Memoize Planting-related methods for performance optimization

This commit introduces memoization to various methods in the Planting model,
PredictPlanting and PredictHarvest concerns, PlantingsHelper, and
PlantingsController.

Specifically:
- Memoized database-intensive lookups like `nearby_same_crop`, `first_harvest_date`,
  and `last_harvest_date`.
- Memoized calculated fields like `finish_predicted_at`, `expected_lifespan`,
  and `age_in_days`.
- Optimized `PlantingsHelper#transplantable_gardens_by_owner` using a hash
  to cache results per planting instance within a request.
- Applied the `defined?(@variable)` pattern where appropriate to ensure
  efficient handling of `nil` results.

These changes reduce redundant database queries and expensive calculations,
particularly during view rendering where these methods are frequently accessed.

Co-authored-by: CloCkWeRX <365751+CloCkWeRX@users.noreply.github.com>

app/controllers/plantings_controller.rb

@@ -160,7 +160,7 @@ class PlantingsController < DataController
   end
 
   def matching_seeds
-    Seed.where(crop: @planting.crop, owner: @planting.owner)
+    @matching_seeds ||= Seed.where(crop: @planting.crop, owner: @planting.owner)
       .where('(finished_at IS NULL OR finished_at >= ?)', @planting.planted_at)
       .where('(saved_at IS NULL OR saved_at <= ?)', @planting.planted_at)
   end

app/helpers/plantings_helper.rb

@@ -46,9 +46,13 @@ module PlantingsHelper
   # Returns a list of gardens the planting can be transplanted to
   # based on the planting's owner.
   def transplantable_gardens_by_owner(planting)
-    garden_ids = planting.owner.gardens.select(:id).to_a + GardenCollaborator.where(member_id: planting.owner.id).select(:garden_id).to_a
+    @transplantable_gardens ||= {}
+    cache_key = planting.id || planting.object_id
+    @transplantable_gardens[cache_key] ||= begin
+      garden_ids = planting.owner.gardens.select(:id).to_a + GardenCollaborator.where(member_id: planting.owner.id).select(:garden_id).to_a
 
-    Garden.active.where.not(id: planting.garden_id).where(id: garden_ids)
+      Garden.active.where.not(id: planting.garden_id).where(id: garden_ids)
+    end
   end
 
   def days_from_now_to_last_harvest(planting)

app/models/concerns/predict_harvest.rb

@@ -6,23 +6,31 @@ module PredictHarvest
   included do
     # dates
     def first_harvest_date
-      harvests_with_dates.minimum(:harvested_at)
+      return @first_harvest_date if defined?(@first_harvest_date)
+
+      @first_harvest_date = harvests_with_dates.minimum(:harvested_at)
     end
 
     def last_harvest_date
-      harvests_with_dates.maximum(:harvested_at)
+      return @last_harvest_date if defined?(@last_harvest_date)
+
+      @last_harvest_date = harvests_with_dates.maximum(:harvested_at)
     end
 
     def first_harvest_predicted_at
-      return unless crop.median_days_to_first_harvest.present? && planted_at.present?
+      return @first_harvest_predicted_at if defined?(@first_harvest_predicted_at)
 
-      planted_at + crop.median_days_to_first_harvest.days
+      @first_harvest_predicted_at = if crop.median_days_to_first_harvest.present? && planted_at.present?
+                                      planted_at + crop.median_days_to_first_harvest.days
+                                    end
     end
 
     def last_harvest_predicted_at
-      return unless crop.median_days_to_last_harvest.present? && planted_at.present?
+      return @last_harvest_predicted_at if defined?(@last_harvest_predicted_at)
 
-      planted_at + crop.median_days_to_last_harvest.days
+      @last_harvest_predicted_at = if crop.median_days_to_last_harvest.present? && planted_at.present?
+                                     planted_at + crop.median_days_to_last_harvest.days
+                                   end
     end
 
