Implementing Version Control System for SUSI Skill CMS

SUSI Skill CMS now has a version control system where users can browse through all the previous revisions of a skill and roll back to a selected version. Users can modify existing skills and push the changes. So a skill could have been edited many times by the same or different users and so have many revisions. The version control functionalities help users to :

  • Browse through all the revisions of a selected skill
  • View the content of a selected revision
  • Compare any two selected revisions highlighting the changes
  • Option to edit and rollback to a selected revision.

Let us visit SUSI Skill CMS and try it out.

  1. Select a skill
  2. Click on versions button
  3. A table populated with previous revisions is displayed

  1. Clicking on a single revision opens the content of that version
  2. Selecting 2 versions and clicking on compare selected versions loads the content of the 2 selected revisions and shows the differences between the two.
  3. Clicking on Undo loads the selected revision and the latest version of that skill, highlighting the differences and also an editor loaded with the code of the selected revision to make changes and save to roll back.

How was this implemented?

Firstly, to get the previous revisions of a selected skill, we need the skills meta data including model, group, language and skill name which is used to make an ajax call to the server using the endpoint :

http://api.susi.ai/cms/getSkillHistory.json?model=MODEL&group=GROUP&language=LANGUAGE&skill=SKILL_NAME

We create a new component SkillVersion and pass the skill meta data in the pathname while accessing that component. The path where SkillVersion component is loaded is /:category/:skill/versions/:lang . We parse this data from the path and set our state with skill meta data. In componentDidMount we use this data to make the ajax call to the server to get all previous version data and update our state. A sample response from getSkillHistory endpoint looks like :

{
  "session": {
    "identity": {
      "type": "",
      "name": "",
      "anonymous":
    }
  },
  "commits": [
    {
      "commitRev": "",
      "author_mail": "AUTHOR_MAIL_ID",
      "author": "AUTOR_NAME",
      "commitID": "COMMIT_ID",
      "commit_message": "COMMIT_MESSAGE",
     "commitName": "COMMIT_NAME",
     "commitDate": "COMMIT_DATE"
    },
  ],
  "accepted": TRUE/FALSE
}

We now populate the table with the obtained revision history. We used Material UI Table for tabulating the data. The first 2 columns of the table have radio buttons to select any 2 revisions. The left side radio buttons are for selecting the older versions and the right side radio buttons to select the more recent versions. We keep track of the selected versions through onCheck function of the radio buttons and updating state accordingly.

if(side === 'right'){
  if(!(index >= currLeft)){
    rightChecks.fill(false);
    rightChecks[index] = true;
    currRight = index;
  }
}
else if(side === 'left'){
  if(!(index <= currRight)){
    leftChecks.fill(false);
    leftChecks[index] = true;
    currLeft = index;
  }
}
this.setState({
  currLeftChecked: currLeft,
  currRightChecked: currRight,
  leftChecks: leftChecks,
  rightChecks: rightChecks,
});

Once 2 versions are selected and we click on compare selected versions button, we get the currently selected versions stored from getCheckedCommits function and we are redirected to /:category/:skill/compare/:lang/:oldid/:recentid where we pass the selected 2 revisions commitIDs in the URL.

{(this.state.commitsChecked.length === 2) &&
<Link to={{
  pathname: '/'+this.state.skillMeta.groupValue+
            '/'+this.state.skillMeta.skillName+
            '/compare/'+this.state.skillMeta.languageValue+
            '/'+checkedCommits[0].commitID+
            '/'+checkedCommits[1].commitID,
}}>
  <RaisedButton
    label='Compare Selected Versions'
    backgroundColor='#4285f4'
    labelColor='#fff'
    style={compareBtnStyle}
  />
</Link>
}

SkillHistory Component is now loaded and the 2 selected revisions commitIDs are parsed from the URL pathname. Once we have the commitIDs we make ajax calls to the server to get the code for that particular commit. The skill meta data is also parsed from the URL path which is required to make the server call to getFileAtCommitID.

http://api.susi.ai/cms/getSkillHistory.json?model=MODEL&group=GROUP&language=LANGUAGE&skill=SKILL_NAME&commitID=COMMIT_ID

We make the ajax calls in componentDidMount and update the state with the received data. A sample response from getFileAtCommitID looks like :

{
  "accepted": TRUE/FALSE,
  "file": "CONTENT",
  "session": {
    "identity": {
       "type": "",
       "name": "",
       "anonymous":
    }
  }
}

We populate the code of each revision in an editor. We used react-ace as our editor component where we use the value prop to populate the content and display it in read-only mode.

