#region Copyright & License Information
/*
 * Copyright 2007-2018 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;
using System.Collections.Generic;
using System.Linq;
using OpenRA.Mods.Common.Activities;
using OpenRA.Mods.Common.Pathfinder;
using OpenRA.Mods.Common.Traits;
using OpenRA.Support;
using OpenRA.Traits;

namespace OpenRA.Mods.Common.AI
{
	class AIHarvesterManager
	{
		readonly HackyAI ai;
		readonly World world;
		readonly IPathFinder pathfinder;
		readonly DomainIndex domainIndex;
		readonly ResourceLayer resLayer;
		readonly ResourceClaimLayer claimLayer;

		public AIHarvesterManager(HackyAI ai, Player p)
		{
			this.ai = ai;
			world = p.World;
			pathfinder = world.WorldActor.Trait<IPathFinder>();
			domainIndex = world.WorldActor.Trait<DomainIndex>();
			resLayer = world.WorldActor.TraitOrDefault<ResourceLayer>();
			claimLayer = world.WorldActor.TraitOrDefault<ResourceClaimLayer>();
		}

		CPos FindNextResource(Actor actor, Harvester harv)
		{
			var locomotorInfo = actor.Info.TraitInfo<MobileInfo>().LocomotorInfo;

			Func<CPos, bool> isValidResource = cell =>
				domainIndex.IsPassable(actor.Location, cell, locomotorInfo) &&
				harv.CanHarvestCell(actor, cell) &&
				claimLayer.CanClaimCell(actor, cell);

			var path = pathfinder.FindPath(
				PathSearch.Search(world, locomotorInfo, actor, true, isValidResource)
					.WithCustomCost(loc => world.FindActorsInCircle(world.Map.CenterOfCell(loc), ai.Info.HarvesterEnemyAvoidanceRadius)
						.Where(u => !u.IsDead && actor.Owner.Stances[u.Owner] == Stance.Enemy)
						.Sum(u => Math.Max(WDist.Zero.Length, ai.Info.HarvesterEnemyAvoidanceRadius.Length - (world.Map.CenterOfCell(loc) - u.CenterPosition).Length)))
					.FromPoint(actor.Location));

			if (path.Count == 0)
				return CPos.Zero;

			return path[0];
		}

		public void Tick(List<Actor> harvesters)
		{
			if (resLayer == null || resLayer.IsResourceLayerEmpty)
				return;

			// Find idle harvesters and give them orders:
			foreach (var harvester in harvesters)
			{
				var harv = harvester.Trait<Harvester>();
				if (!harv.IsEmpty)
					continue;

				if (!harvester.IsIdle)
				{
					var act = harvester.CurrentActivity;
					if (!harv.LastSearchFailed || act.NextActivity == null || act.NextActivity.GetType() != typeof(FindResources))
						continue;
				}

				var para = harvester.TraitOrDefault<Parachutable>();
				if (para != null && para.IsInAir)
					continue;

				// Tell the idle harvester to quit slacking:
				var newSafeResourcePatch = FindNextResource(harvester, harv);
				HackyAI.BotDebug("AI: Harvester {0} is idle. Ordering to {1} in search for new resources.".F(harvester, newSafeResourcePatch));
				ai.QueueOrder(new Order("Harvest", harvester, Target.FromCell(world, newSafeResourcePatch), false));
			}
		}
	}
}