wayfind 1.1.0

A speedy, flexible router.
Documentation 
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use crate::node::Node;

/// Pre-computed path length bounds for pruning during search.
#[derive(Clone, Debug)]
pub(crate) struct Bounds {
    /// Lower bound on remaining path bytes to reach any match.
    lower: usize,

    /// Upper bound on remaining path bytes that could still match.
    upper: usize,
}

impl Default for Bounds {
    fn default() -> Self {
        Self {
            lower: usize::MAX,
            upper: 0,
        }
    }
}

impl Bounds {
    pub(crate) fn compute<S, T>(node: &Node<S, T>) -> Self {
        Self {
            lower: Self::compute_lower(node),
            upper: Self::compute_upper(node),
        }
    }

    pub(crate) const fn lower(&self) -> usize {
        self.lower
    }

    pub(crate) const fn upper(&self) -> usize {
        self.upper
    }

    fn compute_lower<S, T>(node: &Node<S, T>) -> usize {
        // A node with data can match here with 0 remaining bytes.
        if node.data.is_some() {
            return 0;
        }

        // An end-wildcard needs at least 1 byte.
        if node.end_wildcard.is_some() {
            return 1;
        }

        let static_lengths = node
            .static_children
            .iter()
            .map(|child| child.state.prefix.len().saturating_add(child.bounds.lower));

        let dynamic_lengths = node
            .dynamic_children
            .iter()
            .map(|child| child.bounds.lower.saturating_add(1));

        let wildcard_lengths = node
            .wildcard_children
            .iter()
            .map(|child| child.bounds.lower.saturating_add(1));

        static_lengths
            .chain(dynamic_lengths)
            .chain(wildcard_lengths)
            .min()
            .unwrap_or(usize::MAX)
    }

    fn compute_upper<S, T>(node: &Node<S, T>) -> usize {
        // Parameters can consume any input.
        if node.has_parameters() {
            return usize::MAX;
        }

        node.static_children
            .iter()
            .map(|child| child.state.prefix.len().saturating_add(child.bounds.upper))
            .max()
            .unwrap_or(0)
    }
}