From 3bb902b03316e422573e1b574c5d4a676f3a4086 Mon Sep 17 00:00:00 2001
From: JP1998 <littlebigjonny06@gmail.com>
Date: Tue, 28 May 2019 16:54:51 +0200
Subject: [PATCH 1/3] Check for invalid inputs before applying new group size

---
 pages/create.js | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/pages/create.js b/pages/create.js
index 5cfa2ec..2fdc781 100644
--- a/pages/create.js
+++ b/pages/create.js
@@ -163,12 +163,14 @@ class CreateTournamentForm extends React.Component {
 
     handleGroupSizeInput(input) {
         const newSize = input.target.value;
-        if (newSize <= this.state.groupAdvance) {
-            this.setState({
-                groupSize: newSize, groupAdvance: newSize - 1
-            });
-        } else {
-            this.setState({groupSize: newSize});
+        if (newSize !== undefined && newSize > 2) {
+            if (newSize <= this.state.groupAdvance) {
+                this.setState({
+                    groupSize: newSize, groupAdvance: newSize - 1
+                });
+            } else {
+                this.setState({groupSize: newSize});
+            }
         }
     }
 

From 2defc3df22dce66eb94274949ed2861156938267 Mon Sep 17 00:00:00 2001
From: JP1998 <littlebigjonny06@gmail.com>
Date: Tue, 28 May 2019 22:55:19 +0200
Subject: [PATCH 2/3] Refactor the handleGroupSizeInput method

---
 pages/create.js | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/pages/create.js b/pages/create.js
index 2fdc781..b49123f 100644
--- a/pages/create.js
+++ b/pages/create.js
@@ -163,14 +163,17 @@ class CreateTournamentForm extends React.Component {
 
     handleGroupSizeInput(input) {
         const newSize = input.target.value;
-        if (newSize !== undefined && newSize > 2) {
-            if (newSize <= this.state.groupAdvance) {
-                this.setState({
-                    groupSize: newSize, groupAdvance: newSize - 1
-                });
-            } else {
-                this.setState({groupSize: newSize});
-            }
+        
+        if (newSize === undefined || newSize < 2) {
+            return;
+        }
+
+        if (newSize <= this.state.groupAdvance) {
+            this.setState({
+                groupSize: newSize, groupAdvance: newSize - 1
+            });
+        } else {
+            this.setState({groupSize: newSize});
         }
     }
 

From 3fc8a5d2917fc30a223dd6472c5ceb96496f2935 Mon Sep 17 00:00:00 2001
From: JP1998 <littlebigjonny06@gmail.com>
Date: Tue, 28 May 2019 22:57:41 +0200
Subject: [PATCH 3/3] Check the group advance input for valid values

---
 pages/create.js | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/pages/create.js b/pages/create.js
index b49123f..97a3755 100644
--- a/pages/create.js
+++ b/pages/create.js
@@ -163,7 +163,7 @@ class CreateTournamentForm extends React.Component {
 
     handleGroupSizeInput(input) {
         const newSize = input.target.value;
-        
+
         if (newSize === undefined || newSize < 2) {
             return;
         }
@@ -178,7 +178,14 @@ class CreateTournamentForm extends React.Component {
     }
 
     handleGroupAdvanceInput(input) {
-        this.setState({groupAdvance: input.target.value});
+        const newAdvance = input.target.value;
+
+        if (newAdvance === undefined || newAdvance <= 0 ||
+            newAdvance >= this.state.groupSize) {
+            return;
+        }
+
+        this.setState({groupAdvance: newAdvance});
     }
 
     handleGroupPhaseEnabledInput(input) {