using Sandbox;

namespace BrickJam;

public partial class NPC
{
	private static readonly string[] moveIgnoreTags = { "player", "npc", "door", "loot", "nocollide" };

	/// <summary>Capsule sweep used by the <see cref="MoveHelper"/> (collides with world geometry only).</summary>
	private SceneTraceResult Sweep( Vector3 from, Vector3 to )
		=> Scene.Trace.Capsule( CollisionCapsule, from, to )
			.IgnoreGameObjectHierarchy( GameObject )
			.WithoutTags( moveIgnoreTags )
			.Run();

	/// <summary>
	/// Move along <see cref="Direction"/> via the custom <see cref="MoveHelper"/>. Scene-System port of the
	/// legacy <c>ComputeMotion</c> (which used Entity-System MoveHelper + NavMesh agent velocity).
	/// </summary>
	public virtual void ComputeMotion()
	{
		if ( !Blocked )
			Velocity = Vector3.Lerp( Velocity, WishVelocity, Time.Delta * 15f ).WithZ( Velocity.z );
		else
			Velocity = Vector3.Zero.WithZ( Velocity.z );

		// Face the victim while attacking, otherwise turn toward the travel direction.
		if ( !CurrentlyMurdering.IsValid() )
		{
			WorldRotation = Rotation.Lerp( WorldRotation, WishRotation, Time.Delta * 5f );
		}
		else
		{
			var look = (CurrentlyMurdering.WorldPosition - WorldPosition).WithZ( 0 );
			if ( look.Length > 0.01f )
				WorldRotation = Rotation.LookAt( look, Vector3.Up );
		}

		// Soft separation from other pushables (players/NPCs).
		Velocity += Pushables.ComputeSeparation( this, WorldPosition, CollisionRadius, PushForce ) * Time.Delta;

		var helper = new MoveHelper( WorldPosition, Velocity, Sweep ) { MaxStandableAngle = 70f };
		helper.TryMoveWithStep( Time.Delta, 24f );
		helper.TryUnstuck();

		WorldPosition = helper.Position;
		Velocity = helper.Velocity;

		// Ground + gravity.
		var down = Sweep( WorldPosition, WorldPosition + Vector3.Down * 2f );
		if ( down.Hit && Vector3.GetAngle( Vector3.Up, down.Normal ) <= 70f )
		{
			IsOnGround = true;
			WorldPosition = down.EndPosition;
			Velocity = Velocity.WithZ( 0 );
		}
		else
		{
			IsOnGround = false;
			Velocity += Scene.PhysicsWorld.Gravity * Time.Delta;
		}
	}

	private Vector3 stuckCheckPos;
	private TimeUntil nextStuckCheck = StuckCheckWindow;
	private const float StuckCheckWindow = 0.5f;

	/// <summary>
	/// If we're trying to move but haven't made real progress over <see cref="StuckCheckWindow"/>, recompute
	/// the path and nudge sideways/up to break contact. Handles wedging in tight doorways and on the mansion
	/// spiral staircase, where the grid path is technically valid but the capsule snags on geometry.
	/// </summary>
	protected void CheckStuck()
	{
		// Only meaningful while actively pathing on the ground and not pinned by an attack/knockback.
		if ( Blocked || CurrentlyMurdering.IsValid() || !IsOnGround || WishSpeed <= 1f )
		{
			stuckCheckPos = WorldPosition;
			nextStuckCheck = StuckCheckWindow;
			return;
		}

		if ( !nextStuckCheck )
			return;

		var moved = WorldPosition.WithZ( 0 ).Distance( stuckCheckPos.WithZ( 0 ) );
		var expected = WishSpeed * StuckCheckWindow;

		// Covered under ~20% of the distance we should have at wish speed => wedged.
		if ( moved < expected * 0.2f )
		{
			RecalculatePath();

			var side = MansionGame.Random.NextSingle() > 0.5f ? 1f : -1f;
			Velocity += WorldRotation.Right * side * WishSpeed + Vector3.Up * 80f; // sidestep + small hop
		}

		stuckCheckPos = WorldPosition;
		nextStuckCheck = StuckCheckWindow;
	}
}