# Liquid tag for embedding video.js players from assets, mirroring how images
# are embedded via plain relative paths (see _includes/head.html's <base> tag).
#
# Syntax:
#   {% video urls [class names] [width height] [preload:auto|metadata|none] %}
#
# `urls` is a comma-separated list of one or more relative asset paths, used
# as <source> elements (multiple formats/resolutions). Everything after that
# is free-form, order-independent tokens classified by shape:
#   - preload:auto|metadata|none -> preload attribute
#   - a bare integer             -> width, then height
#   - anything else              -> appended to the CSS class list
#
# The rendered markup is a plain HTML5 <video controls> element with
# class="video-js" and data-setup='{}', which is exactly what video.js
# progressively enhances if/when its script loads (see head.html). If it
# never loads, the element is already a fully working native player.
require 'cgi'

module Jekyll
  class VideoTag < Liquid::Tag
    PRELOAD_TOKEN = /\Apreload:(auto|metadata|none)\z/
    INTEGER_TOKEN = /\A\d+\z/

    MIME_TYPES = {
      '.mp4' => 'video/mp4',
      '.m4v' => 'video/mp4',
      '.webm' => 'video/webm',
      '.ogv' => 'video/ogg',
    }.freeze

    def initialize(tag_name, markup, tokens)
      super
      args = markup.strip.split(/\s+/)

      urls_arg = args.shift
      if urls_arg.nil? || urls_arg.empty?
        raise Liquid::SyntaxError, "Syntax error in tag 'video' - valid syntax: {% video urls [class names] [width height] [preload:auto|metadata|none] %}"
      end
      @urls = urls_arg.split(',').map(&:strip).reject(&:empty?)

      @classes = []
      @width = nil
      @height = nil
      @preload = nil

      args.each do |token|
        case token
        when PRELOAD_TOKEN
          @preload = Regexp.last_match(1)
        when INTEGER_TOKEN
          if @width.nil?
            @width = token
          else
            @height = token
          end
        else
          @classes << token
        end
      end
    end

    def render(_context)
      classes = (['video-js'] + @classes).join(' ')

      attrs = [%(class="#{escape(classes)}")]
      attrs << 'controls'
      attrs << %(width="#{escape(@width)}") if @width
      attrs << %(height="#{escape(@height)}") if @height
      attrs << %(preload="#{escape(@preload)}") if @preload
      attrs << %(data-setup='{}')

      sources = @urls.map do |url|
        %(  <source src="#{escape(url)}" type="#{mime_type_for(url)}">)
      end.join("\n")

      "<video #{attrs.join(' ')}>\n#{sources}\n</video>"
    end

    private

    def mime_type_for(url)
      ext = File.extname(url).downcase
      MIME_TYPES.fetch(ext, 'video/mp4')
    end

    def escape(value)
      CGI.escapeHTML(value.to_s)
    end
  end
end

Liquid::Template.register_tag('video', Jekyll::VideoTag)