From 78e0adb1750546923ac6da44614df060b8e080de Mon Sep 17 00:00:00 2001
From: Adam Janicki <adamjanicki2@gmail.com>
Date: Tue, 12 Mar 2024 16:29:10 -0400
Subject: [PATCH 1/3] `walkUp` function

---
 src/index-fn.js |  1 +
 src/walkUp.js   | 22 ++++++++++++++++++++++
 test/walkUp.js  | 26 ++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)
 create mode 100644 src/walkUp.js
 create mode 100644 test/walkUp.js

diff --git a/src/index-fn.js b/src/index-fn.js
index f2640da..e03f685 100644
--- a/src/index-fn.js
+++ b/src/index-fn.js
@@ -9,3 +9,4 @@ export {default as closest}       from "./closest.js";
 export {default as find}          from "./find.js";
 export {default as map}           from "./map.js";
 export {default as walk}          from "./walk.js";
+export {default as walkUp}        from "./walkUp.js";
diff --git a/src/walkUp.js b/src/walkUp.js
new file mode 100644
index 0000000..a72be55
--- /dev/null
+++ b/src/walkUp.js
@@ -0,0 +1,22 @@
+import * as parents from "./parents.js";
+
+/**
+ * Walk up the tree from the given node, calling the callback on each node.
+ * @param {object} node 
+ * @param {function} callback 
+ * @returns {any} The first non-undefined value returned by the callback, or the highest ancestor node if no undefined value is ever returned.
+ */
+export default function walkUp (node, callback) {
+    let previousNode;
+    while (node) {
+        const ret = callback(node);
+        if (ret !== undefined) {
+            return ret;
+        }
+        previousNode = node;
+        const parent = parents.getParent.call(this, node);
+        // TODO: what should happen if parent is undefined (meaning no parent pointers have been set?)
+        node = parent;
+    }
+    return previousNode;
+}
\ No newline at end of file
diff --git a/test/walkUp.js b/test/walkUp.js
new file mode 100644
index 0000000..20e1d14
--- /dev/null
+++ b/test/walkUp.js
@@ -0,0 +1,26 @@
+import walkUp from "../src/walkUp.js";
+import trees from "./utils/trees.js";
+import updateParents from "../src/updateParents.js";
+import copy from "./utils/copy.js"
+
+const tree = copy(trees[0]);
+updateParents(tree);
+
+export default {
+	name: "walkUp()",
+	run (node, cb) {
+		return walkUp(node, cb);
+	},
+	tests: [
+		{
+            name: "No callback",
+			args: [tree.right, () => {}],
+			expect: tree
+		},
+        {
+            name: "Callback returns a value",
+            args: [tree.right, n => n.name === "1" ? n : undefined],
+            expect: tree
+        }
+	]
+};

From 47ef510df79b38c51fbd58a3810488cb1be74bef Mon Sep 17 00:00:00 2001
From: Adam Janicki <adamjanicki2@gmail.com>
Date: Tue, 19 Mar 2024 09:34:48 -0400
Subject: [PATCH 2/3] lint

---
 src/walkUp.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/walkUp.js b/src/walkUp.js
index 3768ac0..5e4dfe0 100644
--- a/src/walkUp.js
+++ b/src/walkUp.js
@@ -1,4 +1,4 @@
-import { getParent }from "./parents.js";
+import { getParent } from "./parents.js";
 
 /**
  * Walk up the tree from the given node, calling the callback on each node.

From f3fb08790b4af662e8dd6195329c77054eaa1193 Mon Sep 17 00:00:00 2001
From: Adam Janicki <adamjanicki2@gmail.com>
Date: Thu, 28 Mar 2024 14:56:14 -0400
Subject: [PATCH 3/3] add assertion of parent pointers

---
 src/walkUp.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/walkUp.js b/src/walkUp.js
index 5e4dfe0..ee50a89 100644
--- a/src/walkUp.js
+++ b/src/walkUp.js
@@ -1,4 +1,5 @@
 import { getParent } from "./parents.js";
+import { assertParentPointers } from "./util.js";
 
 /**
  * Walk up the tree from the given node, calling the callback on each node.
@@ -12,8 +13,7 @@ export default function walkUp (node, callback) {
 		if (ret !== undefined) {
 			return ret;
 		}
-		const parent = getParent.call(this, node);
-		// TODO: what should happen if parent is undefined (meaning no parent pointers have been set?)
-		node = parent;
+		assertParentPointers.call(this, node, "Cannot walk up the tree from a node with no parent pointer.");
+		node = getParent.call(this, node);
 	}
 }