UPDATE: Adds web app (#79)

Things missing:

* Browse mode
* Front end tests
* Storybook

base/src/test/user_model/test_on_area_selection.rs

@@ -0,0 +1,33 @@
+#![allow(clippy::unwrap_used)]
+
+use crate::{
+    constants::{DEFAULT_COLUMN_WIDTH, DEFAULT_WINDOW_WIDTH},
+    test::util::new_empty_model,
+    UserModel,
+};
+
+#[test]
+fn basic_test() {
+    let model = new_empty_model();
+    let mut model = UserModel::from_model(model);
+
+    model.on_area_selecting(2, 4).unwrap();
+    let view = model.get_selected_view();
+    assert_eq!(view.range, [1, 1, 2, 4]);
+}
+
+// this checks that is we select in the boundary we automatically scroll
+#[test]
+fn scroll_right() {
+    let model = new_empty_model();
+    let mut model = UserModel::from_model(model);
+    let window_width = DEFAULT_WINDOW_WIDTH as f64;
+    let column_width = DEFAULT_COLUMN_WIDTH;
+    let column_count = f64::floor(window_width / column_width) as i32;
+    model.set_selected_cell(3, column_count).unwrap();
+
+    model.on_area_selecting(3, column_count + 3).unwrap();
+    let view = model.get_selected_view();
+    assert_eq!(view.range, [3, column_count, 3, column_count + 3]);
+    assert_eq!(view.left_column, 4);
+}