From 1062cd4fe31ffe3f443c2199834c758d0723bd84 Mon Sep 17 00:00:00 2001
From: Samantaz Fox <coding@samantaz.fr>
Date: Tue, 16 Nov 2021 18:21:19 +0100
Subject: [PATCH] Add an Atom feed builder helper

---
 src/invidious/rss_atom.cr | 95 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 src/invidious/rss_atom.cr

diff --git a/src/invidious/rss_atom.cr b/src/invidious/rss_atom.cr
new file mode 100644
index 00000000..2e48e4c5
--- /dev/null
+++ b/src/invidious/rss_atom.cr
@@ -0,0 +1,95 @@
+require "xml"
+require "http/server"
+
+module Invidious::RssAtom
+  extend self
+
+  # TODO: Merge all of those in a single type
+  alias AnyVideo = SearchVideo | ChannelVideo | PlaylistVideo
+
+  alias AltLinks = NamedTuple(type: String, url: String)
+
+  #
+  # Atom Feed builder
+  #
+
+  def atom_feed_builder(
+    # Mandatory parameters
+    env : HTTP::Server::Context,
+    videos : Array(AnyVideo),
+    *, # All parameters after this must be named
+    id : String,
+    title : String,
+    # Optional parameters
+    icon_url : String = "",
+    author : String = "",
+    author_url : String = "",
+    date_updated : Time | String = Time.utc,
+    date_published : Time | String | Nil = nil,
+    alt_links : Array(AltLinks) | Nil = nil
+  )
+    locale = LOCALES[env.get("preferences").as(Preferences).locale]?
+    params = HTTP::Params.parse(env.params.query["params"]? || "")
+
+    return XML.build(indent: "  ", encoding: "UTF-8") do |xml|
+      xml.element("feed",
+        xmlns: "http://www.w3.org/2005/Atom",
+        "xmlns:media": "http://search.yahoo.com/mrss/",
+        "xml:lang": "en-US"
+      ) do
+        # The id must be unique, and an IANA-approved IRI, so use "ni://"
+        # Relevant RFC documents:
+        #  - https://datatracker.ietf.org/doc/html/rfc4287#section-4.2.6
+        #  - https://datatracker.ietf.org/doc/html/rfc6920
+        #
+        xml.element("id") { xml.text "ni://invidious/sha-256;" + sha256(id) }
+
+        # Feed title. Use author name if no title was provided
+        xml.element("title") do
+          xml.text(title.empty? ? author : title)
+        end
+
+        if !icon_url.empty?
+          icon_url = "#{HOST_URL}/gghpt" + URI.parse(icon_url).request_target
+          xml.element("icon") { xml.text icon_url }
+          xml.element("logo") { xml.text icon_url }
+        end
+
+        # Feed creation (if available) and update (mandatory) dates
+        date_published = date_published.to_rfc3339 if date_published.is_a?(Time)
+        xml.element("published") { xml.text date_published } if date_published
+
+        date_updated = date_updated.to_rfc3339 if date_updated.is_a?(Time)
+        xml.element("updated") { xml.text date_updated }
+
+        # Links
+        xml.element("link", rel: "self",
+          type: "application/atom+xml",
+          href: "#{HOST_URL}#{env.request.resource}"
+        )
+
+        if alt_links
+          alt_links.each do |link|
+            xml.element("link", rel: "alternate", type: link[:type], href: link[:url])
+          end
+        end
+
+        # Author infos
+        xml.element("author") do
+          xml.element("name") { xml.text author }
+          xml.element("uri") { xml.text author_url } if !author_url.empty?
+        end
+
+        # Video entries
+        # TODO: Unify `.to_xml` methods
+        videos.each do |video|
+          case video
+          when .is_a?(PlaylistVideo) then video.to_xml(xml)
+          when .is_a?(ChannelVideo)  then video.to_xml(locale, params, xml)
+          when .is_a?(SearchVideo)   then video.to_xml(false, params, xml)
+          end
+        end
+      end
+    end
+  end
+end