rewrite to use AR (was SQL), some logic moved to the Model

app/controllers/lab_tests_controller.rb

@@ -10,19 +10,12 @@ class LabTestsController < ApplicationController
   def index
     authorize LabTest
 
-    # Get unique dates first, using the latest record for each date
     @recordables = policy_scope(LabTest)
-                   .select(<<~SQL.squish)
-                     DISTINCT ON (DATE(lab_tests.created_at))#{' '}
-                     DATE(lab_tests.created_at) as created_at,#{' '}
-                     lab_tests.recordable_id,#{' '}
-                     lab_tests.created_at as full_created_at
-                   SQL
                    .where(user_id: @chosen_user_id)
-                   .where(date_range_condition)
-                   .order('DATE(lab_tests.created_at) ASC, lab_tests.created_at DESC, lab_tests.recordable_id DESC')
+                   .in_date_range(params[:start_date], params[:end_date])
+                   .latest_records
+                   .ordered_by_date
 
-    # Keep existing biomarkers query
     @biomarkers = policy_scope(Biomarker)
                   .includes(:reference_ranges, :lab_tests)
                   .where(lab_tests: { user_id: @chosen_user_id })
@@ -147,24 +140,5 @@ def lab_test_params
   def filter_params
     params.permit(:user_id)
   end
-
-  def date_range_condition
-    return nil unless params[:start_date].present? || params[:end_date].present?
-
-    values = {}
-    conditions = []
-
-    add_date_condition(conditions, values, :start_date, '>=')
-    add_date_condition(conditions, values, :end_date, '<=')
-
-    [conditions.join(' AND '), values]
-  end
-
-  def add_date_condition(conditions, values, date_param, operator)
-    return if params[date_param].blank?
-
-    conditions << "DATE(lab_tests.created_at) #{operator} :#{date_param}"
-    values[date_param] = Date.parse(params[date_param])
-  end
 end
 # rubocop:enable Metrics/ClassLength

app/models/lab_test.rb

@@ -13,6 +13,35 @@ class LabTest < ApplicationRecord
                       message: :must_be_nonnegative_and_numeric
                     }
 
+  scope :in_date_range, lambda { |start_date, end_date|
+    scope = all
+    scope = scope.where(created_at: Date.parse(start_date).beginning_of_day..) if start_date.present?
+    scope = scope.where(created_at: ..Date.parse(end_date).end_of_day) if end_date.present?
+    scope
+  }
+
+  scope :by_date, lambda { |date|
+    where(created_at: date.all_day)
+  }
+
+  # Show all records, ordered by newest first
+  scope :latest_records, lambda {
+    order(created_at: :asc)
+  }
+
+  # Changed to descending order to match the requirement
+  scope :ordered_by_date, lambda {
+    order(created_at: :asc, id: :asc)
+  }
+
+  # here code with group by tests by day (...DISTINCT ON)
+  # scope :latest_records, lambda {
+  #   records = all.group_by { |record| record.created_at.to_date }
+  #                .transform_values { |group| group.max_by(&:created_at) }
+  #                .values
+  #   where(id: records)
+  # }
+
   class Status
     NORMAL = :normal
     HIGH = :high