add chunks controller and service

app/controllers/v1/learning_objects/chunks_controller.rb

+class LearningObjects::ChunksController < ApplicationController
+  before_action :chunk_service
+
+  # GET /learning_objects/:learning_object_id/chunk
+  def show
+    if @chunk.exist?
+      post_file
+      render nothing: true, status: :ok
+    else
+      render nothing: true, status: :not_found # chunk doesnt exists and needs to be uploaded
+    end
+  end
+
+  # POST /learning_objects/:learning_object_id/chunk
+  def create
+    @chunk.save
+
+    post_file
+
+    render nothing: true, status: :ok
+  end
+
+  private
+
+  def chunk_service
+    @chunk = ChunksService.new(chunks_params)
+    return render(nothing: true, status: :unsupported_media_type) if @chunk.nil?
+  end
+
+  # Never trust parameters from the scary internet, only allow the white list through.
+  def chunks_params
+    params.permit(:file, :learning_object_id, :resumableIdentifier, :resumableFilename, :resumableChunkNumber, :resumableTotalChunks, :resumableChunkSize)
+  end
+
+  def post_file
+    return false unless @chunk.last?
+
+    publisher = LearningObjectPublisher.new(DspaceService.create_client)
+    publisher.post @chunk.learning_object, @chunk.resumable_filename
+  end
+end

app/services/chunks_service.rb

+class ChunksService
+  attr_reader :learning_object, :resumable_filename
+
+  def initialize(params)
+    @learning_object = LearningObject.find params[:learning_object_id]
+    return nil if @learning_object.blank?
+
+    @dir = "/tmp/#{chunks_params[:resumableIdentifier]}"
+    @resumable_filename = "#{@dir}/#{params[:resumableFilename]}"
+    @resumable_file_extension = File.extname(@resumable_filename)[1..-1]
+    return nil unless valid_mime_type?
+
+    @total_chunks = params[:resumableTotalChunks].to_i
+    @chunk_number = params[:resumableChunkNumber].to_i
+    @chunk_size = params[:resumableChunkSize].to_i
+    @chunk_tmpfile = params[:file].tempfile
+    @chunk = resumable_chunk @chunk_number
+  end
+
+  def exist?
+    File.exist? @chunk
+  end
+
+  def save
+    # Create chunks directory when not present on system
+    FileUtils.mkdir(@dir, mode: 0700) unless File.directory?(@dir)
+
+    # Move the uploaded chunk to the directory
+    FileUtils.mv @chunk_tmpfile, @chunk
+
+    concatenate_chunks if last?
+  end
+
+  def last?
+    @chunk_number == @total_chunks
+  end
+
+  private
+
+  def valid_mime_type?
+    mime_types = @learning_object.object_type.mime_types.map(&:extension)
+    return true if mime_types.empty?
+    mime_types.include? @resumable_file_extension
+  end
+
+  def resumable_chunk(part)
+    "#{@resumable_filename}.part#{part}"
+  end
+
+  def concatenate_chunks
+    File.open(@resumable_filename, 'a') do |target|
+      [1..@chunk_number].each do |i|
+        chunk = File.open(resumable_chunk(i), 'r').read
+        chunk.each_line { |line| target << line }
+        FileUtils.rm resumable_chunk(i), force: true
+      end
+      logger.info "File saved to #{@resumable_filename}"
+    end
+  end
+end