RedcarpetYT: Markdown with YouTube Embedding

RedcarpetYT is a Ruby library for Markdown processing with YouTube embedding based on Redcarpet

RedcarpetYT was written by Scott Werwath.

RedcarpetYT is an extension of Redcarpet, which was written by Vicent Martí. It is maintained by Robin Dupret and Matt Rogers.

Redcarpet would not be possible without the Sundown library and its authors (Natacha Porté, Vicent Martí, and its many awesome contributors).

Redcarpet is readily available as a Ruby gem. It will build some native extensions, but the parser is standalone and requires no installed libraries. Starting with Redcarpet 3.0, the minimum required Ruby version is 1.9.2 (or Rubinius in 1.9 mode).

$ [sudo] gem install redcarpet_yt

The RedcarpetYT source is available at GitHub:

$ git clone git://github.com/swerwath/redcarpet_yt.git

The core of the Redcarpet library is the Redcarpet::Markdown class. Each instance of the class is attached to a Renderer object; the Markdown class performs parsing of a document and uses the attached renderer to generate output.

The Redcarpet::Markdown object is encouraged to be instantiated once with the required settings, and reused between parses.

# Initializes a Markdown parser
markdown = Redcarpet::Markdown.new(renderer, extensions = {})

Here, the renderer variable refers to a renderer object, inheriting from Redcarpet::Render::Base. If the given object has not been instantiated, the library will do it with default arguments.

Rendering with the Markdown object is done through Markdown#render. Unlike in the RedCloth API, the text to render is passed as an argument and not stored inside the Markdown instance, to encourage reusability. Example:

markdown.render("This is *bongos*, indeed.")
# => "<p>This is <em>bongos</em>, indeed.</p>"

You can also specify a hash containing the Markdown extensions which the parser will identify. The following extensions are accepted:

• :no_intra_emphasis: do not parse emphasis inside of words. Strings such as foo_bar_baz will not generate <em> tags.

• :tables: parse tables, PHP-Markdown style.

• :fenced_code_blocks: parse fenced code blocks, PHP-Markdown style. Blocks delimited with 3 or more ~ or backticks will be considered as code, without the need to be indented. An optional language name may be added at the end of the opening fence for the code block.

• :autolink: parse links even when they are not enclosed in <> characters. Autolinks for the http, https and ftp protocols will be automatically detected. Email addresses and http links without protocol, but starting with www are also handled.

• :disable_indented_code_blocks: do not parse usual markdown code blocks. Markdown converts text with four spaces at the front of each line to code blocks. This option prevents it from doing so. Recommended to use with fenced_code_blocks: true.

• :strikethrough: parse strikethrough, PHP-Markdown style. Two ~ characters mark the start of a strikethrough, e.g. this is ~~good~~ bad.

• :lax_spacing: HTML blocks do not require to be surrounded by an empty line as in the Markdown standard.

• :space_after_headers: A space is always required between the hash at the beginning of a header and its name, e.g. #this is my header would not be a valid header.

• :superscript: parse superscripts after the ^ character; contiguous superscripts are nested together, and complex values can be enclosed in parenthesis, e.g. this is the 2^(nd) time.

• :underline: parse underscored emphasis as underlines. This is _underlined_ but this is still *italic*.

• :highlight: parse highlights. This is ==highlighted==. It looks like this: <mark>highlighted</mark>

• :quote: parse quotes. This is a "quote". It looks like this: <q>quote</q>

• :footnotes: parse footnotes, PHP-Markdown style. A footnote works very much like a reference-style link: it consists of a marker next to the text (e.g. This is a sentence.[^1]) and a footnote definition on its own line anywhere within the document (e.g. [^1]: This is a footnote.).

Example:

markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML, autolink: true, tables: true)

First, make sure your markdown object uses the YouTube class:

markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTMLwithYouTube, autolink: true, tables: true)

Then, you can embed YouTube videos in your Markdown with the same syntax as you do with images. The renderer is smart enough to recognize if you're linking to a video. For example,

my_markdown_string = "![crazy alt text](https://www.youtube.com/watch?v=e79SuHotazs)"

Then, just feed that Markdown into your renderer:

html_string = markdown.render(my_markdown_string)