<AceEditor
  mode='java'
  readOnly={true}
  theme={this.state.editorTheme}
  width='100%'
  fontSize={this.state.fontSizeCode}
  height= '400px'
  value={this.state.commitData[0].code}
  showPrintMargin={false}
  name='skill_code_editor'
  editorProps={{$blockScrolling: true}}
/>

We then show the differences between the 2 selected versions content. To compare and highlight the differences, we used react-diff package which takes in the content of both the commits as inputA and inputB props and we compare character by character using the type chars prop. Here input A is compared with input B. The component compares and returns the highlighted element which we display in a scrollable div preventing overflows.

{/* latest code should be inputB */}
<Diff
  inputA={this.state.commitData[0].code}
  inputB={this.state.commitData[1].code}
  type='chars'
/>

Clicking on Undo then redirects to /:category/:skill/edit/:lang/:latestid/:revertid where latest id is the commitID of the latest revision and revert id is the commitID of the oldest commit ID selected amongst the 2 commits selected initially. This redirects to SkillRollBack component where we again parse the skill meta data and the commit IDs from the URL pathname and call getFileAtCommitID to get the content for the latest and the reverting commit and again populate the content in editor using react-ace and also show the differences using react-diff and finally load the modify skill component where an editor is preloaded with the content of the reverting commit and a similar interface like modify skill is shown where user can edit the content of the reverting commit and push the changes.

let baseUrl = this.getSkillAtCommitIDUrl() ;
let self = this;
var url1 = baseUrl + self.state.latestCommit;
$.ajax({
  url: url1,
  jsonpCallback: 'pc',
  dataType: 'jsonp',
  jsonp: 'callback',
  crossDomain: true,
  success: function (data1) {
    var url2 = baseUrl + self.state.revertingCommit;
    $.ajax({
      url: url2,
      jsonpCallback: 'pd',
      dataType: 'jsonp',
      jsonp: 'callback',
      crossDomain: true,
      success: function (data2) {
        self.updateData([{
        code:data1.file,
        commitID:self.state.latestCommit,
      },{
        code:data2.file,
        commitID:self.state.revertingCommit,
      }])
      }
    });
  }
});

Here, we make nested ajax calls to maintain synchronization and update state after we receive data from both the calls else if we make ajax calls in a loop, then the second ajax call doesn’t wait for the first one to finish and is most likely to fail.

This is how the skill version system was implemented in SUSI Skill CMS. You can find the complete code at SUSI Skill CMS Repository. Feel free to contribute.

Resources:

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Link Preview Service from SUSI Server

 SUSI Webchat, SUSI Android app, SUSI iOS app are various SUSI clients which depend on response from SUSI Server. The most common response of SUSI Server is in form of links. Clients usually need to show the preview of the links to the user. This preview may include featured image, description and the title of the link.  Clients show this information by using various 3rd party APIs and libraries. We planned to create an API endpoint for this on SUSI Server to give the preview of the link. This service is called LinkPreviewService.
String url = post.get("url", "");
        if(url==null || url.isEmpty()){
            jsonObject.put("message","URL Not given");
            jsonObject.put("accepted",false);
            return new ServiceResponse(jsonObject);
        }

This API Endpoint accept only 1 get parameter which is the URL whose preview is to be shown.

Here we also check if no parameter or wrong URL parameter was sent. If that was the the case then we return an error message to the user.

