Prevent targeting unreachable turreted entities

Introduce CanEverReachTarget in the Attack component to check whether
a target is geometrically reachable at all, accounting for height
offsets and turreted units inside buildings.

For non-parabolic attacks (e.g. melee), a simple 3D distance check
from the closest approach point is used.

For parabolic attacks (e.g. ranged), the parabolic range formula
is used to determine if the height difference is surmountable
from the closest horizontal distance to the target.

Add GetClosestApproachDistanceToTurretPoint to TurretHolder
to estimate the minimum horizontal distance to a turret point,
using its local offset and the holder's obstruction size.
Passable buildings are not considered obstacles.

Fixes units on the ground trying to attack unreachable units on walls
or towers when the projectile's arc cannot reach the required height.

binaries/data/mods/public/simulation/components/Attack.js

@@ -292,11 +292,6 @@ Attack.prototype.CanAttack = function(target, wantedTypes)
 	const cmpCapturable = QueryMiragedInterface(target, IID_Capturable);
 	const cmpDiplomacy = QueryPlayerIDInterface(entityOwner, IID_Diplomacy);
 
-	// Check if the relative height difference is larger than the attack range
-	// If the relative height is bigger, it means they will never be able to
-	// reach each other, no matter how close they come.
-	const heightDiff = Math.abs(cmpThisPosition.GetHeightOffset() - cmpTargetPosition.GetHeightOffset());
-
 	for (const type of types)
 	{
 		if (type != "Capture" && (!cmpDiplomacy?.IsEnemy(targetOwner) || !cmpHealth || !cmpHealth.GetHitpoints()))
@@ -305,7 +300,8 @@ Attack.prototype.CanAttack = function(target, wantedTypes)
 		if (type == "Capture" && (!cmpCapturable || !cmpCapturable.CanCapture(entityOwner)))
 			continue;
 
-		if (heightDiff > this.GetRange(type).max)
+		// Check if the target is currently in range, or could ever be reached
+		if (!this.IsTargetInRange(target, type) && !this.CanEverReachTarget(target, type))
 			continue;
 
 		const restrictedClasses = this.GetRestrictedClasses(type);
@@ -319,6 +315,77 @@ Attack.prototype.CanAttack = function(target, wantedTypes)
 	return false;
 };
 
+/**
+ * Check if the target could potentially ever be reached with the given attack type,
+ * as an optimistic estimate. This assumes the attacker can move to the closest
+ * possible position to the target — ignoring obstructions and terrain features
+ * (e.g., hills) that might help or hinder.
+ *
+ * This is a best-effort guess:
+ *  - It may return true even when the target is actually unreachable (e.g., turreted
+ *    units on walls with a height offset too large for the projectile to overcome).
+ *  - It may return false even when the target is reachable (e.g., a nearby hill could
+ *    provide enough elevation to hit a "too high" target, but we don't check for that).
+ *
+ * Currently these checks are mostly useful to determine if we can reach turreted units
+ * (e.g. on a wall, outpost...).
+ *
+ * @param {number} targetId - The target entity ID.
+ * @param {string} type - The attack type.
+ * @return {boolean} - Whether the target is estimated to be reachable (see caveats above).
+ */
+Attack.prototype.CanEverReachTarget = function(targetId, type)
+{
+	const cmpThisPosition = Engine.QueryInterface(this.entity, IID_Position);
+	const cmpTargetPosition = Engine.QueryInterface(targetId, IID_Position);
+
+	const thisHeightOffset = cmpThisPosition.GetHeightOffset();
+	const targetHeightOffset = cmpTargetPosition.GetHeightOffset();
+
+	const range = this.GetRange(type);
+
+	// Find the closest horizontal distance we could ever get to the target.
+	// We first determine the closest horizontal distance we could ever get to the target,
+	// accounting for turreted units inside buildings:
+	//  - If the building blocks movement, we can only reach its exterior edge.
+	//  - If the building is passable, we can walk right up to the turret point.
+	const cmpTurretable = Engine.QueryInterface(targetId, IID_Turretable);
+	const holderId = cmpTurretable?.HolderID();
+	let closestDistance = 0;
+	if (holderId && holderId != INVALID_ENTITY)
+	{
+		const cmpTurretHolder = Engine.QueryInterface(holderId, IID_TurretHolder);
+		if (cmpTurretHolder)
+		{
+			const turretPoint = cmpTurretHolder.GetOccupiedTurretPoint(targetId);
+			closestDistance = cmpTurretHolder.GetClosestApproachDistanceToTurretPoint(turretPoint);
+		}
+	}
+
+	if (!range.parabolic)
+	{
+		// For non-parabolic attacks (e.g., "Melee" attack type), we check if the height offset
+		// is within max range at the closest possible horizontal distance (simple 3D distance check).
+		const heightDiff = Math.abs(targetHeightOffset - thisHeightOffset);
+		return Math.sqrt(closestDistance * closestDistance + heightDiff * heightDiff) <= range.max;
+	}
+
+	// For parabolic attacks (generally "Ranged" attack type), we use the parabolic formula
+	// to determine if the height offset is surmountable at the closest possible distance.
+	// Typical scenario: units on walls/towers may be unreachable if the attacker's
+	// projectiles can't arc high enough, even at point-blank range.
+	const cmpRangeManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_RangeManager);
+	if (!cmpRangeManager)
+		return true;
+
+	const yOrigin = this.GetAttackYOrigin(type);
+
+	const maxReachableHeightDiff = cmpRangeManager.GetMaxReachableParabolicHeight(
+		range.max, yOrigin, closestDistance);
+
+	return targetHeightOffset - thisHeightOffset <= maxReachableHeightDiff;
+};
+
 /**
  * Returns undefined if we have no preference or the lowest index of a preferred class.
  */

