From bcc3f761137301555bdb2597448ff5b3b890b5f0 Mon Sep 17 00:00:00 2001
From: Weird Constructor <weirdconstructor@gmail.com>
Date: Thu, 18 Aug 2022 20:02:39 +0200
Subject: [PATCH] comment Kahns algorithm

---
 src/nodes/node_graph_ordering.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/nodes/node_graph_ordering.rs b/src/nodes/node_graph_ordering.rs
index 443e6f1..bef2240 100644
--- a/src/nodes/node_graph_ordering.rs
+++ b/src/nodes/node_graph_ordering.rs
@@ -139,18 +139,22 @@ impl NodeGraphOrdering {
             *indeg = 0;
         }
 
+        // Calculate the number of inputs for each node:
         for node in self.nodes.iter().take(self.node_count) {
             for out_node_idx in node.edges.iter().take(node.unused_idx) {
                 self.in_degree[*out_node_idx] += 1;
             }
         }
 
+        // Find the "input" nodes by looking at the nodes without any input. These
+        // are the first that must be executed!
         for idx in 0..self.node_count {
             if self.in_degree[idx] == 0 {
                 deq.push_back(idx);
             }
         }
 
+        // Track visit count for cycle detection:
         let mut visited_count = 0;
 
         while let Some(node_idx) = deq.pop_front() {
@@ -160,9 +164,13 @@ impl NodeGraphOrdering {
 
             out.push(node.node_id);
 
+            // Push the nodes we output to, to the end of the dequeue:
             for neigh_node_idx in node.edges.iter().take(node.unused_idx) {
+                // by reducing the input count of the to be visited node:
                 self.in_degree[*neigh_node_idx] -= 1;
 
+                // we know when that node has been fully supplied with all it's inputs,
+                // so we push it to the end of the dequeue to be executed then:
                 if self.in_degree[*neigh_node_idx] == 0 {
                     deq.push_back(*neigh_node_idx);
                 }