using System.Collections.Generic;
using UnityEngine;

namespace NecromancerTome
{
	/// <summary>
	/// Keeps a summoned pet (see SummonPatch.cs) from wandering off and getting permanently
	/// lost/unsummonable - user report 2026-08-28: the Zombie Dog didn't follow like a drone
	/// would, wandered off (heard, not seen), and a second summon attempt did nothing while the
	/// first was presumably still out there somewhere.
	///
	/// Two separate problems, one fix:
	///
	///   1. "Doesn't follow": there is no generic "follow a specific entity" AI task anywhere in
	///      this game - confirmed by listing every EAI*-named type in Assembly-CSharp (EAIWander,
	///      EAITerritorial, EAIApproachSpot, EAIApproachAndAttackTarget, etc. - nothing
	///      follow-shaped). EntityDrone's follow behavior is hardcoded C# specific to that one
	///      class, not something an XML entity_class can opt into. Writing a real custom AITask
	///      (actual pathfinding, priority-tuned against the pet's existing Wander/Territorial/
	///      ApproachSpot tasks) is real engineering the backlog didn't ask for - so this copies
	///      vanilla's own fallback for the identical problem instead: DroneManager.Update()
	///      teleports a drone back near its owner once it's more than 32m away (sqrMagnitude >
	///      1024) and not doing something else (OrderState != Stay) - confirmed by decompiling
	///      it. Same threshold, same idea, generalized to any pet class instead of drones only,
	///      and skipped while the pet has a live attack target (don't yank it out of a fight).
	///
	///   2. "Doesn't reappear on retry": SummonPatch.cs's one-pet-per-species limit checks
	///      EntityAlive.ownedEntities, but nothing was ever removing a pet from that list once it
	///      died or its chunk unloaded - unlike the drone, where DroneManager's own death/unload
	///      callbacks do that cleanup. A dead or vanished pet left the slot "occupied" forever.
	///      The same periodic check below detects a tracked pet that's gone (world.GetEntity
	///      returns null - dead, or its chunk unloaded and it despawned like any untracked
	///      entity, per the known persistence gap documented in SummonPatch.cs) and clears
	///      ownership so the player can summon a fresh one.
	///
	///   3. (added 2026-08-28) Insect Swarm only: makes it move on to the next zombie once its
	///      current target is already Deviator-charmed, instead of camping the same converted
	///      zombie forever - see the inline comment below, right where it happens.
	///
	/// Hooked via ModEvents.UnityUpdate - the same supported per-frame mod event GameManager's own
	/// gmUpdate() fires DroneManager.Update() from (confirmed by decompiling GameManager) - not a
	/// Harmony patch, since this is a genuine public extension point, no reason to patch around
	/// it. Throttled to run the real check once a second (CheckInterval): a distance/liveness
	/// check on a handful of pets is cheap, but no reason to do it 60x/sec either.
	/// </summary>
	public static class PetFollowPatch
	{
		public const float LeashDistance = 32f; // matches DroneManager's own 32m leash
		public const float LeashDistanceSq = LeashDistance * LeashDistance;
		public const float CheckInterval = 1f;

		public class TrackedPet
		{
			public int OwnerEntityId;
			public int PetEntityId;
		}

		public static readonly List<TrackedPet> TrackedPets = new List<TrackedPet>();

		public static float timer;

		public static void Init()
		{
			ModEvents.UnityUpdate.RegisterHandler(OnUnityUpdate);
		}

		/// <summary>Called from SummonPatch.cs right after a pet is created and owned.</summary>
		public static void Register(EntityAlive owner, Entity pet)
		{
			TrackedPets.Add(new TrackedPet { OwnerEntityId = owner.entityId, PetEntityId = pet.entityId });
		}

