From 218e792d879dafae0ceadd5ddd29926b044b1fac Mon Sep 17 00:00:00 2001
From: Brenda Wallace <brenda@wallace.net.nz>
Date: Thu, 5 Nov 2026 13:33:28 +1300
Subject: [PATCH] Predict first harvest from heat, using EcoCrop figures

---
 .claude/worktrees/neighbours-load-more    |  1 +
 .gitignore                                |  1 +
 app/models/concerns/predict_harvest.rb    | 24 +++++++-
 app/models/crop.rb                        |  9 +++
 app/models/ecocrop_data.rb                | 20 +++++++
 app/models/planting.rb                    | 11 ++--
 app/services/growing_degree_days.rb       | 28 +++++++++
 spec/factories/ecocrop_data.rb            | 13 ++++
 spec/models/ecocrop_data_spec.rb          | 72 +++++++++++++++++++++++
 spec/models/harvest_prediction_spec.rb    | 62 +++++++++++++++++++
 spec/services/growing_degree_days_spec.rb | 53 +++++++++++++++++
 11 files changed, 285 insertions(+), 9 deletions(-)
 create mode 160000 .claude/worktrees/neighbours-load-more
 create mode 100644 app/services/growing_degree_days.rb
 create mode 100644 spec/factories/ecocrop_data.rb
 create mode 100644 spec/services/growing_degree_days_spec.rb

diff --git a/.claude/worktrees/neighbours-load-more b/.claude/worktrees/neighbours-load-more
new file mode 160000
index 000000000..e633e2963
--- /dev/null
+++ b/.claude/worktrees/neighbours-load-more
@@ -0,0 +1 @@
+Subproject commit e633e2963781c15b3ce9d6989a003eeb12f4a31c
diff --git a/.gitignore b/.gitignore
index 431032cfd..ebc0c5eb7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,3 +33,4 @@ config/database.yml
 cc-test-reporter
 
 .envrc
+db/seeds/crop_job_templates/*.json
diff --git a/app/models/concerns/predict_harvest.rb b/app/models/concerns/predict_harvest.rb
index 7ce6cc2cf..6b5481eba 100644
--- a/app/models/concerns/predict_harvest.rb
+++ b/app/models/concerns/predict_harvest.rb
@@ -20,9 +20,7 @@ module PredictHarvest
     def first_harvest_predicted_at
       return @first_harvest_predicted_at if defined?(@first_harvest_predicted_at)
 
-      @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
+      @first_harvest_predicted_at = heat_predicted_first_harvest_at || days_predicted_first_harvest_at
     end
 
     def last_harvest_predicted_at
@@ -98,5 +96,25 @@ module PredictHarvest
     def harvests_with_dates
       harvests.where.not(harvested_at: nil)
     end
+
+    # The crop's median days to a first harvest after planting, when it has one.
+    def days_predicted_first_harvest_at
+      planted_at + crop.median_days_to_first_harvest.days if crop.median_days_to_first_harvest.present? && planted_at.present?
+    end
+
+    # When the heat this crop needs for a first harvest has been felt in the garden's weather, so far
+    # and as expected, or nil when we don't know the heat it needs or have no weather for the garden.
+    def heat_predicted_first_harvest_at
+      heat = crop.ecocrop_heat_data
+      return unless heat && planted_at.present? && weather_located?
+
+      Rails.cache.fetch("#{cache_key_with_version}/heat_predicted_first_harvest_at", expires_in: 8.hours) do
+        degree_days = GrowingDegreeDays.new(base: heat.tmin)
+        observed = weather_cell_readings.select(*WeatherReading::CHARTED).between(planted_at, Time.zone.today).order(:date).to_a
+        degree_days.date_reaching(heat.first_harvest_degree_days, observed) ||
+          degree_days.date_reaching(heat.first_harvest_degree_days,
+                                    observed + expected_weather_readings(after: observed.last&.date, through: planted_at + heat.gmax))
+      end
+    end
   end
 end
diff --git a/app/models/crop.rb b/app/models/crop.rb
index a8b33abda..ee4edd827 100644
--- a/app/models/crop.rb
+++ b/app/models/crop.rb
@@ -131,6 +131,15 @@ class Crop < ApplicationRecord
     nil
   end
 
