CS142 Project 5: Single Page Applications

Setup

You should already have installed Node.js and the npm package manager to your system. If not, follow the installation instructions now.

Create a directory project5 and extract the contents of this zip file into the directory. The zip file contains the starter files for this assignment.

This assignment requires many node modules that contain the tools (e.g. Webpack, Babel, ESLint) needed to build a ReactJS web application as well as a simple Node.js web server (ExpressJS) to serve it to your browser. It also fetches Material-UI, which contains the React components and style sheets we will be using. These modules can be fetched by running the following command in the project5 directory:

npm install

As with the previous assignment, we can use npm to run the various tools we had it fetch. The following npm scripts are available in the package.json file:

• npm run lint - Runs ESLint on all the project's JavaScript files. The code you submit should run ESLint without warnings.
• npm run build - Runs Webpack using the configuration file webpack.config.js to package all of the projects JSX files into a single JavaScipt bundle in the directory compiled.
• npm run build:w - Runs Webpack like the "run build" command except it invokes webpack with --watch so it will monitor the React components and regenerates the bundle if any of them change.

Your solutions for all of the problems below should be implemented in the project5 directory. As was done with on the previous project you will need to run a web server we provide for you by running a command in your project5 directory:

node webServer.js

As in the last project, you can run the node webserver (node webServer.js) and webpack (npm run build:w) in different command line tabs at the same time.

Problem 1: Create the Photo Sharing Application (40 points)

As starter code for your PhotoApp we provide you a skeleton (photo-share.html which loads photoShare.jsx) that can be started using the URL http://localhost:3000/photo-share.html. The skeleton:

• Loads a ReactJS web application that uses Material-UI to layout a Master-Detail pattern as described in class. It has a header made from a Material-UI App Bar accross the top, places a UserList component along the side, and has a content area beside it with either a UserDetail or UserPhotos component.
• Uses the React Router to enable deep linking for our single page application by configuring routes to three stubbed out components:
  1. /users is routed to the component UserList in components/UserList/
  2. /users/:userId is routed to the component UserDetail in components/UserDetail/
  3. /photos/:userId is routed to the component UserPhotos in components/UserPhotos/
  See the use of HashRouter, and Route in photoShare.jsx for details. For the stubbed out components in components/*, we provide an empty CSS file and a simple render function that includes some description of what it needs to do and the model data to use.

For this problem, we will continue to use our magic cs142models hack to provide the model data so we display a pre-entered set of information. As before, the models can be accessed using window.cs142Models. The schema of the model data is defined below.

Your assignment is to extend the skeleton into a working web app operating on the fake model data. Since the skeleton is already wired to either display components UserList, UserDetail, and UserPhotos with the appropriate parameters passed by React Router, most of the work will be implementing the stubbed out components. They should be filled in so that:

• components/UserList component should provide navigation to the user details of all the users in the system. The component is embedded in the side bar and should provide a list of user names so that when a name is clicked, the content view area switches to display the details of that user.
• components/UserDetail component is passed a userId in the props.match by React Router. The view should display the details of the user in a pleasing way along with a link to switch the view area to the photos of the user using the UserPhotos component.
• components/UserPhotos component is passed a userId, and should display all the photos of the specified user. It must display all of the photos belonging to that user. For each photo you must display the photo itself, the creation date/time for the photo, and all of the comments for that photo. For each comment you must display the date/time when the comment was created, the name of the user who created the comment, and the text of the comment. The creator for each comment should be a link that can be clicked to switch to the user detail page for that user. Note: The date/time for photos and comments should be formatted as user-friendly strings and not as raw JavaScript dates.

Besides these components, you need to update the TopBar component in components/TopBar as follows:

• The left side of the TopBar should have your name.
• The right side of the TopBar should provide app context by reflecting what is being shown in the main content region. For example, if the main content is displaying details on a user, the TopBar should have the user's name. If it is displaying a user's photos it should say "Photos of " and the user's name.

The use of React Router in the skeleton we provide allows for deep-linking to the different views of the application. Make sure the components you build do not break this capability. It should be possible to do a browser refresh on any view and have it come back as before. Our standard approach to building components handles deep-linking automatically. Care must be taken when doing things like sharing objects between components. A quick browser refresh test on each view will show when you broke something.

Although you don't need to spend a lot of time on the appearance of the app, it should be neat and understandable. The information layout should be clean (e.g., it should be clear which photo each comment applies to).

Photo App Model Data

For this problem we keep the magic DOM loaded model data we used in the previous project. The model consists of four types of objects: user, photo, comment, and SchemaInfo types.

• Photos in the photo-sharing site are organized by user. We will represent users as an object user with the following properties:

  _id:	The ID of this user.
  first_name:	First name of the user.
  last_name:	Last name of the user.
  location:	Location of the user.
  description:	A brief user description.
  occupation:	Occupation of the user.

  The DOM function window.cs142models.userModel(user_id) returns the user object of the user with id user_id. The DOM function window.cs142models.userListModel() returns an array with all user objects, one for each the users of the app.
• Each user can upload multiple photos. We represent each photo by a photo object with the following properties:

  _id:	The ID for this photo.
  user_id:	The ID of the user who created the photo.
  date_time:	The date and time when the photo was added to the database.
  file_name:	Name of a file containing the actual photo (in the directory project5/images).
  comments:	An array of the comment objects representing the comments made on this photo.

