Delta-v/Content.Server/Explosion/EntitySystems/ExplosionSystem.cs

using System.Linq;
using System.Numerics;
using Content.Server.Administration.Logs;
using Content.Server.Atmos.Components;
using Content.Server.Chat.Managers;
using Content.Server.Explosion.Components;
using Content.Server.NodeContainer.EntitySystems;
using Content.Server.NPC.Pathfinding;
using Content.Shared.Armor;
using Content.Shared.Camera;
using Content.Shared.CCVar;
using Content.Shared.Damage;
using Content.Shared.Database;
using Content.Shared.Explosion;
using Content.Shared.GameTicking;
using Content.Shared.Inventory;
using Content.Shared.Throwing;
using Robust.Server.GameStates;
using Robust.Server.Player;
using Robust.Shared.Audio;
using Robust.Shared.Configuration;
using Robust.Shared.Map;
using Robust.Shared.Player;
using Robust.Shared.Prototypes;
using Robust.Shared.Random;
using Robust.Shared.Utility;

namespace Content.Server.Explosion.EntitySystems;

public sealed partial class ExplosionSystem : EntitySystem
{
    [Dependency] private readonly IMapManager _mapManager = default!;
    [Dependency] private readonly IRobustRandom _robustRandom = default!;
    [Dependency] private readonly ITileDefinitionManager _tileDefinitionManager = default!;
    [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
    [Dependency] private readonly IConfigurationManager _cfg = default!;
    [Dependency] private readonly IPlayerManager _playerManager = default!;

    [Dependency] private readonly SharedAppearanceSystem _appearance = default!;
    [Dependency] private readonly DamageableSystem _damageableSystem = default!;
    [Dependency] private readonly NodeGroupSystem _nodeGroupSystem = default!;
    [Dependency] private readonly PathfindingSystem _pathfindingSystem = default!;
    [Dependency] private readonly SharedCameraRecoilSystem _recoilSystem = default!;
    [Dependency] private readonly IAdminLogManager _adminLogger = default!;
    [Dependency] private readonly IChatManager _chat = default!;
    [Dependency] private readonly ThrowingSystem _throwingSystem = default!;
    [Dependency] private readonly PvsOverrideSystem _pvsSys = default!;
    [Dependency] private readonly SharedTransformSystem _transformSystem = default!;

    /// <summary>
    ///     "Tile-size" for space when there are no nearby grids to use as a reference.
    /// </summary>
    public const ushort DefaultTileSize = 1;

    private AudioParams _audioParams = AudioParams.Default.WithVolume(-3f);

    /// <summary>
    ///     The "default" explosion prototype.
    /// </summary>
    /// <remarks>
    ///     Generally components should specify an explosion prototype via a yaml datafield, so that the yaml-linter can
    ///     find errors. However some components, like rogue arrows, or some commands like the admin-smite need to have
    ///     a "default" option specified outside of yaml data-fields. Hence this const string.
    /// </remarks>
    [ValidatePrototypeId<ExplosionPrototype>]
    public const string DefaultExplosionPrototypeId = "Default";

    public override void Initialize()
    {
        base.Initialize();

        DebugTools.Assert(_prototypeManager.HasIndex<ExplosionPrototype>(DefaultExplosionPrototypeId));

        // handled in ExplosionSystem.GridMap.cs
        SubscribeLocalEvent<GridRemovalEvent>(OnGridRemoved);
        SubscribeLocalEvent<GridStartupEvent>(OnGridStartup);
        SubscribeLocalEvent<ExplosionResistanceComponent, GetExplosionResistanceEvent>(OnGetResistance);

        // as long as explosion-resistance mice are never added, this should be fine (otherwise a mouse-hat will transfer it's power to the wearer).
        SubscribeLocalEvent<ExplosionResistanceComponent, InventoryRelayedEvent<GetExplosionResistanceEvent>>(RelayedResistance);

        SubscribeLocalEvent<TileChangedEvent>(OnTileChanged);

        SubscribeLocalEvent<RoundRestartCleanupEvent>(OnReset);

        SubscribeLocalEvent<ExplosionResistanceComponent, ArmorExamineEvent>(OnArmorExamine);

        // Handled by ExplosionSystem.Processing.cs
        SubscribeLocalEvent<MapChangedEvent>(OnMapChanged);

        // handled in ExplosionSystemAirtight.cs
        SubscribeLocalEvent<AirtightComponent, DamageChangedEvent>(OnAirtightDamaged);
        SubscribeCvars();
        InitAirtightMap();
        InitVisuals();
    }

    private void OnReset(RoundRestartCleanupEvent ev)
    {
        _explosionQueue.Clear();
        if (_activeExplosion != null)
            QueueDel(_activeExplosion.VisualEnt);
        _activeExplosion = null;
        _nodeGroupSystem.PauseUpdating = false;
        _pathfindingSystem.PauseUpdating = false;
    }

    public override void Shutdown()
    {
        base.Shutdown();
        UnsubscribeCvars();
        _nodeGroupSystem.PauseUpdating = false;
        _pathfindingSystem.PauseUpdating = false;
    }

    private void RelayedResistance(EntityUid uid, ExplosionResistanceComponent component,
        InventoryRelayedEvent<GetExplosionResistanceEvent> args)
    {
        var a = args.Args;
        OnGetResistance(uid, component, ref a);
    }

    private void OnGetResistance(EntityUid uid, ExplosionResistanceComponent component, ref GetExplosionResistanceEvent args)
    {
        args.DamageCoefficient *= component.DamageCoefficient;
        if (component.Modifiers.TryGetValue(args.ExplosionPrototype, out var modifier))
            args.DamageCoefficient *= modifier;
    }

