#region Copyright & License Information
/*
 * Copyright 2007-2017 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.GameRules;
using OpenRA.Mods.Common.Traits;
using OpenRA.Traits;

namespace OpenRA.Mods.Common.Warheads
{
	public class SpreadDamageWarhead : DamageWarhead, IRulesetLoaded<WeaponInfo>
	{
		[Desc("Range between falloff steps.")]
		public readonly WDist Spread = new WDist(43);

		[Desc("Damage percentage at each range step")]
		public readonly int[] Falloff = { 100, 37, 14, 5, 0 };

		[Desc("Ranges at which each Falloff step is defined. Overrides Spread.")]
		public WDist[] Range = null;

		[Desc("Extra search radius beyond maximum spread. If set to a negative value (default), it will automatically scale to the largest health shape.",
			"Custom overrides should not be necessary under normal circumstances.")]
		public WDist VictimScanRadius = new WDist(-1);

		void IRulesetLoaded<WeaponInfo>.RulesetLoaded(Ruleset rules, WeaponInfo info)
		{
			if (VictimScanRadius < WDist.Zero)
				VictimScanRadius = Util.MinimumRequiredVictimScanRadius(rules);

			if (Range != null)
			{
				if (Range.Length != 1 && Range.Length != Falloff.Length)
					throw new YamlException("Number of range values must be 1 or equal to the number of Falloff values.");

				for (var i = 0; i < Range.Length - 1; i++)
					if (Range[i] > Range[i + 1])
						throw new YamlException("Range values must be specified in an increasing order.");
			}
			else
				Range = Exts.MakeArray(Falloff.Length, i => i * Spread);
		}

		public override void DoImpact(WPos pos, Actor firedBy, IEnumerable<int> damageModifiers)
		{
			var world = firedBy.World;

			var debugVis = world.WorldActor.TraitOrDefault<DebugVisualizations>();
			if (debugVis != null && debugVis.CombatGeometry)
				world.WorldActor.Trait<WarheadDebugOverlay>().AddImpact(pos, Range, DebugOverlayColor);

			// This only finds actors where the center is within the search radius,
			// so we need to search beyond the maximum spread to account for actors with large health radius
			var hitActors = world.FindActorsInCircle(pos, Range[Range.Length - 1] + VictimScanRadius);

			foreach (var victim in hitActors)
			{
				// Cannot be damaged without a Health trait
				var healthInfo = victim.Info.TraitInfoOrDefault<HealthInfo>();
				if (healthInfo == null)
					continue;

				// Cannot be damaged without an active HitShape
				var activeShapes = victim.TraitsImplementing<HitShape>().Where(Exts.IsTraitEnabled);
				if (!activeShapes.Any())
					continue;

				var distance = activeShapes.Min(t => t.Info.Type.DistanceFromEdge(pos, victim));
				var localModifiers = damageModifiers.Append(GetDamageFalloff(distance.Length));

				DoImpact(victim, firedBy, localModifiers);
			}
		}

		int GetDamageFalloff(int distance)
		{
			var inner = Range[0].Length;
			for (var i = 1; i < Range.Length; i++)
			{
				var outer = Range[i].Length;
				if (outer > distance)
					return int2.Lerp(Falloff[i - 1], Falloff[i], distance - inner, outer - inner);

				inner = outer;
			}

			return 0;
		}
	}
}