// Can't use pub const fn constructor due to Copy trait, so allow directly creating struct publicly for now.
pub struct TrieNode<V: 'static + Copy> {
    // Using a children array of size 256 would probably be fastest, but waste too much memory and cause slow compiles
    // and large binaries. Instead, we only store the children between the first and last defined (see `gen/trie.ts`).
    // When getting a child, use `index - offset`.
    pub offset: usize,
    pub value: Option<V>,
    pub children: &'static [Option<&'static TrieNode<V>>],
}

pub enum TrieNodeMatch<V: 'static + Copy> {
    Found { len: usize, value: V },
    NotFound { reached: usize },
}

impl<V: 'static + Copy> TrieNodeMatch<V> {
    pub fn found(&self) -> bool {
        match self {
            TrieNodeMatch::Found { .. } => true,
            TrieNodeMatch::NotFound { .. } => false,
        }
    }
}

impl<V: 'static + Copy> TrieNode<V> {
    // Find the node that matches the shortest prefix of {@param text} and has a value, or the entire text.
    #[inline(always)]
    pub fn next_matching_node(&self, text: &[u8], from: usize) -> Option<(&TrieNode<V>, usize)> {
        let mut node: &TrieNode<V> = self;
        let mut next_pos = from;
        while let Some(&c) = text.get(next_pos) {
            // Let it underflow for performance, it should be safe as the largest index is 256.
            match node.children.get((c as usize).wrapping_sub(node.offset)) {
                Some(Some(child)) => node = child,
                None | Some(None) => return None,
            };
            next_pos += 1;
            if node.value.is_some() {
                break;
            };
        };
        Some((node, next_pos))
    }

    #[inline(always)]
    pub fn longest_matching_prefix(&self, text: &[u8]) -> TrieNodeMatch<V> {
        let mut node: &TrieNode<V> = self;
        let mut value: Option<TrieNodeMatch<V>> = None;
        let mut pos = 0;
        while let Some((new_node, new_pos)) = node.next_matching_node(text, pos) {
            if new_pos == pos || new_node.value.is_none() {
                break;
            };
            node = new_node;
            pos = new_pos;
            value = Some(TrieNodeMatch::Found { len: pos, value: node.value.unwrap() });
        };
        value.unwrap_or(TrieNodeMatch::NotFound { reached: pos })
    }
}