#region Copyright & License Information
/*
 * Copyright 2007-2020 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.GameRules;
using OpenRA.Graphics;
using OpenRA.Mods.Common.Effects;
using OpenRA.Mods.Common.Graphics;
using OpenRA.Mods.Common.Traits;
using OpenRA.Primitives;
using OpenRA.Traits;

namespace OpenRA.Mods.Common.Projectiles
{
	public class BulletInfo : IProjectileInfo
	{
		[Desc("Projectile speed in WDist / tick, two values indicate variable velocity.")]
		public readonly WDist[] Speed = { new WDist(17) };

		[Desc("Maximum offset at the maximum range.")]
		public readonly WDist Inaccuracy = WDist.Zero;

		[Desc("Image to display.")]
		public readonly string Image = null;

		[SequenceReference("Image")]
		[Desc("Loop a randomly chosen sequence of Image from this list while this projectile is moving.")]
		public readonly string[] Sequences = { "idle" };

		[PaletteReference]
		[Desc("The palette used to draw this projectile.")]
		public readonly string Palette = "effect";

		[Desc("Palette is a player palette BaseName")]
		public readonly bool IsPlayerPalette = false;

		[Desc("Does this projectile have a shadow?")]
		public readonly bool Shadow = false;

		[PaletteReference]
		[Desc("Palette to use for this projectile's shadow if Shadow is true.")]
		public readonly string ShadowPalette = "shadow";

		[Desc("Trail animation.")]
		public readonly string TrailImage = null;

		[SequenceReference("TrailImage")]
		[Desc("Loop a randomly chosen sequence of TrailImage from this list while this projectile is moving.")]
		public readonly string[] TrailSequences = { "idle" };

		[Desc("Interval in ticks between each spawned Trail animation.")]
		public readonly int TrailInterval = 2;

		[Desc("Delay in ticks until trail animation is spawned.")]
		public readonly int TrailDelay = 1;

		[PaletteReference("TrailUsePlayerPalette")]
		[Desc("Palette used to render the trail sequence.")]
		public readonly string TrailPalette = "effect";

		[Desc("Use the Player Palette to render the trail sequence.")]
		public readonly bool TrailUsePlayerPalette = false;

		[Desc("Is this blocked by actors with BlocksProjectiles trait.")]
		public readonly bool Blockable = true;

		[Desc("Width of projectile (used for finding blocking actors).")]
		public readonly WDist Width = new WDist(1);

		[Desc("Arc in WAngles, two values indicate variable arc.")]
		public readonly WAngle[] LaunchAngle = { WAngle.Zero };

		[Desc("Up to how many times does this bullet bounce when touching ground without hitting a target.",
			"0 implies exploding on contact with the originally targeted position.")]
		public readonly int BounceCount = 0;

		[Desc("Modify distance of each bounce by this percentage of previous distance.")]
		public readonly int BounceRangeModifier = 60;

		[Desc("If projectile touches an actor with one of these stances during or after the first bounce, trigger explosion.")]
		public readonly Stance ValidBounceBlockerStances = Stance.Enemy | Stance.Neutral;

		[Desc("Altitude above terrain below which to explode. Zero effectively deactivates airburst.")]
		public readonly WDist AirburstAltitude = WDist.Zero;

		public readonly int ContrailLength = 0;
		public readonly int ContrailZOffset = 2047;
		public readonly Color ContrailColor = Color.White;
		public readonly bool ContrailUsePlayerColor = false;
		public readonly int ContrailDelay = 1;
		public readonly WDist ContrailWidth = new WDist(64);

		public IProjectile Create(ProjectileArgs args) { return new Bullet(this, args); }
	}

	public class Bullet : IProjectile, ISync
	{
		readonly BulletInfo info;
		readonly ProjectileArgs args;
		readonly Animation anim;
		readonly int facing;
		readonly WAngle angle;
		readonly WDist speed;
		readonly string trailPalette;

		ContrailRenderable contrail;

		[Sync]
		WPos pos, target, source;

		int length;
		int ticks, smokeTicks;
		int remainingBounces;

		public Bullet(BulletInfo info, ProjectileArgs args)
		{
			this.info = info;
			this.args = args;
			pos = args.Source;
			source = args.Source;

			var world = args.SourceActor.World;

			if (info.LaunchAngle.Length > 1)
				angle = new WAngle(world.SharedRandom.Next(info.LaunchAngle[0].Angle, info.LaunchAngle[1].Angle));
			else
				angle = info.LaunchAngle[0];

			if (info.Speed.Length > 1)
				speed = new WDist(world.SharedRandom.Next(info.Speed[0].Length, info.Speed[1].Length));
			else
				speed = info.Speed[0];

			target = args.PassiveTarget;
			if (info.Inaccuracy.Length > 0)
			{
				var inaccuracy = Util.ApplyPercentageModifiers(info.Inaccuracy.Length, args.InaccuracyModifiers);
				var range = Util.ApplyPercentageModifiers(args.Weapon.Range.Length, args.RangeModifiers);
				var maxOffset = inaccuracy * (target - pos).Length / range;
				target += WVec.FromPDF(world.SharedRandom, 2) * maxOffset / 1024;
			}

			if (info.AirburstAltitude > WDist.Zero)
				target += new WVec(WDist.Zero, WDist.Zero, info.AirburstAltitude);