+  # The EcoCrop record with the figures for a heat estimate: this crop's if it has them, else its parent's,
+  # so a variety of tomato follows tomato.
+  def ecocrop_heat_data
+    return @ecocrop_heat_data if defined?(@ecocrop_heat_data)
+
+    data = ecocrop_data
+    @ecocrop_heat_data = data&.heat_data? ? data : parent&.ecocrop_heat_data
+  end
+
   # returns hash indicating whether this crop is grown in
   # sun/semi-shade/shade
   # key: sunniness (eg. 'sun')
diff --git a/app/models/ecocrop_data.rb b/app/models/ecocrop_data.rb
index e570fd8fd..cb7e6acff 100644
--- a/app/models/ecocrop_data.rb
+++ b/app/models/ecocrop_data.rb
@@ -4,10 +4,30 @@ class EcocropData < ApplicationRecord
   validates :ecoportcode, presence: true, uniqueness: true
   validates :scientificname, presence: true
 
+  # The figures a heat estimate needs: the lowest temperature the crop grows at, its optimal range,
+  # and the shortest and longest growing cycle in days.
+  HEAT_FIELDS = %i(tmin topmn topmx gmin gmax).freeze
+
   def self.by_scientific_name(name)
     return nil if name.blank?
 
     cleaned = name.to_s.strip
     where('lower(scientificname) = lower(?)', cleaned).first
   end
+
+  # Whether there is enough here to estimate the heat a crop needs.
+  def heat_data?
+    HEAT_FIELDS.all? { |field| self[field].present? } && optimal_temp > tmin
+  end
+
+  # The middle of the optimal temperature range, in °C.
+  def optimal_temp
+    (topmn + topmx) / 2.0
+  end
+
+  # The heat to a first harvest, in growing degree days: the shortest growing cycle, grown at the optimal
+  # temperature, above the lowest temperature the crop grows at.
+  def first_harvest_degree_days
+    (optimal_temp - tmin) * gmin
+  end
 end
diff --git a/app/models/planting.rb b/app/models/planting.rb
index 39baebb9c..8718836bf 100644
--- a/app/models/planting.rb
+++ b/app/models/planting.rb
@@ -242,15 +242,14 @@ class Planting < ApplicationRecord
 
   # For a planting still growing: the weather the rest of its life will probably bring, as the readings
   # for the same days a year earlier, moved forward a year. A prediction, not an observation. `after` is the
-  # newest day already observed, when the caller has it.
-  def expected_weather_readings(after: weather_readings.maximum(:date))
-    due = weather_due_on
-    return [] if finished? || failed? || due.nil? || !weather_located?
+  # newest day already observed, when the caller has it, and `through` the last day to expect, by default the day it is due.
+  def expected_weather_readings(after: weather_readings.maximum(:date), through: weather_due_on)
+    return [] if finished? || failed? || through.nil? || !weather_located?
 
     from = (after || (weather_first_day - 1)) + 1
-    return [] if from > due
+    return [] if from > through
 
