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use std::collections::{HashMap, HashSet};
use smol::lock::RwLock;
pub type NodeId = String;
pub type TopologyDesc = HashMap<NodeId, HashSet<NodeId>>;
pub struct Topology(RwLock<TopologyDesc>);
impl Topology {
/// Create a new topology in which all nodes are connected to each other.
pub fn dense(node_ids: Vec<String>) -> Self {
let mut top = TopologyDesc::new();
for node_id in node_ids.iter() {
top.insert(node_id.clone(), node_ids.iter().cloned().collect());
}
Self::filter_desc(&mut top);
Topology(RwLock::new(top))
}
/// Replace the current topology with a new one.
pub async fn replace(&self, mut new: TopologyDesc) {
Self::filter_desc(&mut new);
*self.0.write().await = new;
}
fn filter_desc(desc: &mut TopologyDesc) {
for (node_id, neighbours) in desc.iter_mut() {
neighbours.remove(node_id);
}
}
/// Get the next targets from the given topology, for a message
/// which has travelled across the given path and is now at node_id.
pub async fn targets(&self, node_id: &String, last_node_id: &String) -> HashSet<String> {
// Ensure we don't keep holding the read lock
let topology = self.0.read().await;
// Get all nodes the last node sent it to
let visited = topology.get(last_node_id);
let neighbours = topology.get(node_id).unwrap();
match visited {
Some(visited) => neighbours
.difference(&visited)
.cloned()
.filter(|n| n != node_id)
.collect(),
None => neighbours.clone(),
}
}
}
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