Move all crates to a top-level crates folder

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/buffer/src/selection.rs

@@ -0,0 +1,75 @@
+use crate::{Anchor, Buffer, Point, ToOffset as _, ToPoint as _};
+use std::{cmp::Ordering, mem, ops::Range};
+
+pub type SelectionSetId = clock::Lamport;
+pub type SelectionsVersion = usize;
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum SelectionGoal {
+    None,
+    Column(u32),
+    ColumnRange { start: u32, end: u32 },
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct Selection {
+    pub id: usize,
+    pub start: Anchor,
+    pub end: Anchor,
+    pub reversed: bool,
+    pub goal: SelectionGoal,
+}
+
+impl Selection {
+    pub fn head(&self) -> &Anchor {
+        if self.reversed {
+            &self.start
+        } else {
+            &self.end
+        }
+    }
+
+    pub fn set_head(&mut self, buffer: &Buffer, cursor: Anchor) {
+        if cursor.cmp(self.tail(), buffer).unwrap() < Ordering::Equal {
+            if !self.reversed {
+                mem::swap(&mut self.start, &mut self.end);
+                self.reversed = true;
+            }
+            self.start = cursor;
+        } else {
+            if self.reversed {
+                mem::swap(&mut self.start, &mut self.end);
+                self.reversed = false;
+            }
+            self.end = cursor;
+        }
+    }
+
+    pub fn tail(&self) -> &Anchor {
+        if self.reversed {
+            &self.end
+        } else {
+            &self.start
+        }
+    }
+
+    pub fn point_range(&self, buffer: &Buffer) -> Range<Point> {
+        let start = self.start.to_point(buffer);
+        let end = self.end.to_point(buffer);
+        if self.reversed {
+            end..start
+        } else {
+            start..end
+        }
+    }
+
+    pub fn offset_range(&self, buffer: &Buffer) -> Range<usize> {
+        let start = self.start.to_offset(buffer);
+        let end = self.end.to_offset(buffer);
+        if self.reversed {
+            end..start
+        } else {
+            start..end
+        }
+    }
+}