From 72f87ec1eb6f8b3e312a3fee1f39c389cb929e8d Mon Sep 17 00:00:00 2001
From: aitsuki <aitsukigo@gmail.com>
Date: Thu, 27 Jan 2022 22:17:24 +0800
Subject: [PATCH] Remove the 'close' and 'opened' fields.

---
 astar.go | 59 ++++++++++++++++++--------------------------------------
 1 file changed, 19 insertions(+), 40 deletions(-)

diff --git a/astar.go b/astar.go
index a3af081..388ef51 100644
--- a/astar.go
+++ b/astar.go
@@ -23,46 +23,24 @@ type node struct {
 	cost   float64
 	rank   float64
 	parent *node
-	open   bool
-	closed bool
 	index  int
 }
 
 // nodeMap is a collection of nodes keyed by Pather nodes for quick reference.
 type nodeMap map[Pather]*node
 
-// get gets the Pather object wrapped in a node, instantiating if required.
-func (nm nodeMap) get(p Pather) *node {
-	n, ok := nm[p]
-	if !ok {
-		n = &node{
-			pather: p,
-		}
-		nm[p] = n
-	}
-	return n
-}
-
 // Path calculates a short path and the distance between the two Pather nodes.
 //
 // If no path is found, found will be false.
 func Path(from, to Pather) (path []Pather, distance float64, found bool) {
-	nm := nodeMap{}
-	nq := &priorityQueue{}
-	heap.Init(nq)
-	fromNode := nm.get(from)
-	fromNode.open = true
-	heap.Push(nq, fromNode)
-	for {
-		if nq.Len() == 0 {
-			// There's no path, return found false.
-			return
-		}
-		current := heap.Pop(nq).(*node)
-		current.open = false
-		current.closed = true
+	fromNode := &node{pather: from}
+	closeset := nodeMap{from: fromNode}
+	openset := &priorityQueue{fromNode}
+	heap.Init(openset)
+	for openset.Len() > 0 {
+		current := heap.Pop(openset).(*node)
 
-		if current == nm.get(to) {
+		if current.pather == to {
 			// Found a path to the goal.
 			p := []Pather{}
 			curr := current
@@ -74,22 +52,23 @@ func Path(from, to Pather) (path []Pather, distance float64, found bool) {
 		}
 
 		for _, neighbor := range current.pather.PathNeighbors() {
-			cost := current.cost + current.pather.PathNeighborCost(neighbor)
-			neighborNode := nm.get(neighbor)
-			if cost < neighborNode.cost {
-				if neighborNode.open {
-					heap.Remove(nq, neighborNode.index)
-				}
-				neighborNode.open = false
-				neighborNode.closed = false
+			neighborNode, exists := closeset[neighbor]
+			if !exists {
+				neighborNode = &node{pather: neighbor}
+				closeset[neighbor] = neighborNode
 			}
-			if !neighborNode.open && !neighborNode.closed {
+			cost := current.cost + current.pather.PathNeighborCost(neighbor)
+			if !exists || cost < neighborNode.cost {
 				neighborNode.cost = cost
-				neighborNode.open = true
 				neighborNode.rank = cost + neighbor.PathEstimatedCost(to)
 				neighborNode.parent = current
-				heap.Push(nq, neighborNode)
+				if exists {
+					heap.Fix(openset, neighborNode.index)
+				} else {
+					heap.Push(openset, neighborNode)
+				}
 			}
 		}
 	}
+	return
 }