From c700d81426328c2aa2c1587c235c3eac8328833c 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 | 124 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 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..305238e1
--- /dev/null
+++ b/src/invidious/rss_atom.cr
@@ -0,0 +1,124 @@
+require "xml"
+require "http/server"
+
+module Invidious::RssAtom
+  extend self
+
+  # TODO: Merge all of those in a single type
+  alias AnyVideo = SearchVideo | ChannelVideo | PlaylistVideo
+
+  #
+  # Feed properties structure
+  #
+
+  alias AltLink = NamedTuple(type: String, url: String)
+
+  struct AtomProperties
+    getter title : String
+    getter icon_url : String
+    getter author : String
+    getter author_url : String
+
+    getter date_published : String
+    getter date_updated : String
+
+    getter alt_links : Array(AltLink)
+
+    def initialize(
+      *, # All parameters must be named
+      @title = "", @icon_url = "",
+      @author = "", @author_url = "",
+      date_updated : Time | String = Time.utc,
+      date_published : Time | String = "",
+      @alt_links = [] of AltLink
+    )
+      # Convert publication date if needed
+      if date_published.is_a?(Time)
+        @date_published = date_published.to_rfc3339
+      else
+        @date_published = date_published
+      end
+
+      # Convert update date if needed
+      if date_updated.is_a?(Time)
+        @date_updated = date_updated.to_rfc3339
+      else
+        @date_updated = date_updated
+      end
+    end
+  end
+
+  #
+  # Atom Feed builder
+  #
+
+  def atom_feed_builder(
+    # Mandatory parameters
+    env : HTTP::Server::Context,
+    videos : Array(AnyVideo),
+    id : String,
+    properties : AtomProperties
+  )
+    locale = 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(properties.title.empty? ? properties.author : properties.title)
+        end
+
+        if !properties.icon_url.empty?
+          icon_url = "#{HOST_URL}/gghpt/#{URI.parse(properties.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
+        if !properties.date_published.empty?
+          xml.element("published") { xml.text properties.date_published }
+        end
+
+        xml.element("updated") { xml.text properties.date_updated }
+
+        # Links
+        xml.element("link", rel: "self",
+          type: "application/atom+xml",
+          href: "#{HOST_URL}#{env.request.resource}"
+        )
+
+        properties.alt_links.each do |link|
+          xml.element("link", rel: "alternate", type: link[:type], href: link[:url])
+        end
+
+        # Author infos
+        xml.element("author") do
+          xml.element("name") { xml.text properties.author }
+          xml.element("uri") { xml.text properties.author_url } if !properties.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