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extern crate sequence_trie;

pub use self::sequence_trie::SequenceTrie;

use self::sequence_trie::TrieKey;

// XXX can we get rid of <K: Clone> by returning ownership from next()?
pub struct TrieState<K: TrieKey + Clone, V> {
    trie: SequenceTrie<K, V>,
    path: Vec<K>
}

impl<K: TrieKey + Clone, V> TrieState<K, V> {
    pub fn new(trie: SequenceTrie<K, V>) -> Self {
        Self {
            trie: trie,
            path: Vec::new()
        }
    }

    pub fn reset(&mut self) {
        self.path.clear();
    }

    pub fn next(&mut self, event: &K) -> Option<&V> {
        if let Some(node) = {
            let key = [event];
            let key = self.path.iter().chain(key.iter().map(|x| *x));
            self.trie.get_node(key)
        } {
            if let Some(cmd) = node.value() {
                self.path.clear();
                Some(cmd)
            } else {
                self.path.push(event.clone());
                None
            }
        } else {
            self.path.clear();
            None
        }
    }
}

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

    #[test]
    fn smoke() {
        let mut state = TrieState::new({
            let mut bindings = SequenceTrie::<&'static str, &'static str>::new();
            bindings.insert(&["up"],            &"up");
            bindings.insert(&["left", "right"], &"left->right");
            bindings
        });

        assert_eq!(None,                 state.next(&"down"));
        assert_eq!(Some(&"up"),          state.next(&"up"));
        assert_eq!(None,                 state.next(&"right"));
        assert_eq!(None,                 state.next(&"left"));
        assert_eq!(Some(&"left->right"), state.next(&"right"));
    }
}