 SourceContent sourceContent =     TextCrawler.scrape(url,3);
        if (sourceContent.getImages() != null) jsonObject.put("image", sourceContent.getImages().get(0));
        if (sourceContent.getDescription() != null) jsonObject.put("descriptionShort", sourceContent.getDescription());
        if(sourceContent.getTitle()!=null)jsonObject.put("title", sourceContent.getTitle());
        jsonObject.put("accepted",true);
        return new ServiceResponse(jsonObject);
    }

The TextCrawler function accept two parameters. One is the url of the website which is to be scraped for the preview data and the other is depth. To get the images, description and title there are methods built in. Here we just call those methods and set them in our JSON Object.

 private String htmlDecode(String content) {
        return Jsoup.parse(content).text();
    }

Text Crawler is based on Jsoup. Jsoup is a java library that is used to scrape HTML pages.

To get anything from Jsoup we need to decode the content of HTML to Text.

public List<String> getImages(Document document, int imageQuantity) {
        Elements media = document.select("[src]");
        while(var5.hasNext()) {
            Element srcElement = (Element)var5.next();
            if(srcElement.tagName().equals("img")) {
                ((List)matches).add(srcElement.attr("abs:src"));
            }
        }

 The getImages method takes the HTML document from the JSoup and find the image tags in that. We have given the imageQuantity parameter in the function, so accordingly it returns the src attribute of the first n images it find.

This API Endpoint can be seen working on

http://127.0.0.1:4000/susi/linkPreview.json?url=<ANY URL>

A real working example of this endpoint would be http://api.susi.ai/susi/linkPreview.json?url=https://techcrunch.com/2017/07/23/dear-tech-dudes-stop-being-such-idiots-about-women/

Resources:

Web Crawlers: https://www.promptcloud.com/data-scraping-vs-data-crawling/

JSoup: https://jsoup.org/

JSoup Api Docs: https://jsoup.org/apidocs/

Parsing HTML with JSoup: http://www.baeldung.com/java-with-jsoup

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Deleting SUSI Skills from Server

SUSI Skill CMS is a web application to create and edit skills. In this blog post I will be covering how we made the skill deleting feature in Skill CMS from the SUSI Server.
The deletion of skill was to be made in such a way that user can click a button to delete the skill. As soon as they click the delete button the skill is deleted it is removed from the directory of SUSI Skills. But admins have an option to recover the deleted skill before completion of 30 days of deleting the skill.

First we will accept all the request parameters from the GET request.

        String model_name = call.get("model", "general");
        String group_name = call.get("group", "Knowledge");
        String language_name = call.get("language", "en");
        String skill_name = call.get("skill", "wikipedia");

In this we get the model name, category, language name, skill name and the commit ID. The above 4 parameters are used to make a file path that is used to find the location of the skill in the Susi Skill Data repository.

 if(!DAO.deleted_skill_dir.exists()){
            DAO.deleted_skill_dir.mkdirs();
   }

We need to move the skill to a directory called deleted_skills_dir. So we check if the directory exists or not. If it not exists then we create a directory for the deleted skills.

  if (skill.exists()) {
   File file = new File(DAO.deleted_skill_dir.getPath()+path);
   file.getParentFile().mkdirs();
   if(skill.renameTo(file)){
   Boolean changed =  new File(DAO.deleted_skill_dir.getPath()+path).setLastModified(System.currentTimeMillis());
     }

This is the part where the real deletion happens. We get the path of the skill and rename that to a new path which is in the directory of deleted skills.

Also here change the last modified time of the skill as the current time. This time is used to check if the skill deleted is older than 30 days or not.

    try (Git git = DAO.getGit()) {
                DAO.pushCommit(git, "Deleted " + skill_name, rights.getIdentity().isEmail() ? rights.getIdentity().getName() : "[email protected]");
                json.put("accepted", true);
                json.put("message", "Deleted " + skill_name);
            } catch (IOException | GitAPIException e) {

Finally we add the changes to Git. DAO.pushCommit pushes to commit to the Susi Skill Data repository. If the user is logged in we get the email of the user and set that email as the commit author. Else we set the username “[email protected]”.

