and migration (task-c)
pub fn content_hash(content: &str) -> String {
    let normalized = normalize_content(content);
    fnv1a64_hex(&normalized)
}

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

    #[test]
    fn test_normalize_lowercases() {
        assert_eq!(normalize_content("Hello World"), "hello world");
    }

    #[test]
    fn test_normalize_collapses_whitespace() {
        assert_eq!(normalize_content("Hello   World"), "hello world");
        assert_eq!(normalize_content("a\tb\nc\nd"), "a b c d");
    }

    #[test]
    fn test_normalize_trims_leading_trailing() {
        assert_eq!(normalize_content("  hello world  "), "hello world");
    }

    #[test]
    fn test_content_hash_deterministic() {
        let h1 = content_hash("hello world");
        let h2 = content_hash("hello world");
        assert_eq!(h1, h2);
    }

    #[test]
    fn test_content_hash_case_and_whitespace_insensitive() {
        assert_eq!(content_hash("Hello   World"), content_hash("hello world"));
    }

    #[test]
    fn test_content_hash_differs_for_different_content() {
        assert_ne!(content_hash("foo bar"), content_hash("bar foo"));
    }

    #[test]
    fn test_fnv1a64_hex_output_format() {
        let h = fnv1a64_hex("x");
        assert_eq!(h.len(), 16);
        assert!(h.chars().all(|c| c.is_ascii_hexdigit()));
    }
}