		/// <summary>Called from SummonPatch.cs's manual recall path so a recalled pet stops being
		/// tracked immediately, instead of lingering until the next tick notices it's gone.</summary>
		public static void Unregister(int petEntityId)
		{
			for (int i = TrackedPets.Count - 1; i >= 0; i--)
			{
				if (TrackedPets[i].PetEntityId == petEntityId)
				{
					TrackedPets.RemoveAt(i);
				}
			}
		}

		public static void OnUnityUpdate(ref ModEvents.SUnityUpdateData _data)
		{
			timer += Time.deltaTime;
			if (timer < CheckInterval)
			{
				return;
			}
			timer = 0f;
			if (TrackedPets.Count == 0)
			{
				return;
			}

			World world = GameManager.Instance != null ? GameManager.Instance.World : null;
			if (world == null)
			{
				return;
			}

			for (int i = TrackedPets.Count - 1; i >= 0; i--)
			{
				TrackedPet tracked = TrackedPets[i];
				EntityAlive pet = world.GetEntity(tracked.PetEntityId) as EntityAlive;
				if (pet == null || pet.IsDead())
				{
					EntityAlive ownerForCleanup = world.GetEntity(tracked.OwnerEntityId) as EntityAlive;
					if (ownerForCleanup != null)
					{
						ownerForCleanup.RemoveOwnedEntity(tracked.PetEntityId);
						Debug.Log("[NecromancerTome] PetFollowPatch: pet " + tracked.PetEntityId + " gone, cleared ownership for " + ownerForCleanup.entityId);
					}
					TrackedPets.RemoveAt(i);
					continue;
				}

				EntityAlive owner = world.GetEntity(tracked.OwnerEntityId) as EntityAlive;
				if (owner == null)
				{
					// Owner not currently loaded (e.g. disconnected) - leave the pet tracked,
					// nothing useful to do until they're back.
					continue;
				}

				// User request 2026-08-28: "рой будет заражать зомби девиацией и лететь к
				// следующему незаражённому?" - not on its own, so this makes it one. EntityVulture
				// (the Swarm's real base class - see SwarmTargetPatch.cs) has no notion of
				// "this target is already converted, go find another" - once it has a live target
				// it just keeps attacking it until that target dies, charmed or not (repeated
				// AddBuff on an already-charmed zombie is a harmless no-op, so it wasn't wrong,
				// just stuck). Clearing the attack target here when it's already charmed makes
				// EntityVulture's own FindTarget()/SetAttackTarget cycle kick back in on its next
				// pass (SwarmTargetPatch.cs redirects that straight to the nearest zombie again,
				// same as any other retarget) - not instant (that cycle runs on its own ~2s timer,
				// not driven by us), but converts-then-moves-on within a couple seconds.
				if (pet.entityClass == Patch_EntityAlive_SetAttackTarget_SwarmRetarget.SwarmOnlyClassId())
				{
					EntityAlive currentTarget = pet.GetAttackTarget();
					if (currentTarget != null && currentTarget.Buffs != null && currentTarget.Buffs.HasBuff(Patch_EntityBuffs_AddBuff_DeviatorCharm.CharmBuffName))
					{
						pet.SetAttackTarget(null, 0);
						Debug.Log("[NecromancerTome] PetFollowPatch: swarm " + pet.entityId + " dropped already-charmed target " + currentTarget.entityId);
					}
				}

				if (pet.GetAttackTarget() != null)
				{
					// Mid-fight - let it finish rather than teleporting it away.
					continue;
				}

				float distSq = (pet.position - owner.position).sqrMagnitude;
				if (distSq > LeashDistanceSq)
				{
					// 2m in front of the owner, not exactly on top of them - landing right on the
					// owner's own position stacks the pet's collider into the player's and shoves
					// them (this is exactly what happened during the "<=0 vs -1" bug above: a pile
					// of a dozen undespawned dogs all teleporting onto the same point as the player
					// every second launched them into the air).
					Vector3 dest = owner.position + owner.qrotation * new Vector3(0f, 0f, 2f);
					pet.SetPosition(dest, true);
					Debug.Log("[NecromancerTome] PetFollowPatch: teleported pet " + pet.entityId + " back to owner " + owner.entityId);
				}
			}
		}
	}
}