lib/asset.rb - minimal way of interfacing with a cdn that can store files and process them on the fly - in this case cloudinary, but applicable to others

asset.rb

# you should rely ONLY in the class leve interface in your views, aka
#
# Asset.thumbnail(path, :dimensions => '42x42').url
# Asset.bw(path).url
#
# and no lib internals for now - this is under development
#
# this lib handles a few things in a simple interface.  highlights:
#
# - file ids are md5s of the file contents
#
# - no file is ever uploaded more than once to cloudinary from anywhere
#
# - api responses are cached and committed back to git, these are used in all
# future builds/lib calls.  this avoids even needing to call 'exists?' during
# builds if an upload have ever been pushed to cloudinary.
#
#
#
#

require_relative '../config/boot.rb'

require 'fattr'
require 'coerce'
require 'map'
require 'systemu'
require 'uuid'
require 'util'
require 'say'


class Asset < ::String
#
  fattr(:processing){ Hash.new }
  fattr(:identifier)
  fattr(:response)

  DEFAULT_PROCESSING = {
    :quality => 75,
    :format => :jpg
  }

  def initialize(path)
    @path = Asset.find(path)
    @identifier = nil
    @response = nil

    processing.update(DEFAULT_PROCESSING)

    if @path =~ /\.gif$/
      processing[:format] = :gif
    end

    super(@path)
  end

  def path
    @path
  end

  def upload
  #
    if((response = metadata)) # NOT A TYPO ;-)
      @identifier = response['public_id'] or abort("no public_id! in #{ metadata_path }")
      @response = response
      return
    end

  #
    return if @response # ALSO NOT A TYPO ;-)

  #
    @identifier = Asset.identifier_for(@path)
    error = nil

  #
    3.times do
      error = nil

      begin
        unless ::Cloudinary::Uploader.exists?(identifier)
          @response = ::Cloudinary::Uploader.upload(path, 'public_id' => identifier)
          cache_metadata(@response)
          Say.say("#{ Util.relative_path(path, :from => Asset.root) } #=> #{ @response['url'] }", :color => :red)
        else
          unless metadata?
            @response = ::Cloudinary::Api.resource(identifier)
            cache_metadata(@response)
          end
        end

        break(@response)
      rescue => e
        Say.say("#{ Util.relative_path(path, :from => Asset.root) } #=> #{ e.message } (#{ e.class })", :color => :yellow)
        error = e
        sleep(rand * 5)
      end
    end

  #
    error ? raise(error) : @response
  end

  def metadata?
    if test(?>, path, metadata_path)
      FileUtils.rm_f(metadata_path)
    end

    test(?f, metadata_path)
  end

  def metadata
    YAML.load(IO.binread(metadata_path)) if metadata?
  end

  def cache_metadata(metadata)
    FileUtils.mkdir_p(File.dirname(metadata_path))

    IO.binwrite(metadata_path, {}.update(metadata).to_yaml)

    Say.say("cached metadata at #{ Util.relative_path(metadata_path, :from => Asset.root) } ...", :color => :yellow)
  end

  def metadata_path
    @metadata_path ||= (
      relative_path = Util.relative_path(@path, :from => Asset.root).to_s
      File.join(Asset.metadata_root.to_s, relative_path) + '.cloudinary.yml'
    )
  end

  def upload!
    @response = nil
  end

  def url_for(processing = {})
    options = self.processing.merge(processing)
    upload
    url = ::Cloudinary::Utils.cloudinary_url(identifier, options)
    url.sub(%r{^https?:}, '') # proto-relative...
  end

  def url(*args, &block)
    url_for(*args, &block)
  end

  def black_and_white
    processing[:effect] ||= {}
    processing[:effect][:saturation] = -100
    self
  end

  def bw
    black_and_white
  end

  def Asset.for(*args, &block)
    new(*args, &block)
  end

  def Asset.black_and_white(*args, &block)
    new(*args, &block).black_and_white
  end

  def Asset.bw(*args, &block)
    black_and_white(*args, &block)
  end

  def thumbnail(options = {})
    options = Map.for(options)

    width = options[:width]
    height = options[:height]
    dimensions = options[:dimensions]

    width = width.to_s.scan(/\d+/).first
    height = height.to_s.scan(/\d+/).first

    dimensions ||= "#{ width }x#{ height }"

    width ||= (dimensions.split('x')[0] || 150)
    height ||= dimensions.split('x')[1]

    if width
      processing[:width] = width
      processing[:crop] = :thumb
    end

    if height
      processing[:height] = height
      processing[:crop] = :thumb
    end

    self
  end

  def Asset.thumbnail(*args, &block)
    new(*args, &block).thumbnail
  end

#
  Fattr(:lib){ File.expand_path(__FILE__) }
  Fattr(:libdir){ File.dirname(lib) }
  Fattr(:root){ File.dirname(libdir) }
  Fattr(:metadata_root){ File.join(Asset.root, 'tmp/cache/cloudinary') }

  Fattr(:source_dir){ File.join(root, 'source') }
  Fattr(:build_dir){ File.join(root, 'build') }
  Fattr(:public_dir){ File.join(root, 'public') }

  Fattr(:images_dir){ File.join(source_dir, 'images') }
  Fattr(:assets_dir){ File.join(build_dir, 'assets') }

  Fattr(:search_path){
    [
      source_dir,
      images_dir,
      public_dir,
      build_dir
    ]
  }

  class Error < ::StandardError
    class NotFound < Error
    end
    class Ambiguous < Error
    end
  end

  def Asset.find(relative_path)
    relative_path = relative_path.to_s
    return relative_path if test(?f, relative_path)

    prefix = relative_path.split('.', 2).first

    relative_globs = [relative_path, "#{ prefix }.*"] 

    Asset.search_path.each do |dirname|
      relative_globs.each do |relative_glob|
        glob = File.join(dirname, relative_glob)

        candidates = Dir.glob(glob).select{|entry| entry !~ /\.cloudinary\.yml$/}

        case candidates.size
          when 0
            next
          when 1
            return(candidates.first)
          else
            raise Error::Ambiguous.new("#{ relative_path } (#{ candidates.join(' | ') })")
        end
      end
    end

    raise Error::NotFound.new(relative_path)
  end

  def Asset.search(*relative_paths)
    relative_paths = Coerce.list_of_strings(relative_paths)

    relative_paths.each do |relative_path|
      begin
        asset = Asset.find(relative_path)
        return asset
      rescue Error::NotFound
        next
      end
    end

    raise Error::NotFound.new(relative_paths.join(', '))
  end

  def Asset.identifier_for(path)
    @identifiers ||= {}

    stat = File.stat(path)

    key = [path, stat.mtime]

    @identifiers[key] ||= (
      Util.md5(IO.binread(path))
    )
  end
end