From 289bddc9172011b34e5cddd6fe54ab5ee3828733 Mon Sep 17 00:00:00 2001
From: Ryan Reilly <ryanreilly703@gmail.com>
Date: Thu, 4 Apr 2024 12:23:24 -0400
Subject: [PATCH] Proof mode does not prevent CTRL+Y on clear

---
 src/ProofHistory/ProofHistory.ts |  2 +-
 src/TreeContext.ts               | 23 +++++++++++++++++------
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/ProofHistory/ProofHistory.ts b/src/ProofHistory/ProofHistory.ts
index 20ad9322..b18ee945 100644
--- a/src/ProofHistory/ProofHistory.ts
+++ b/src/ProofHistory/ProofHistory.ts
@@ -86,5 +86,5 @@ export function deleteButtons(stopIndex: number): void {
  * Removes the most recent move's button from the proof bar.
  */
 export function deleteMostRecentButton(): void {
-    document.getElementById("Row: " + TreeContext.proof.length)?.remove();
+    document.getElementById("Row: " + (TreeContext.proof.length + 1))?.remove();
 }
diff --git a/src/TreeContext.ts b/src/TreeContext.ts
index 70c5948c..fb2a9d7b 100644
--- a/src/TreeContext.ts
+++ b/src/TreeContext.ts
@@ -147,17 +147,22 @@ export class TreeContext {
      */
     public static undoProofStep(): void {
         if (this.proof.length <= 1) {
-            this.clearProof();
             return;
         }
 
-        const stepToRemove: ProofModeNode = this.proof[this.proof.length - 1];
+        const mostRecentStep: ProofModeNode | undefined = this.proof.pop();
+
+        if (mostRecentStep === undefined) {
+            return;
+        } else if (this.proof.length === 0) {
+            deleteMostRecentButton();
+            return;
+        }
 
         deleteMostRecentButton();
 
-        this.proofHistoryRedoStack.push(stepToRemove);
+        this.proofHistoryRedoStack.push(mostRecentStep);
 
-        this.proof.pop();
         stepBack(this.proof[this.proof.length - 1]);
         redrawProof();
 
@@ -174,7 +179,13 @@ export class TreeContext {
 
         const mostRecentStep: ProofModeNode | undefined = this.proofHistoryRedoStack.pop();
 
-        if (mostRecentStep === undefined || this.proof[this.proof.length - 1] === undefined) {
+        if (mostRecentStep === undefined) {
+            return;
+        } else if (
+            this.proofHistoryRedoStack[this.proofHistoryRedoStack.length - 1] === undefined
+        ) {
+            this.pushToProof(mostRecentStep);
+            redrawProof();
             return;
         }
 
@@ -182,7 +193,7 @@ export class TreeContext {
 
         this.pushToProof(mostRecentStep);
 
-        stepBack(this.proof[this.proof.length - 1]);
+        stepBack(mostRecentStep);
         redrawProof();
     }