Integration of generating PDF using 'wicked_pdf' and uploading to AWS using 'aws-sdk'

pdf_file.rb

# This Rails Model can be used to generate a PDF, upload to AWS, and store bucket/key
# of the PDF. Uses Wicked PDF and the AWS SDK.
# 
# Gems:
#     gem 'aws-sdk'       # https://github.com/aws/aws-sdk-ruby
#     gem 'wicked_pdf'    # https://github.com/mileszs/wicked_pdf
# 
# Sources: 
#     https://github.com/thoughtbot/paperclip/wiki/PDF-Email-Attachments-with-Paperclip-and-wicked_pdf
#     https://gist.github.com/micahroberson/5988843

class PdfFile < ApplicationRecord
  # START HERE:
  # Validation is used to trigger the upload. If the PDF upload fails, this model will
  # not be saved to the Database. The order is important here, since the :key and :bucket
  # values will be set by the :upload_to_s3_and_validate_response method.
  validate :upload_to_s3_and_validate_response, :on => :create
  validates_presence_of :key, :bucket

  # For this model to work, the bucket must be set up on S3. You must have an AWS account
  # and have it linked to your Rails App. More info here:
  # http://docs.aws.amazon.com/sdk-for-ruby/v2/developer-guide/setup-config.html
  def bucket_name
    return "your-bucket-name"
  end

  # Uploads the PDF to the AWS bucket, returns a response.
  def upload_to_s3
    # Set Buket and Key
    filename    = "#{self.id}-#{Time.now.strftime('%Y%m%d%H%M%S')}.pdf"
    self.key    = "pdf/#{filename}"
    self.bucket = bucket_name

    # Get path for generated PDF. This is performed by the :create_pdf_path method.
    pdf_path    = create_pdf_path

    # Open temp file
    pdf         = File.open(pdf_path)

    # Upload to AWS
    s3          = Aws::S3::Client.new
    response    = s3.put_object(
      bucket: self.bucket, 
      key:    self.key, 
      body:   pdf, 
      acl:    "public-read" # optional: makes the file readable by anyone
    )

    # Remove Temp file after upload
    File.delete(pdf_path) if File.exist?(pdf_path)

    return response
  end

  # Generates the PDF from a view and returns a path to the Temp File where the PDF is
  # currently located. This path is used by the :upload_to_s3 method to perform upload.
  def create_pdf_path
    # use wicked_pdf gem to create a PDF from an html template.
    doc_pdf = WickedPdf.new.pdf_from_string(
      ActionController::Base.new().render_to_string(
        template: "pdfs/show",            # <- this is the location of the PDF template.
        layout:   "layouts/pdf.html.erb", # <- layout used for PDF files.
        locals:   { x: "example" }        # <- any local variables in template.
      ),
      pdf:         "Document Name",
      page_size:   "Letter",
      orientation: "Landscape",
      margin: { top:    "0.5in",
                bottom: "0.5in",
                left:   "0.5in",
                right:  "0.5in" },
      disposition: "attachment"
    )

    pdf_path = Rails.root.join("tmp", "temp_pdf_file_#{self.id}_#{Date.today.iso8601}.pdf")
    File.open(pdf_path, "wb") do |file|
      file << doc_pdf
    end

    # Returns the path of the temporary PDF file. eg: "/tmp/temp_pdf_file_132_2017-12-12.pdf"
    return pdf_path
  end

  private
  
    # This validation generates the PDF, performs the upload, and makes sure that it 
    # was all done succesfully.
    def upload_to_s3_and_validate_response
      response = self.upload_to_s3
      self.errors.add :base, "unable upload PDF" if response.error.present?
    end

end