#region Copyright & License Information
/*
 * Copyright 2007-2019 The OpenRA Developers (see AUTHORS)
 * 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.Collections.Generic;
using System.Linq;
using OpenRA.Traits;

namespace OpenRA.Mods.Common.Traits
{
	[Desc("Controls AI unit production.")]
	public class UnitBuilderBotModuleInfo : ConditionalTraitInfo
	{
		// TODO: Investigate whether this might the (or at least one) reason why bots occasionally get into a state of doing nothing.
		// Reason: If this is less than SquadSize, the bot might get stuck between not producing more units due to this,
		// but also not creating squads since there aren't enough idle units.
		[Desc("Only produce units as long as there are less than this amount of units idling inside the base.")]
		public readonly int IdleBaseUnitsMaximum = 12;

		[Desc("Production queues AI uses for producing units.")]
		public readonly HashSet<string> UnitQueues = new HashSet<string> { "Vehicle", "Infantry", "Plane", "Ship", "Aircraft" };

		[Desc("What units to the AI should build.", "What relative share of the total army must be this type of unit.")]
		public readonly Dictionary<string, int> UnitsToBuild = null;

		[Desc("What units should the AI have a maximum limit to train.")]
		public readonly Dictionary<string, int> UnitLimits = null;

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

	public class UnitBuilderBotModule : ConditionalTrait<UnitBuilderBotModuleInfo>, IBotTick, IBotNotifyIdleBaseUnits, IBotRequestUnitProduction
	{
		public const int FeedbackTime = 30; // ticks; = a bit over 1s. must be >= netlag.

		readonly World world;
		readonly Player player;

		readonly List<string> queuedBuildRequests = new List<string>();

		IBotRequestPauseUnitProduction[] requestPause;

		List<Actor> idleUnits = new List<Actor>();

		int ticks;

		public UnitBuilderBotModule(Actor self, UnitBuilderBotModuleInfo info)
			: base(info)
		{
			world = self.World;
			player = self.Owner;
		}

		protected override void TraitEnabled(Actor self)
		{
			requestPause = player.PlayerActor.TraitsImplementing<IBotRequestPauseUnitProduction>().ToArray();
		}

		void IBotNotifyIdleBaseUnits.UpdatedIdleBaseUnits(List<Actor> idleUnits)
		{
			this.idleUnits = idleUnits;
		}

		void IBotTick.BotTick(IBot bot)
		{
			if (requestPause.Any(rp => rp.PauseUnitProduction))
				return;

			ticks++;

			if (ticks % FeedbackTime == 0)
			{
				var buildRequest = queuedBuildRequests.FirstOrDefault();
				if (buildRequest != null)
				{
					BuildUnit(bot, buildRequest);
					queuedBuildRequests.Remove(buildRequest);
				}

				foreach (var q in Info.UnitQueues)
					BuildUnit(bot, q, idleUnits.Count < Info.IdleBaseUnitsMaximum);
			}
		}

		void IBotRequestUnitProduction.RequestUnitProduction(IBot bot, string requestedActor)
		{
			queuedBuildRequests.Add(requestedActor);
		}

		int IBotRequestUnitProduction.RequestedProductionCount(IBot bot, string requestedActor)
		{
			return queuedBuildRequests.Count(r => r == requestedActor);
		}

		void BuildUnit(IBot bot, string category, bool buildRandom)
		{
			// Pick a free queue
			var queue = AIUtils.FindQueues(player, category).FirstOrDefault(q => !q.AllQueued().Any());
			if (queue == null)
				return;

			var unit = buildRandom ?
				ChooseRandomUnitToBuild(queue) :
				ChooseUnitToBuild(queue);

			if (unit == null)
				return;

			var name = unit.Name;

			if (Info.UnitsToBuild != null && !Info.UnitsToBuild.ContainsKey(name))
				return;

			if (Info.UnitLimits != null &&
				Info.UnitLimits.ContainsKey(name) &&
				world.Actors.Count(a => a.Owner == player && a.Info.Name == name) >= Info.UnitLimits[name])
				return;

			bot.QueueOrder(Order.StartProduction(queue.Actor, name, 1));
		}

		// In cases where we want to build a specific unit but don't know the queue name (because there's more than one possibility)
		void BuildUnit(IBot bot, string name)
		{
			var actorInfo = world.Map.Rules.Actors[name];
			if (actorInfo == null)
				return;

			var buildableInfo = actorInfo.TraitInfoOrDefault<BuildableInfo>();
			if (buildableInfo == null)
				return;

			ProductionQueue queue = null;
			foreach (var pq in buildableInfo.Queue)
			{
				queue = AIUtils.FindQueues(player, pq).FirstOrDefault(q => !q.AllQueued().Any());
				if (queue != null)
					break;
			}

			if (queue != null)
			{
				bot.QueueOrder(Order.StartProduction(queue.Actor, name, 1));
				AIUtils.BotDebug("AI: {0} decided to build {1} (external request)", queue.Actor.Owner, name);
			}
		}

		ActorInfo ChooseRandomUnitToBuild(ProductionQueue queue)
		{
			var buildableThings = queue.BuildableItems();
			if (!buildableThings.Any())
				return null;

			var unit = buildableThings.Random(world.LocalRandom);
			return HasAdequateAirUnitReloadBuildings(unit) ? unit : null;
		}

		ActorInfo ChooseUnitToBuild(ProductionQueue queue)
		{
			var buildableThings = queue.BuildableItems();
			if (!buildableThings.Any())
				return null;

			var myUnits = player.World
				.ActorsHavingTrait<IPositionable>()
				.Where(a => a.Owner == player)
				.Select(a => a.Info.Name).ToList();

			foreach (var unit in Info.UnitsToBuild.Shuffle(world.LocalRandom))
				if (buildableThings.Any(b => b.Name == unit.Key))
					if (myUnits.Count(a => a == unit.Key) * 100 < unit.Value * myUnits.Count)
						if (HasAdequateAirUnitReloadBuildings(world.Map.Rules.Actors[unit.Key]))
							return world.Map.Rules.Actors[unit.Key];

			return null;
		}

		// For mods like RA (number of RearmActors must match the number of aircraft)
		bool HasAdequateAirUnitReloadBuildings(ActorInfo actorInfo)
		{
			var aircraftInfo = actorInfo.TraitInfoOrDefault<AircraftInfo>();
			if (aircraftInfo == null)
				return true;

			// If actor isn't Rearmable, it doesn't need a RearmActor to reload
			var rearmableInfo = actorInfo.TraitInfoOrDefault<RearmableInfo>();
			if (rearmableInfo == null)
				return true;

			var countOwnAir = AIUtils.CountActorsWithTrait<IPositionable>(actorInfo.Name, player);
			var countBuildings = rearmableInfo.RearmActors.Sum(b => AIUtils.CountActorsWithTrait<Building>(b, player));
			if (countOwnAir >= countBuildings)
				return false;

			return true;
		}
	}
}