Add more fns to update selection ranges (#38)

* feat: add push-range & set-primary-index fns

* feat: add remove-range fn

---------

Co-authored-by: meepleek <ergocrab@gmail.com>

helix-term/src/commands/engine/steel.rs

@@ -384,6 +384,21 @@ fn load_static_commands(engine: &mut Engine, generate_sources: bool) {
         set_selection,
         "Update the selection object to the current selection within the editor"
     );
+    function1!(
+        "push-range-to-selection!",
+        push_range_to_selection,
+        "Push a new range to a selection. The new selection will be the primary one"
+    );
+    function1!(
+        "set-current-selection-primary-index!",
+        set_selection_primary_index,
+        "Set the primary index of the current selection"
+    );
+    function1!(
+        "remove-current-selection-range!",
+        remove_selection_range,
+        "Remove a range from the current selection"
+    );
 
     function1!(
         "regex-selection",
@@ -4429,6 +4444,25 @@ fn set_selection(cx: &mut Context, selection: Selection) {
     doc.set_selection(view.id, selection)
 }
 
+fn push_range_to_selection(cx: &mut Context, range: Range) {
+    let (view, doc) = current!(cx.editor);
+    let selection = doc.selection(view.id).clone();
+    doc.set_selection(view.id, selection.push(range))
+}
+
+fn set_selection_primary_index(cx: &mut Context, primary_index: usize) {
+    let (view, doc) = current!(cx.editor);
+    let mut selection = doc.selection(view.id).clone();
+    selection.set_primary_index(primary_index);
+    doc.set_selection(view.id, selection)
+}
+
+fn remove_selection_range(cx: &mut Context, index: usize) {
+    let (view, doc) = current!(cx.editor);
+    let selection = doc.selection(view.id).clone();
+    doc.set_selection(view.id, selection.remove(index))
+}
+
 fn current_line_number(cx: &mut Context) -> usize {
     let (view, doc) = current_ref!(cx.editor);
     helix_core::coords_at_pos(