1 files changed, 36 insertions, 0 deletions
diff --git a/activestorage/lib/active_storage/previewer/mupdf_previewer.rb b/activestorage/lib/active_storage/previewer/mupdf_previewer.rb
new file mode 100644
index 0000000000..ae02a4889d
--- /dev/null
+++ b/activestorage/lib/active_storage/previewer/mupdf_previewer.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Previewer::MuPDFPreviewer < Previewer
+    class << self
+      def accept?(blob)
+        blob.content_type == "application/pdf" && mutool_exists?
+      end
+
+      def mutool_path
+        ActiveStorage.paths[:mutool] || "mutool"
+      end
+
+      def mutool_exists?
+        return @mutool_exists unless @mutool_exists.nil?
+
+        system mutool_path, out: File::NULL, err: File::NULL
+
+        @mutool_exists = $?.exitstatus == 1
+      end
+    end
+
+    def preview
+      download_blob_to_tempfile do |input|
+        draw_first_page_from input do |output|
+          yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
+        end
+      end
+    end
+
+    private
+      def draw_first_page_from(file, &block)
+        draw self.class.mutool_path, "draw", "-F", "png", "-o", "-", file.path, "1", &block
+      end
+  end
+end