#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 AI.Fuzzy.Library;
using OpenRA.Mods.Common.Traits;
using OpenRA.Mods.Common.Warheads;
using OpenRA.Traits;

namespace OpenRA.Mods.Common.AI
{
	sealed class AttackOrFleeFuzzy
	{
		static readonly string[] DefaultRulesNormalOwnHealth = new[]
		{
			"if ((OwnHealth is Normal) " +
			"and ((EnemyHealth is NearDead) or (EnemyHealth is Injured) or (EnemyHealth is Normal)) " +
			"and ((RelativeAttackPower is Weak) or (RelativeAttackPower is Equal) or (RelativeAttackPower is Strong)) " +
			"and ((RelativeSpeed is Slow) or (RelativeSpeed is Equal) or (RelativeSpeed is Fast))) " +
			"then AttackOrFlee is Attack"
		};

		static readonly string[] DefaultRulesInjuredOwnHealth = new[]
		{
			"if ((OwnHealth is Injured) " +
			"and (EnemyHealth is NearDead) " +
			"and ((RelativeAttackPower is Weak) or (RelativeAttackPower is Equal) or (RelativeAttackPower is Strong)) " +
			"and ((RelativeSpeed is Slow) or (RelativeSpeed is Equal) or (RelativeSpeed is Fast))) " +
			"then AttackOrFlee is Attack",

			"if ((OwnHealth is Injured) " +
			"and ((EnemyHealth is Injured) or (EnemyHealth is Normal)) " +
			"and ((RelativeAttackPower is Equal) or (RelativeAttackPower is Strong)) " +
			"and ((RelativeSpeed is Slow) or (RelativeSpeed is Equal) or (RelativeSpeed is Fast))) " +
			"then AttackOrFlee is Attack",

			"if ((OwnHealth is Injured) " +
			"and ((EnemyHealth is Injured) or (EnemyHealth is Normal)) " +
			"and (RelativeAttackPower is Weak) " +
			"and (RelativeSpeed is Slow)) " +
			"then AttackOrFlee is Attack",

			"if ((OwnHealth is Injured) " +
			"and ((EnemyHealth is Injured) or (EnemyHealth is Normal)) " +
			"and (RelativeAttackPower is Weak) " +
			"and ((RelativeSpeed is Equal) or (RelativeSpeed is Fast))) " +
			"then AttackOrFlee is Flee",

			"if ((OwnHealth is Injured) " +
			"and ((EnemyHealth is NearDead) or (EnemyHealth is Injured) or (EnemyHealth is Normal)) " +
			"and ((RelativeAttackPower is Weak) or (RelativeAttackPower is Equal) or (RelativeAttackPower is Strong)) " +
			"and (RelativeSpeed is Slow)) " +
			"then AttackOrFlee is Attack"
		};

		static readonly string[] DefaultRulesNearDeadOwnHealth = new[]
		{
			"if ((OwnHealth is NearDead) " +
			"and ((EnemyHealth is NearDead) or (EnemyHealth is Injured)) " +
			"and ((RelativeAttackPower is Equal) or (RelativeAttackPower is Strong)) " +
			"and ((RelativeSpeed is Slow) or (RelativeSpeed is Equal))) " +
			"then AttackOrFlee is Attack",

			"if ((OwnHealth is NearDead) " +
			"and ((EnemyHealth is NearDead) or (EnemyHealth is Injured)) " +
			"and (RelativeAttackPower is Weak) " +
			"and ((RelativeSpeed is Equal) or (RelativeSpeed is Fast))) " +
			"then AttackOrFlee is Flee",

			"if ((OwnHealth is NearDead) " +
			"and (EnemyHealth is Normal) " +
			"and (RelativeAttackPower is Weak) " +
			"and ((RelativeSpeed is Equal) or (RelativeSpeed is Fast))) " +
			"then AttackOrFlee is Flee",

			"if (OwnHealth is NearDead) " +
			"and (EnemyHealth is Normal) " +
			"and ((RelativeAttackPower is Equal) or (RelativeAttackPower is Strong)) " +
			"and (RelativeSpeed is Fast) " +
			"then AttackOrFlee is Flee",

			"if (OwnHealth is NearDead) " +
			"and (EnemyHealth is Injured) " +
			"and (RelativeAttackPower is Equal) " +
			"and (RelativeSpeed is Fast) " +
			"then AttackOrFlee is Flee"
		};

		public static readonly AttackOrFleeFuzzy Default = new AttackOrFleeFuzzy(null, null, null);
		public static readonly AttackOrFleeFuzzy Rush = new AttackOrFleeFuzzy(new[]
		{
			"if ((OwnHealth is Normal) " +
			"and ((EnemyHealth is NearDead) or (EnemyHealth is Injured) or (EnemyHealth is Normal)) " +
			"and (RelativeAttackPower is Strong) " +
			"and ((RelativeSpeed is Slow) or (RelativeSpeed is Equal) or (RelativeSpeed is Fast))) " +
			"then AttackOrFlee is Attack",

