feat(ui): allow zooming in/out/reset (#61)

* feat(ui): allow zooming in/out/reset

* style(format): rustfmt

* refactor(state): consolidate percentage calculation

* style(format): rustfmt

* fix(tests): clean up temporary files in specific test

40 files changed, 665 insertions, 51 deletions

diff --git a/src/app.rs b/src/app.rs
index 9865d4d..7e6e68c 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -164,15 +164,14 @@ where
         self.render();
     }
     pub fn enter_selected(&mut self) {
-        if let Some(index) = &self.board.get_selected_index() {
-            &self.board.push_previous_index(&index);
-        }
+        self.board.record_current_index_and_zoom_level();
         if let Some(tile) = &self.board.currently_selected() {
             let selected_name = &tile.name;
             if let Some(file_or_folder) = self.file_tree.item_in_current_folder(&selected_name) {
                 match file_or_folder {
                     FileOrFolder::Folder(_) => {
                         self.file_tree.enter_folder(&selected_name);
+                        self.board.reset_zoom_index();
                         self.board.reset_selected_index();
                         self.render_and_update_board();
                     }
@@ -182,10 +181,13 @@ where
         }
     }
     pub fn go_up(&mut self) {
-        if let Some(index) = self.board.pop_previous_index() {
-            self.board.set_selected_index(&index);
-        }
         let succeeded = self.file_tree.leave_folder();
+        if let Some((index, zoom_level)) = self.board.pop_previous_index_and_zoom_level() {
+            if let Some(index) = index {
+                self.board.set_selected_index(&index);
+            }
+            self.board.set_zoom_index(zoom_level);
+        }
         self.render_and_update_board();
         if !succeeded {
             let _ = self.event_sender.try_send(Event::PathError);
@@ -250,6 +252,21 @@ where
     pub fn increment_failed_to_read(&mut self) {
         self.file_tree.failed_to_read += 1;
     }
+    pub fn zoom_in(&mut self) {
+        let current_folder = self.file_tree.get_current_folder();
+        self.board.zoom_in(current_folder);
+        self.render();
+    }
+    pub fn zoom_out(&mut self) {
+        let current_folder = self.file_tree.get_current_folder();
+        self.board.zoom_out(current_folder);
+        self.render();
+    }
+    pub fn reset_zoom(&mut self) {
+        let current_folder = self.file_tree.get_current_folder();
+        self.board.reset_zoom(current_folder);
+        self.render();
+    }
     fn remove_file_from_ui(&mut self, file_to_delete: &FileToDelete) {
         self.file_tree.space_freed += file_to_delete.size;
         self.file_tree.delete_file(file_to_delete);
diff --git a/src/input/controls.rs b/src/input/controls.rs
index 14b8ee1..4adaca9 100644
--- a/src/input/controls.rs
+++ b/src/input/controls.rs
@@ -49,6 +49,15 @@ pub fn handle_keypress_loading_mode<B: Backend>(evt: Event, app: &mut App<B>) {
         key!(char 'k') | key!(Up) | key!(ctrl 'p') => {
             app.move_selected_up();
         }
+        key!(char '+') => {
+            app.zoom_in();
+        }
+        key!(char '-') => {
+            app.zoom_out();
+        }
+        key!(char '0') => {
+            app.reset_zoom();
+        }
         key!(char '\n') => {
             app.handle_enter();
         }
@@ -82,6 +91,15 @@ pub fn handle_keypress_normal_mode<B: Backend>(evt: Event, app: &mut App<B>) {
         key!(char 'k') | key!(Up) | key!(ctrl 'p') => {
