Function parse_single_chain

nodedb/src/engine/graph/pattern/compiler/mod.rs:174–212

Parse a single pattern chain: `(a:Person)-[:KNOWS]->(b:Person)-[:KNOWS]->(c)`.

(text: &str)

/// Parse a single pattern chain: `(a:Person)-[:KNOWS]->(b:Person)-[:KNOWS]->(c)`.
fn parse_single_chain(text: &str) -> crate::Result<PatternChain> {
    let mut triples = Vec::new();
    let mut pos = 0;

    let (first_node, consumed) = bindings::parse_node_binding(&text[pos..])?;
    pos += consumed;
    let mut prev_node = first_node;

    while pos < text.len() {
        let remaining = text[pos..].trim_start();
        if remaining.is_empty() {
            break;
        }
        pos = text.len() - remaining.len();

        let (edge, edge_consumed) = bindings::parse_edge_binding(&text[pos..])?;
        pos += edge_consumed;

        let remaining = text[pos..].trim_start();
        pos = text.len() - remaining.len();
        let (next_node, node_consumed) = bindings::parse_node_binding(&text[pos..])?;
        pos += node_consumed;

        triples.push(PatternTriple {
            src: prev_node,
            edge,
            dst: next_node.clone(),
        });
        prev_node = next_node;
    }

    if triples.is_empty() {
        return Err(crate::Error::BadRequest {
            detail: format!("empty pattern chain: '{text}'"),
        });
    }

    Ok(PatternChain { triples })
}

#[cfg(test)]
mod tests {