    /// <summary>
    ///     Given an entity with an explosive component, spawn the appropriate explosion.
    /// </summary>
    /// <remarks>
    ///     Also accepts radius or intensity arguments. This is useful for explosives where the intensity is not
    ///     specified in the yaml / by the component, but determined dynamically (e.g., by the quantity of a
    ///     solution in a reaction).
    /// </remarks>
    public void TriggerExplosive(EntityUid uid, ExplosiveComponent? explosive = null, bool delete = true, float? totalIntensity = null, float? radius = null, EntityUid? user = null)
    {
        // log missing: false, because some entities (e.g. liquid tanks) attempt to trigger explosions when damaged,
        // but may not actually be explosive.
        if (!Resolve(uid, ref explosive, logMissing: false))
            return;

        // No reusable explosions here.
        if (explosive.Exploded)
            return;

        explosive.Exploded = true;

        // Override the explosion intensity if optional arguments were provided.
        if (radius != null)
            totalIntensity ??= RadiusToIntensity((float) radius, explosive.IntensitySlope, explosive.MaxIntensity);
        totalIntensity ??= explosive.TotalIntensity;

        QueueExplosion(uid,
            explosive.ExplosionType,
            (float) totalIntensity,
            explosive.IntensitySlope,
            explosive.MaxIntensity,
            explosive.TileBreakScale,
            explosive.MaxTileBreak,
            explosive.CanCreateVacuum,
            user);

        if (explosive.DeleteAfterExplosion ?? delete)
            EntityManager.QueueDeleteEntity(uid);
    }

    /// <summary>
    ///     Find the strength needed to generate an explosion of a given radius. More useful for radii larger then 4, when the explosion becomes less "blocky".
    /// </summary>
    /// <remarks>
    ///     This assumes the explosion is in a vacuum / unobstructed. Given that explosions are not perfectly
    ///     circular, here radius actually means the sqrt(Area/pi), where the area is the total number of tiles
    ///     covered by the explosion. Until you get to radius 30+, this is functionally equivalent to the
    ///     actual radius.
    /// </remarks>
    public float RadiusToIntensity(float radius, float slope, float maxIntensity = 0)
    {
        // If you consider the intensity at each tile in an explosion to be a height. Then a circular explosion is
        // shaped like a cone. So total intensity is like the volume of a cone with height = slope * radius. Of
        // course, as the explosions are not perfectly circular, this formula isn't perfect, but the formula works
        // reasonably well.

        // This should actually use the formula for the volume of a distorted octagonal frustum. But this is good
        // enough.

        var coneVolume = slope * MathF.PI / 3 * MathF.Pow(radius, 3);

        if (maxIntensity <= 0 || slope * radius < maxIntensity)
            return coneVolume;

        // This explosion is limited by the maxIntensity.
        // Instead of a cone, we have a conical frustum.

        // Subtract the volume of the missing cone segment, with height:
        var h = slope * radius - maxIntensity;
        return coneVolume - h * MathF.PI / 3 * MathF.Pow(h / slope, 2);
    }

    /// <summary>
    ///     Inverse formula for <see cref="RadiusToIntensity"/>
    /// </summary>
    public float IntensityToRadius(float totalIntensity, float slope, float maxIntensity)
    {
        // max radius to avoid being capped by max-intensity
        var r0 = maxIntensity / slope;

        // volume at r0
        var v0 = RadiusToIntensity(r0, slope);

        if (totalIntensity <= v0)
        {
            // maxIntensity is a non-issue, can use simple inverse formula
            return MathF.Cbrt(3 * totalIntensity / (slope * MathF.PI));
        }

        return r0 * (MathF.Sqrt(12 * totalIntensity / v0 - 3) / 6 + 0.5f);
    }

    /// <summary>
    ///     Queue an explosions, centered on some entity.
    /// </summary>
    public void QueueExplosion(EntityUid uid,
        string typeId,
        float totalIntensity,
        float slope,
        float maxTileIntensity,
        float tileBreakScale = 1f,
        int maxTileBreak = int.MaxValue,
        bool canCreateVacuum = true,
        EntityUid? user = null,
        bool addLog = true)
    {
        var pos = Transform(uid);