             app.move_selected_up();
         }
+        key!(char '+') => {
+            app.zoom_in();
+        }
+        key!(char '-') => {
+            app.zoom_out();
+        }
+        key!(char '0') => {
+            app.reset_zoom();
+        }
         key!(char '\n') => {
             app.handle_enter();
         }
diff --git a/src/state/tiles/board.rs b/src/state/tiles/board.rs
index 851a6f9..6537371 100644
--- a/src/state/tiles/board.rs
+++ b/src/state/tiles/board.rs
@@ -8,7 +8,8 @@ pub struct Board {
     pub tiles: Vec<Tile>,
     pub unrenderable_tile_coordinates: Option<(u16, u16)>,
     pub selected_index: Option<usize>, // None means nothing is selected
-    pub previous_indices: Vec<usize>,  // Stack of previously selected indices
+    pub previous_indices_and_zoom_level: Vec<(Option<usize>, usize)>, // Stack of previous stats
+    pub zoom_level: usize,
     area: Rect,
     files: Vec<FileMetadata>,
 }
@@ -18,9 +19,10 @@ impl Board {
         Board {
             tiles: vec![],
             unrenderable_tile_coordinates: None,
-            files: files_in_folder(folder),
+            files: files_in_folder(folder, 0),
             selected_index: None,
-            previous_indices: vec![],
+            previous_indices_and_zoom_level: vec![],
+            zoom_level: 0,
             area: Rect {
                 x: 0,
                 y: 0,
@@ -30,7 +32,7 @@ impl Board {
         }
     }
     pub fn change_files(&mut self, folder: &Folder) {
-        self.files = files_in_folder(folder);
+        self.files = files_in_folder(folder, self.zoom_level);
         self.fill();
     }
     pub fn change_area(&mut self, area: &Rect) {
@@ -63,11 +65,8 @@ impl Board {
             None => None,
         }
     }
-    pub fn push_previous_index(&mut self, index: &usize) {
-        self.previous_indices.push(*index);
-    }
-    pub fn pop_previous_index(&mut self) -> Option<usize> {
-        self.previous_indices.pop()
+    pub fn pop_previous_index_and_zoom_level(&mut self) -> Option<(Option<usize>, usize)> {
+        self.previous_indices_and_zoom_level.pop()
     }
     pub fn move_to_largest_folder(&mut self) {
         let next_index = self
@@ -170,4 +169,33 @@ impl Board {
             None => self.set_selected_index(&0),
         }
     }
+    pub fn zoom_in(&mut self, folder: &Folder) {
+        if self.zoom_level < self.files.len() {
+            self.zoom_level += 1;
+            self.files = files_in_folder(folder, self.zoom_level);
+            self.fill();
+        }
+    }
+    pub fn zoom_out(&mut self, folder: &Folder) {
+        if self.zoom_level > 0 {
+            self.zoom_level -= 1;
+            self.files = files_in_folder(folder, self.zoom_level);
+            self.fill();
+        }
+    }
+    pub fn reset_zoom(&mut self, folder: &Folder) {
+        self.zoom_level = 0;
+        self.files = files_in_folder(folder, self.zoom_level);
+        self.fill();
+    }
+    pub fn reset_zoom_index(&mut self) {
+        self.zoom_level = 0;
+    }
+    pub fn set_zoom_index(&mut self, index: usize) {
+        self.zoom_level = index;
+    }
+    pub fn record_current_index_and_zoom_level(&mut self) {
+        self.previous_indices_and_zoom_level
+            .push((self.get_selected_index(), self.zoom_level));
+    }
 }
diff --git a/src/state/tiles/files_in_folder.rs b/src/state/tiles/files_in_folder.rs
index e6c696f..a8a0065 100644
--- a/src/state/tiles/files_in_folder.rs
+++ b/src/state/tiles/files_in_folder.rs
@@ -17,7 +17,17 @@ pub struct FileMetadata {
     pub file_type: FileType,
 }
 
