using System;
using System.Collections.Generic;
using OpenRa.Game.GameRules;
using OpenRa.Game.Graphics;

namespace OpenRa.Game
{
	class Bullet : IEffect
	{
		public Player Owner { get; private set; }
		readonly Actor FiredBy;
		readonly WeaponInfo Weapon;
		readonly ProjectileInfo Projectile;
		readonly WarheadInfo Warhead;
		readonly int2 Src;
		readonly int2 Dest;
		readonly int2 VisualDest;

		int t = 0;
		Animation anim;

		const int BaseBulletSpeed = 100;		/* pixels / 40ms frame */

		/* src, dest are *pixel* coords */
		public Bullet(string weapon, Player owner, Actor firedBy, 
			int2 src, int2 dest)
		{
			Owner = owner;
			FiredBy = firedBy;
			Src = src;
			Dest = dest;
			VisualDest = Dest + new int2(
						Game.CosmeticRandom.Next(-10, 10),
						Game.CosmeticRandom.Next(-10, 10));
			Weapon = Rules.WeaponInfo[weapon];
			Projectile = Rules.ProjectileInfo[Weapon.Projectile];
			Warhead = Rules.WarheadInfo[Weapon.Warhead];

			if (Projectile.Image != null && Projectile.Image != "none")
			{
				anim = new Animation(Projectile.Image);
				if (Projectile.Rotates)
					anim.PlayFetchIndex("idle",
						() => Traits.Util.QuantizeFacing(
							Traits.Util.GetFacing((dest - src).ToFloat2(), 0),
							anim.CurrentSequence.Length));
				else
					anim.PlayRepeating("idle");
			}
		}

		int TotalTime() { return (Dest - Src).Length * BaseBulletSpeed / Weapon.Speed; }

		public void Tick()
		{
			if (t == 0)
				Game.PlaySound(Weapon.Report + ".aud", false);

			t += 40;

			if (t > TotalTime())		/* remove finished bullets */
			{
				Game.world.AddFrameEndTask(w =>
				{
					w.Remove(this);

					var targetTile = ((1f / Game.CellSize) * Dest.ToFloat2()).ToInt2();

					var isWater = Game.IsWater(targetTile);
					var hitWater = Game.IsCellBuildable(targetTile, UnitMovementType.Float);

					if (Warhead.Explosion != 0)
						w.Add(new Explosion(VisualDest, Warhead.Explosion, hitWater));

					var impact = Warhead.ImpactSound;
					if (hitWater && Warhead.WaterImpactSound != null)
						impact = Warhead.WaterImpactSound;

					if (impact != null) 
						Game.PlaySound(impact+ ".aud", false);

					if (!isWater)
						switch( Warhead.Explosion )		/* todo: push the scorch/crater behavior into data */
						{
							case 4:
							case 5:
								Smudge.AddSmudge(true, targetTile.X, targetTile.Y);
								break;

							case 3:
							case 6:
								Smudge.AddSmudge(false, targetTile.X, targetTile.Y);
								break;
						}
				});

				var maxSpread = GetMaximumSpread();
				var hitActors = Game.FindUnitsInCircle(Dest, GetMaximumSpread());

				foreach (var victim in hitActors)
					victim.InflictDamage(FiredBy, this, (int)GetDamageToInflict(victim));
			}
		}

		const float height = .1f;

		public IEnumerable<Tuple<Sprite, float2, int>> Render()
		{
			if (anim != null)
			{
				var pos = float2.Lerp(
						Src.ToFloat2(),
						VisualDest.ToFloat2(),
						(float)t / TotalTime()) - 0.5f * anim.Image.size;

				if (Projectile.High || Projectile.Arcing)
				{
					if (Projectile.Shadow)
						yield return Tuple.New(anim.Image, pos, 8);	/* todo: shadow pal */

					var at = (float)t / TotalTime();
					var highPos = pos - new float2(0, (VisualDest - Src).Length * height * 4 * at * (1 - at));

					yield return Tuple.New(anim.Image, highPos, Owner.Palette);
				}
				else
					yield return Tuple.New(anim.Image, pos, Owner.Palette);
			}
		}

		float GetMaximumSpread()
		{
			return (int)(Warhead.Spread * Math.Log(Weapon.Damage, 2));
		}

		float GetDamageToInflict(Actor target)
		{
			if( target.unitInfo == null ) // tree or other doodad
				return 0;

			/* todo: some things can't be damaged AT ALL by certain weapons! */
			var distance = (target.CenterLocation - Dest).Length;
			var rawDamage = Weapon.Damage * (float)Math.Exp(-distance / Warhead.Spread);
			var multiplier = Warhead.EffectivenessAgainst(target.unitInfo.Armor);

			return rawDamage * multiplier;
		}
	}
}