feat: manually mirror opencoze's code from bytedance

Change-Id: I09a73aadda978ad9511264a756b2ce51f5761adf

frontend/packages/common/chat-area/utils/src/parse-markdown/parse-markdown-to-text.ts

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2025 coze-dev Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+ 
+import { type Text, type Link, type Parent, type Image } from 'mdast';
+import { isObject, isUndefined } from 'lodash-es';
+/**
+ * 将markdown转为纯文本
+ * @param markdown Markdown文本
+ * @returns string 纯文本
+ */
+export const getTextFromAst = (ast: unknown): string => {
+  if (isParent(ast)) {
+    return `${ast.children.map(child => getTextFromAst(child)).join('')}`;
+  }
+
+  if (isText(ast)) {
+    return ast.value;
+  }
+
+  if (isLink(ast)) {
+    return `[${getTextFromAst(ast.children)}](${ast.url})`;
+  }
+
+  if (isImage(ast)) {
+    return `![${ast.alt}](${ast.url})`;
+  }
+
+  return '';
+};
+
+const isParent = (ast: unknown): ast is Parent =>
+  !!ast && isObject(ast) && 'children' in ast && !isUndefined(ast?.children);
+
+const isLink = (ast: unknown): ast is Link =>
+  isObject(ast) && 'type' in ast && !isUndefined(ast) && ast.type === 'link';
+
+const isImage = (ast: unknown): ast is Image =>
+  !isUndefined(ast) && isObject(ast) && 'type' in ast && ast.type === 'image';
+
+const isText = (ast: unknown): ast is Text =>
+  !isUndefined(ast) && isObject(ast) && 'type' in ast && ast.type === 'text';
+
+export const parseMarkdownHelper = {
+  isParent,
+  isLink,
+  isImage,
+  isText,
+};