add pdf processor class

lib/pdf_processor.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+class PdfProcessor < HexaPDF::Content::Processor
+  attr_reader :result, :contents
+  attr_accessor :handler
+
+  def initialize(page)
+    super
+
+    @contents = ''.b
+    @result = []
+
+    @serializer = HexaPDF::Serializer.new
+  end
+
+  def process(operator, operands = [])
+    super
+
+    contents << @operators[operator].serialize(
+      @serializer,
+      *handler.call(self, operator, operands)
+    )
+  end
+
+  def self.call(data, pdf_handler, result_handler, acc = {})
+    doc = HexaPDF::Document.new(io: StringIO.new(data))
+
+    doc.pages.each do |page|
+      processor = PdfProcessor.new(page)
+      processor.handler = pdf_handler
+
+      page.process_contents(processor)
+
+      page.contents = processor.contents
+
+      processor.result.each do |item|
+        result_handler.call(item, page, acc)
+      end
+    end
+
+    new_io = StringIO.new
+
+    doc.write(new_io)
+
+    [new_io.tap(&:rewind).read, acc]
+  end
+end