ArachnaeSwarm/Source/ArachnaeSwarm/World/WorldObject_CatastropheMissile.cs

using RimWorld.Planet;
using UnityEngine;
using Verse;
using RimWorld;

namespace ArachnaeSwarm
{
    public class WorldObject_CatastropheMissile : WorldObject
    {
        public int destinationTile = -1;
        public IntVec3 destinationCell = IntVec3.Invalid;
        public ThingDef Projectile;
        
        private int initialTile = -1;
        private float traveledPct;
        private const float TravelSpeed = 0.0002f;

        public override void ExposeData()
        {
            base.ExposeData();
            Scribe_Values.Look(ref destinationTile, "destinationTile", 0);
            Scribe_Values.Look(ref destinationCell, "destinationCell");
            Scribe_Defs.Look(ref Projectile, "Projectile");
            Scribe_Values.Look(ref initialTile, "initialTile", 0);
            Scribe_Values.Look(ref traveledPct, "traveledPct", 0f);
        }

        public override void PostAdd()
        {
            base.PostAdd();
            this.initialTile = this.Tile;
        }
        
        private Vector3 StartPos => Find.WorldGrid.GetTileCenter(this.initialTile);
        private Vector3 EndPos => Find.WorldGrid.GetTileCenter(this.destinationTile);

        public override Vector3 DrawPos => Vector3.Slerp(StartPos, EndPos, traveledPct);

        protected override void Tick()
        {
            base.Tick();
            float distance = GenMath.SphericalDistance(StartPos.normalized, EndPos.normalized);
            if(distance > 0)
            {
                traveledPct += TravelSpeed / distance;
            }
            else
            {
                traveledPct = 1;
            }

            if (traveledPct >= 1f)
            {
                Arrived();
            }
        }

        private void Arrived()
        {
            Map targetMap = Current.Game.FindMap(this.destinationTile);
            if (targetMap != null)
            {
                // Find a random entry point at the north edge of the target map
                IntVec3 entryCell = CellFinder.RandomEdgeCell(Rot4.North, targetMap);
                
                // Spawn the final projectile (the cruise missile) at the entry point
                Projectile_CruiseMissile missile = (Projectile_CruiseMissile)GenSpawn.Spawn(this.Projectile, entryCell, targetMap, WipeMode.Vanish);

                // Launch it from the entry point towards the final destination cell
                missile.Launch(null, entryCell.ToVector3Shifted(), new LocalTargetInfo(this.destinationCell), new LocalTargetInfo(this.destinationCell), ProjectileHitFlags.IntendedTarget);
            }
            
            Find.WorldObjects.Remove(this);
        }
    }
}