added a helper for handling at:// URIs

app/at_uri.rb

···
+class AT_URI
+  class InvalidURIError
+  end
+
+  attr_reader :repo, :collection, :rkey
+
+  def initialize(uri)
+    raise InvalidURIError, "Invalid AT URI: #{uri}" if uri.include?(' ') || !uri.start_with?('at://')
+
+    parts = uri.split('/')
+    parts.each(&:freeze)
+
+    raise InvalidURIError, "Invalid AT URI: #{uri}" if parts.length != 5 || parts[2..4].any?(&:empty?)
+
+    @uri = uri
+    @repo, @collection, @rkey = parts[2..4]
+  end
+
+  def to_ary
+    [@repo, @collection, @rkey]
+  end
+
+  alias split to_ary
+
+  def to_s
+    @uri
+  end
+end
+
+def AT_URI(uri)
+  AT_URI.new(uri)
+end

app/importer.rb

···
 require 'didkit'
 require 'minisky'
 
+require_relative 'at_uri'
 require_relative 'models/import'
 require_relative 'models/like'
 require_relative 'models/post'
···
   def process_likes(likes)
     likes.each do |record|
       begin
-        like_rkey = record['uri'].split('/').last
+        like_rkey = AT_URI(record['uri']).rkey
         next if @user.likes.where(rkey: like_rkey).exists?
 
         like_time = Time.parse(record['value']['createdAt'])
 
-        post_uri = record['value']['subject']['uri']
-        parts = post_uri.split('/')
-        next if parts[3] != 'app.bsky.feed.post'
+        post_uri = AT_URI(record['value']['subject']['uri'])
+        next if post_uri.collection != 'app.bsky.feed.post'
 
-        post_did, _, post_rkey = parts[2..4]
+        post_did = post_uri.repo
 
         if @uid_cache[post_did].nil?
           post_author = User.find_or_create_by!(did: post_did)
           @uid_cache[post_did] = post_author.id
         end
 
-        post = Post.find_by(user_id: @uid_cache[post_did], rkey: post_rkey)
+        post = Post.find_by(user_id: @uid_cache[post_did], rkey: post_uri.rkey)
 
         if post
           @user.likes.create!(rkey: like_rkey, time: like_time, post: post)

app/post_downloader.rb

···
 require 'didkit'
 require 'minisky'
 
+require_relative 'at_uri'
 require_relative 'models/post'
 require_relative 'models/user'
 
···
   end
 
   def save_post(post_uri, record)
-    did, _, rkey = post_uri.split('/')[2..4]
+    did, _, rkey = AT_URI(post_uri)
 
     text = record.delete('text')
     created = record.delete('createdAt')