From 86877cfd9e9dda8e8e6309707a9c7329081f4680 Mon Sep 17 00:00:00 2001
From: eugen neagoe <eneagoe@gmail.com>
Date: Mon, 15 Jul 2019 14:54:49 +0300
Subject: [PATCH] Lazy load image content

  Instead of reading the image content from files/objects at
  declaration, use a lambda to delay reading the image data only when
  the image is actually inserted in the template.
---
 lib/sablon/content.rb    | 16 ++++++++++++----
 lib/sablon/operations.rb |  2 +-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/lib/sablon/content.rb b/lib/sablon/content.rb
index 34d7a036..aa3c3711 100644
--- a/lib/sablon/content.rb
+++ b/lib/sablon/content.rb
@@ -184,15 +184,23 @@ def inspect
         "#<Image #{name}:#{@rid_by_file}>"
       end
 
+      # image data being lazily loaded by procs, we need to actually execute
+      # the procs to test that the generated images are the same
+      def ==(other)
+        self.class == other.class &&
+          name == other.name && properties == other.properties &&
+            data.call == other.data.call
+      end
+
       def initialize(source, attributes = {})
         attributes = Hash[attributes.map { |k, v| [k.to_s, v] }]
         # If the source object is readable, use it as such otherwise open
-        # and read the content
+        # and lazily read the content
         if source.respond_to?(:read)
           name, img_data = process_readable(source, attributes)
         else
           name = File.basename(source)
-          img_data = IO.binread(source)
+          img_data = -> { IO.binread(source) }
         end
         #
         super name, img_data
@@ -233,8 +241,8 @@ def process_readable(source, attributes)
             raise ArgumentError, "Error: Could not determine filename from source, try: `Sablon.content(readable_obj, filename: '...')`"
           end
         end
-        #
-        [File.basename(name), source.read]
+        # delay loading the image with a lambda
+        [File.basename(name), -> { source.read } ]
       end
 
       # Convert centimeters or inches to Word specific emu format
diff --git a/lib/sablon/operations.rb b/lib/sablon/operations.rb
index a2cf7a83..0f2992d6 100644
--- a/lib/sablon/operations.rb
+++ b/lib/sablon/operations.rb
@@ -136,7 +136,7 @@ def set_local_rid(env, image)
           rel_attr = {
             Type: 'http://schemas.openxmlformats.org/officeDocument/2006/relationships/image'
           }
-          rid = env.document.add_media(image.name, image.data, rel_attr)
+          rid = env.document.add_media(image.name, image.data.call, rel_attr)
           image.rid_by_file[env.document.current_entry] = rid
         elsif image.rid_by_file[env.document.current_entry].nil?
           # locate an existing relationship and duplicate it