-pub fn files_in_folder(folder: &Folder) -> Vec<FileMetadata> {
+fn calculate_percentage(size: u64, total_size: u64, total_files_in_parent: usize) -> f64 {
+    if size == 0 && total_size == 0 {
+        // if all files in the folder are of size 0, we'll want to display them all as
+        // the same size
+        1.0 / total_files_in_parent as f64
+    } else {
+        size as f64 / total_size as f64
+    }
+}
+
+pub fn files_in_folder(folder: &Folder, offset: usize) -> Vec<FileMetadata> {
     let mut files = Vec::new();
     let total_size = folder.size;
     for (name, file_or_folder) in &folder.contents {
@@ -28,13 +38,7 @@ pub fn files_in_folder(folder: &Folder) -> Vec<FileMetadata> {
                 FileOrFolder::Folder(folder) => (Some(folder.num_descendants), FileType::Folder),
                 FileOrFolder::File(_file) => (None, FileType::File),
             };
-            let percentage = if size == 0 && total_size == 0 {
-                // if all files in the folder are of size 0, we'll want to display them all as
-                // the same size
-                1.0 / folder.contents.len() as f64
-            } else {
-                size as f64 / total_size as f64
-            };
+            let percentage = calculate_percentage(size, total_size, folder.contents.len());
             FileMetadata {
                 size,
                 name,
@@ -53,5 +57,18 @@ pub fn files_in_folder(folder: &Folder) -> Vec<FileMetadata> {
                 .expect("could not compare percentage")
         }
     });
+    if offset > 0 {
+        let removed_items = files.drain(..offset);
+        let number_of_files_without_removed_contents = folder.contents.len() - removed_items.len();
+        let removed_size = removed_items.fold(0, |acc, file| acc + file.size);
+        let size_without_removed_items = total_size - removed_size;
+        for i in 0..files.len() {
+            files[i].percentage = calculate_percentage(
+                files[i].size,
+                size_without_removed_items,
+                number_of_files_without_removed_contents,
+            );
+        }
+    }
     files
 }
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__cannot_move_into_small_files.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__cannot_move_into_small_files.snap
index a08c8fd..1e4b6fe 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__cannot_move_into_small_files.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__cannot_move_into_small_files.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                                                                          │xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx│
 └──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴─────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__clear_selection_when_moving_off_screen_edges.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__clear_selection_when_moving_off_screen_edges.snap
index 149da00..f5f0d6a 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__clear_selection_when_moving_off_screen_edges.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__clear_selection_when_moving_off_screen_edges.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                                             │                                                              │
 └─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────────────────────────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_file.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_file.snap
index e13f850..3f86673 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_file.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_file.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                                             │                                                              │
 └─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────────────────────────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_file_press_n.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_file_press_n.snap
index 8c5cc1f..901267c 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_file_press_n.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_file_press_n.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                                             │                                                              │
 └─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────────────────────────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_folder.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_folder.snap
index cf2d4a0..dade986 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_folder.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_folder.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                                             │                                                              │
 └─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────────────────────────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_folder_with_multiple_children.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_folder_with_multiple_children.snap
index c1b9450..7ee834d 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_folder_with_multiple_children.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__delete_folder_with_multiple_children.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                                                        │                                                   │
 └────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────────────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__eleven_files.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__eleven_files.snap
index dceda71..5bcf46e 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__eleven_files.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__eleven_files.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                         │                                              │             8.0K (2%)             │
 └─────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────────────────────────────────────┴───────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__empty_folder.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__empty_folder.snap
index b61e3bf..e561220 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__empty_folder.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__empty_folder.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████│
 └────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__enter_folder.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__enter_folder.snap
index 7d7fad2..2de6006 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__enter_folder.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__enter_folder.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                                                             │                                              │
 └─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__enter_largest_folder_with_no_selected_tile.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__enter_largest_folder_with_no_selected_tile.snap
index 5f82bd2..deafd8c 100644
--- a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__enter_largest_folder_with_no_selected_tile.snap
+++ b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__enter_largest_folder_with_no_selected_tile.snap
@@ -51,5 +51,5 @@ expression: "&terminal_draw_events_mirror[0]"
 │                                                                                                                                             │                                              │
 └─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────────────────────────────────────┘
                                                                                                                                                                             (x = Small files) 
- <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <q> - quit                                                                                         
+ <arrows> - move around, <ENTER> - enter folder, <ESC> - parent folder, <DELETE> - delete, <+/-/0> - zoom in/out/reset, <q> - quit                                                            
 
diff --git a/src/tests/cases/snapshots/diskonaut__tests__cases__ui__esc_to_go_up.snap b/src/tests/cases/snapshots/diskonaut__tests__cases__ui__esc_to_go_up.snap
index 47ff99c..79bae57 100644
--- a/src/tests/cases/sna