Add function to calculate seasonal uncertainty

priv/repo/migrations/20241209014803_season_uncertainty_function.exs

@@ -0,0 +1,58 @@
+defmodule Teiserver.Repo.Migrations.SeasonUncertaintyFunction do
+  use Ecto.Migration
+
+  def up do
+    query = """
+    create or replace function calculate_season_uncertainty(current_uncertainty float, last_updated timestamp, min_uncertainty float default 5)
+       returns float
+       language plpgsql
+      as
+    $$
+    declare
+       -- variable declaration
+    	default_uncertainty float;
+    	days_not_played float;
+    	one_month float;
+    	one_year float;
+    	interpolated_uncertainty float;
+    	min_days float;
+    	max_days float;
+    	max_uncertainty float;
+    begin
+       -- Your new uncertainty will be: greatest(target_uncertainty, current_uncertainty)
+    	-- Where target_uncertainty will be default if you have not played for over a year
+    	-- 5 (min_uncertainty) if you have played within one month
+    	-- And use linear interpolation for values in between
+    	one_year = 365.0;
+    	default_uncertainty = 25.0/3;
+    	one_month = one_year / 12;
+    	days_not_played = abs(DATE_PART('day', (now()- last_updated )));
+    	min_days = one_month;
+    	max_days = one_year;
+    	max_uncertainty = default_uncertainty;
+
+    	if(days_not_played >= max_days) then
+    		return default_uncertainty;
+    	elsif days_not_played <= min_days then
+    		return GREATEST(current_uncertainty, min_uncertainty);
+    	else
+    		-- Use linear interpolation
+    		interpolated_uncertainty =  min_uncertainty +(days_not_played - min_days) * (max_uncertainty - min_uncertainty) /(max_days - min_days);
+
+            return GREATEST(current_uncertainty, interpolated_uncertainty);
+
+    	end if;
+     end;
+    $$;
+
+
+    """
+
+    execute(query)
+  end
+
+  def down do
+    query = "drop function calculate_season_uncertainty"
+    execute(query)
+  end
+end

test/teiserver/sql/season_uncertainty_reset_test.exs

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+defmodule Teiserver.Sql.SeasonUncertaintyResetTest do
+  @moduledoc false
+  use Teiserver.DataCase
+
+  test "it can calculate seasonal uncertainty reset target" do
+    # Start by removing all anon properties
+    {:ok, now} = DateTime.now("Etc/UTC")
+
+    result = calculate_seasonal_uncertainty(now)
+    assert result == 5
+
+    # Now 30 days ago
+    month = 365 / 12
+    last_updated = DateTime.add(now, -month |> trunc(), :day)
+    result = calculate_seasonal_uncertainty(last_updated)
+
+    # assert_in_delta checks that the result is close to expected. Helps deal with rounding issues
+    assert_in_delta(result, 5, 0.1)
+
+    # Now 2 months ago
+    last_updated = DateTime.add(now, (-2 * month) |> trunc(), :day)
+    result = calculate_seasonal_uncertainty(last_updated)
+    assert_in_delta(result, 5.294728102947281, 0.1)
+
+    # Now 3 months ago
+    last_updated = DateTime.add(now, (-3 * month) |> trunc(), :day)
+    result = calculate_seasonal_uncertainty(last_updated)
+    assert_in_delta(result, 5.6035699460357, 0.1)
+
+    # Now 6 months ago
+    last_updated = DateTime.add(now, (-6 * month) |> trunc(), :day)
+    result = calculate_seasonal_uncertainty(last_updated)
+    assert_in_delta(result, 6.510170195101702, 0.1)
+
+    # Now 9 months ago
+    last_updated = DateTime.add(now, (-9 * month) |> trunc(), :day)
+    result = calculate_seasonal_uncertainty(last_updated)
+    assert_in_delta(result, 7.416770444167705, 0.1)
+
+    # Now 11 months ago
+    last_updated = DateTime.add(now, (-11 * month) |> trunc(), :day)
+    result = calculate_seasonal_uncertainty(last_updated)
+    assert_in_delta(result, 8.024491490244916, 0.1)
+
+    # Now 12 months ago
+    last_updated = DateTime.add(now, (-12 * month) |> trunc(), :day)
+    result = calculate_seasonal_uncertainty(last_updated)
+    assert_in_delta(result, 8.333333333333334, 0.1)
+
+    # Now 13 months ago
+    last_updated = DateTime.add(now, (-13 * month) |> trunc(), :day)
+
+    result = calculate_seasonal_uncertainty(last_updated)
+    assert_in_delta(result, 8.333333333333334, 0.1)
+  end
+
+  # This will calculate the new uncertainty during a season reset
+  # The longer your last_updated is from today, the more your uncertainty will be reset
+  # The number should range from min_uncertainty and default_uncertainty (8.333)
+  # Your new_uncertainty can grow from current_uncertainty but never reduce
+  # Full details in comments of the sql function calculate_season_uncertainty
+  defp calculate_seasonal_uncertainty(last_updated) do
+    current_uncertainty = 1
+    min_uncertainty = 5
+    query = "SELECT calculate_season_uncertainty($1, $2, $3);"
+
+    results =
+      Ecto.Adapters.SQL.query!(Repo, query, [current_uncertainty, last_updated, min_uncertainty])
+
+    [new_uncertainty] =
+      results.rows
+      |> Enum.at(0)
+
+    new_uncertainty
+  end
+end