fix: page up and down stop at the table edges instead of wrapping

A page is 20 rows and the index wrapped modulo one less than the row
count, so the last row was unreachable by paging, 21-row and 5-row tables
did nothing on page down from the first row, and 4-row tables cycled
0, 2, 1 and never reached row 3. Page down now clamps to the last row and
page up clamps to the first.

With no division left, a single-row table is safe, so the early return
only guards the empty table again, matching scroll_to_top and
scroll_to_bottom.

src/handlers/handler_proptest.rs

@@ -171,10 +171,19 @@ mod property_tests {
       table.set_items(movies);
 
       for i in 0..page_ops {
+        let previous_index = table.state.selected().unwrap();
+
         if i % 2 == 0 {
           table.page_down();
+
+          prop_assert_eq!(
+            table.state.selected(),
+            Some((previous_index + 20).min(list_size - 1))
+          );
         } else {
           table.page_up();
+
+          prop_assert_eq!(table.state.selected(), Some(previous_index.saturating_sub(20)));
         }
 
         let current = table.current_selection();

src/handlers/table_handler_tests.rs

@@ -606,17 +606,18 @@ mod tests {
       .take(100)
       .collect();
       app.data.radarr_data.movies.set_items(movies_vec);
+      app.data.radarr_data.movies.state.select(Some(50));
       TableHandlerUnit::new(key, &mut app, ActiveRadarrBlock::Movies, None).handle();
 
       if key == Key::PgUp {
         assert_str_eq!(
           app.data.radarr_data.movies.current_selection().title.text,
-          "Test 79"
+          "Test 30"
         );
       } else {
         assert_str_eq!(
           app.data.radarr_data.movies.current_selection().title.text,
-          "Test 20"
+          "Test 70"
         );
       }
     }

src/models/stateful_table.rs

@@ -100,29 +100,26 @@ where
 {
   fn page_down(&mut self) {
     let items_len = self.active_items().len();
-    if items_len <= 1 {
+    if items_len == 0 {
       return;
     }
 
     let state = self.active_state_mut();
     match state.selected() {
-      Some(i) => state.select(Some(i.saturating_add(20) % (items_len - 1))),
+      Some(i) => state.select(Some(i.saturating_add(20).min(items_len - 1))),
       None => state.select_first(),
     }
   }
 
   fn page_up(&mut self) {
     let items_len = self.active_items().len();
-    if items_len <= 1 {
+    if items_len == 0 {
       return;
     }
 
     let state = self.active_state_mut();
     match state.selected() {
-      Some(i) => {
-        let len = items_len - 1;
-        state.select(Some((i + len - (20 % len)) % len));
-      }
+      Some(i) => state.select(Some(i.saturating_sub(20))),
       None => state.select_last(),
     }
   }

src/models/stateful_table_tests.rs

@@ -318,6 +318,69 @@ mod tests {
       20
     );
 
+    stateful_table.page_down();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      40
+    );
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      60
+    );
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      80
+    );
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      99
+    );
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      99
+    );
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      79
+    );
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      59
+    );
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      39
+    );
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(
+      stateful_table.filtered_state.as_ref().unwrap().selected(),
+      19
+    );
+
     stateful_table.page_up();
 
     assert_some_eq_x!(
@@ -327,33 +390,10 @@ mod tests {
 
     stateful_table.page_up();
 
-    assert_some_eq_x!(
-      stateful_table.filtered_state.as_ref().unwrap().selected(),
-      stateful_table.filtered_items.as_ref().unwrap().len() - 21
-    );
-
-    stateful_table.page_down();
-
     assert_some_eq_x!(
       stateful_table.filtered_state.as_ref().unwrap().selected(),
       0
     );
-
-    stateful_table.scroll_down();
-    stateful_table.page_up();
-
-    assert_some_eq_x!(
-      stateful_table.filtered_state.as_ref().unwrap().selected(),
-      stateful_table.filtered_items.as_ref().unwrap().len() - 20
-    );
-
-    stateful_table.scroll_down();
-    stateful_table.page_down();
-
-    assert_some_eq_x!(
-      stateful_table.filtered_state.as_ref().unwrap().selected(),
-      2
-    );
   }
 
   #[test]
@@ -376,33 +416,105 @@ mod tests {
 
     assert_some_eq_x!(stateful_table.state.selected(), 20);
 
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 40);
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 60);
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 80);
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 99);
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 99);
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 79);
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 59);
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 39);
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 19);
+
     stateful_table.page_up();
 
     assert_some_eq_x!(stateful_table.state.selected(), 0);
 
     stateful_table.page_up();
 
-    assert_some_eq_x!(
-      stateful_table.state.selected(),
-      stateful_table.items.len() - 21
-    );
+    assert_some_eq_x!(stateful_table.state.selected(), 0);
+  }
 
-    stateful_table.page_down();
+  #[test]
+  fn test_stateful_table_pagination_on_twenty_one_item_table_stops_at_last_item() {
+    let mut stateful_table = StatefulTable::default();
+    stateful_table.set_items((0..21).collect());
 
     assert_some_eq_x!(stateful_table.state.selected(), 0);
 
-    stateful_table.scroll_down();
-    stateful_table.page_up();
-
-    assert_some_eq_x!(
-      stateful_table.state.selected(),
-      stateful_table.items.len() - 20
-    );
-
-    stateful_table.scroll_down();
     stateful_table.page_down();
 
-    assert_some_eq_x!(stateful_table.state.selected(), 2);
+    assert_some_eq_x!(stateful_table.state.selected(), 20);
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 20);
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 0);
+  }
+
+  #[test]
+  fn test_stateful_table_pagination_on_five_item_table_stops_at_last_item() {
+    let mut stateful_table = StatefulTable::default();
+    stateful_table.set_items((0..5).collect());
+
+    assert_some_eq_x!(stateful_table.state.selected(), 0);
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 4);
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 4);
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 0);
+  }
+
+  #[test]
+  fn test_stateful_table_pagination_on_four_item_table_reaches_last_item() {
+    let mut stateful_table = StatefulTable::default();
+    stateful_table.set_items((0..4).collect());
+
+    assert_some_eq_x!(stateful_table.state.selected(), 0);
+
+    stateful_table.page_down();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 3);
+
+    stateful_table.page_up();
+
+    assert_some_eq_x!(stateful_table.state.selected(), 0);
   }
 
   #[test]