using System.Collections.Generic;
using HarmonyLib;

namespace NecromancerTome
{
	/// <summary>
	/// Lets a charmed ("Devi­ator"-hit) zombie actually hurt other zombies.
	///
	/// EntityAlive.DamageEntity has a hardcoded block, independent of anything AI/targeting
	/// related: `if (!isHeatDamage &amp;&amp; (entityFlags &amp; attacker.entityFlags &amp; EntityFlags.Zombie) != None)
	/// return -1;` - i.e. any two entities that are BOTH flagged EntityFlags.Zombie (which is
	/// every zombie, always) simply cannot damage each other, full stop, no matter what
	/// CharmPatch.cs did to the attacker's AI targeting. Without this, a charmed zombie would
	/// walk up to another zombie and "attack" it forever with every hit landing as a no-op.
	///
	/// Fix: for the duration of a single DamageEntity call where the attacker currently has
	/// buffNecroDeviatorCharm and the target is also a zombie, temporarily clear
	/// EntityFlags.Zombie on the ATTACKER only (never the target, never persisted) so the AND
	/// check in the original method comes up empty and damage proceeds normally. Restored
	/// immediately afterward, so nothing else about that zombie (kill-counting via its Tags
	/// property, quest tracking, anything else keyed off EntityFlags) is ever affected outside
	/// this one call. A Stack (not a single field) survives re-entrant DamageEntity calls
	/// correctly (e.g. explosions/knockback triggering further damage inside the same callstack).
	/// </summary>
	[HarmonyPatch(typeof(EntityAlive), "DamageEntity")]
	public static class Patch_EntityAlive_DamageEntity_CharmedZombieVsZombie
	{
		public static readonly Stack<EntityZombie> ToggledAttackers = new Stack<EntityZombie>();

		public static void Prefix(EntityAlive __instance, DamageSource _damageSource)
		{
			EntityZombie toggled = null;
			if (__instance is EntityZombie && __instance.world != null)
			{
				EntityAlive attacker = __instance.world.GetEntity(_damageSource.getEntityId()) as EntityAlive;
				if (attacker is EntityZombie attackerZombie
					&& attackerZombie.Buffs != null
					&& attackerZombie.Buffs.HasBuff(Patch_EntityBuffs_AddBuff_DeviatorCharm.CharmBuffName)
					&& (attackerZombie.entityFlags & EntityFlags.Zombie) != EntityFlags.None)
				{
					attackerZombie.entityFlags &= ~EntityFlags.Zombie;
					toggled = attackerZombie;
				}
			}
			ToggledAttackers.Push(toggled);
		}

		public static void Postfix()
		{
			EntityZombie toggled = ToggledAttackers.Pop();
			if (toggled != null)
			{
				toggled.entityFlags |= EntityFlags.Zombie;
			}
		}
	}
}