fix: keep config precision for stats with a global offset

src/main/java/net/tfminecraft/advancedcrafting/utils/StatTemplateMath.java

@@ -1,6 +1,7 @@
 package net.tfminecraft.advancedcrafting.utils;
 
 import java.math.BigDecimal;
+import java.math.MathContext;
 import java.math.RoundingMode;
 import java.util.ArrayList;
 import java.util.HashSet;
@@ -27,34 +28,33 @@ public static double getFactor(StatTemplate template, String statId) {
 		return template.getFactor(statId);
 	}
 
-	public static double applyGlobalOffset(double raw, String statId) {
+	/**
+	 * Value written to the item. A stat with a global offset (movement_speed: 100) is rounded in
+	 * config units and then divided, so the item keeps the precision the config shows. Rounding
+	 * after the division kept 2 decimals of the divided value, which turned 1.4 into 1.
+	 */
+	public static double applyScaledValue(double raw, String statId, StatTemplate template) {
+		double scaled = applyScaledValueForPreview(raw, statId, template);
 		Double offset = Cache.globalStatOffsets.get(statId.toLowerCase());
 		if (offset == null || offset == 0) {
-			return raw;
+			return scaled;
 		}
-		return round(raw / offset);
-	}
-
-	public static double applyScaledValue(double raw, String statId, StatTemplate template) {
-		return applyFactor(applyGlobalOffset(raw, statId), getFactor(template, statId));
+		return BigDecimal.valueOf(scaled)
+				.divide(BigDecimal.valueOf(offset), MathContext.DECIMAL64)
+				.doubleValue();
 	}
 
-	/** Config-scale value for converter preview (reverses global offset division). */
+	/** Config-scale value for converter preview: the factor applied, before any global offset. */
 	public static double applyScaledValueForPreview(double raw, String statId, StatTemplate template) {
-		double scaled = applyScaledValue(raw, statId, template);
-		Double offset = Cache.globalStatOffsets.get(statId.toLowerCase());
-		if (offset == null || offset == 0) {
-			return scaled;
-		}
-		return round(scaled * offset);
+		return applyFactor(raw, getFactor(template, statId));
 	}
 
 	public static double applyFactor(double raw, double factor) {
 		return round(raw * factor);
 	}
 
 	private static double round(double value) {
-		BigDecimal bd = new BigDecimal(value);
+		BigDecimal bd = BigDecimal.valueOf(value); // decimal digits, so 1.005 rounds half-up to 1.01
 		double abs = Math.abs(value);
 		if (abs >= 0.01 || abs == 0) {
 			return bd.setScale(2, RoundingMode.HALF_UP).doubleValue();

src/main/resources/stats.yml

@@ -153,7 +153,7 @@ greataxe:
   base-stats:
     - attack_speed(1.2)
     - blunt_power(3)
-    - movement_speed(0.6)
+    - movement_speed(0.1)
   stats:
     - attack_damage
     - attack_speed
@@ -165,6 +165,11 @@ greataxe:
     - lifesteal
     - movement_speed
     - max_item_damage
+  # Two-handed, so it never has an off-hand shortsword: movement is (0.1 + leather/wool) x 2,
+  # what a battleaxe plus an off-hand shortsword with a 0.2 movement base give with the same
+  # leather and wool.
+  factors:
+    movement_speed: 2.0
 
 light_armor:
   name: "§fLight Armor"

src/test/java/net/tfminecraft/advancedcrafting/MathCoverageTest.java

@@ -52,18 +52,47 @@ void templateScalingFiltersAddsBaseStatsAndRendersPreview() throws Exception {
     assertTrue(StatTemplateMath.formatPercentSuffix(1.001).contains("0%"));
     assertEquals(.005, StatTemplateMath.applyFactor(.01, .5));
     assertEquals(0, StatTemplateMath.applyFactor(0, 3));
-    assertEquals(2, StatTemplateMath.applyGlobalOffset(2, "missing"));
+    assertEquals(2, StatTemplateMath.applyScaledValue(2, "missing", template));
     Cache.globalStatOffsets.put("attack", 0.);
-    assertEquals(2, StatTemplateMath.applyGlobalOffset(2, "attack"));
+    assertEquals(3, StatTemplateMath.applyScaledValue(2, "attack", template));
     assertEquals(3, StatTemplateMath.applyScaledValueForPreview(2, "attack", template));
     Cache.globalStatOffsets.put("attack", 100.);
-    assertEquals(.02, StatTemplateMath.applyGlobalOffset(2, "ATTACK"));
+    assertEquals(.03, StatTemplateMath.applyScaledValue(2, "ATTACK", template));
     assertEquals(3, StatTemplateMath.applyScaledValueForPreview(2, "attack", template));
     assertEquals(0, StatTemplateMath.getFactor(template, "attack") - 1.5);
     assertNotNull(new StatTemplate("invalid", yaml("icon: bad")).getName());
     assertNotNull(new StatTemplate("default", yaml("")).getIcon());
   }
 
+  @Test
+  void offsetStatsKeepTheirConfigPrecisionOnTheItem() throws Exception {
+    Cache.globalStatOffsets.put("movement_speed", 100.);
+    var axe =
+        new StatTemplate(
+            "greataxe",
+            yaml(
+                "stats: [movement_speed]\n"
+                    + "factors:\n"
+                    + "  movement_speed: 2.0\n"
+                    + "base-stats: ['movement_speed(0.1)']"));
+    var shield =
+        new StatTemplate(
+            "shield", yaml("stats: [movement_speed]\nbase-stats: ['movement_speed(-1.6)']"));
+    var leather = new StatData(List.of("movement_speed(0.6)"));
+    var mod = new StatModifier("movement_speed", 0);
+    // (0.1 + 0.6) x 2 = 1.4 movement; rounding after the division used to store 0.01 (1.0)
+    assertEquals(.014, StatTemplateMath.filterAndApply(leather, axe).getAmount(mod));
+    assertEquals(-.01, StatTemplateMath.filterAndApply(leather, shield).getAmount(mod));
+    var wool = new StatData(List.of("movement_speed(0.3)"));
+    assertEquals(-.013, StatTemplateMath.filterAndApply(wool, shield).getAmount(mod));
+    // Below 1.0 the old 3-decimal rounding also lost the second config decimal (0.65 -> 0.7)
+    assertEquals(.0065, StatTemplateMath.applyScaledValue(.65, "movement_speed", shield));
+    assertEquals(1.4, StatTemplateMath.applyScaledValueForPreview(.7, "movement_speed", axe));
+    // Half-up on the decimal digits: 1.005 is 1.00499... as a binary double
+    assertEquals(1.01, StatTemplateMath.applyFactor(1.005, 1));
+    assertEquals(.0101, StatTemplateMath.applyScaledValue(1.005, "movement_speed", shield));
+  }
+
   @Test
   void bucketAveragesCountMissingStatsAsZeroAndSumSeparateBuckets() throws Exception {
     ingredient("iron", "stats: ['armor(6)', 'speed(2)']");