active_storage_from_url.rb

active_storage_from_url.rb

# config/initializers/active_storage_from_url.rb
# frozen_string_literal: true

require "open-uri"
require "securerandom"
require "marcel"

# This initializer extends Active Storage attachments to support attaching files directly from a remote URL.
#
# Example Usage:
#
#   class User < ApplicationRecord
#     has_one_attached :avatar
#   end
#
#   user = User.find(params[:id])
#   user.avatar.attach_from_url("https://example.com/image.jpg")
#
#   class Gallery < ApplicationRecord
#     has_many_attached :photos
#   end
#
#   gallery = Gallery.find(params[:id])
#   gallery.photos.attach_from_url("https://example.com/another_image.jpg")
#
module ActiveStorage
  class Attached
    # Common logic for attaching files from remote URLs.
    module URLAttachment # :nodoc:
      private

      def attach_from_url_impl(url)
        return if url.blank?

        uri = validate_remote_url!(url)
        downloaded_file = nil

        begin
          downloaded_file = URI.open(uri)
          filename        = extract_filename(uri) || default_filename
          content_type    = determine_content_type(downloaded_file)

          attach(io: downloaded_file, filename: filename, content_type: content_type)
        ensure
          cleanup_file(downloaded_file)
        end
      end

      def validate_remote_url!(url)
        uri = URI.parse(url)
        unless uri.is_a?(URI::HTTP) || uri.is_a?(URI::HTTPS)
          raise URI::InvalidURIError, "Invalid URL scheme: #{uri.scheme.inspect}"
        end
        uri
      end

      def extract_filename(uri)
        path = uri.path
        File.basename(path) if path.present? && path != "/"
      end

      def default_filename
        "image_#{SecureRandom.uuid}.jpg"
      end

      def determine_content_type(file)
        if file.respond_to?(:content_type) && file.content_type.present?
          file.content_type
        else
          Marcel::MimeType.for(
            file,
            name: file.respond_to?(:path) ? File.basename(file.path) : nil
          )
        end
      end

      def cleanup_file(file)
        return unless file

        if file.respond_to?(:close!)
          file.close!
        else
          file.close if file.respond_to?(:close)
          file.unlink if file.respond_to?(:unlink)
        end
      end
    end

    # Reopen the One class to add attach_from_url.
    class One
      include URLAttachment

      # Attaches a file from a remote URL to a has_one_attached association.
      #
      # @param url [String] The URL of the remote file.
      # @raise [URI::InvalidURIError] If the URL is invalid or uses an unsupported scheme.
      # @return [void]
      def attach_from_url(url)
        attach_from_url_impl(url)
      end
    end

    # Reopen the Many class to add attach_from_url.
    class Many
      include URLAttachment

      # Attaches a file from a remote URL to a has_many_attached association.
      #
      # @param url [String] The URL of the remote file.
      # @raise [URI::InvalidURIError] If the URL is invalid or uses an unsupported scheme.
      # @return [void]
      def attach_from_url(url)
        attach_from_url_impl(url)
      end
    end
  end
end