From 3fa58bc6df66fc1b5fe3e94762328ab9b2da46f3 Mon Sep 17 00:00:00 2001
From: Nekojimi <Jim@nekojimi.moe>
Date: Mon, 12 May 2025 11:19:52 +0100
Subject: [PATCH] Add "Chase" unit action, and make enemies use it to chase
 citizens.

---
 scripts/units/action.gd | 41 +++++++++++++++++++++++++++++++++++++++++
 scripts/units/enemy.gd  |  8 +++++++-
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/scripts/units/action.gd b/scripts/units/action.gd
index e1a7e5d..a341522 100644
--- a/scripts/units/action.gd
+++ b/scripts/units/action.gd
@@ -53,6 +53,47 @@ class MoveAction extends UnitAction:
 			#DebugDraw3D.draw_text(global_position + Vector3(0,1,0), "%f" % nav_agent_3d.distance_to_target())
 		return Unit.TaskStatus.IN_PROGRESS
 		
+class ChaseAction extends UnitAction:
+	var target: Unit
+	var target_position: Vector3
+	var last_distance_to_target: float = 99999999.9
+	var stuck_timer: float = 0.0
+	
+	func process(delta: float) -> Unit.TaskStatus:
+		if target == null or target.is_queued_for_deletion():
+			return Unit.TaskStatus.IMPOSSIBLE
+		if target.global_position.distance_squared_to(target_position) >= 4.0:
+			# TODO: we could try to intercept the target by:
+			# - calculating our approximate time to reach the target
+			# - forcasting the target's position that time in the future based on it's velocity
+			# 	- do a raycast in that direction to prevent the future position from going through a wall
+			target_position = target.global_position
+			unit.nav_agent_3d.target_position = target_position
+			
+		if unit.nav_agent_3d.is_navigation_finished():
+			if unit.nav_agent_3d.is_target_reachable():
+				return Unit.TaskStatus.DONE
+			else:
+				return Unit.TaskStatus.IMPOSSIBLE
+		else:
+			var next_point: Vector3 = unit.nav_agent_3d.get_next_path_position()
+			if unit.shapecast_3d.is_colliding():
+				var distance_to_target: float = unit.global_position.distance_to(next_point)
+				var progress_rate: float = (last_distance_to_target - distance_to_target) / delta
+				last_distance_to_target = distance_to_target
+				if progress_rate < unit.minimum_progress_rate:
+					stuck_timer += delta
+					if stuck_timer >= unit.stuck_time:
+						unit.unstuck()
+				else:
+					unit.label_3d.modulate = Color.WHITE
+					stuck_timer = 0
+			DebugDraw3D.draw_sphere(unit.nav_agent_3d.target_position, 0.5, Color.RED)
+			var direction: Vector3 = (next_point - unit.global_position).normalized()
+			unit.target_velocity = direction * unit.max_speed
+			unit.nav_agent_3d.velocity = unit.target_velocity
+			return Unit.TaskStatus.IN_PROGRESS
+		
 class BuildAction extends UnitAction:
 	var building: Building
 	
diff --git a/scripts/units/enemy.gd b/scripts/units/enemy.gd
index aeca187..d19afaa 100644
--- a/scripts/units/enemy.gd
+++ b/scripts/units/enemy.gd
@@ -8,4 +8,10 @@ var sighted: bool = true:
 
 func _ready() -> void:
 	sighted = false
-	go_to_destination(Vector3(17,1,15))
+	var target_citizen: Citizen = get_tree().get_nodes_in_group("Citizens").pick_random() as Citizen
+	if target_citizen != null:
+		var chase_action: UnitAction.ChaseAction = UnitAction.ChaseAction.new()
+		chase_action.unit = self
+		chase_action.target = target_citizen
+		action = chase_action
+	#go_to_destination(Vector3(17,1,15))