fix(console-wallet): fix possible subtract underflow panic in list (#…

…5535)

Description
---
Fix possible subtract with underflow panic in console wallet list state

Motivation and Context
---
Ref #5465 

Unable to reproduce this exact panic manually however added a test case
which causes the same panic. I was previously able to reproduce this
every time, either this has been fixed in other changes or the
reproduction steps did not include some mix of circumstances that were
pertinent to the bug. In any case, this PR fixes a bug in select_first
function which uses the binary compliment where a boolean inequality
check was likely intended !self.num_items == 0 vs self.num_items != 0,
though strangely the correct logic is 'if self.num_items == 0 {'. On an
empty list this causes a non-existent first item at index 0 to be
selected, a call to update_list_state would panic.

How Has This Been Tested?
---
Unit test that reproduces the same underflow panic in #5465, although
the send to contact list does not use select_first
Manually

What process can a PR reviewer use to test or verify this change?
---

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Breaking Changes
---

- [x] None
- [ ] Requires data directory on base node to be deleted
- [ ] Requires hard fork
- [ ] Other - Please specify

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applications/tari_console_wallet/src/ui/components/burn_tab.rs

@@ -234,7 +234,7 @@ impl BurnTab {
 
         let mut list_state = self
             .proofs_list_state
-            .get_list_state((list_areas[1].height as usize).saturating_sub(3));
+            .update_list_state((list_areas[1].height as usize).saturating_sub(3));
 
         let window = self.proofs_list_state.get_start_end();
         let windowed_view = app_state.get_burnt_proofs_slice(window.0, window.1);

applications/tari_console_wallet/src/ui/components/contacts_tab.rs

@@ -76,7 +76,7 @@ impl ContactsTab {
         self.contacts_list_state.set_num_items(app_state.get_contacts().len());
         let mut list_state = self
             .contacts_list_state
-            .get_list_state((list_areas[1].height as usize).saturating_sub(3));
+            .update_list_state((list_areas[1].height as usize).saturating_sub(3));
         let window = self.contacts_list_state.get_start_end();
         let windowed_view = app_state.get_contacts_slice(window.0, window.1);
 

applications/tari_console_wallet/src/ui/components/network_tab.rs

@@ -113,7 +113,7 @@ impl NetworkTab {
         self.base_node_list_state.set_num_items(capacity);
         let mut base_node_list_state = self
             .base_node_list_state
-            .get_list_state((areas[1].height as usize).saturating_sub(3));
+            .update_list_state((areas[1].height as usize).saturating_sub(3));
 
         let column_list = MultiColumnList::new()
             .highlight_style(Style::default().add_modifier(Modifier::BOLD).fg(Color::Magenta))

applications/tari_console_wallet/src/ui/components/send_tab.rs

@@ -198,7 +198,6 @@ impl SendTab {
         }
     }
 
-    #[allow(dead_code)]
     fn draw_contacts<B>(&mut self, f: &mut Frame<B>, area: Rect, app_state: &AppState)
     where B: Backend {
         let block = Block::default().borders(Borders::ALL).title(Span::styled(
@@ -223,7 +222,7 @@ impl SendTab {
         self.contacts_list_state.set_num_items(app_state.get_contacts().len());
         let mut list_state = self
             .contacts_list_state
-            .get_list_state((list_areas[1].height as usize).saturating_sub(3));
+            .update_list_state((list_areas[1].height as usize).saturating_sub(3));
         let window = self.contacts_list_state.get_start_end();
         let windowed_view = app_state.get_contacts_slice(window.0, window.1);
 

applications/tari_console_wallet/src/ui/components/transactions_tab.rs

@@ -86,7 +86,7 @@ impl TransactionsTab {
         self.pending_list_state.set_num_items(app_state.get_pending_txs().len());
         let mut pending_list_state = self
             .pending_list_state
-            .get_list_state((area.height as usize).saturating_sub(3));
+            .update_list_state((area.height as usize).saturating_sub(3));
         let window = self.pending_list_state.get_start_end();
         let windowed_view = app_state.get_pending_txs_slice(window.0, window.1);
 
