fix: clade mismatch against nearest node

packages/nextclade/src/tree/tree_builder.rs

@@ -8,11 +8,14 @@ use crate::coord::range::NucRefGlobalRange;
 use crate::graph::node::{GraphNodeKey, Node};
 use crate::tree::params::TreeBuilderParams;
 use crate::tree::split_muts::{difference_of_muts, split_muts, union_of_muts, SplitMutsResult};
-use crate::tree::tree::{AuspiceGraph, AuspiceGraphEdgePayload, AuspiceGraphNodePayload, TreeBranchAttrsLabels};
+use crate::tree::tree::{
+  AuspiceGraph, AuspiceGraphEdgePayload, AuspiceGraphNodePayload, TreeBranchAttrsLabels, TreeNodeAttr,
+};
 use crate::tree::tree_attach_new_nodes::create_new_auspice_node;
 use crate::tree::tree_preprocess::add_auspice_metadata_in_place;
 use crate::types::outputs::NextcladeOutputs;
 use crate::utils::collections::concat_to_vec;
+use crate::utils::stats::mode;
 use eyre::{Report, WrapErr};
 use itertools::Itertools;
 use std::collections::BTreeMap;
@@ -361,7 +364,7 @@ pub fn knit_into_graph(
     // generate new internal node
     // add private mutations, divergence, name and branch attrs to new internal node
     let new_internal_node = {
-      let mut new_internal_node: AuspiceGraphNodePayload = target_node_auspice.clone();
+      let mut new_internal_node: AuspiceGraphNodePayload = target_node_auspice.to_owned();
       new_internal_node.tmp.private_mutations = muts_common_branch;
       new_internal_node.node_attrs.div = Some(divergence_middle_node);
       new_internal_node.branch_attrs.mutations =
@@ -378,6 +381,23 @@ pub fn knit_into_graph(
         format!("nextclade__copy_of_{target_name}_for_placement_of_{qry_name}_#{qry_index}")
       };
 
+      // Vote for the most plausible clade
+      let (clade, should_relabel) = vote_for_clade(graph, target_node, result);
+      new_internal_node.node_attrs.clade_membership = clade.as_deref().map(TreeNodeAttr::new);
+
+      // If decided, then move the clade label from target node to the internal node
+      if should_relabel {
+        let target_node = graph.get_node_mut(target_key)?;
+        if let Some(target_labels) = &mut target_node.payload_mut().branch_attrs.labels {
+          target_labels.clade = None;
+          new_internal_node
+            .branch_attrs
+            .labels
+            .get_or_insert(TreeBranchAttrsLabels::default())
+            .clade = clade;
+        }
+      }
+
       new_internal_node
     };
 
@@ -433,3 +453,28 @@ fn set_branch_attrs_aa_labels(node: &mut AuspiceGraphNodePayload) {
     });
   }
 }
+
+// Vote for the most plausible clade for the new internal node
+fn vote_for_clade(
+  graph: &AuspiceGraph,
+  target_node: &Node<AuspiceGraphNodePayload>,
+  result: &NextcladeOutputs,
+) -> (Option<String>, bool) {
+  let query_clade = &result.clade;
+
+  let parent_node = &graph.parent_of(target_node);
+  let parent_clade = &parent_node.and_then(|node| node.payload().clade());
+
+  let target_clade = &target_node.payload().clade();
+
+  let possible_clades = [parent_clade, query_clade, target_clade].into_iter().flatten(); // exclude None
+  let clade = mode(possible_clades).cloned();
+
+  // We will need to change branch label if both:
+  //  - clade transition happens from parent to the new node
+  // AND
+  //  -  when the target node's clade wins the vote
+  let should_relabel = (parent_clade != &clade) && (target_clade.is_some() && target_clade == &clade);
+
+  (clade, should_relabel)
+}

packages/nextclade/src/utils/mod.rs

@@ -10,6 +10,7 @@ pub mod info;
 pub mod map;
 pub mod num;
 pub mod option;
+pub mod stats;
 pub mod string;
 pub mod vec2d;
 pub mod wraparound;

packages/nextclade/src/utils/stats.rs

@@ -0,0 +1,13 @@
+use itertools::Itertools;
+use std::hash::Hash;
+
+/// Calculate mode (the most frequently occurring element) of an iterator.
+/// In case of a tie, the first occurrence is returned. Returns `None` if the iterator is empty.
+pub fn mode<T: Hash + Eq + Clone>(items: impl IntoIterator<Item = T>) -> Option<T> {
+  items
+    .into_iter()
+    .counts()
+    .into_iter()
+    .max_by_key(|&(_, count)| count)
+    .map(|(item, _)| item)
+}