using System.Linq;
using System.Numerics;
using Content.Shared.Camera;
using Robust.Shared.Noise;
using Robust.Shared.Player;
using Robust.Shared.Random;
using Robust.Shared.Timing;

namespace Content.Shared._ES.Camera;

/// <summary>
///     Handles sending rotational or translational screenshake to an entity, managing the screenshake commands
///     of every entity currently screenshaking, and setting offset/rotation when updated
/// </summary>
// DeltaV - renamed from ESScreenshakeSystem to SharedESScreenshakeSystem
public sealed class SharedESScreenshakeSystem : EntitySystem
{
    // [Dependency] private readonly IRobustRandom _random = default!; // Delta V - Never used
    [Dependency] private readonly IGameTiming _timing = default!;

    #region Internal

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

        // SubscribeLocalEvent<ESScreenshakeComponent, ESGetEyeRotationEvent>(OnGetEyeRotation); // DeltaV - Moved to Client system
        // SubscribeLocalEvent<ESScreenshakeComponent, GetEyeOffsetEvent>(OnGetEyeOffset); // DeltaV - Moved to Client system
        SubscribeLocalEvent<ESScreenshakeComponent, EntityUnpausedEvent>(OnEntityUnpaused);
    }


    public override void Update(float frameTime)
    {
        base.Update(frameTime);

        // TODO mirror might make sense to never remove individual commands and only remove the comp if theyre all > calculatedend instead.
        var shakers = EntityQueryEnumerator<EyeComponent, ESScreenshakeComponent>();
        while (shakers.MoveNext(out var ent, out var eye, out var shake))
        {
            if (shake.Commands.Count == 0)
            {
                RemCompDeferred<ESScreenshakeComponent>(ent);
                continue;
            }

            foreach (var command in shake.Commands.ToList())
            {
                // handle removing old commands
                if (_timing.CurTime < command.CalculatedEnd)
                    continue;
                shake.Commands.Remove(command);
                Dirty(ent, shake);
            }
        }
    }

    private void OnEntityUnpaused(Entity<ESScreenshakeComponent> ent, ref EntityUnpausedEvent args)
    {
        // rebuild screenshake commands but with offset times
        var newSet = new HashSet<ESScreenshakeCommand>();
        foreach (var command in ent.Comp.Commands)
        {
            var newCommand = command with
            {
                CalculatedEnd = command.CalculatedEnd + args.PausedTime,
                Start = command.Start + args.PausedTime,
            };

            newSet.Add(newCommand);
        }

        ent.Comp.Commands = newSet;
        Dirty(ent);
    }

    /// <summary>
    ///     Calculates when both traumas will be at least = 0 given the decay rate and start time.
    /// </summary>
    private TimeSpan CalculateEndTimeForCommand(Entity<ESScreenshakeComponent> ent, ESScreenshakeParameters? translation, ESScreenshakeParameters? rotation, TimeSpan start)
    {
        // https://www.desmos.com/calculator/optip8eucx
        var secsUntilRotationalEnd = rotation != null ? MathF.Sqrt(rotation.Trauma / rotation.DecayRate) : 0f;
        var secsUntilTranslationalEnd = translation != null ? MathF.Sqrt(translation.Trauma / translation.DecayRate) : 0f;
        var larger = secsUntilTranslationalEnd >= secsUntilRotationalEnd
            ? secsUntilTranslationalEnd
            : secsUntilRotationalEnd;

        return start + TimeSpan.FromSeconds(larger);
    }

    /// <summary>
    ///     Gets the trauma value for the current time, given the decay rate and start time.
    /// </summary>
    // DeltaV - make public
    public float CalculateTraumaValueForCurrentTime(ESScreenshakeParameters parameters, TimeSpan start)
    {
        var timeDiff = _timing.CurTime - start;

        // erm
        if (timeDiff < TimeSpan.Zero)
            return 0f;

        // trauma decays quadratically with seconds passed
        // https://www.desmos.com/calculator/optip8eucx
        var totalSecsSquared = (float) (timeDiff.TotalSeconds * timeDiff.TotalSeconds);
        return -totalSecsSquared * parameters.DecayRate + parameters.Trauma;
    }

    #endregion

    #region Public API

    public void Screenshake(EntityUid uid, ESScreenshakeParameters? translation, ESScreenshakeParameters? rotation)
    {
        if (!HasComp<EyeComponent>(uid))
            return;

        var comp = EnsureComp<ESScreenshakeComponent>(uid);
        var time = _timing.CurTime;
        var end = CalculateEndTimeForCommand((uid, comp), translation, rotation, time);
        var command = new ESScreenshakeCommand(translation, rotation, time, end);

        comp.Commands.Add(command);
        Dirty(uid, comp);
    }

    public void Screenshake(Filter filter, ESScreenshakeParameters? translation, ESScreenshakeParameters? rotation)
    {
        foreach (var player in filter.Recipients)
        {
            if (player.AttachedEntity is {} ent)
                Screenshake(ent, translation, rotation);
        }
    }

    #endregion
}