From ab49af9bcb064b3aa5d93c7b0d47db025524d384 Mon Sep 17 00:00:00 2001
From: Alex Turchyn <lexfox777@gmail.com>
Date: Wed, 10 Jul 2024 01:42:10 +0300
Subject: [PATCH] add tool to merge pdf files

---
 app/controllers/api/tools_controller.rb | 18 ++++++++++++++++++
 config/routes.rb                        |  3 +++
 lib/pdf_utils.rb                        | 15 +++++++++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 app/controllers/api/tools_controller.rb

diff --git a/app/controllers/api/tools_controller.rb b/app/controllers/api/tools_controller.rb
new file mode 100644
index 00000000..9eaa1486
--- /dev/null
+++ b/app/controllers/api/tools_controller.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Api
+  class ToolsController < ApiBaseController
+    skip_authorization_check
+
+    def merge
+      files = params[:files] || []
+
+      return render json: { error: 'Files are required' }, status: :unprocessable_entity if files.blank?
+      return render json: { error: 'At least 2 files are required' }, status: :unprocessable_entity if files.size < 2
+
+      render json: {
+        data: Base64.encode64(PdfUtils.merge(files.map { |base64| StringIO.new(Base64.decode64(base64)) }).string)
+      }
+    end
+  end
+end
diff --git a/config/routes.rb b/config/routes.rb
index fdd24e9d..a91dd94b 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -41,6 +41,9 @@ Rails.application.routes.draw do
       resources :clone, only: %i[create], controller: 'templates_clone'
       resources :submissions, only: %i[index create]
     end
+    resources :tools, only: %i[] do
+      post :merge, on: :collection
+    end
   end
 
   resources :verify_pdf_signature, only: %i[create]
diff --git a/lib/pdf_utils.rb b/lib/pdf_utils.rb
index 7cfaa487..e4c22400 100644
--- a/lib/pdf_utils.rb
+++ b/lib/pdf_utils.rb
@@ -26,4 +26,19 @@ module PdfUtils
 
     decrypted_io.tap(&:rewind).read
   end
+
+  def merge(files)
+    merged_pdf = HexaPDF::Document.new
+
+    files.each do |file|
+      pdf = HexaPDF::Document.new(io: file)
+      pdf.pages.each { |page| merged_pdf.pages << merged_pdf.import(page) }
+    end
+
+    merged_content = StringIO.new
+    merged_pdf.write(merged_content)
+    merged_content.rewind
+
+    merged_content
+  end
 end