using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;

namespace Chiller
{
    public class ModuleChiller : PartModule
    {
        /// <summary>
        /// Maximum electric power this Chiller unit can draw, in KSP Electric Charge per second. Since this mod assumes 1 EC = 1 kW.s, the value indicated here can be considered to be in kilowatts.
        /// </summary>
        [KSPField(isPersistant = false, guiActive = false)]
        public float MaxPower = 10;

        /// <summary>
        /// Coefficient Of Performance (heat removed from the chilled part, divided by the electric power consumed)
        /// Note that the electric power also ends up heating the radiator panel (in addition to the heat taken from the cooled part)
        /// </summary>
        [KSPField(isPersistant = false, guiActive = false)]
        public float COP = 4;

        /// <summary>
        /// Target temperature for the part on which the Chiller is attached, in Kelvins. If the temperature of that part is above the set-point, the Chiller turns on to cool it.
        /// </summary>
        [KSPField(isPersistant=true, guiActive=true, guiName="Set-point (K)")]
        [UI_FloatRange(minValue = 10, maxValue = 400)]
        public float SetPoint = 100;

        [KSPField(isPersistant = false, guiActive = false)]
        public float SetPointThreshold = 5;

        [KSPField(isPersistant = false, guiActive = true)]
        public string Status = "Offline";

        [KSPField(isPersistant = false, guiActive = true, guiName="Heat transfer")]
        public string HeatTransferStatus = "Offline";

        [KSPField(isPersistant = false, guiActive = true, guiName = "Temperature")]
        public string CurrentTemperature = "";

        [KSPField(isPersistant = false, guiActive = true, guiName = "Electric consumption")]
        public string ElectricStatus = "";

        private bool WasCooling = false;
        private float CurrentHeatTransfer = 0;

        public void FixedUpdate()
        {
            var cooledPart = part.parent;
            bool isActive = part.FindModuleImplementing<ModuleActiveRadiator>().IsCooling;

            Status = "Stand-by";
            CurrentTemperature = cooledPart.temperature.ToString("0.00") + " K";
            ElectricStatus = "";
            bool cooling = false;

            float energyToTransfer = 0;

            if (isActive)
            {
                if (cooledPart.temperature > SetPoint + (WasCooling ? 0 : SetPointThreshold))
                {
                    float maxRadiatorTemperature = (float)part.maxTemp * (float)part.radiatorHeadroom;
                    if ((float)part.temperature >= maxRadiatorTemperature - (WasCooling ? 0 : SetPointThreshold))
                    {
                        Status = "Radiator too hot";
                    }
                    else
                    {
                        float neededCoolingEnergy = ((float)cooledPart.temperature - SetPoint) * (float)cooledPart.thermalMass / TimeWarp.fixedDeltaTime;
                        float availableHeatEnergy = (maxRadiatorTemperature - (float)part.temperature) * (float)part.thermalMass * (COP / (COP + 1)) / TimeWarp.fixedDeltaTime;
                        energyToTransfer = Mathf.Min(neededCoolingEnergy, availableHeatEnergy, MaxPower * COP);
                    }
                }
            }
            else
            {
                Status = "Off";
            }

            if (energyToTransfer > CurrentHeatTransfer)
            {
                // slow transfer startup, to simulate progressive refrigerant compression as the pump is started
                float c = 1.0f / (1.0f + TimeWarp.fixedDeltaTime);
                CurrentHeatTransfer = CurrentHeatTransfer * c + energyToTransfer * (1.0f - c);
            }
            else
            {
                // immediate reactivity when slowing down to avoid overshooting
                CurrentHeatTransfer = energyToTransfer;
            }

            if(energyToTransfer > 0)
            {
                float requiredElectricCharge = CurrentHeatTransfer * TimeWarp.fixedDeltaTime / COP;
                var electricCharge = vessel.GetActiveResources().SingleOrDefault(r => r.info.name == "ElectricCharge");
                float totalAvailableElectricEnergy = electricCharge == null ? 0.0f : (float)electricCharge.amount;

                // we don't use electric charge at all if battery is low, to avoid disabling more critical systems, such as command modules etc.
                float electricChargeMargin = 10;
                float availableElectricEnergy;
                if (totalAvailableElectricEnergy > requiredElectricCharge + electricChargeMargin)
                {
                    availableElectricEnergy = part.RequestResource(electricCharge.info.id, Math.Min(requiredElectricCharge, totalAvailableElectricEnergy - electricChargeMargin));
                }
                else
                {
                    availableElectricEnergy = 0;
                }

                if (availableElectricEnergy < requiredElectricCharge * 0.9f)
                {
                    Status = "Not enough power";
                    CurrentHeatTransfer = availableElectricEnergy * COP;
                }
                else
                {
                    Status = "Cooling";
                }

                cooledPart.AddThermalFlux(-CurrentHeatTransfer * 2);
                part.AddThermalFlux(CurrentHeatTransfer * 2 * (COP + 1) / COP);

                ElectricStatus = availableElectricEnergy.ToString("0.00") + " kW";

                cooling = true;
            }

            HeatTransferStatus = CurrentHeatTransfer.ToString("0.00") + " kW (" + (CurrentHeatTransfer / (float)cooledPart.thermalMass).ToString("0.00") + " K/s)";

            WasCooling = cooling;
        }
    }
}