binaries/data/mods/public/simulation/components/TurretHolder.js

@@ -240,6 +240,39 @@ class TurretHolder
 		return turret ? turret.name : "";
 	}
 
+	/**
+	 * Calculate the closest horizontal distance an external entity could ever get
+	 * to the specified turret point. If the holder is passable, returns 0.
+	 * Otherwise returns the perpendicular distance from the turret point to the
+	 * nearest edge of the holder's obstruction.
+	 *
+	 * @param {string|Object} turretPoint - The turret point name or object.
+	 * @return {number} - The minimum possible horizontal distance.
+	 */
+	GetClosestApproachDistanceToTurretPoint(turretPoint)
+	{
+		if (typeof turretPoint === "string")
+			turretPoint = this.TurretPointByName(turretPoint);
+		if (!turretPoint)
+			return 0;
+
+		const cmpObstruction = Engine.QueryInterface(this.entity, IID_Obstruction);
+		if (!cmpObstruction || !cmpObstruction.GetBlockMovementFlag(false))
+			return 0;
+
+		const dxLocal = turretPoint.offset.x;
+		const dzLocal = turretPoint.offset.z;
+
+		const halfSizes = cmpObstruction.GetObstructionHalfSizes();
+		const hw = halfSizes.x;
+		const hh = halfSizes.y;
+
+		if (hw == null || hh == null || hw < 0 || hh < 0)
+			return 0;
+
+		return Math.max(0, Math.min(hw - Math.abs(dxLocal), hh - Math.abs(dzLocal)));
+	}
+
 	/**
 	 * @return {number[]} - The turretted entityIDs.
 	 */

binaries/data/mods/public/simulation/components/tests/test_Attack.js

@@ -32,6 +32,8 @@ Engine.LoadComponentScript("interfaces/Formation.js");
 Engine.LoadComponentScript("interfaces/Health.js");
 Engine.LoadComponentScript("interfaces/Resistance.js");
 Engine.LoadComponentScript("interfaces/TechnologyManager.js");
+Engine.LoadComponentScript("interfaces/Turretable.js");
+Engine.LoadComponentScript("interfaces/TurretHolder.js");
 Engine.LoadComponentScript("Attack.js");
 
 let entityID = 903;
@@ -52,6 +54,16 @@ function attackComponentTest(defenderClass, isEnemy, test_function)
 		"IsEnemy": () => isEnemy
 	});
 
+	AddMock(SYSTEM_ENTITY, IID_ObstructionManager, {
+		"IsInTargetRange": () => true
+	});
+
+	AddMock(SYSTEM_ENTITY, IID_RangeManager, {
+		"GetEffectiveParabolicRange": () => 25,
+		"GetMaxReachableParabolicHeight": () => 15,
+		"GetLosVisibility": (target, owner) => "visible"
+	});
+
 	const attacker = entityID;
 
 	AddMock(attacker, IID_Position, {
@@ -416,3 +428,4 @@ function testAttackPreference()
 	TS_ASSERT_EQUALS(cmpAttack.GetPreference(attacker+4), undefined);
 }
 testAttackPreference();
+