			"if ((OwnHealth is Normal) " +
			"and ((EnemyHealth is NearDead) or (EnemyHealth is Injured) or (EnemyHealth is Normal)) " +
			"and ((RelativeAttackPower is Weak) or (RelativeAttackPower is Equal)) " +
			"and ((RelativeSpeed is Slow) or (RelativeSpeed is Equal) or (RelativeSpeed is Fast))) " +
			"then AttackOrFlee is Flee"
		}, null, null);

		readonly MamdaniFuzzySystem fuzzyEngine = new MamdaniFuzzySystem();

		public AttackOrFleeFuzzy(
			IEnumerable<string> rulesForNormalOwnHealth,
			IEnumerable<string> rulesForInjuredOwnHealth,
			IEnumerable<string> rulesForNeadDeadOwnHealth)
		{
			lock (fuzzyEngine)
			{
				var playerHealthFuzzy = new FuzzyVariable("OwnHealth", 0.0, 100.0);
				playerHealthFuzzy.Terms.Add(new FuzzyTerm("NearDead", new TrapezoidMembershipFunction(0, 0, 20, 40)));
				playerHealthFuzzy.Terms.Add(new FuzzyTerm("Injured", new TrapezoidMembershipFunction(30, 50, 50, 70)));
				playerHealthFuzzy.Terms.Add(new FuzzyTerm("Normal", new TrapezoidMembershipFunction(50, 80, 100, 100)));
				fuzzyEngine.Input.Add(playerHealthFuzzy);

				var enemyHealthFuzzy = new FuzzyVariable("EnemyHealth", 0.0, 100.0);
				enemyHealthFuzzy.Terms.Add(new FuzzyTerm("NearDead", new TrapezoidMembershipFunction(0, 0, 20, 40)));
				enemyHealthFuzzy.Terms.Add(new FuzzyTerm("Injured", new TrapezoidMembershipFunction(30, 50, 50, 70)));
				enemyHealthFuzzy.Terms.Add(new FuzzyTerm("Normal", new TrapezoidMembershipFunction(50, 80, 100, 100)));
				fuzzyEngine.Input.Add(enemyHealthFuzzy);

				var relativeAttackPowerFuzzy = new FuzzyVariable("RelativeAttackPower", 0.0, 1000.0);
				relativeAttackPowerFuzzy.Terms.Add(new FuzzyTerm("Weak", new TrapezoidMembershipFunction(0, 0, 70, 90)));
				relativeAttackPowerFuzzy.Terms.Add(new FuzzyTerm("Equal", new TrapezoidMembershipFunction(85, 100, 100, 115)));
				relativeAttackPowerFuzzy.Terms.Add(new FuzzyTerm("Strong", new TrapezoidMembershipFunction(110, 150, 150, 1000)));
				fuzzyEngine.Input.Add(relativeAttackPowerFuzzy);

				var relativeSpeedFuzzy = new FuzzyVariable("RelativeSpeed", 0.0, 1000.0);
				relativeSpeedFuzzy.Terms.Add(new FuzzyTerm("Slow", new TrapezoidMembershipFunction(0, 0, 70, 90)));
				relativeSpeedFuzzy.Terms.Add(new FuzzyTerm("Equal", new TrapezoidMembershipFunction(85, 100, 100, 115)));
				relativeSpeedFuzzy.Terms.Add(new FuzzyTerm("Fast", new TrapezoidMembershipFunction(110, 150, 150, 1000)));
				fuzzyEngine.Input.Add(relativeSpeedFuzzy);

				var attackOrFleeFuzzy = new FuzzyVariable("AttackOrFlee", 0.0, 50.0);
				attackOrFleeFuzzy.Terms.Add(new FuzzyTerm("Attack", new TrapezoidMembershipFunction(0, 15, 15, 30)));
				attackOrFleeFuzzy.Terms.Add(new FuzzyTerm("Flee", new TrapezoidMembershipFunction(25, 35, 35, 50)));
				fuzzyEngine.Output.Add(attackOrFleeFuzzy);

				foreach (var rule in rulesForNormalOwnHealth ?? DefaultRulesNormalOwnHealth)
					AddFuzzyRule(rule);
				foreach (var rule in rulesForInjuredOwnHealth ?? DefaultRulesInjuredOwnHealth)
					AddFuzzyRule(rule);
				foreach (var rule in rulesForNeadDeadOwnHealth ?? DefaultRulesNearDeadOwnHealth)
					AddFuzzyRule(rule);
			}
		}