Then in the caretaker class there is a method deleteOldFiles that checks for all the files whose last modified time was older than 30 days. If there is any file whose last modified time was older than 30 days then it quietly delete the files.

public void deleteOldFiles() {
     Collection<File> filesToDelete = FileUtils.listFiles(new         File(DAO.deleted_skill_dir.getPath()),
     new 
(DateTime.now().withTimeAtStartOfDay().minusDays(30).toDate()),
            TrueFileFilter.TRUE);    // include sub dirs
        for (File file : filesToDelete) {
               boolean success = FileUtils.deleteQuietly(file);
            if (!success) {
                System.out.print("Deleted skill older than 30 days.");
            }
      }
}

To test this API endpoint, we need to call http://localhost:4000/cms/deleteSkill.txt?model=general&group=Knowledge&language=en&skill=<skill_name>

Resources

JGit Documentation: https://eclipse.org/jgit/documentation/

Commons IO: https://commons.apache.org/proper/commons-io/

Age Filter: https://commons.apache.org/proper/commons-io/javadocs/api-1.4/org/apache/commons/io/filefilter/AgeFileFilter.html

JGit User Guide: http://wiki.eclipse.org/JGit/User_Guide

JGit Repository access: http://www.codeaffine.com/2014/09/22/access-git-repository-with-jgit/

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Getting SUSI Skill at a Commit ID

Susi Skill CMS is a web app to edit and create new skills. We use Git for storing different versions of Susi Skills. So what if we want to roll back to a previous version of the skill? To implement this feature in Susi Skill CMS, we needed an API endpoint which accepts the name of the skill and the commit ID and returns the file at that commit ID.

In this blog post I will tell about making an API endpoint which works similar to git show.

First we will accept all the request parameters from the GET request.

        String model_name = call.get("model", "general");
        String group_name = call.get("group", "Knowledge");
        String language_name = call.get("language", "en");
        String skill_name = call.get("skill", "wikipedia");
        String commitID  = call.get("commitID", null);

In this we get the model name, category, language name, skill name and the commit ID. The above 4 parameters are used to make a file path that is used to find the location of the skill in the Susi Skill Data repository.

This servlet need CommitID to work and if commit ID is not given in the request parameters then we send an error message saying that the commit id is null and stop the servlet execution.

    Repository repository = DAO.getRepository();
    ObjectId CommitIdObject = repository.resolve(commitID);

Then we get the git repository of the skill from the DAO and initialize the repository object.

From the commitID that we got in the request parameters we create a CommitIdObject.

   (RevWalk revWalk = new RevWalk(repository)) {
   RevCommit commit = revWalk.parseCommit(CommitIdObject);
   RevTree tree = commit.getTree();


Now using commit’s tree, we will find the find the path and get the tree of the commit.

From the TreeWalk in the repository we will set a filter to find a file. This searches recursively for the files inside all the folders.

                revWalk = new RevWalk(repository)) {
                try (TreeWalk treeWalk = new TreeWalk(repository)) {
                    treeWalk.addTree(tree);
                    treeWalk.setRecursive(true);
                    treeWalk.setFilter(PathFilter.create(path));
                    if (!treeWalk.next()) {
                        throw new IllegalStateException("Did not find expected file");
                    }

If the TreeWalk reaches to an end and does not find the specified skill path then it returns anIllegal State Exception with an message saying did not found the file on that commit ID.

       ObjectId objectId = treeWalk.getObjectId(0);
       ObjectLoader loader = repository.open(objectId);
       OutputStream output = new OutputStream();
       loader.copyTo(output);

And then one can the loader to read the file. From the treeWalk we get the object and create an output stream to copy the file content in it. After that we create the JSON and put the OutputStream object as as String in it.

       json.put("file",output);

This Servlet can be seen working api.susi.ai: http://api.susi.ai/cms/getFileAtCommitID.json?model=general&group=knowledge&language=en&skill=bitcoin&commitID=214791f55c19f24d7744364495541b685539a4ee

Resources

JGit Documentation: https://eclipse.org/jgit/documentation/

JGit User Guide: http://wiki.eclipse.org/JGit/User_Guide

JGit Repository access: http://www.codeaffine.com/2014/09/22/access-git-repository-with-jgit/

JGit Github: https://github.com/eclipse/jgit

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