			facing = (target - pos).Yaw.Facing;
			length = Math.Max((target - pos).Length / speed.Length, 1);

			if (!string.IsNullOrEmpty(info.Image))
			{
				anim = new Animation(world, info.Image, new Func<int>(GetEffectiveFacing));
				anim.PlayRepeating(info.Sequences.Random(world.SharedRandom));
			}

			if (info.ContrailLength > 0)
			{
				var color = info.ContrailUsePlayerColor ? ContrailRenderable.ChooseColor(args.SourceActor) : info.ContrailColor;
				contrail = new ContrailRenderable(world, color, info.ContrailWidth, info.ContrailLength, info.ContrailDelay, info.ContrailZOffset);
			}

			trailPalette = info.TrailPalette;
			if (info.TrailUsePlayerPalette)
				trailPalette += args.SourceActor.Owner.InternalName;

			smokeTicks = info.TrailDelay;
			remainingBounces = info.BounceCount;
		}

		int GetEffectiveFacing()
		{
			var at = (float)ticks / (length - 1);
			var attitude = angle.Tan() * (1 - 2 * at) / (4 * 1024);

			var u = (facing % 128) / 128f;
			var scale = 512 * u * (1 - u);

			return (int)(facing < 128
				? facing - scale * attitude
				: facing + scale * attitude);
		}

		public void Tick(World world)
		{
			if (anim != null)
				anim.Tick();

			var lastPos = pos;
			pos = WPos.LerpQuadratic(source, target, angle, ticks, length);

			// Check for walls or other blocking obstacles
			var shouldExplode = false;
			WPos blockedPos;
			if (info.Blockable && BlocksProjectiles.AnyBlockingActorsBetween(world, lastPos, pos, info.Width,
				out blockedPos))
			{
				pos = blockedPos;
				shouldExplode = true;
			}

			if (!string.IsNullOrEmpty(info.TrailImage) && --smokeTicks < 0)
			{
				var delayedPos = WPos.LerpQuadratic(source, target, angle, ticks - info.TrailDelay, length);
				world.AddFrameEndTask(w => w.Add(new SpriteEffect(delayedPos, w, info.TrailImage, info.TrailSequences.Random(world.SharedRandom),
					trailPalette, facing: GetEffectiveFacing())));

				smokeTicks = info.TrailInterval;
			}

			if (info.ContrailLength > 0)
				contrail.Update(pos);

			var flightLengthReached = ticks++ >= length;
			var shouldBounce = remainingBounces > 0;

			if (flightLengthReached && shouldBounce)
			{
				shouldExplode |= AnyValidTargetsInRadius(world, pos, info.Width, args.SourceActor, true);
				target += (pos - source) * info.BounceRangeModifier / 100;
				var dat = world.Map.DistanceAboveTerrain(target);
				target += new WVec(0, 0, -dat.Length);
				length = Math.Max((target - pos).Length / speed.Length, 1);
				ticks = 0;
				source = pos;
				remainingBounces--;
			}

			// Flight length reached / exceeded
			shouldExplode |= flightLengthReached && !shouldBounce;

			// Driving into cell with higher height level
			shouldExplode |= world.Map.DistanceAboveTerrain(pos).Length < 0;

			// After first bounce, check for targets each tick
			if (remainingBounces < info.BounceCount)
				shouldExplode |= AnyValidTargetsInRadius(world, pos, info.Width, args.SourceActor, true);

			if (shouldExplode)
				Explode(world);
		}

		public IEnumerable<IRenderable> Render(WorldRenderer wr)
		{
			if (info.ContrailLength > 0)
				yield return contrail;

			if (anim == null || ticks >= length)
				yield break;

			var world = args.SourceActor.World;
			if (!world.FogObscures(pos))
			{
				if (info.Shadow)
				{
					var dat = world.Map.DistanceAboveTerrain(pos);
					var shadowPos = pos - new WVec(0, 0, dat.Length);
					foreach (var r in anim.Render(shadowPos, wr.Palette(info.ShadowPalette)))
						yield return r;
				}

				var palette = wr.Palette(info.Palette + (info.IsPlayerPalette ? args.SourceActor.Owner.InternalName : ""));
				foreach (var r in anim.Render(pos, palette))
					yield return r;
			}
		}

		void Explode(World world)
		{
			if (info.ContrailLength > 0)
				world.AddFrameEndTask(w => w.Add(new ContrailFader(pos, contrail)));

			world.AddFrameEndTask(w => w.Remove(this));

			args.Weapon.Impact(Target.FromPos(pos), new WarheadArgs(args));
		}

		bool AnyValidTargetsInRadius(World world, WPos pos, WDist radius, Actor firedBy, bool checkTargetType)
		{
			foreach (var victim in world.FindActorsOnCircle(pos, radius))
			{
				if (checkTargetType && !Target.FromActor(victim).IsValidFor(firedBy))
					continue;

				if (!info.ValidBounceBlockerStances.HasStance(victim.Owner.Stances[firedBy.Owner]))
					continue;

				// If the impact position is within any actor's HitShape, we have a direct hit
				var activeShapes = victim.TraitsImplementing<HitShape>().Where(Exts.IsTraitEnabled);
				if (activeShapes.Any(i => i.DistanceFromEdge(victim, pos).Length <= 0))
					return true;
			}

			return false;
		}
	}
}
