selection update

lib/selection.js

@@ -0,0 +1,38 @@
+export function hasSelection(selection) {
+  return selection.anchor !== null &&
+    (selection.anchor.line !== selection.head.line ||
+      selection.anchor.col !== selection.head.col);
+}
+
+export function selectedRange(selection) {
+  if (selection.anchor === null || selection.head === null) return null;
+  const a = selection.anchor;
+  const h = selection.head;
+  if (a.line === h.line && a.col === h.col) return null;
+  if (a.line < h.line || (a.line === h.line && a.col < h.col))
+    return { start: { ...a }, end: { ...h } };
+  return { start: { ...h }, end: { ...a } };
+}
+
+export function clearSelection(selection) {
+  selection.anchor = null;
+  selection.head = null;
+}
+
+export function deleteSelection(buffer, cursor, selection) {
+  const range = selectedRange(selection);
+  if (!range) return;
+  const { start, end } = range;
+  if (start.line === end.line) {
+    const line = buffer[start.line];
+    buffer[start.line] = line.slice(0, start.col) + line.slice(end.col);
+  } else {
+    const before = buffer[start.line].slice(0, start.col);
+    const after = buffer[end.line].slice(end.col);
+    buffer[start.line] = before + after;
+    buffer.splice(start.line + 1, end.line - start.line);
+  }
+  cursor.line = start.line;
+  cursor.col = start.col;
+  clearSelection(selection);
+}