社内の「どれが最新のエクセルかわからない」をなくす知恵：
〜探す時間と転記ミスをなくす『1か所直せばすべて揃う原本共有台帳』の仕組み〜

#![forbid(unsafe_code)]

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct DocNodeHeader<'a> {
    pub id: &'a str,
    pub title: &'a str,
    pub domain: &'a str,
    pub content_hash_fnv1a: u64,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DocVerifyError<'a> {
    MissingRequiredField(&'a str),
    DuplicateNodeId(&'a str),
    CompiledIndexDriftDetected { node_id: &'a str, expected: u64, actual: u64 },
}

/// Computes deterministic 64-bit FNV-1a hash over normalized master document bytes.
#[inline]
pub fn fnv1a_64(bytes: &[u8]) -> u64 {
    let mut hash: u64 = 0xcbf29ce484222325;
    for &b in bytes {
        if b != b'
' {
            hash ^= b as u64;
            hash = hash.wrapping_mul(0x100000001b3);
        }
    }
    hash
}

/// Verifies that all master document nodes have non-empty metadata, unique IDs,
/// and zero hash drift against the compiled master index.
pub fn verify_doc_manifest<'a>(
    source_nodes: &'a [DocNodeHeader<'a>],
    compiled_index_hashes: &'a [(&'a str, u64)],
) -> Result<usize, DocVerifyError<'a>> {
    for (i, node) in source_nodes.iter().enumerate() {
        if node.id.trim().is_empty() || node.title.trim().is_empty() || node.domain.trim().is_empty() {
            return Err(DocVerifyError::MissingRequiredField(node.id));
        }
        for prev in &source_nodes[..i] {
            if prev.id == node.id {
                return Err(DocVerifyError::DuplicateNodeId(node.id));
            }
        }
        if let Some(&(_, indexed_hash)) = compiled_index_hashes.iter().find(|&&(id, _)| id == node.id) {
            if indexed_hash != node.content_hash_fnv1a {
                return Err(DocVerifyError::CompiledIndexDriftDetected {
                    node_id: node.id,
                    expected: node.content_hash_fnv1a,
                    actual: indexed_hash,
                });
            }
        }
    }
    Ok(source_nodes.len())
}