# Generate migrations and set up storage tables
rails active_storage:install
rails db:migrate

local:
  service: Disk
  root: <%= Rails.root.join("storage") %>

amazon:
  service: S3
  access_key_id: <%= Rails.application.credentials.dig(:aws, :access_key_id) %>
  secret_access_key: <%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
  region: us-east-1
  bucket: my-app-<%= Rails.env %>

google:
  service: GCS
  credentials: <%= Rails.root.join("path/to/keyfile.json") %>
  project: my-project
  bucket: my-app-<%= Rails.env %>

config.active_storage.service = :local

class User < ApplicationRecord
  has_one_attached :avatar
end

<%= form.file_field :avatar, direct_upload: true %>

class UsersController < ApplicationController
  def create
    @user = User.create!(user_params)
    redirect_to @user
  end

  private
    def user_params
      params.expect(user: [:name, :email, :avatar])
    end
end

user.avatar.attach(params[:avatar])
user.avatar.attached?  # => true

class Message < ApplicationRecord
  has_many_attached :images
end

@message.images.attach(params[:images])
@message.images.attached?  # => true

url_for(user.avatar)
# => https://www.example.com/rails/active_storage/blobs/redirect/:signed_id/avatar.png

rails_blob_path(user.avatar, disposition: "attachment")
# => Download link

<%= image_tag user.avatar %>
<%= link_to "Download", rails_blob_path(user.avatar, disposition: "attachment") %>

class User < ApplicationRecord
  has_one_attached :avatar do |attachable|
    attachable.variant :thumb, resize_to_limit: [100, 100]
  end
end

<%= image_tag user.avatar.variant(:thumb) %>

user.avatar.purge       # Synchronous
user.avatar.purge_later # Async via Active Job

class User < ApplicationRecord
  has_one_attached :avatar do |attachable|
    attachable.variant :medium, resize_to_limit: [400, 400]
    attachable.variant :thumb, resize_to_limit: [150, 150]
  end
  
  validate :avatar_content_type
  
  private
    def avatar_content_type
      return unless avatar.attached?
      unless avatar.content_type.in?(%w[image/jpeg image/png image/gif])
        errors.add(:avatar, "must be a valid image")
      end
    end
end

class Document < ApplicationRecord
  has_one_attached :file
  
  after_create_commit :analyze_document
  
  private
    def analyze_document
      return unless file.attached?
      puts "File: #{file.filename}"
      puts "Size: #{file.byte_size} bytes"
      puts "Type: #{file.content_type}"
      puts "Analyzed: #{file.analyzed?}"
      # Use metadata from file.metadata for further processing
    end
end

class Post < ApplicationRecord
  has_many_attached :images do |attachable|
    attachable.variant :display, resize_to_limit: [800, 600]
    attachable.variant :thumb, resize_to_limit: [200, 200]
  end
end

# In view:
<%= @post.images.each do |image| %>
  <%= image_tag image.variant(:display) %>
<% end %>

# Find users with avatars
User.joins(:avatar_attachment).distinct

# Find messages with only video attachments
Message.joins(:images_blobs).where(active_storage_blobs: { content_type: "video/mp4" })

# Eager load to prevent N+1
Post.includes(:images_attachments, :images_blobs)