cantaloupe delegate script for hyrax

delegates.rb

require 'net/http'
require 'uri'
require 'json'
require 'java'

##
# Delegate script to connect Cantaloupe to Fedora. It slices a piece of
# Cantaloupe for Samvera to consume.
#
# This is a first pass and doesn't have a lot of error checking built in yet.
# It also assumes a very basic use case of a single image on an item.
#
class CustomDelegate
  ##
  # Attribute for the request context, which is a hash containing information
  # about the current request.
  #
  # This attribute will be set by the server before any other methods are
  # called. Methods can access its keys like:
  #
  # ```
  # identifier = context['identifier']
  # ```
  #
  # The hash will contain the following keys in response to all requests:
  #
  # * `client_ip`       [String] Client IP address.
  # * `cookies`         [Hash<String,String>] Hash of cookie name-value pairs.
  # * `identifier`      [String] Image identifier.
  # * `request_headers` [Hash<String,String>] Hash of header name-value pairs.
  # * `request_uri`     [String] Public request URI.
  #
  # It will contain the following additional string keys in response to image
  # requests:
  #
  # * `full_size`      [Hash<String,Integer>] Hash with `width` and `height`
  #                    keys corresponding to the pixel dimensions of the
  #                    source image.
  # * `operations`     [Array<Hash<String,Object>>] Array of operations in
  #                    order of application. Only operations that are not
  #                    no-ops will be included. Every hash contains a `class`
  #                    key corresponding to the operation class name, which
  #                    will be one of the `e.i.l.c.operation.Operation`
  #                    implementations.
  # * `output_format`  [String] Output format media (MIME) type.
  # * `resulting_size` [Hash<String,Integer>] Hash with `width` and `height`
  #                    keys corresponding to the pixel dimensions of the
  #                    resulting image after all operations have been applied.
  #
  # @return [Hash] Request context.
  #
  attr_accessor :context

  ##
  # Tells the server whether to redirect in response to the request. Will be
  # called upon all image requests.
  #
  # @param options [Hash] Empty hash.
  # @return [Hash<String,Object>,nil] Hash with `location` and `status_code`
  #         keys. `location` must be a URI string; `status_code` must be an
  #         integer from 300 to 399. Return nil for no redirect.
  #
  def redirect(_options = {})
    nil
  end

  ##
  # Tells the server whether the given request is authorized. Will be called
  # upon all image requests to any endpoint.
  #
  # Implementations should assume that the underlying resource is available,
  # and not try to check for it.
  #
  # @param options [Hash] Empty hash.
  # @return [Boolean] Whether the request is authorized.
  #
  def authorized?(_options = {})
    true
  end

  ##
  # Used to add additional keys to an information JSON response. See the
  # [Image API specification](http://iiif.io/api/image/2.1/#image-information).
  #
  # @param options [Hash] Empty hash.
  # @return [Hash] Hash that will be merged into an IIIF Image API 2.x
  #                information response. Return an empty hash to add nothing.
  #
  def extra_iiif2_information_response_keys(_options = {})
    {}
  end

  ##
  # Tells the server which source to use for the given identifier.
  #
  # @param options [Hash] Empty hash.
  # @return [String] Source name.
  #
  def source(_options = {})
    'HttpSource'
  end

  ##
  # Gets the HTTP-sourced image resource information.
  #
  # @param options [Hash] Empty hash.
  # @return [String,Hash<String,String>,nil] String URI; Hash with `uri` key,
  #         and optionally `username` and `secret` keys; or nil if not found.
  #
  def httpsource_resource_info(_options = {})
    file_id = context['identifier']

    # Split the parts into Fedora's pseudo-pairtree (only first four pairs)
    paths = file_id.split(/(.{0,2})/).reject!(&:empty?)[0, 4]

    fedora_base_url = ENV['FEDORA_URL'] + ENV['FEDORA_BASE_PATH']

    ## DCE: Add CGI Unescape
    url = fedora_base_url + '/' + paths.join('/') + '/' + file_id
    require "cgi"
    CGI::unescape(url)
  end
end