-    weather_cell_readings.select(*WeatherReading::CHARTED).between(from.prev_year, due.prev_year).order(:date).map do |reading|
+    weather_cell_readings.select(*WeatherReading::CHARTED).between(from.prev_year, through.prev_year).order(:date).map do |reading|
       reading.tap do
         reading.date = reading.date.next_year
         reading.readonly!
diff --git a/app/services/growing_degree_days.rb b/app/services/growing_degree_days.rb
new file mode 100644
index 000000000..f928b07ba
--- /dev/null
+++ b/app/services/growing_degree_days.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+# Warmth measured the way growers do, in growing degree days: each day counts how far its average
+# temperature is above the base, below which a crop barely grows. A crop reaches harvest after roughly
+# the same heat wherever it grows, even when that takes fifty days in summer and ninety in autumn.
+class GrowingDegreeDays
+  def initialize(base:)
+    @base = base
+  end
+
+  # One day's heat, from a reading's high and low. Nothing when it is colder than the base,
+  # or when the reading has no temperatures.
+  def for_day(reading)
+    return 0 unless reading.temp_max_c && reading.temp_min_c
+
+    [((reading.temp_max_c + reading.temp_min_c) / 2.0) - @base, 0].max
+  end
+
+  # The day the heat of these readings, in date order, adds up to the target, or nil if it never does.
+  def date_reaching(target, readings)
+    total = 0
+    readings.each do |reading|
+      total += for_day(reading)
+      return reading.date if total >= target
+    end
+    nil
+  end
+end
diff --git a/spec/factories/ecocrop_data.rb b/spec/factories/ecocrop_data.rb
new file mode 100644
index 000000000..6dd6baf19
--- /dev/null
+++ b/spec/factories/ecocrop_data.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :ecocrop_data do
+    sequence(:ecoportcode) { |n| 10_000 + n }
+    scientificname { 'Solanum lycopersicum' }
+    tmin { 10 }
+    topmn { 20 }
+    topmx { 30 }
+    gmin { 60 }
+    gmax { 120 }
+  end
+end
diff --git a/spec/models/ecocrop_data_spec.rb b/spec/models/ecocrop_data_spec.rb
index fdd84292b..fbab35b31 100644
--- a/spec/models/ecocrop_data_spec.rb
+++ b/spec/models/ecocrop_data_spec.rb
@@ -81,4 +81,76 @@ describe EcocropData do
       end
     end
   end
+
+  describe '#heat_data?' do
+    subject(:data) { build(:ecocrop_data, **attributes) }
+
+    let(:attributes) { {} }
+
+    it { is_expected.to be_heat_data }
+
+    context 'without a shortest growing cycle' do
+      let(:attributes) { { gmin: nil } }
+
+      it { is_expected.not_to be_heat_data }
+    end
+
+    context 'when the optimal temperature is no higher than the lowest the crop grows at' do
+      let(:attributes) { { tmin: 25 } }
+
+      it { is_expected.not_to be_heat_data }
+    end
+  end
+
+  describe '#first_harvest_degree_days' do
+    subject(:data) { build(:ecocrop_data, tmin: 10, topmn: 20, topmx: 30, gmin: 60) }
+
+    it 'is the shortest cycle at the optimal temperature, above the lowest the crop grows at' do
+      expect(data.first_harvest_degree_days).to eq 900
+    end
+  end
+
+  describe 'Crop#ecocrop_heat_data' do
+    subject(:heat_data) { variety.ecocrop_heat_data }
+
+    let(:member) { create(:member) }
+    let(:parent) { create(:crop, name: 'Tomato') }
+    let(:variety) { create(:crop, name: 'Roma tomato', parent:) }
+    let!(:tomato_data) { create(:ecocrop_data, scientificname: 'Solanum lycopersicum') }
+
+    before { parent.scientific_names.create!(name: 'Solanum lycopersicum', creator: member) }
+
+    context 'when only the parent crop has data' do
+      it "is the parent's" do
+        expect(heat_data).to eq tomato_data
+      end
+    end
+
+    context 'when the variety has data of its own' do
+      let!(:roma_data) { create(:ecocrop_data, scientificname: 'Solanum lycopersicum var. roma') }
+
+      before { variety.scientific_names.create!(name: 'Solanum lycopersicum var. roma', creator: member) }
+
+      it 'is its own' do
+        expect(heat_data).to eq roma_data
+      end
+    end
+
+    context 'when the variety has data that is not enough for a heat estimate' do
+      before do
+        create(:ecocrop_data, scientificname: 'Solanum lycopersicum var. roma', gmin: nil)
+        variety.scientific_names.create!(name: 'Solanum lycopersicum var. roma', creator: member)
+      end
+
+      it "is the parent's" do
+        expect(heat_data).to eq tomato_data
+      end
+    end
+
+    context 'when neither crop has data' do
+      before { parent.scientific_names.destroy_all }
+
