From bfa5b6ab5fecf4f1919e2396a92eb9794bdd8ed4 Mon Sep 17 00:00:00 2001
From: Alex Vasile <48962821+Alex-Vasile@users.noreply.github.com>
Date: Mon, 5 Sep 2022 00:30:45 -0400
Subject: [PATCH] [NPH] Fix Hex Parasite wrong behaviour when X=0. Closes
 #9446.

---
 Mage.Sets/src/mage/cards/h/HexParasite.java   | 57 ++++++++++---------
 .../cards/single/nph/HexParasiteTest.java     | 44 ++++++++++++++
 2 files changed, 74 insertions(+), 27 deletions(-)
 create mode 100644 Mage.Tests/src/test/java/org/mage/test/cards/single/nph/HexParasiteTest.java

diff --git a/Mage.Sets/src/mage/cards/h/HexParasite.java b/Mage.Sets/src/mage/cards/h/HexParasite.java
index 2d3c7988bb..cbf0e0bec8 100644
--- a/Mage.Sets/src/mage/cards/h/HexParasite.java
+++ b/Mage.Sets/src/mage/cards/h/HexParasite.java
@@ -66,34 +66,37 @@ class HexParasiteEffect extends OneShotEffect {
         TargetPermanent target = (TargetPermanent) source.getTargets().get(0);
         Permanent permanent = game.getPermanent(target.getFirstTarget());
         Player controller = game.getPlayer(source.getControllerId());
-        if (permanent != null
-                && controller != null) {
-            int toRemove = source.getManaCostsToPay().getX();
-            int removed = 0;
-            String[] counterNames = permanent.getCounters(game).keySet().toArray(new String[0]);
-            for (String counterName : counterNames) {
-                if (controller.chooseUse(Outcome.Neutral, "Remove " + counterName + " counters?", source, game)) {
-                    if (permanent.getCounters(game).get(counterName).getCount() == 1 || (toRemove - removed == 1)) {
-                        permanent.removeCounters(counterName, 1, source, game);
-                        removed++;
-                    } else {
-                        int amount = controller.getAmount(1, Math.min(permanent.getCounters(game).get(counterName).getCount(), toRemove - removed), "How many?", game);
-                        if (amount > 0) {
-                            removed += amount;
-                            permanent.removeCounters(counterName, amount, source, game);
-                        }
-                    }
-                }
-                if (removed >= toRemove) {
-                    break;
-                }
-            }
-            if (removed > 0) {
-                game.addEffect(new BoostSourceEffect(removed, 0, Duration.EndOfTurn), source);
-            }
+        if (permanent == null || controller == null) {
+            return false;
+        }
+
+        int toRemove = source.getManaCostsToPay().getX();
+        if (toRemove == 0) {
             return true;
         }
-        return false;
-    }
 
+        int removed = 0;
+        String[] counterNames = permanent.getCounters(game).keySet().toArray(new String[0]);
+        for (String counterName : counterNames) {
+            if (controller.chooseUse(Outcome.Neutral, "Remove " + counterName + " counters?", source, game)) {
+                if (permanent.getCounters(game).get(counterName).getCount() == 1 || (toRemove - removed == 1)) {
+                    permanent.removeCounters(counterName, 1, source, game);
+                    removed++;
+                } else {
+                    int amount = controller.getAmount(1, Math.min(permanent.getCounters(game).get(counterName).getCount(), toRemove - removed), "How many?", game);
+                    if (amount > 0) {
+                        removed += amount;
+                        permanent.removeCounters(counterName, amount, source, game);
+                    }
+                }
+            }
+            if (removed >= toRemove) {
+                break;
+            }
+        }
+        if (removed > 0) {
+            game.addEffect(new BoostSourceEffect(removed, 0, Duration.EndOfTurn), source);
+        }
+        return true;
+    }
 }
diff --git a/Mage.Tests/src/test/java/org/mage/test/cards/single/nph/HexParasiteTest.java b/Mage.Tests/src/test/java/org/mage/test/cards/single/nph/HexParasiteTest.java
new file mode 100644
index 0000000000..b9f7bfb983
--- /dev/null
+++ b/Mage.Tests/src/test/java/org/mage/test/cards/single/nph/HexParasiteTest.java
@@ -0,0 +1,44 @@
+package org.mage.test.cards.single.nph;
+
+import mage.constants.PhaseStep;
+import mage.constants.Zone;
+import mage.counters.CounterType;
+import org.junit.Test;
+import org.mage.test.serverside.base.CardTestPlayerBase;
+
+/**
+ * {@link mage.cards.h.HexParasite Hex Parasite}
+ *
+ * {X}{B/P}: Remove up to X counters from target permanent.
+ *           For each counter removed this way, Hex Parasite gets +1/+0 until end of turn.
+ *
+ * @author Alex-Vasile
+ */
+public class HexParasiteTest extends CardTestPlayerBase {
+
+    private static final String hexParasite = "Hex Parasite";
+
+    /**
+     * Reported bug: https://github.com/magefree/mage/issues/9446
+     *      Removing 0 counters results in "Server's error: (minimum = value = maximum) is false"
+     */
+    @Test
+    public void remove0Counters() {
+        addCard(Zone.BATTLEFIELD, playerA, hexParasite);
+        addCard(Zone.HAND, playerA, "Urza's Saga");
+
+        setStrictChooseMode(true);
+
+        playLand(1, PhaseStep.PRECOMBAT_MAIN, playerA, "Urza's Saga");
+
+        activateAbility(1, PhaseStep.POSTCOMBAT_MAIN, playerA, "{X}");
+        setChoice(playerA, "X=0");
+        setChoice(playerA, "Yes"); // Pay 2 life
+        addTarget(playerA, "Urza's Saga");
+
+        setStopAt(1, PhaseStep.END_TURN);
+        execute();
+        assertCounterCount(playerA, "Urza's Saga", CounterType.LORE, 1);
+        assertLife(playerA, 20 - 2);
+    }
+}