# Wiki

Design a Wikipedia-like online encyclopedia.

## Background

Wikipedia is a free online encyclopedia that consists of a number of encyclopedia entries on various topics.

Each encyclopedia entry can be viewed by visiting that entry’s page. Visiting https://en.wikipedia.org/wiki/HTML, for example, shows the Wikipedia entry for HTML. Notice that the name of the requested page (HTML) is specified in the route /wiki/HTML. Recognize too, that the page’s content must just be HTML that your browser renders.

In practice, it would start to get tedious if every page on Wikipedia had to be written in HTML. Instead, it can be helpful to store encyclopedia entries using a lighter-weight human-friendly markup language. Wikipedia happens to use a markup language called Wikitext, but for this project we’ll store encyclopedia entries using a markup language called Markdown.

Read through GitHub’s Markdown guide to get an understanding for how Markdown’s syntax works. Pay attention in particular to what Markdown syntax looks like for headings, bold text, links, and lists.

By having one Markdown file represent each encyclopedia entry, we can make our entries more human-friendly to write and edit. When a user views our encyclopedia entry, though, we’ll need to convert that Markdown into HTML before displaying it to the user.

## Understanding

In the distribution code is a Django project called wiki that contains a single app called encyclopedia.

First, open up encyclopedia/urls.py, where the URL configuration for this app is defined. Notice that we’ve started you with a single default route that is associated with the views.index function.

Next, look at encyclopedia/util.py. You won’t need to change anything in this file, but notice that there are three functions that may prove useful for interacting with encyclopedia entries. list_entries returns a list of the names of all encyclopedia entries currently saved. save_entry will save a new encyclopedia entry, given its title and some Markdown content. get_entry will retrieve an encyclopedia entry by its title, returning its Markdown contents if the entry exists or None if the entry does not exist. Any of the views you write may use these functions to interact with encyclopedia entries.

Each encyclopedia entry will be saved as a Markdown file inside of the entries/ directory. If you check there now, you’ll see we’ve pre-created a few sample entries. You’re welcome to add more!

Now, let’s look at encyclopedia/views.py. There’s just one view here now, the index view. This view returns a template encyclopedia/index.html, providing the template with a list of all of the entries in the encyclopedia (obtained by calling util.list_entries, which we saw defined in util.py).

You can find the template by looking at encyclopedia/templates/encyclopedia/index.html. This template inherits from a base layout.html file and specifies what the page’s title should be, and what should be in the body of the page: in this case, an unordered list of all of the entries in the encyclopedia. layout.html, meanwhile, defines the broader structure of the page: each page has a sidebar with a search field (that for now does nothing), a link to go home, and links (that don’t yet work) to create a new page or visit a random page.

## Specification

Complete the implementation of your Wiki encyclopedia. You must fulfill the following requirements:

• Entry Page: Visiting /wiki/TITLE, where TITLE is the title of an encyclopedia entry, should render a page that displays the contents of that encyclopedia entry.
• The view should get the content of the encyclopedia entry by calling the appropriate util function.
• If an entry is requested that does not exist, the user should be presented with an error page indicating that their requested page was not found.
• If the entry does exist, the user should be presented with a page that displays the content of the entry. The title of the page should include the name of the entry.
• Index Page: Update index.html such that, instead of merely listing the names of all pages in the encyclopedia, user can click on any entry name to be taken directly to that entry page.
• Search: Allow the user to type a query into the search box in the sidebar to search for an encyclopedia entry.
• If the query matches the name of an encyclopedia entry, the user should be redirected to that entry’s page.
• If the query does not match the name of an encyclopedia entry, the user should instead be taken to a search results page that displays a list of all encyclopedia entries that have the query as a substring. For example, if the search query were ytho, then Python should appear in the search results.
• Clicking on any of the entry names on the search results page should take the user to that entry’s page.
• New Page: Clicking “Create New Page” in the sidebar should take the user to a page where they can create a new encyclopedia entry.
• Users should be able to enter a title for the page and, in a textarea, should be able to enter the Markdown content for the page.
• Users should be able to click a button to save their new page.
• When the page is saved, if an encyclopedia entry already exists with the provided title, the user should be presented with an error message.
• Otherwise, the encyclopedia entry should be saved to disk, and the user should be taken to the new entry’s page.
• Edit Page: On each entry page, the user should be able to click a link to be taken to a page where the user can edit that entry’s Markdown content in a textarea.
• The textarea should be pre-populated with the existing Markdown content of the page. (i.e., the existing content should be the initial value of the textarea).
• The user should be able to click a button to save the changes made to the entry.
• Once the entry is saved, the user should be redirected back to that entry’s page.
• Random Page: Clicking “Random Page” in the sidebar should take user to a random encyclopedia entry.
• Markdown to HTML Conversion: On each entry’s page, any Markdown content in the entry file should be converted to HTML before being displayed to the user. You may use the python-markdown2 package to perform this conversion, installable via pip3 install markdown2.
• Challenge for those more comfortable: If you’re feeling more comfortable, try implementing the Markdown to HTML conversion without using any external libraries, supporting headings, boldface text, unordered lists, links, and paragraphs. You may find using regular expressions in Python helpful.

## Hints

• By default, when substituting a value in a Django template, Django HTML-escapes the value to avoid outputting unintended HTML. If you want to allow for an HTML string to be outputted, you can do so with the safe filter (as by adding |safe after the variable name you’re substituting).

## How to Submit

2. Install Git and, optionally, install submit50.
1. If you’ve installed submit50, execute
submit50 web50/projects/2020/x/wiki

Otherwise, using Git, push your work to https://github.com/me50/USERNAME.git, where USERNAME is your GitHub username, on a branch called web50/projects/2020/x/wiki.