슬래시 명령 커서 복원 계산 분리

lib/markdown-slash-commands.js

@@ -279,3 +279,25 @@ export const getSlashCommandFocusTarget = (startLine, lines) => {
 
   return { line: safeStart + 1, offset: 0 }
 }
+
+/**
+ * 슬래시 명령 적용 후 textarea 선택 위치를 계산한다.
+ * @param {Object} options - 계산 옵션
+ * @param {string} options.markdown - 현재 마크다운
+ * @param {number} options.startLine - 교체 시작 줄(0-based)
+ * @param {string[]} options.lines - 삽입 줄
+ * @returns {{ start: number, end: number }} 선택 범위
+ */
+export const getSlashCommandTextareaSelection = ({ markdown, startLine, lines }) => {
+  const sourceLines = String(markdown ?? '').split('\n')
+  const safeStart = Math.max(0, Math.min(Number.isFinite(startLine) ? startLine : 0, sourceLines.length))
+  const { line, offset } = getSlashCommandFocusTarget(safeStart, lines)
+  const safeLine = Math.max(0, Math.min(line, sourceLines.length))
+  const lineStart = sourceLines.slice(0, safeLine).join('\n').length + (safeLine > 0 ? 1 : 0)
+  const selection = lineStart + offset
+
+  return {
+    start: selection,
+    end: selection
+  }
+}