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);
}