carrierwave_tasks.rb

# Examples:
#
# Reprocess all versions of User#avatar
# rake carrierwave:reprocess class=User mounted_uploader=avatar
#
# Reprocess the versions: thumb, small, medium for User#avatar
# rake carrierwave:reprocess class=User mounted_uploader=avatar versions='thumb, small, medium'

namespace :carrierwave do
  
  ##
  # Only tested with Amazon S3 Storage
  # Needs some minor modifications if you want to use this for File System Store, Cloud Files and GridFS probably.
  # This should work without Ruby on Rails as well, just set a different TMP_PATH.
  desc "Reprocesses Carrier Wave file versions of a given model."
  task :reprocess => :environment do

    ##
    # Load in the OPEN URI library to be able
    # to pull down and store the original file in a temp directory
    require 'open-uri'
    
    ##
    # Default constants
    TMP_PATH          = "#{Rails.root}/tmp/carrierwave"
    
    ##
    # Set environment constants
    CLASS             = ENV['class'].capitalize
    MOUNTED_UPLOADER  = ENV['mounted_uploader'].to_sym
    VERSIONS          = ENV['versions'].nil? ? Array.new : ENV['versions'].split(',').map {|version| version.strip.to_sym}

    ##
    # Find the Model
    MODEL = Kernel.const_get(CLASS)
        
    ##
    # Create the temp directory
    %x(mkdir -p "#{TMP_PATH}")

    ##
    # Find all records for the provided Model
    records = MODEL.all
    
    ##
    # Output to console
    puts "\nCarrier Wave Version Reprocessing!"
    puts "======================================="
    puts "Model:              #{CLASS}"
    puts "Mounted Uploader:   #{MOUNTED_UPLOADER}"
    puts "Versions:           #{VERSIONS.empty? ? "all" : VERSIONS.join(', ')}\n\n"
    
    ##
    # Run through all records
    records.each do |record|
      
      ##
      # Set the mounted uploader object
      mounted_object = record.send(MOUNTED_UPLOADER)
      
      ##
      # Retrieve Filename
      filename = mounted_object.path.split('/').last
      
      ##
      # Output to console
      puts "Reprocessing: #{filename}"
      
      ##
      # Read out the original file from the remote location
      # and write it out to the temp directory (TMP_PATH)
      # This file will be used as the base file to reprocess
      # the versions. Once all versions have been processed,
      # this temp file will be directly removed.
      open(mounted_object.url) do |original_object|
        File.open(File.join(TMP_PATH, filename), 'w') do |temp_file|
          temp_file.write(original_object.read)
        end
      end
      
      ##
      # By default it will add all available versions to the versions variable
      # which means that all available versions will be reprocessed.
      # If the "versions" argument has been provided, then only the specified
      # version(s) will be set to the versions variable, and thus, only these
      # will be reprocessed.
      versions = mounted_object.versions.map {|version| version[0]}
      versions = VERSIONS unless VERSIONS.empty?
      
      ##
      # Reprocesses the versions
      versions.each do |version|
        mounted_object.send(version).cache!(File.open(File.join(TMP_PATH, filename)))
        mounted_object.send(version).store!
      end
      
      ##
      # Removes the temp file
      %x(rm "#{TMP_PATH}/#{filename}")
    end

  end
end