From f8f580283bfde48503be11bbd8a6274580be6076 Mon Sep 17 00:00:00 2001
From: Martin Crawford <mcrawford@touchbistro.com>
Date: Sat, 13 Nov 2021 13:56:41 -0500
Subject: [PATCH] feat: add blocked paths function

---
 a-star/a-greedy-star.js   |  8 ++++++++
 a-star/a-star.js          |  8 ++++++++
 a-star/defaultSettings.js |  5 +++++
 package-lock.json         |  1 +
 test/a-star.js            | 43 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 65 insertions(+)

diff --git a/a-star/a-greedy-star.js b/a-star/a-greedy-star.js
index 05e0c35..4f8cb53 100644
--- a/a-star/a-greedy-star.js
+++ b/a-star/a-greedy-star.js
@@ -40,6 +40,9 @@ function aStarBi(graph, options) {
   // whether traversal should be considered over oriented graph.
   var oriented = options.oriented;
 
+  var blocked = options.blocked;
+  if (!blocked) blocked = defaultSettings.blocked;
+
   var heuristic = options.heuristic;
   if (!heuristic) heuristic = defaultSettings.heuristic;
 
@@ -182,6 +185,11 @@ function aStarBi(graph, options) {
         return;
       }
 
+      if (blocked(otherSearchState.node, cameFrom.node, link)) {
+        // Path is blocked. Ignore this route
+        return;
+      }
+
       if (canExit(otherSearchState, cameFrom)) {
         // this node was opened by alternative opener. The sets intersect now,
         // we found an optimal path, that goes through *this* node. However, there
diff --git a/a-star/a-star.js b/a-star/a-star.js
index 190a2a4..6a3b4e3 100644
--- a/a-star/a-star.js
+++ b/a-star/a-star.js
@@ -38,6 +38,9 @@ function aStarPathSearch(graph, options) {
   // whether traversal should be considered over oriented graph.
   var oriented = options.oriented;
 
+  var blocked = options.blocked;
+  if (!blocked) blocked = defaultSettings.blocked;
+
   var heuristic = options.heuristic;
   if (!heuristic) heuristic = defaultSettings.heuristic;
 
@@ -112,6 +115,11 @@ function aStarPathSearch(graph, options) {
         otherSearchState.open = 1;
       }
 
+      if (blocked(otherNode, cameFrom.node, link)) {
+        // Path is blocked. Ignore this route
+        return;
+      }
+
       var tentativeDistance = cameFrom.distanceToSource + distance(otherNode, cameFrom.node, link);
       if (tentativeDistance >= otherSearchState.distanceToSource) {
         // This would only make our path longer. Ignore this route.
diff --git a/a-star/defaultSettings.js b/a-star/defaultSettings.js
index d8ddb5d..e2c4ba2 100644
--- a/a-star/defaultSettings.js
+++ b/a-star/defaultSettings.js
@@ -7,6 +7,7 @@ module.exports = {
   // Path search settings
   heuristic: blindHeuristic,
   distance: constantDistance,
+  blocked: neverBlocked,
   compareFScore: compareFScore,
   NO_PATH: NO_PATH,
 
@@ -29,6 +30,10 @@ function constantDistance(/* a, b */) {
   return 1;
 }
 
+function neverBlocked(/* a, b, c */) {
+  return false;
+}
+
 function compareFScore(a, b) {
   var result = a.fScore - b.fScore;
   // TODO: Can I improve speed with smarter ties-breaking?
diff --git a/package-lock.json b/package-lock.json
index ee8d9ef..f2cab16 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,6 +5,7 @@
   "requires": true,
   "packages": {
     "": {
+      "name": "ngraph.path",
       "version": "1.3.1",
       "license": "MIT",
       "devDependencies": {
diff --git a/test/a-star.js b/test/a-star.js
index 5793fb8..b61edf4 100644
--- a/test/a-star.js
+++ b/test/a-star.js
@@ -27,6 +27,49 @@ test('it can find weighted', t => {
   t.end();
 });
 
+test('A* does not follow blocked paths', t => {
+  let graph = createGraph();
+
+  graph.addLink('a', 'b', {blocked: true});
+  graph.addLink('a', 'c', {blocked: false});
+  graph.addLink('c', 'd', {blocked: false});
+  graph.addLink('b', 'd', {blocked: false});
+
+
+  var pathFinder = aStar(graph, {
+    blocked(a, b, link) {
+      return link.data.blocked;
+    }
+  });
+  let path = pathFinder.find('a', 'd');
+
+  t.equal(path[0].id, 'd', 'd is here');
+  t.equal(path[1].id, 'c', 'c is here');
+  t.equal(path[2].id, 'a', 'a is here');
+  t.end();
+});
+
+test('A* greedy does not follow blocked paths', t => {
+  let graph = createGraph();
+
+  graph.addLink('a', 'b', {blocked: true});
+  graph.addLink('a', 'c', {blocked: false});
+  graph.addLink('c', 'd', {blocked: false});
+  graph.addLink('b', 'd', {blocked: false});
+
+  var pathFinder = aGreedy(graph, {
+    blocked(a, b, link) {
+      return link.data.blocked;
+    }
+  });
+  let path = pathFinder.find('a', 'd');
+
+  t.equal(path[2].id, 'd', 'd is here');
+  t.equal(path[1].id, 'c', 'c is here');
+  t.equal(path[0].id, 'a', 'a is here');
+  t.end();
+});
+
 test('A* can find directed path', t => {
   let graph = createGraph();