+      it { is_expected.to be_nil }
+    end
+  end
 end
diff --git a/spec/models/harvest_prediction_spec.rb b/spec/models/harvest_prediction_spec.rb
index 9501ead7a..ed6b1edcf 100644
--- a/spec/models/harvest_prediction_spec.rb
+++ b/spec/models/harvest_prediction_spec.rb
@@ -38,4 +38,66 @@ describe "Harvest prediction logic" do
       expect(planting.harvest_in_next_week?).to be false
     end
   end
+
+  describe "#first_harvest_predicted_at" do
+    subject(:predicted_at) { planting.first_harvest_predicted_at }
+
+    let(:today) { Time.zone.today }
+    let(:planted_at) { today - 20 }
+    let(:garden) { create(:garden).tap { |g| g.update_columns(latitude: -41.29, longitude: 174.78) } } # rubocop:disable Rails/SkipsModelValidations
+    let(:planting) { create(:planting, crop:, garden:, owner: garden.owner, planted_at:) }
+
+    def add_weather(dates, **attributes)
+      dates.each { |date| create(:weather_reading, date:, temp_max_c: 22.0, temp_min_c: 12.0, **attributes) }
+    end
+
+    context "without heat figures for the crop" do
+      it "is the median days after planting" do
+        expect(predicted_at).to eq planted_at + 20
+      end
+    end
+
+    context "with heat figures for the crop" do
+      # Each day gives 7 degree days above the base of 10°C, so the 30 a first harvest needs come on the fifth day.
+      before do
+        crop.scientific_names.create!(name: "Solanum lycopersicum", creator: create(:member))
+        create(:ecocrop_data, scientificname: "Solanum lycopersicum", tmin: 10, topmn: 20, topmx: 30, gmin: 2, gmax: 60)
+      end
+
+      context "with the weather already here" do
+        before { add_weather(planted_at..(planted_at + 9)) }
+
+        it "is the day the heat adds up" do
+          expect(predicted_at).to eq planted_at + 4
+        end
+      end
+
+      context "when some of the heat is still to come" do
+        let(:planted_at) { today - 2 }
+
+        before do
+          add_weather(planted_at..(planted_at + 1))
+          add_weather(((planted_at + 2)..(planted_at + 6)).map(&:prev_year))
+        end
+
+        it "is the day it adds up, counting last year's weather for the days ahead" do
+          expect(predicted_at).to eq planted_at + 4
+        end
+      end
+
+      context "without weather in the garden" do
+        it "is the median days after planting" do
+          expect(predicted_at).to eq planted_at + 20
+        end
+      end
+
+      context "when the garden has no location" do
+        before { garden.update_columns(latitude: nil, longitude: nil) } # rubocop:disable Rails/SkipsModelValidations
+
+        it "is the median days after planting" do
+          expect(predicted_at).to eq planted_at + 20
+        end
+      end
+    end
+  end
 end
diff --git a/spec/services/growing_degree_days_spec.rb b/spec/services/growing_degree_days_spec.rb
new file mode 100644
index 000000000..1805155a2
--- /dev/null
+++ b/spec/services/growing_degree_days_spec.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe GrowingDegreeDays do
+  subject(:degree_days) { described_class.new(base: 10) }
+
+  let(:warm_day) { build(:weather_reading, temp_max_c: 22.0, temp_min_c: 12.0) }
+
+  describe '#for_day' do
+    it 'is how far the average temperature is above the base' do
+      expect(degree_days.for_day(warm_day)).to eq 7
+    end
+
+    context 'when the day is colder than the base' do
+      let(:cold_day) { build(:weather_reading, temp_max_c: 11.0, temp_min_c: 3.0) }
+
+      it 'is nothing' do
+        expect(degree_days.for_day(cold_day)).to eq 0
+      end
+    end
+
+    context 'without temperatures' do
+      let(:unknown_day) { build(:weather_reading, temp_max_c: nil, temp_min_c: nil) }
+
+      it 'is nothing' do
+        expect(degree_days.for_day(unknown_day)).to eq 0
+      end
+    end
+  end
+
+  describe '#date_reaching' do
+    let(:readings) do
+      (Date.new(2026, 10, 1)..Date.new(2026, 10, 3)).map { |date| build(:weather_reading, date:, temp_max_c: 22.0, temp_min_c: 12.0) }
+    end
+
+    it 'is the day the total passes the target' do
+      expect(degree_days.date_reaching(10, readings)).to eq Date.new(2026, 10, 2)
+    end
+
+    it 'is the day the total just equals the target' do
+      expect(degree_days.date_reaching(14, readings)).to eq Date.new(2026, 10, 2)
+    end
+
+    it 'is nil when the readings never add up to the target' do
+      expect(degree_days.date_reaching(100, readings)).to be_nil
+    end
+
+    it 'is nil without readings' do
+      expect(degree_days.date_reaching(10, [])).to be_nil
+    end
+  end
+end