#region Copyright & License Information
/*
 * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version. For more
 * information, see COPYING.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using OpenRA.Graphics;
using OpenRA.Traits;

namespace OpenRA.Mods.Common.Traits
{
	[TraitLocation(SystemActors.Player)]
	[Desc("Automatically activates a classic AI bot for the local human player so the match starts as bot-vs-bot.")]
	public sealed class BotTakeoverManagerInfo : TraitInfo
	{
		[Desc("Automatically enable takeover when the world is loaded.")]
		public readonly bool AutoActivate = false;

		[Desc("Delay in ticks before activating after world load (lets other world init settle).")]
		public readonly int AutoActivateDelayTicks = 1;

		[Desc("Bot type to activate (e.g. normal/rush/turtle/naval). Must match an IBotInfo.Type on the Player actor.")]
		public readonly string BotType = "normal";

		[Desc("Conditions to grant when takeover is enabled. If empty, will infer enable-<bot>-ai for known bot types.")]
		public readonly ImmutableArray<string> GrantConditions = [];

		public override object Create(ActorInitializer init)
		{
			return new BotTakeoverManager(init.Self, this);
		}
	}

	public sealed class BotTakeoverManager : ITick, IWorldLoaded
	{
		readonly Actor self;
		readonly World world;
		readonly BotTakeoverManagerInfo info;

		IBot activeBot;
		readonly List<int> conditionTokens = new();

		bool pendingAutoActivate;
		int autoActivateRemainingTicks;

		public BotTakeoverManager(Actor self, BotTakeoverManagerInfo info)
		{
			this.self = self;
			world = self.World;
			this.info = info;
		}

		public bool IsActive
		{
			get
			{
				if (activeBot == null)
					return false;

				return activeBot switch
				{
					ModularBot mb => mb.IsEnabled,
					_ => false
				};
			}
		}

		public void Toggle()
		{
			SetActive(!IsActive);
		}

		public void SetActive(bool active)
		{
			if (active)
				ActivateTakeover();
			else
				DeactivateTakeover();
		}

		void IWorldLoaded.WorldLoaded(World w, WorldRenderer wr)
		{
			if (info.AutoActivate)
			{
				pendingAutoActivate = true;
				autoActivateRemainingTicks = Math.Max(0, info.AutoActivateDelayTicks);
			}
		}

		void ITick.Tick(Actor self)
		{
			if (!pendingAutoActivate)
				return;

			if (autoActivateRemainingTicks-- > 0)
				return;

			pendingAutoActivate = false;
			ActivateTakeover();
		}

		bool CanTakeover()
		{
			// Bot logic is host-authoritative. Avoid enabling during replays or on non-host clients.
			if (!Game.IsHost || world.IsReplay)
				return false;

			var player = self.Owner;

			// If this player is already a lobby bot, then the engine will have activated it already.
			if (player == null || player.IsBot)
				return false;

			// Only takeover the local player (avoid accidentally hijacking other human slots).
			return world.LocalPlayer != null && world.LocalPlayer == player;
		}

		void ActivateTakeover()
		{
			if (!CanTakeover())
				return;

			if (IsActive)
				return;

			var botType = info.BotType ?? "";
			if (string.IsNullOrWhiteSpace(botType))
				botType = "normal";

			var bot = self.TraitsImplementing<IBot>().FirstOrDefault(b => b.Info.Type == botType);
			if (bot == null)
			{
				Console.WriteLine($"[Bot Takeover] No IBot found for type '{botType}'.");
				return;
			}

			GrantTakeoverConditions(botType);

			bot.Activate(self.Owner);
			activeBot = bot;
			Console.WriteLine($"[Bot Takeover] Activated bot type '{botType}' for player {self.Owner.PlayerName}.");
		}

		void DeactivateTakeover()
		{
			if (activeBot is ModularBot mb)
				mb.IsEnabled = false;

			activeBot = null;

			for (var i = conditionTokens.Count - 1; i >= 0; i--)
			{
				var token = conditionTokens[i];
				if (self.TokenValid(token))
					self.RevokeCondition(token);
			}

			conditionTokens.Clear();
			Console.WriteLine("[Bot Takeover] Deactivated.");
		}

		void GrantTakeoverConditions(string botType)
		{
			if (conditionTokens.Count > 0)
				return;

			var conditions = info.GrantConditions;
			if (conditions.Length == 0)
			{
				var inferred = botType.ToLowerInvariant() switch
				{
					"rush" => "enable-rush-ai",
					"normal" => "enable-normal-ai",
					"turtle" => "enable-turtle-ai",
					"naval" => "enable-naval-ai",
					_ => null
				};

				if (!string.IsNullOrEmpty(inferred))
					conditions = conditions.Add(inferred);
			}

			foreach (var c in conditions.Where(c => !string.IsNullOrWhiteSpace(c)).Distinct(StringComparer.OrdinalIgnoreCase))
				conditionTokens.Add(self.GrantCondition(c));
		}
	}
}