use anyhow::Result;
use async_trait::async_trait;

#[derive(Copy, Clone, Eq, PartialEq, std::hash::Hash, Debug)]
pub struct Id(pub(crate) usize);

impl crate::NodeId for Id {}

#[derive(Clone, Debug)]
pub struct Node {
    pub(crate) id: Id,
    pub(crate) parents: Vec<Id>,
    pub(crate) data: u8,
}

impl crate::Node for Node {
    type Id = Id;

    fn id(&self) -> &Self::Id {
        &self.id
    }

    fn parent_ids(&self) -> Vec<Self::Id> {
        self.parents.clone()
    }
}

#[derive(Debug)]
pub struct Backend(pub(crate) Vec<Option<Node>>);

#[async_trait]
impl crate::DagBackend<Id, Node> for Backend {
    async fn get(&self, id: Id) -> Result<Option<Node>> {
        if self.0.len() < id.0 + 1 {
            Ok(None)
        } else {
            Ok(self.0[id.0].clone())
        }
    }

    async fn put(&mut self, node: Node) -> Result<Id> {
        while self.0.len() < node.id.0 + 1 {
            self.0.push(None)
        }

        let idx = node.id.0;
        self.0[idx] = Some(node);
        Ok(Id(idx))
    }
}