Customer Facing/Friendly Identifiers for Rails

cfid.rb

class Cfid

  attr_reader :prefix
  attr_reader :id

  def initialize(prefix:, id:)
    @prefix = prefix
    @id     = id
  end

  def encoded_id
    sqids.encode([id])
  end

  def model
    self.class.models[prefix]
  end

  def record
    if model.present? && id.present?
      model.find_by(id:)
    end
  end

  def to_s
    "#{ prefix }_#{ encoded_id }"
  end

  def self.alphabet
    # Rails.application.credentials.dig(:cfid, :alphabet)
    # - or -
    # ENV["CFID_ALPHABET"]
    #
    # This is a hard-coded example for this explanation:

    "GWkjSVLyXKsoJ1nziMNue8Rafqlgxb4IhQCBtr03HUYAd9v7mP2D6FE5wOpTcZ"
  end

  def self.find(cfid)
    prefix, encoded_id = cfid.to_s.strip.split("_")
    return nil unless prefix.present? && encoded_id.present?

    ids = sqids.decode(encoded_id)
    return nil unless ids.present?

    new(prefix:, id: ids.last)
  end

  # A memoized list of models and prefix for easy lookup later
  #
  # If any prefixes are changed, make sure you restart your server or console
  # to reload this value.
  def self.models
    return @models if defined?(@models)

    @models = {}

    Dir.glob(Rails.root.join("app/models/**/*.rb")).each do |path|
      class_name = path.gsub(Rails.root.join("app/models/").to_s, "").gsub(/\.rb$/, "").gsub("concerns/", "").classify
      klass = class_name.safe_constantize
      next unless klass&.respond_to?(:cfid_prefix)

      clean_prefix = klass.cfid_prefix.to_s.gsub(/_$/, "").to_s
      next unless clean_prefix.present?

      @models[clean_prefix] = klass
    end

    @models
  end

  def self.sqids
    @sqids ||= Sqids.new(alphabet:, min_length: 8)
  end

  private

    def sqids
      self.class.sqids
    end

end

customer_facing_identifiable.rb

module CustomerFacingIdentifiable

  extend ActiveSupport::Concern

  def cfid
    return nil if new_record?

    @cfid ||= Cfid.new(prefix: cfid_prefix, id:)
  end

  def cfid_prefix
    self.class.cfid_prefix
  end

  def key
    [ to_param ]
  end

  def to_cfid
    cfid&.to_s
  end

  def to_param
    to_cfid
  end

  class_methods do

    def cfid_prefix=(prefix)
      @cfid_prefix = prefix.to_s
    end

    def cfid_prefix
      @cfid_prefix || default_prefix_for_cfid
    end

    def customer_facing_prefix(value)
      self.cfid_prefix = value
    end

    # Fallback to a calculated prefix, if none is provided for this model.
    #
    # User => "us"
    # UserAccount => "usac"
    def default_prefix_for_cfid
      self.model_name.name.underscore.split("_").map { |s| s[0..1] }.join("")
    end

    def find_by_cfid(cfid_str)
      cfid = Cfid.find(cfid_str)
      return nil unless cfid.present?
      return nil unless cfid.prefix == cfid_prefix

      cfid.record
    end

    def find_by_cfid!(cfid)
      if record = find_by_cfid(cfid)
        record
      else
        raise ActiveRecord::RecordNotFound
      end
    end

  end
end

project.rb

class Project < ApplicationRecord
  
  include CustomerFacingIdentifiable
  
  customer_facing_prefix :proj
  
end

projects_controller.rb

class ProjectsController < ApplicationController
  
   # GET /projects/proj_123
   def show
     @project = Project.find_by_cfid!(params[:id])
   end
  
end