extract email assets

lib/email_messages.rb

@@ -1,13 +1,70 @@
 # frozen_string_literal: true
 
 module EmailMessages
+  MIN_BODY_SIZE = 2.kilobytes
+  MIN_ASSET_SIZE = 256.bytes
+  STYLE_REGEXP = %r{<style[^>]*>.*?</style>(?:\s*<style[^>]*>.*?</style>)*}mi
+  BASE64_REGEXP = %r{(data:[^,]*;base64,)([A-Za-z0-9+/=]+)}
+  ASSET_REGEXP = Regexp.union(STYLE_REGEXP, BASE64_REGEXP)
+  ASSET_PREFIX = '[[asset:'
+  PLACEHOLDER_REGEXP = /\[\[asset:(\h{40})\]\]/
+
   module_function
 
   def find_or_create_for_account_user(account, user, subject, body)
     subject = I18n.t(:you_are_invited_to_sign_a_document) if subject.blank?
 
-    message = account.email_messages.new(author: user, subject:, body:).tap(&:validate)
+    body, assets = maybe_extract_assets(account, body)
 
-    account.email_messages.find_by(sha1: message.sha1) || message.tap { |m| m.save!(validate: false) }
+    new_message = account.email_messages.new(author: user, subject:, body:).tap(&:validate)
+
+    message = account.email_messages.find_by(sha1: new_message.sha1)
+
+    message ||= new_message.tap do |m|
+      m.save!(validate: false)
+
+      save_new_assets!(account, assets)
+    end
+
+    message
+  end
+
+  def save_new_assets!(account, assets)
+    return if assets.blank?
+
+    existing_assets_sha1 = account.email_message_assets.where(sha1: assets.map(&:sha1)).pluck(:sha1)
+
+    assets.each do |asset|
+      asset.save!(validate: false) if existing_assets_sha1.exclude?(asset.sha1)
+    rescue ActiveRecord::RecordNotUnique
+      nil
+    end
+  end
+
+  def maybe_extract_assets(account, body)
+    return [body, []] if body.blank? || body.bytesize < MIN_BODY_SIZE
+
+    assets_index = {}
+
+    result = body.gsub(ASSET_REGEXP) do
+      match = Regexp.last_match
+      prefix, data = match[1] ? [match[1], match[2]] : ['', match[0]]
+
+      next match[0] if data.blank? || data.bytesize < MIN_ASSET_SIZE
+
+      asset = account.email_message_assets.new(data:).tap(&:validate)
+      assets_index[asset.sha1] = asset
+
+      "#{prefix}#{ASSET_PREFIX}#{asset.sha1}]]"
+    end
+
+    [result, assets_index.values]
+  end
+
+  def rebuild_body_with_assets(account_id, body)
+    shas = body.scan(PLACEHOLDER_REGEXP).flatten.uniq
+    data = EmailMessageAsset.where(account_id:, sha1: shas).pluck(:sha1, :data).to_h
+
+    body.gsub(PLACEHOLDER_REGEXP) { data[Regexp.last_match(1)] || Regexp.last_match(0) }
   end
 end