1 files changed, 216 insertions, 0 deletions
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
new file mode 100644
index 00000000..269a7743
--- /dev/null
+++ b/helix-term/src/commands.rs
@@ -0,0 +1,216 @@
+use helix_core::{
+    graphemes,
+    state::{Direction, Granularity, Mode, State},
+    ChangeSet, Range, Selection, Tendril, Transaction,
+};
+
+use crate::editor::View;
+
+/// A command is a function that takes the current state and a count, and does a side-effect on the
+/// state (usually by creating and applying a transaction).
+pub type Command = fn(view: &mut View, count: usize);
+
+pub fn move_char_left(view: &mut View, count: usize) {
+    // TODO: use a transaction
+    let selection = view
+        .state
+        .move_selection(Direction::Backward, Granularity::Character, count);
+    view.state.selection = selection;
+}
+
+pub fn move_char_right(view: &mut View, count: usize) {
+    // TODO: use a transaction
+    view.state.selection =
+        view.state
+            .move_selection(Direction::Forward, Granularity::Character, count);
+}
+
+pub fn move_line_up(view: &mut View, count: usize) {
+    // TODO: use a transaction
+    view.state.selection = view
+        .state
+        .move_selection(Direction::Backward, Granularity::Line, count);
+}
+
+pub fn move_line_down(view: &mut View, count: usize) {
+    // TODO: use a transaction
+    view.state.selection = view
+        .state
+        .move_selection(Direction::Forward, Granularity::Line, count);
+}
+
+// avoid select by default by having a visual mode switch that makes movements into selects
+
+// insert mode:
+// first we calculate the correct cursors/selections
+// then we just append at each cursor
+// lastly, if it was append mode we shift cursor by 1?
+
+// inserts at the start of each selection
+pub fn insert_mode(view: &mut View, _count: usize) {
+    view.state.mode = Mode::Insert;
+
+    view.state.selection = view
+        .state
+        .selection
+        .transform(|range| Range::new(range.to(), range.from()))
+}
+
+// inserts at the end of each selection
+pub fn append_mode(view: &mut View, _count: usize) {
+    view.state.mode = Mode::Insert;
+
+    // TODO: as transaction
+    let text = &view.state.doc.slice(..);
+    view.state.selection = view.state.selection.transform(|range| {
+        // TODO: to() + next char
+        Range::new(
+            range.from(),
+            graphemes::next_grapheme_boundary(text, range.to()),
+        )
+    })
+}
+
+// TODO: I, A, o and O can share a lot of the primitives.
+
+// calculate line numbers for each selection range
+fn selection_lines(state: &State) -> Vec<usize> {
+    let mut lines = state
+        .selection
+        .ranges()
+        .iter()
+        .map(|range| state.doc.char_to_line(range.head))
+        .collect::<Vec<_>>();
+
+    lines.sort();
+    lines.dedup();
+
+    lines
+}
+
+// I inserts at the start of each line with a selection
+pub fn prepend_to_line(view: &mut View, _count: usize) {
+    view.state.mode = Mode::Insert;
+
+    let lines = selection_lines(&view.state);
+
+    let positions = lines
+        .into_iter()
+        .map(|index| {
+            // adjust all positions to the start of the line.
+            view.state.doc.line_to_char(index)
+        })
+        .map(|pos| Range::new(pos, pos));
+
+    let selection = Selection::new(positions.collect(), 0);
+
+    let transaction = Transaction::new(&mut view.state).with_selection(selection);
+
+    transaction.apply(&mut view.state);
+    // TODO: need to store into history if successful
+}
+
+// A inserts at the end of each line with a selection
+pub fn append_to_line(view: &mut View, _count: usize) {
+    view.state.mode = Mode::Insert;
+
+    let lines = selection_lines(&view.state);
+
+    let positions = lines
+        .into_iter()
+        .map(|index| {
+            // adjust all positions to the end of the line.
+            let line = view.state.doc.line(index);
+            let line_start = view.state.doc.line_to_char(index);
+            line_start + line.len_chars() - 1
+        })
+        .map(|pos| Range::new(pos, pos));
+
+    let selection = Selection::new(positions.collect(), 0);
+
+    let transaction = Transaction::new(&mut view.state).with_selection(selection);
+
+    transaction.apply(&mut view.state);
+    // TODO: need to store into history if successful
+}
+
+// o inserts a new line after each line with a selection
+pub fn open_below(view: &mut View, _count: usize) {
+    view.state.mode = Mode::Insert;
+
+    let lines = selection_lines(&view.state);
+
+    let positions: Vec<_> = lines
+        .into_iter()
+        .map(|index| {
+            // adjust all positions to the end of the line.
+            let line = view.state.doc.line(index);
+            let line_start = view.state.doc.line_to_char(index);
+            line_start + line.len_chars()
+        })
+        .collect();
+
+    let changes = positions.iter().copied().map(|index|
+        // generate changes
+        (index, index, Some(Tendril::from_char('\n'))));
+
+    // TODO: count actually inserts "n" new lines and starts editing on all of them.
+    // TODO: append "count" newlines and modify cursors to those lines
+
+    let selection = Selection::new(
+        positions
+            .iter()
+            .copied()
+            .map(|pos| Range::new(pos, pos))
+            .collect(),
+        0,
+    );
+
+    let transaction = Transaction::change(&view.state, changes).with_selection(selection);
+
+    transaction.apply(&mut view.state);
+    // TODO: need to store into history if successful
+}
+
+// O inserts a new line before each line with a selection
+
+pub fn normal_mode(view: &mut View, _count: usize) {
+    // TODO: if leaving append mode, move cursor back by 1
+    view.state.mode = Mode::Normal;
+}
+
+// TODO: insert means add text just before cursor, on exit we should be on the last letter.
+pub fn insert_char(view: &mut View, c: char) {
+    let c = Tendril::from_char(c);
+    let transaction = Transaction::insert(&view.state, c);
+
+    transaction.apply(&mut view.state);
+    // TODO: need to store into history if successful
+}
+
+// TODO: handle indent-aware delete
+pub fn delete_char_backward(view: &mut View, count: usize) {
+    let text = &view.state.doc.slice(..);
+    let transaction = Transaction::change_by_selection(&view.state, |range| {
+        (
+            graphemes::nth_prev_grapheme_boundary(text, range.head, count),
+            range.head,
+            None,
+        )
+    });
+    transaction.apply(&mut view.state);
+    // TODO: need to store into history if successful
+}
+
+pub fn delete_char_forward(view: &mut View, count: usize) {
+    let text = &view.state.doc.slice(..);
+    let transaction = Transaction::change_by_selection(&view.state, |range| {
+        (
+            graphemes::nth_next_grapheme_boundary(text, range.head, count),
+            range.head,
+            None,
+        )
+    });
+    transaction.apply(&mut view.state);
+    // TODO: need to store into history if successful
+}