        QueueExplosion(pos.MapPosition, typeId, totalIntensity, slope, maxTileIntensity, tileBreakScale, maxTileBreak, canCreateVacuum, addLog: false);

        if (!addLog)
            return;

        if (user == null)
        {
            _adminLogger.Add(LogType.Explosion, LogImpact.High,
                $"{ToPrettyString(uid):entity} exploded ({typeId}) at {pos.Coordinates:coordinates} with intensity {totalIntensity} slope {slope}");
        }
        else
        {
            _adminLogger.Add(LogType.Explosion, LogImpact.High,
                $"{ToPrettyString(user.Value):user} caused {ToPrettyString(uid):entity} to explode ({typeId}) at {pos.Coordinates:coordinates} with intensity {totalIntensity} slope {slope}");
            var alertMinExplosionIntensity = _cfg.GetCVar(CCVars.AdminAlertExplosionMinIntensity);
            if (alertMinExplosionIntensity > -1 && totalIntensity >= alertMinExplosionIntensity)
                _chat.SendAdminAlert(user.Value, $"caused {ToPrettyString(uid)} to explode ({typeId}:{totalIntensity}) at {pos.Coordinates:coordinates}");
        }
    }

    /// <summary>
    ///     Queue an explosion, with a specified epicenter and set of starting tiles.
    /// </summary>
    public void QueueExplosion(MapCoordinates epicenter,
        string typeId,
        float totalIntensity,
        float slope,
        float maxTileIntensity,
        float tileBreakScale = 1f,
        int maxTileBreak = int.MaxValue,
        bool canCreateVacuum = true,
        bool addLog = true)
    {
        if (totalIntensity <= 0 || slope <= 0)
            return;

        if (!_prototypeManager.TryIndex<ExplosionPrototype>(typeId, out var type))
        {
            Logger.Error($"Attempted to spawn unknown explosion prototype: {type}");
            return;
        }

        if (addLog) // dont log if already created a separate, more detailed, log.
            _adminLogger.Add(LogType.Explosion, LogImpact.High, $"Explosion ({typeId}) spawned at {epicenter:coordinates} with intensity {totalIntensity} slope {slope}");

        _explosionQueue.Enqueue(() => SpawnExplosion(epicenter, type, totalIntensity,
            slope, maxTileIntensity, tileBreakScale, maxTileBreak, canCreateVacuum));
    }

    /// <summary>
    ///     This function actually spawns the explosion. It returns an <see cref="Explosion"/> instance with
    ///     information about the affected tiles for the explosion system to process. It will also trigger the
    ///     camera shake and sound effect.
    /// </summary>
    private Explosion? SpawnExplosion(MapCoordinates epicenter,
        ExplosionPrototype type,
        float totalIntensity,
        float slope,
        float maxTileIntensity,
        float tileBreakScale,
        int maxTileBreak,
        bool canCreateVacuum)
    {
        if (!_mapManager.MapExists(epicenter.MapId))
            return null;

        var results = GetExplosionTiles(epicenter, type.ID, totalIntensity, slope, maxTileIntensity);

        if (results == null)
            return null;

        var (area, iterationIntensity, spaceData, gridData, spaceMatrix) = results.Value;

        var visualEnt = CreateExplosionVisualEntity(epicenter, type.ID, spaceMatrix, spaceData, gridData.Values, iterationIntensity);

        // camera shake
        CameraShake(iterationIntensity.Count * 2.5f, epicenter, totalIntensity);

        //For whatever bloody reason, sound system requires ENTITY coordinates.
        var mapEntityCoords = EntityCoordinates.FromMap(EntityManager, _mapManager.GetMapEntityId(epicenter.MapId), epicenter);

        // play sound.
        var audioRange = iterationIntensity.Count * 5;
        var filter = Filter.Pvs(epicenter).AddInRange(epicenter, audioRange);
        SoundSystem.Play(type.Sound.GetSound(), filter, mapEntityCoords, _audioParams);

        return new Explosion(this,
            type,
            spaceData,
            gridData.Values.ToList(),
            iterationIntensity,
            epicenter,
            spaceMatrix,
            area,
            tileBreakScale,
            maxTileBreak,
            canCreateVacuum,
            EntityManager,
            _mapManager,
            visualEnt);
    }

    private void CameraShake(float range, MapCoordinates epicenter, float totalIntensity)
    {
        var players = Filter.Empty();
        players.AddInRange(epicenter, range, _playerManager, EntityManager);

        foreach (var player in players.Recipients)
        {
            if (player.AttachedEntity is not EntityUid uid)
                continue;

            var playerPos = Transform(player.AttachedEntity!.Value).WorldPosition;
            var delta = epicenter.Position - playerPos;

            if (delta.EqualsApprox(Vector2.Zero))
                delta = new(0.01f, 0);

            var distance = delta.Length();
            var effect = 5 * MathF.Pow(totalIntensity, 0.5f) * (1 - distance / range);
            if (effect > 0.01f)
                _recoilSystem.KickCamera(uid, -delta.Normalized() * effect);
        }
    }

    private void OnArmorExamine(EntityUid uid, ExplosionResistanceComponent component, ref ArmorExamineEvent args)
    {
        args.Msg.PushNewline();
        args.Msg.AddMarkup(Loc.GetString("explosion-resistance-coefficient-value",
            ("value", MathF.Round((1f - component.DamageCoefficient) * 100, 1))
            ));
    }
}