using System;
using Content.Server.Atmos.Piping.Components;
using Content.Server.Atmos.Piping.Trinary.Components;
using Content.Server.NodeContainer;
using Content.Server.NodeContainer.Nodes;
using Content.Shared.Atmos;
using JetBrains.Annotations;
using Robust.Shared.GameObjects;

namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
{
    [UsedImplicitly]
    public class GasMixerSystem : EntitySystem
    {
        public override void Initialize()
        {
            base.Initialize();

            SubscribeLocalEvent<GasMixerComponent, AtmosDeviceUpdateEvent>(OnMixerUpdated);
        }

        private void OnMixerUpdated(EntityUid uid, GasMixerComponent mixer, AtmosDeviceUpdateEvent args)
        {
            // TODO ATMOS: Cache total moles since it's expensive.

            if (!mixer.Enabled)
                return;

            if (!EntityManager.TryGetComponent(uid, out NodeContainerComponent? nodeContainer))
                return;

            if (!nodeContainer.TryGetNode(mixer.InletOneName, out PipeNode? inletOne)
                || !nodeContainer.TryGetNode(mixer.InletTwoName, out PipeNode? inletTwo)
                || !nodeContainer.TryGetNode(mixer.OutletName, out PipeNode? outlet))
                return;

            var outputStartingPressure = outlet.Air.Pressure;

            if (outputStartingPressure >= mixer.TargetPressure)
                return; // Target reached, no need to mix.

            var generalTransfer = (mixer.TargetPressure - outputStartingPressure) * outlet.Air.Volume / Atmospherics.R;

            var transferMolesOne = inletOne.Air.Temperature > 0 ? mixer.InletOneConcentration * generalTransfer / inletOne.Air.Temperature : 0f;
            var transferMolesTwo = inletTwo.Air.Temperature > 0 ? mixer.InletTwoConcentration * generalTransfer / inletTwo.Air.Temperature : 0f;

            if (mixer.InletTwoConcentration <= 0f)
            {
                if (inletOne.Air.Temperature <= 0f)
                    return;

                transferMolesOne = MathF.Min(transferMolesOne, inletOne.Air.TotalMoles);
                transferMolesTwo = 0f;
            }

            else if (mixer.InletOneConcentration <= 0)
            {
                if (inletTwo.Air.Temperature <= 0f)
                    return;

                transferMolesOne = 0f;
                transferMolesTwo = MathF.Min(transferMolesTwo, inletTwo.Air.TotalMoles);
            }
            else
            {
                if (inletOne.Air.Temperature <= 0f || inletTwo.Air.Temperature <= 0f)
                    return;

                if (transferMolesOne <= 0 || transferMolesTwo <= 0)
                    return;

                if (inletOne.Air.TotalMoles < transferMolesOne || inletTwo.Air.TotalMoles < transferMolesTwo)
                {
                    var ratio = MathF.Min(inletOne.Air.TotalMoles / transferMolesOne, inletTwo.Air.TotalMoles / transferMolesTwo);
                    transferMolesOne *= ratio;
                    transferMolesTwo *= ratio;
                }
            }

            // Actually transfer the gas now.

            if (transferMolesOne > 0f)
            {
                var removed = inletOne.Air.Remove(transferMolesOne);
                outlet.AssumeAir(removed);
            }

            if (transferMolesTwo > 0f)
            {
                var removed = inletTwo.Air.Remove(transferMolesTwo);
                outlet.AssumeAir(removed);
            }
        }
    }
}