class AT_URI
  class InvalidURIError
  end

  TID_PATTERN = /^[234567abcdefghij][234567abcdefghijklmnopqrstuvwxyz]{12}$/

  attr_reader :repo, :collection, :rkey

  def initialize(uri)
    uri = uri.to_s
    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

  def has_valid_tid?
    @rkey =~ TID_PATTERN
  end

  def is_post?
    @collection == 'app.bsky.feed.post' && has_valid_tid?
  end
end

def AT_URI(uri)
  return uri if uri.is_a?(AT_URI)
  AT_URI.new(uri)
end