From 53dbbbaf46e84e7ffe18c3befd6eeecd472e5c60 Mon Sep 17 00:00:00 2001
From: Brenda Wallace <brenda@wallace.net.nz>
Date: Sun, 11 Oct 2026 19:42:07 +1300
Subject: [PATCH] Remove ruby-units gem and implement weight unit conversion
 directly in Harvest model

---
 Gemfile               |  1 -
 Gemfile.lock          |  2 --
 app/models/harvest.rb | 10 ++++++++--
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/Gemfile b/Gemfile
index 522a0c158..5543aa6a6 100644
--- a/Gemfile
+++ b/Gemfile
@@ -58,7 +58,6 @@ gem 'gibbon', '~>1.2.0'            # for Mailchimp newsletter subscriptions
 gem 'leaflet-rails', '>= 1.9.2'
 
 gem 'pg'
-gem 'ruby-units'                   # for unit conversion
 
 gem "comfortable_mexican_sofa", git: "https://github.com/restarone/comfortable-mexican-sofa.git"
 
diff --git a/Gemfile.lock b/Gemfile.lock
index c42f4e1e2..5a1534de2 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -660,7 +660,6 @@ GEM
       rubocop (~> 1.72, >= 1.72.1)
       rubocop-rspec (~> 3.5)
     ruby-progressbar (1.13.0)
-    ruby-units (4.1.0)
     ruby-vips (2.3.0)
       ffi (~> 1.12)
       logger
@@ -851,7 +850,6 @@ DEPENDENCIES
   rubocop-rake
   rubocop-rspec
   rubocop-rspec_rails
-  ruby-units
   sassc-rails
   scout_apm
   searchkick
diff --git a/app/models/harvest.rb b/app/models/harvest.rb
index 18900319c..519c9ab3d 100644
--- a/app/models/harvest.rb
+++ b/app/models/harvest.rb
@@ -31,6 +31,13 @@ class Harvest < ApplicationRecord
     "oz" => "oz"
   }.freeze
 
+  # Exact definitions of the international avoirdupois units, in kilograms.
+  KG_PER_WEIGHT_UNIT = {
+    "kg" => BigDecimal("1"),
+    "lb" => BigDecimal("0.45359237"),
+    "oz" => BigDecimal("0.028349523125")
+  }.freeze
+
   ##
   ## Triggers
   after_validation :cleanup_quantities
@@ -91,8 +98,7 @@ class Harvest < ApplicationRecord
   def set_si_weight
     return if weight_unit.nil?
 
-    weight_string = "#{weight_quantity} #{weight_unit}"
-    self.si_weight = Unit.new(weight_string).convert_to("kg").to_s("%0.3f").delete(" kg").to_f
+    self.si_weight = (weight_quantity * KG_PER_WEIGHT_UNIT.fetch(weight_unit)).round(3).to_f
   end
 
   def cleanup_quantities