feat: do all the backend balancing on the invidious side

This will make invidious easier to maintain and escalate without the need of an overcomplicated reverse proxy configuration and multiple invidious instances with each one with a different configuration (in this case, invidious companion)

src/invidious/routes/api/manifest.cr

@@ -9,7 +9,8 @@ module Invidious::Routes::API::Manifest
     region = env.params.query["region"]?
 
     if CONFIG.invidious_companion.present?
-      invidious_companion = CONFIG.invidious_companion.sample
+      current_companion = env.get("current_companion").as(Int32)
+      invidious_companion = CONFIG.invidious_companion[current_companion]
       return env.redirect "#{invidious_companion.public_url}/api/manifest/dash/id/#{id}?#{env.params.query}"
     end
 

src/invidious/routes/backend_switcher.cr

@@ -0,0 +1,16 @@
+{% skip_file if flag?(:api_only) %}
+
+module Invidious::Routes::BackendSwitcher
+  def self.switch(env)
+    referer = get_referer(env)
+    backend_id = env.params.query["backend_id"]?.try &.to_i
+
+    if backend_id.nil?
+      return error_template(400, "Backend ID is required")
+    end
+
+    env.response.cookies[CONFIG.server_id_cookie_name] = Invidious::User::Cookies.server_id(env.request.headers["Host"], backend_id)
+
+    env.redirect referer
+  end
+end

src/invidious/routes/before_all.cr

@@ -24,12 +24,33 @@ module Invidious::Routes::BeforeAll
     extra_connect_csp = ""
 
     if CONFIG.invidious_companion.present?
-      extra_media_csp = " #{CONFIG.invidious_companion.sample.public_url}"
-      extra_connect_csp = " #{CONFIG.invidious_companion.sample.public_url}"
-      exvpp_url = BackendInfo.get_exvpp
-      if !exvpp_url.empty?
-        extra_media_csp += " #{exvpp_url}"
-        extra_connect_csp += " #{exvpp_url}"
+      if env.request.cookies[CONFIG.server_id_cookie_name]?.nil?
+        env.response.cookies[CONFIG.server_id_cookie_name] = Invidious::User::Cookies.server_id(env.request.headers["Host"])
+      end
+
+      begin
+        current_companion = env.request.cookies[CONFIG.server_id_cookie_name].value.try &.to_i
+      rescue
+        current_companion = rand(CONFIG.invidious_companion.size)
+      end
+
+      if current_companion > CONFIG.invidious_companion.size
+        current_companion = current_companion % CONFIG.invidious_companion.size
+        env.response.cookies[CONFIG.server_id_cookie_name] = Invidious::User::Cookies.server_id(env.request.headers["Host"], current_companion)
+      end
+
+      env.set "current_companion", current_companion
+
+      CONFIG.invidious_companion.each do |companion|
+        extra_media_csp += " #{companion.public_url}"
+        extra_connect_csp += " #{companion.public_url}"
+      end
+      exvpp_urls = BackendInfo.get_exvpp
+      exvpp_urls.each do |exvpp_url|
+        if !exvpp_url.empty?
+          extra_media_csp += " #{exvpp_url}"
+          extra_connect_csp += " #{exvpp_url}"
+        end
       end
     end
 

src/invidious/routes/video_playback.cr

@@ -267,7 +267,8 @@ module Invidious::Routes::VideoPlayback
   # so we have a mechanism here to redirect to the latest version
   def self.latest_version(env)
     if CONFIG.invidious_companion.present?
-      invidious_companion = CONFIG.invidious_companion.sample
+      current_companion = env.get("current_companion").as(Int32)
+      invidious_companion = CONFIG.invidious_companion[current_companion]
       return env.redirect "#{invidious_companion.public_url}/latest_version?#{env.params.query}"
     end
 

src/invidious/routes/watch.cr

@@ -52,7 +52,7 @@ module Invidious::Routes::Watch
     env.params.query.delete_all("listen")
 
     begin
-      video = get_video(id, region: params.region)
+      video = get_video(id, region: params.region, env: env)
     rescue ex : NotFoundException
       LOGGER.error("get_video not found: #{id} : #{ex.message}")
       return error_template(404, ex)
@@ -214,7 +214,8 @@ module Invidious::Routes::Watch
     end
 
     if CONFIG.invidious_companion.present?
-      invidious_companion = CONFIG.invidious_companion.sample
+      current_companion = env.get("current_companion").as(Int32)
+      invidious_companion = CONFIG.invidious_companion[current_companion]
       env.response.headers["Content-Security-Policy"] =
         env.response.headers["Content-Security-Policy"]
           .gsub("media-src", "media-src #{invidious_companion.public_url}")
@@ -350,8 +351,9 @@ module Invidious::Routes::Watch
       env.params.query["local"] = "true"
 
       if (CONFIG.invidious_companion.present?)
-        video = get_video(video_id)
-        invidious_companion = CONFIG.invidious_companion.sample
+        video = get_video(video_id, env: env)
+        current_companion = env.get("current_companion").as(Int32)
+        invidious_companion = CONFIG.invidious_companion[current_companion]
         return env.redirect "#{invidious_companion.public_url}/latest_version?#{env.params.query}"
       else
         return Invidious::Routes::VideoPlayback.latest_version(env)