		void AddFuzzyRule(string rule)
		{
			fuzzyEngine.Rules.Add(fuzzyEngine.ParseRule(rule));
		}

		public bool CanAttack(IEnumerable<Actor> ownUnits, IEnumerable<Actor> enemyUnits)
		{
			double attackChance;
			var inputValues = new Dictionary<FuzzyVariable, double>();
			lock (fuzzyEngine)
			{
				inputValues.Add(fuzzyEngine.InputByName("OwnHealth"), NormalizedHealth(ownUnits, 100));
				inputValues.Add(fuzzyEngine.InputByName("EnemyHealth"), NormalizedHealth(enemyUnits, 100));
				inputValues.Add(fuzzyEngine.InputByName("RelativeAttackPower"), RelativePower(ownUnits, enemyUnits));
				inputValues.Add(fuzzyEngine.InputByName("RelativeSpeed"), RelativeSpeed(ownUnits, enemyUnits));

				var result = fuzzyEngine.Calculate(inputValues);
				attackChance = result[fuzzyEngine.OutputByName("AttackOrFlee")];
			}

			return !double.IsNaN(attackChance) && attackChance < 30.0;
		}

		static float NormalizedHealth(IEnumerable<Actor> actors, float normalizeByValue)
		{
			var sumOfMaxHp = 0;
			var sumOfHp = 0;
			foreach (var a in actors)
			{
				if (a.Info.HasTraitInfo<HealthInfo>())
				{
					sumOfMaxHp += a.Trait<Health>().MaxHP;
					sumOfHp += a.Trait<Health>().HP;
				}
			}

			if (sumOfMaxHp == 0)
				return 0.0f;

			// Cast to long to avoid overflow when multiplying by the health
			return (int)((long)sumOfHp * normalizeByValue / sumOfMaxHp);
		}

		static float RelativePower(IEnumerable<Actor> own, IEnumerable<Actor> enemy)
		{
			return RelativeValue(own, enemy, 100, SumOfValues<AttackBaseInfo>, a =>
			{
				var sumOfDamage = 0;
				var arms = a.TraitsImplementing<Armament>();
				foreach (var arm in arms)
				{
					var burst = arm.Weapon.Burst;

					// For simplicity's sake, we're only factoring in the first burst delay, as more than one burst delay is extremely rare.
					// Additionally, clamping total delay to minimum of 1 (ReloadDelay: 0 is technically possible) and maximum of 200.
					// High dmg/low ROF weapons shouldn't be rated too low as high dmg/shot can outweigh mere dps due to likelier 1-hit-kills.
					// TODO: Revisit this at some point to replace the arbitrary cap with something smarter.
					var totalReloadDelay = arm.Weapon.ReloadDelay + (arm.Weapon.BurstDelays[0] * (burst - 1)).Clamp(1, 200);
					var damageWarheads = arm.Weapon.Warheads.OfType<DamageWarhead>();
					foreach (var warhead in damageWarheads)
						sumOfDamage += (warhead.Damage * burst / totalReloadDelay) * 100;
				}

				return sumOfDamage;
			});
		}

		static float RelativeSpeed(IEnumerable<Actor> own, IEnumerable<Actor> enemy)
		{
			return RelativeValue(own, enemy, 100, Average<MobileInfo>, (Actor a) => a.Info.TraitInfo<MobileInfo>().Speed);
		}

		static float RelativeValue(IEnumerable<Actor> own, IEnumerable<Actor> enemy, float normalizeByValue,
					Func<IEnumerable<Actor>, Func<Actor, int>, float> relativeFunc, Func<Actor, int> getValue)
		{
			if (!enemy.Any())
				return 999.0f;

			if (!own.Any())
				return 0.0f;

			var relative = (relativeFunc(own, getValue) / relativeFunc(enemy, getValue)) * normalizeByValue;
			return relative.Clamp(0.0f, 999.0f);
		}

		static float SumOfValues<TTraitInfo>(IEnumerable<Actor> actors, Func<Actor, int> getValue) where TTraitInfo : ITraitInfo
		{
			var sum = 0;
			foreach (var a in actors)
				if (a.Info.HasTraitInfo<TTraitInfo>())
					sum += getValue(a);

			return sum;
		}

		static float Average<TTraitInfo>(IEnumerable<Actor> actors, Func<Actor, int> getValue) where TTraitInfo : ITraitInfo
		{
			var sum = 0;
			var countActors = 0;
			foreach (var a in actors)
			{
				if (a.Info.HasTraitInfo<TTraitInfo>())
				{
					sum += getValue(a);
					countActors++;
				}
			}

			if (countActors == 0)
				return 0.0f;

			return sum / countActors;
		}
	}
}