@@ -186,7 +186,7 @@ impl TransactionsTab {
         }
         let mut completed_list_state = self
             .completed_list_state
-            .get_list_state((area.height as usize).saturating_sub(3));
+            .update_list_state((area.height as usize).saturating_sub(3));
         let (start, end) = self.completed_list_state.get_start_end();
         let windowed_view = &completed_txs[start..end];
 

applications/tari_console_wallet/src/ui/widgets/list_state.rs

@@ -41,7 +41,7 @@ impl WindowedListState {
         }
     }
 
-    pub fn get_list_state(&mut self, height: usize) -> ListState {
+    pub fn update_list_state(&mut self, height: usize) -> ListState {
         // Update the offset based on current offset, selected value and height
         self.start = self.offset;
         let view_height = height.min(self.num_items);
@@ -123,7 +123,7 @@ impl WindowedListState {
     }
 
     pub fn select_first(&mut self) {
-        if !self.num_items == 0 {
+        if self.num_items == 0 {
             self.selected = None;
         } else {
             self.selected = Some(0);
@@ -136,8 +136,7 @@ impl WindowedListState {
 
     pub fn set_num_items(&mut self, num_items: usize) {
         if num_items < self.num_items {
-            let new_offset = self.offset.saturating_sub(self.num_items - num_items);
-            self.offset = new_offset;
+            self.offset = self.offset.saturating_sub(self.num_items - num_items);
         }
         self.num_items = num_items;
         if num_items > 0 {
@@ -157,6 +156,38 @@ mod test {
     use std::convert::TryFrom;
 
     use crate::ui::widgets::WindowedListState;
+
+    #[test]
+    fn test_zero_items() {
+        let mut list_state = WindowedListState::new();
+        list_state.previous();
+        assert_eq!(list_state.selected(), None);
+        list_state.next();
+        assert_eq!(list_state.selected(), None);
+        list_state.update_list_state(5);
+        assert_eq!(list_state.selected(), None);
+        assert_eq!(list_state.get_start_end(), (0, 0));
+
+        list_state.set_num_items(5);
+        list_state.set_num_items(0);
+        list_state.previous();
+        assert_eq!(list_state.selected(), None);
+        list_state.next();
+        assert_eq!(list_state.selected(), None);
+        list_state.update_list_state(5);
+        assert_eq!(list_state.selected(), None);
+        assert_eq!(list_state.get_start_end(), (0, 0));
+    }
+
+    #[test]
+    fn test_select_first() {
+        let mut list_state = WindowedListState::new();
+        list_state.set_num_items(0);
+        list_state.select_first();
+        list_state.update_list_state(5);
+        assert_eq!(list_state.selected(), None);
+    }
+
     #[test]
     fn test_list_offset_update() {
         let slist = vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
@@ -165,24 +196,24 @@ mod test {
         let height = 4;
         for i in 0..6 {
             list_state.next();
-            let state = list_state.get_list_state(height);
+            let state = list_state.update_list_state(height);
             assert_eq!(state.selected(), Some(i.min(height - 1)));
         }
-        list_state.get_list_state(height);
+        list_state.update_list_state(height);
         let window = list_state.get_start_end();
         assert_eq!(slist[window.0..window.1], [2, 3, 4, 5]);
 
         for i in (0..5).rev() {
             list_state.previous();
-            let state = list_state.get_list_state(height);
+            let state = list_state.update_list_state(height);
             assert_eq!(state.selected(), Some(usize::try_from((i - 2i32).max(0)).unwrap()));
         }
-        list_state.get_list_state(height);
+        list_state.update_list_state(height);
         let window = list_state.get_start_end();
         assert_eq!(slist[window.0..window.1], [0, 1, 2, 3]);
 
         list_state.previous();
-        let state = list_state.get_list_state(height);
+        let state = list_state.update_list_state(height);
         assert_eq!(state.selected(), Some(height - 1));
         let window = list_state.get_start_end();
         assert_eq!(slist[window.0..window.1], [7, 8, 9, 10]);
@@ -194,12 +225,12 @@ mod test {
         list_state.set_num_items(11);
         for _ in 0..11 {
             list_state.next();
-            let _state = list_state.get_list_state(4);
+            let _state = list_state.update_list_state(4);
         }
 
         list_state.set_num_items(9);
 
-        let _state = list_state.get_list_state(4);
+        let _state = list_state.update_list_state(4);
         let window = list_state.get_start_end();
         assert_eq!(window, (5, 9));
     }
@@ -212,13 +243,13 @@ mod test {
         // Go to the last item (2 times previous).
         list_state.previous();
         list_state.previous();
-        list_state.get_list_state(5);
+        list_state.update_list_state(5);
         assert_eq!(list_state.get_start_end(), (15, 20));
         // Resize to 10.
-        list_state.get_list_state(10);
+        list_state.update_list_state(10);
         assert_eq!(list_state.get_start_end(), (10, 20));
         // Resize to 50.
-        list_state.get_list_state(50);
+        list_state.update_list_state(50);
         assert_eq!(list_state.get_start_end(), (0, 20));
     }
 }