1 files changed, 81 insertions, 5 deletions

diff --git a/helix-core/src/state.rs b/helix-core/src/state.rs
index 22de6ca7..682d298a 100644
--- a/helix-core/src/state.rs
+++ b/helix-core/src/state.rs
@@ -1,17 +1,30 @@
-use crate::{Buffer, Selection};
+use crate::graphemes::{nth_next_grapheme_boundary, nth_prev_grapheme_boundary};
+use crate::{Buffer, Selection, SelectionRange};
 
 /// A state represents the current editor state of a single buffer.
 pub struct State {
-    // TODO: maybe doc: ?
-    buffer: Buffer,
+    doc: Buffer,
     selection: Selection,
 }
 
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum Direction {
+    Forward,
+    Backward,
+}
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum Granularity {
+    Character,
+    Word,
+    Line,
+    // LineBoundary
+}
+
 impl State {
     #[must_use]
-    pub fn new(buffer: Buffer) -> Self {
+    pub fn new(doc: Buffer) -> Self {
         Self {
-            buffer,
+            doc,
             selection: Selection::single(0, 0),
         }
     }
@@ -40,4 +53,67 @@ impl State {
     // syntax
     // foldable
     // changeFilter/transactionFilter
+
+    pub fn move_pos(
+        &self,
+        pos: usize,
+        dir: Direction,
+        granularity: Granularity,
+        n: usize,
+    ) -> usize {
+        let text = &self.doc.contents;
+        match (dir, granularity) {
+            (Direction::Backward, Granularity::Character) => {
+                nth_prev_grapheme_boundary(&text.slice(..), pos, n)
+            }
+            (Direction::Forward, Granularity::Character) => {
+                nth_next_grapheme_boundary(&text.slice(..), pos, n)
+            }
+            _ => pos,
+        }
+    }
+
+    pub fn move_selection(
+        &self,
+        sel: Selection,
+        dir: Direction,
+        granularity: Granularity,
+        // TODO: n
+    ) -> Selection {
+        // TODO: move all selections according to normal cursor move semantics by collapsing it
+        // into cursors and moving them vertically
+
+        let ranges = sel.ranges.into_iter().map(|range| {
+            // let pos = if !range.is_empty() {
+            //     // if selection already exists, bump it to the start or end of current select first
+            //     if dir == Direction::Backward {
+            //         range.from()
+            //     } else {
+            //         range.to()
+            //     }
+            // } else {
+                let pos = self.move_pos(range.head, dir, granularity, 1)
+            // };
+            SelectionRange::new(pos, pos)
+        });
+
+        Selection::new(ranges.collect(), sel.primary_index)
+        // TODO: update selection in state via transaction
+    }
+
+    pub fn extend_selection(
+        &self,
+        sel: Selection,
+        dir: Direction,
+        granularity: Granularity,
+        n: usize,
+    ) -> Selection {
+        let ranges = sel.ranges.into_iter().map(|range| {
+            let pos = self.move_pos(range.head, dir, granularity, n);
+            SelectionRange::new(range.anchor, pos)
+        });
+
+        Selection::new(ranges.collect(), sel.primary_index)
+        // TODO: update selection in state via transaction
+    }
 }