     # actions
@@ -65,16 +73,18 @@ module PredictHarvest
     end
 
     def neighbours_for_harvest_predictions
-      # use this planting's harvest if any
-      return harvests if harvests.size.positive?
-
-      # otherwise use nearby plantings
-      if location
-        return Harvest.where(planting: nearby_same_crop.has_harvests)
-            .where.not(planting_id: nil)
+      @neighbours_for_harvest_predictions ||= begin
+        # use this planting's harvest if any
+        if harvests.size.positive?
+          harvests
+        # otherwise use nearby plantings
+        elsif location
+          Harvest.where(planting: nearby_same_crop.has_harvests)
+              .where.not(planting_id: nil)
+        else
+          Harvest.none
+        end
       end
-
-      Harvest.none
     end
 
     private

app/models/concerns/predict_planting.rb

@@ -13,40 +13,49 @@ module PredictPlanting
 
     # dates
     def finish_predicted_at
-      if planted_at.blank? || failed?
-        nil
-      elsif crop.median_lifespan.present?
-        planted_at + crop.median_lifespan.days
-      elsif crop.parent.present? && crop.parent.median_lifespan.present?
-        planted_at + crop.parent.median_lifespan.days
-      end
+      return @finish_predicted_at if defined?(@finish_predicted_at)
+
+      @finish_predicted_at = if planted_at.blank? || failed?
+                               nil
+                             elsif crop.median_lifespan.present?
+                               planted_at + crop.median_lifespan.days
+                             elsif crop.parent.present? && crop.parent.median_lifespan.present?
+                               planted_at + crop.parent.median_lifespan.days
+                             end
     end
 
     # days
     def expected_lifespan
-      if actual_lifespan.present?
-        actual_lifespan
-      elsif crop.median_lifespan.present?
-        crop.median_lifespan
-      elsif crop.parent.present? && crop.parent.median_lifespan.present?
-        crop.parent.median_lifespan
-      end
+      return @expected_lifespan if defined?(@expected_lifespan)
+
+      @expected_lifespan = if actual_lifespan.present?
+                             actual_lifespan
+                           elsif crop.median_lifespan.present?
+                             crop.median_lifespan
+                           elsif crop.parent.present? && crop.parent.median_lifespan.present?
+                             crop.parent.median_lifespan
+                           end
     end
 
     def actual_lifespan
-      return unless planted_at.present? && finished_at.present? && !failed?
+      return @actual_lifespan if defined?(@actual_lifespan)
 
-      (finished_at - planted_at).to_i
+      @actual_lifespan = if planted_at.present? && finished_at.present? && !failed?
+                           (finished_at - planted_at).to_i
+                         end
     end
 
     def age_in_days
-      return if planted_at.blank?
-      return if failed?
+      return @age_in_days if defined?(@age_in_days)
 
-      known_last_day ||= finished_at || Time.zone.today
-      known_last_day = Time.zone.today if known_last_day > Time.zone.today
+      @age_in_days = if planted_at.blank? || failed?
+                       nil
+                     else
+                       known_last_day = finished_at || Time.zone.today
+                       known_last_day = Time.zone.today if known_last_day > Time.zone.today
 
-      (known_last_day - planted_at).to_i
+                       (known_last_day - planted_at).to_i
+                     end
     end
 
     def percentage_grown

app/models/planting.rb

@@ -119,14 +119,18 @@ class Planting < ApplicationRecord
   end
 
   def nearby_same_crop
-    return Planting.none if location.blank? || latitude.blank? || longitude.blank?
+    return @nearby_same_crop if defined?(@nearby_same_crop)
 
-    # latitude, longitude = Geocoder.coordinates(location, params: { limit: 1 })
-    Planting.joins(:garden)
-      .where(crop:)
-      .located
-      .where('gardens.latitude < ? AND gardens.latitude > ?',
-             latitude + 10, latitude - 10)
+    @nearby_same_crop = if location.blank? || latitude.blank? || longitude.blank?
+                          Planting.none
+                        else
+                          # latitude, longitude = Geocoder.coordinates(location, params: { limit: 1 })
+                          Planting.joins(:garden)
+                            .where(crop:)
+                            .located
+                            .where('gardens.latitude < ? AND gardens.latitude > ?',
+                                   latitude + 10, latitude - 10)
+                        end
   end
 
   private