fix bulk upload line ending parsing

app/services/bulk_upload/lettings/log_creator.rb

@@ -56,14 +56,10 @@ private
     contents = ""
 
     File.open(path, "r") do |f|
-      f.seek(9900)
       contents = f.read
     end
 
-    rn_count = contents.scan("\r\n").count
-    n_count = contents.scan(/[^\r]\n/).count
-
-    if rn_count > n_count
+    if contents[-2..] == "\r\n"
       "\r\n"
     else
       "\n"

app/services/bulk_upload/lettings/validator.rb

@@ -212,14 +212,10 @@ private
     contents = ""
 
     File.open(path, "r") do |f|
-      f.seek(9900)
       contents = f.read
     end
 
-    rn_count = contents.scan("\r\n").count
-    n_count = contents.scan(/[^\r]\n/).count
-
-    if rn_count > n_count
+    if contents[-2..] == "\r\n"
       "\r\n"
     else
       "\n"

spec/services/bulk_upload/lettings/validator_spec.rb

@@ -46,6 +46,39 @@ RSpec.describe BulkUpload::Lettings::Validator do
         expect(error.row).to eq("7")
       end
     end
+
+    context "with unix line endings" do
+      let(:fixture_path) { file_fixture("2022_23_lettings_bulk_upload.csv") }
+      let(:file) { Tempfile.new }
+      let(:path) { file.path }
+
+      before do
+        string = File.read(fixture_path)
+        string.gsub!("\r\n", "\n")
+        file.write(string)
+        file.rewind
+      end
+
+      it "creates validation errors" do
+        expect { validator.call }.to change(BulkUploadError, :count)
+      end
+    end
+
+    context "without headers" do
+      let(:log) { build(:lettings_log, :completed) }
+      let(:file) { Tempfile.new }
+      let(:path) { file.path }
+
+      before do
+        file.write("\r\n" * 5)
+        file.write(BulkUpload::LogToCsv.new(log:, line_ending: "\r\n").to_csv_row)
+        file.rewind
+      end
+
+      it "creates validation errors" do
+        expect { validator.call }.to change(BulkUploadError, :count)
+      end
+    end
   end
 
   describe "#should_create_logs?" do

spec/support/bulk_upload/log_to_csv.rb

@@ -1,8 +1,9 @@
 class BulkUpload::LogToCsv
-  attr_reader :log
+  attr_reader :log, :line_ending
 
-  def initialize(log:)
+  def initialize(log:, line_ending: "\n")
     @log = log
+    @line_ending = line_ending
   end
 
   def to_csv_row
@@ -152,7 +153,7 @@ class BulkUpload::LogToCsv
       log.declaration,
       log.joint,
       renewal,
-      "\n",
+      line_ending,
     ].join(",")
   end