SupaLidlGame/Characters/NPC.cs

using Godot;
using SupaLidlGame.Extensions;
using SupaLidlGame.Items;
using System;

namespace SupaLidlGame.Characters
{
    public partial class NPC : Character
    {
        /// <summary>
        /// Time in seconds it takes for the NPC to think FeelsDankCube
        /// </summary>
        public const float ThinkTime = 0.125f;

        public float[] Weights => _weights;

        protected float _preferredWeightDistance = 64.0f;
        protected float _maxWeightDistance = 8.0f;
        protected float _preferredWeightDistanceSq = 4096.0f;
        protected float _maxWeightDistanceSq = 64.0f;

        [Export]
        public float PreferredWeightDistance
        { 
            get => _preferredWeightDistance;
            protected set
            {
                _preferredWeightDistance = value;
                _preferredWeightDistanceSq = value * value;
            }
        }

        [Export]
        public float MaxWeightDistance
        { 
            get => _maxWeightDistance;
            protected set
            {
                _maxWeightDistance = value;
                _maxWeightDistanceSq = value * value;
            }
        }

        protected float[] _weights = new float[16];
        protected int _bestWeightIdx;
        protected double _thinkTimeElapsed = 0;
        protected Vector2 _blockingDir;
        protected static readonly Vector2[] _weightDirs = new Vector2[16];

        static NPC()
        {
            for (int i = 0; i < 16; i++)
            {
                float y = Mathf.Sin(Mathf.Pi * i * 2 / 16);
                float x = Mathf.Cos(Mathf.Pi * i * 2 / 16);
                _weightDirs[i] = new Vector2(x, y);
            }
        }

        public override void _Ready()
        {
            base._Ready();
            Array.Fill(_weights, 0);
        }

        public override void _Draw()
        {
#if DEBUG
            for (int i = 0; i < 16; i++)
            {
                Vector2 vec = _weightDirs[i] * _weights[i] * 32;
                Color c = Colors.Green;
                if (_bestWeightIdx == i)
                {
                    c = Colors.Blue;
                }
                else if (_weights[i] < 0)
                {
                    c = Colors.Red;
                    vec = -vec;
                }
                DrawLine(Vector2.Zero, vec, c);
            }
#endif

            base._Draw();
        }

        protected virtual Character FindBestTarget()
        {
            float bestDist = float.MaxValue;
            Character bestChar = null;
            foreach (Node node in GetParent().GetChildren())
            {
                if (node is Character character && character.Faction != Faction)
                {
                    float dist = Position.DistanceTo(character.Position);
                    if (dist < bestDist)
                    {
                        bestDist = dist;
                        bestChar = character;
                    }
                }
            }
            return bestChar;
        }

        public void ThinkProcess(double delta)
        {
            if ((_thinkTimeElapsed += delta) > ThinkTime)
            {
                _thinkTimeElapsed = 0;
                Think();
#if DEBUG
                QueueRedraw();
#endif
            }

            Direction = _weightDirs[_bestWeightIdx];
        }

        public void UpdateWeights(Vector2 pos)
        {
            // FIXME: TODO: remove all the spaghetti
            Vector2 dir = Target.Normalized();
            float distSq = GlobalPosition.DistanceSquaredTo(pos);

            var spaceState = GetWorld2D().DirectSpaceState;
            var exclude = new Godot.Collections.Array<Godot.Rid>();
            exclude.Add(this.GetRid());

            // calculate weights based on distance
            for (int i = 0; i < 16; i++)
            {
                float directDot = _weightDirs[i].Dot(dir);
                // clamp dot from [-1, 1] to [0, 1]
                directDot = (directDot + 1) / 2;

                float strafeDot = Math.Abs(_weightDirs[i].Dot(dir.Clockwise90()));
                float currDirDot = (_weightDirs[i].Dot(Direction) + 1) / 16;
                strafeDot = Mathf.Pow((strafeDot + 1) / 2, 2) + currDirDot;

                // favor strafing when getting closer
                if (distSq > _preferredWeightDistanceSq)
                {
                    _weights[i] = directDot;
                }
                else if (distSq > _maxWeightDistanceSq)
                {
                    float dDotWeight = Mathf.Sqrt(distSq / 4096);
                    float sDotWeight = 1 - dDotWeight;
                    _weights[i] = (dDotWeight * directDot) +
                        (sDotWeight * strafeDot);
                }
                else
                {
                    _weights[i] = strafeDot;
                }
            }

            // subtract weights that collide
            for (int i = 0; i < 16; i++)
            {
                var rayParams = new PhysicsRayQueryParameters2D
                {
                    Exclude = exclude,
                    CollideWithBodies = true,
                    From = GlobalPosition,
                    To = GlobalPosition + (_weightDirs[i] * 24),
                    CollisionMask = 1 + 2 + 16
                };

                var result = spaceState.IntersectRay(rayParams);

                // if we hit something
                if (result.Count > 0)
                {
                    // then we subtract the value of this from the other weights
                    float oldWeight = _weights[i];
                    for (int j = 0; j < 16; j++)
                    {
                        if (i == j)
                        {
                            _weights[i] = 0;
                        }
                        else
                        {
                            float dot = _weightDirs[i].Dot(_weightDirs[j]);
                            _weights[j] -= _weights[j] * dot;
                        }
                    }
                }
            }


            float bestWeight = 0;
            for (int i = 0; i < 16; i++)
            {
                if (_weights[i] > bestWeight)
                {
                    _bestWeightIdx = i;
                    bestWeight = _weights[i];
                }
            }
        }

        protected virtual void Think()
        {
            // TODO: the entity should wander if it doesn't find a best target
            Character bestTarget = FindBestTarget();
            if (bestTarget is not null)
            {
                Vector2 pos = FindBestTarget().GlobalPosition;
                Target = pos - GlobalPosition;
                Vector2 dir = Target;
                float dist = GlobalPosition.DistanceSquaredTo(pos);
                UpdateWeights(pos);

                if (dist < 1024)
                {
                    if (Inventory.SelectedItem is Weapon weapon)
                    {
                        UseCurrentItem();
                    }
                }
            }
        }
    }
}