Add iCalendar endpoint for Twitch.

app.rb

@@ -998,6 +998,20 @@
   erb :"twitch.atom"
 end
 
+get %r{/twitch/(?<id>\d+)/(?<user>.+)\.ics} do |id, user|
+  @title = "#{user} on Twitch"
+
+  type = %w[all upload archive highlight].pick(params[:type]) || "all"
+  response = Twitch.get("/videos", query: { user_id: id, type: type })
+  raise(TwitchError, response) if !response.success?
+
+  @data = response.json["data"]
+  user = @data[0]["user_name"] || CGI.unescape(user)
+  @alternate_url = Addressable::URI.parse("https://www.twitch.tv/#{user.downcase}").normalize.to_s
+
+  erb :"twitch.ics"
+end
+
 get %r{/twitch/(?<id>\d+)/(?<user>.+)} do |id, user|
   @id = id
   @type = "user"

views/twitch.ics.erb

@@ -0,0 +1,38 @@
+<%- content_type :ics -%>
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//RSSBox//RSSBox <%= ENV["APP_VERSION"] %>//EN
+CALSCALE:GREGORIAN
+METHOD:PUBLISH
+X-WR-CALNAME:<%= @title %>
+X-WR-CALDESC:<%= @alternate_url %>
+
+<%-
+@data.each do |video|
+  duration = video["duration"].parse_duration
+  if video["thumbnail_url"] == ""
+    # video is currently live
+    duration += 7200
+  end
+  dtstart = Time.parse(video["created_at"])
+  dtend = dtstart + duration
+  published_at = Time.parse(video["published_at"])
+
+  dtstart = dtstart.strftime("%Y%m%dT%H%M%SZ")
+  dtend = dtend.strftime("%Y%m%dT%H%M%SZ")
+  published_at = published_at.strftime("%Y%m%dT%H%M%SZ")
+-%>
+BEGIN:VEVENT
+UID:video-<%= video["id"] %>@twitch.com
+DTSTART:<%= dtstart %>
+DTEND:<%= dtend %>
+DTSTAMP:<%= published_at %>
+CREATED:<%= published_at %>
+LAST-MODIFIED:<%= published_at %>
+SUMMARY:<%= video["title"].to_line %>
+LOCATION:https://www.twitch.tv/videos/<%= video["id"] %>
+DESCRIPTION:<%= video["description"].gsub("\n", "\\n") %>
+END:VEVENT
+
+<%- end -%>
+END:VCALENDAR