  The DOM function window.cs142models.photoOfUserModel(user_id) returns an array of the photo objects belonging to the user with id user_id.
• For each photo there can be multiple comments (any user can comment on any photo). comment objects have the following properties:

  _id:	The ID for this comment.
  photo_id:	The ID of the photo to which this comment belongs.
  user:	The user object of the user who created the comment.
  date_time:	The date and time when the comment was created.
  comment:	The text of the comment.

• For testing purposes we have SchemaInfo objects have the following properties:

  _id:	The ID for this SchemaInfo.
  __v:	Version number of the SchemaInfo object.
  load_date_time:	The date and time when the SchemaInfo was loaded. A string.

Problem 2: Fetch model data from the web server (20 points)

After doing Problem 1, our photo sharing app front-end is looking like a real web application. The big barrier to be considered real is the fakery we are doing with the model data loaded as JavaScript into the DOM. In Problem 2, we remove this hack and have the app fetch models from the web server as would typically be done in a real application.

The webServer.js given out with this project reads in the cs142Models we were loading into the DOM in Problem 1 and makes them available using ExpressJS routes. The API exported by webServer.js uses HTTP GET requests to particular URLs to return the cs142Models models. The HTTP response to these GET requests is encoded in JSON. The API is:

• /test/info - Returns cs142models.schemaInfo(). This URL is useful for testing your model fetching method.
• /user/list - Returns cs142models.userListModel().
• /user/:id - Returns cs142models.userModel(id).
• /photosOfUser/:id - Returns cs142models.photoOfUserModel(id).

You can see the APIs in action by pointing your browser at above URLs. For example, the links http://localhost:3000/test/info and http://localhost:3000/user/list wiil return the JSON-encoded model data in the browser's window.

To convert your app to fetch models from the web server you should implement a fetchModel function in lib/fetchModelData.js. The function should be declared as follows:

/**
 * fetchModel - Fetch a model from the web server.
 *
 * @param {string} url      The URL to issue the GET request.
 *
 * @returns a Promise that should be filled with the response of the GET request
 * parsed as a JSON object and returned in the property named "data" of an
 * object. If the request has an error, the Promise should be rejected with an
 * object that contains the properties:
 * {number} status          The HTTP response status
 * {string} statusText      The statusText from the xhr request
 */

Although there are many modules that would make implementing this function trivial, we want you to learn about the low-level details of AJAX. You may not use other libraries to implement fetchModel; you must write Javascript code that creates XMLHttpRequest DOM objects and responds to their events.

Your solution needs to be able to handle multiple outstanding fetchModel requests. To demonstrate your fetchModel routine works, your web application should work so that visiting http://localhost:3000/photo-share.html displays the version number returned by sending an AJAX request to the http://localhost:3000/test/info URL. The version number should be displayed in the TopBar component of your app.

After successfully implementing the fetchModel function in lib/fetchModelData.js, you should modify the code in

• components/UserDetail/index.jsx
• components/UserList/index.jsx
• components/UserPhotos/index.jsx

<script src="modelData/photoApp.js"><script>

Style Points (5 points)

These points will be awarded if your problem solutions have proper MVC decomposition. In addition, your code and components must be clean and readable, and your app must be at least "reasonably nice" in appearance and convenience.

Note that we are using Material-UI, React components that implement Google's Material Design. We have used Material-UI's Grid component to layout the Master-Detail pattern as described in class, and an App Bar header for you. Although you don't need to build a fully Material Design compatible app, you should use Material-UI components when possible.

In addition, remember to run ESLint before submitting. ESLint should raise no errors.

Extra Credit (5 points)

The UserPhotos component specifies that the display should include all of a user's photos along the photos' comments. This approach doesn't work well for users with a large numbers of photos. For extra credit you can implement a photo viewer that only shows one photo at a time (along with the photo's comments) and provides a mechanism to step forward or backward through the user's photos (i.e. a stepper).

In order to get extra credit on this assignment your solution must:

• Introduce the concept of "Advanced Features" to your photo app. On app startup, "Advanced Features" is always disabled. The TopBar should have a checkbox labeled "Enable Advanced Features" that is checked when "Advanced Features" is enabled and unchecked otherwise. Clicking the checkbox should enable/disable "Advanced Features."
• Your app should use the original photo view unless "Advanced Features" has been enabled by the checkbox. If enabled, viewing the photos of a user should use the single photo with stepper functionality.
• The user interface for stepping should be something obvious and the mechanism should indicate (e.g., a disabled button) if stepping is not possible in a direction because the user is at the first (for backward stepping) or last photo (for forward stepping).
• Your app should allow individual photos to be bookmarked and shared by copying the URL from the browser location bar. The browser's forward and back buttons should do what would be expected. When entering the app using a deep linked URL to individual photos the stepper functionality should operate as expected.

Warning: Doing this extra credit involves touching various pieces used in the non-extra credit part of the assignment. Adding new functionality guarded by a feature flag is common practice in web applications but has a risk in that if you break the non-extra credit part of the assignment you can lose more points than you could get from the extra credit. Take care.

Deliverables

Use the standard class submission mechanism to submit the entire application (everything in the project5 directory). Please clean up your project directory before submitting, as described in the instructions. In particular, the node_modules/ directory is 180MB in size so you won't be able to Gradescope. Remember to delete your compiled/ directory as well.