sysadmin reconstruct terms and conditions pages (#4231)

* sysadmin reconstruct terms and conditions pages

* update seafile-js version

* add term content dialog

* optimized code struct

* fix redirect logic after add term

* optimized code

* optimized code

* update seafile-editor version

frontend/src/utils/markdown-utils.js

@@ -0,0 +1,54 @@
+const hrefReg = /\[.+\]\(\S+\)|<img src=(\S+).+\/>|!\[\]\(\S+\)|<\S+>/g,
+  imageReg1 = /^<img src="(\S+)" .+\/>/,
+  imageReg2 = /^!\[\]\((\S+)\)/,
+  linkReg1 = /^\[.+\]\(\S+\)/,
+  linkReg2 = /^<\S+>$/;
+
+const getLinks = (hrefs) => {
+  const hrefObj = {
+    links: [],
+    images: []
+  };
+  hrefs.forEach((href) => {
+    if (href.search(linkReg1) >= 0 || href.search(linkReg2) >= 0) {
+      hrefObj.links.push(href);
+    } else {
+      let imageSrcs = href.match(imageReg1);
+      let imageSrcs1 = href.match(imageReg2);
+      if (imageSrcs) {
+        hrefObj.images.push(imageSrcs[1]);
+      } else if (imageSrcs1) {
+        hrefObj.images.push(imageSrcs1[1]);
+      }
+    }
+  });
+  return hrefObj;
+};
+
+
+const getPreviewContent = (markdownContent) => {
+  let previewText = '';
+  let newMarkdownContent = markdownContent.replace(hrefReg, '');
+  for (let index = 0; index < newMarkdownContent.length; index++) {
+    if (newMarkdownContent[index] === '#') {
+      continue;
+    } else if (newMarkdownContent[index] === '\n') {
+      previewText += ' ';
+    } else {
+      previewText += newMarkdownContent[index];
+    }
+    if (previewText.length === 30) {
+      break;
+    }
+  }
+
+  const hrefs = markdownContent.match(hrefReg);
+  if (hrefs) {
+    const { images, links } = getLinks(hrefs);
+    return { previewText, images, links };
+  }
+  return { previewText, images: [], links: [] };
+};
+
+
+export default getPreviewContent;