using Sandbox.ModAPI.Ingame;
using SpaceEngineers.Game.ModAPI.Ingame;
using System.Collections.Generic;
using VRageMath;

namespace IngameScript
{
    public class Airlock
    {
        enum AirlockLightState
        {
            Off,
            Cycling,
            Cooldown,
            Error,
        }

        public bool DoorsClosed
        {
            get
            {
                return innerDoor.Status == DoorStatus.Closed && outerDoor.Status == DoorStatus.Closed;
            }
        }

        // TODO: this should check for depressurizing to the *reference* amount
        public bool PressureStabilized
        {
            get
            {
                return ((airVent.Depressurize && airVent.GetOxygenLevel() <= targetOxygenLevel) ||
                        (!airVent.Depressurize && airVent.Status == VentStatus.Pressurized));
            }
        }

        public bool OxygenBalanced
        {
            get { return oxygenTank.FilledRatio > 0.25; }
        }

        public bool Functional { get; private set; } = true;

        public bool Cycling { get; private set; } = false;

        private bool DoorOpened
        {
            get
            {
                return innerDoor.Status == DoorStatus.Open || outerDoor.Status == DoorStatus.Open;
            }
        }

        // Returns false if we are in a state where we can't or don't need to balance
        private bool balanceOxygen()
        {
            if (innerDoor.Status == DoorStatus.Closed || outerDoor.Status == DoorStatus.Open || OxygenBalanced) { return false; }

            _p.Echo("DEBUG: Balancing Oxygen Tank");

            // Configure the vent to suck in Oxygen.
            airVent.Depressurize = true;
            airVent.Enabled = true;
            return true;
        }

        private string _name;
        private MyGridProgram _p;
        private float targetOxygenLevel = 0.0F;

        private IMyDoor innerDoor;
        private IMyDoor outerDoor;
        private List<IMyLightingBlock> lights;
        private IMyGasTank oxygenTank;
        private IMyAirVent airVent;
        private IMyAirVent airSensor;
        private const int CooldownTicks = 120;

        public Airlock(MyGridProgram p, string name)
        {
            _p = p;
            _name = name;

            // Find the appropriate blocks given the airlock name
            initDoors();
            initLights();
            initVents();
            initOxygen();
        }

        private void initDoors()
        {
            List<IMyDoor> onlyDoors = new List<IMyDoor>();
            _p.GridTerminalSystem.GetBlocksOfType(onlyDoors);
            foreach (IMyDoor door in onlyDoors)
            {
                if (!door.CustomName.StartsWith(_name)) continue;

                if (door.CustomName.Contains("Inner"))
                {
                    innerDoor = door;
                }
                else if (door.CustomName.Contains("Outer"))
                {
                    outerDoor = door;
                }

                if (innerDoor != null && outerDoor != null)
                {
                    return;
                }
            }

            Functional = false;
        }

        private void initVents()
        {
            List<IMyAirVent> onlyFans = new List<IMyAirVent>();
            _p.GridTerminalSystem.GetBlocksOfType(onlyFans);
            foreach (IMyAirVent vent in onlyFans)
            {
                if (!vent.CustomName.StartsWith(_name)) continue;

                if (vent.CustomName.StartsWith(_name))
                {
                    if (vent.CustomName.Contains("Main"))
                    {
                        airVent = vent;
                        continue;
                    }
                    else if (vent.CustomName.Contains("Reference"))
                    {
                        airSensor = vent;
                        continue;
                    }
                }

                // A global reference vent will be used if we don't have one specific to our airlock.
                //   A specific vent found later will overwrite this assignment.
                if (vent.CustomName.StartsWith("Airlock Reference") && airSensor == null)
                {
                    airSensor = vent;
                }
            }

            if (airVent == null) Functional = false;
        }

        private void initLights()
        {
            lights = new List<IMyLightingBlock>();
            List<IMyLightingBlock> allLights = new List<IMyLightingBlock>();
            _p.GridTerminalSystem.GetBlocksOfType(allLights);
            foreach (IMyLightingBlock light in allLights)
            {
                if (!light.CustomName.StartsWith(_name)) continue;
                lights.Add(light);
            }
        }

        private void initOxygen()
        {
            List<IMyGasTank> allTanks = new List<IMyGasTank>();
            _p.GridTerminalSystem.GetBlocksOfType(allTanks);
            foreach (IMyGasTank tank in allTanks)
            {
                if (!tank.CustomName.StartsWith(_name)) continue;
                oxygenTank = tank;
                return;
            }
            Functional = false;
        }

        public IEnumerator<bool> CycleAirlock()
        {
            Cycling = true;
            setLights(AirlockLightState.Cycling);

            closeDoors();
            while (!DoorsClosed) { yield return true; }
            lockDoors();

            if (!airVent.CanPressurize)
            {
                error("Airlock is not airtight.");
                yield return false;
            }

            pressurizeDepressurize();
            while (!PressureStabilized) { yield return true; }
            airVent.Enabled = false;

            openDoor();
            while (!DoorOpened) { yield return true; }
            lockDoors();

            // Balance oxygen storage
            setLights(AirlockLightState.Cooldown);
            if (balanceOxygen())
            {
                while (!OxygenBalanced) { yield return true; }
            }
            airVent.Enabled = false;

            // Cooldown period
            int cooldown = 0;
            while(cooldown < CooldownTicks) {
                cooldown++;
                yield return true;
            }

            setLights(AirlockLightState.Off);
        }

        private void closeDoors()
        {
            _p.Echo("DEBUG: Closing Doors");

            // close the doors
            innerDoor.Enabled = true;
            outerDoor.Enabled = true;
            innerDoor.CloseDoor();
            outerDoor.CloseDoor();
        }

        private void pressurizeDepressurize()
        {
            _p.Echo("DEBUG: Cycling");

            // toggle the current state
            airVent.Depressurize = !airVent.Depressurize;
            airVent.Enabled = true;

            // When depressurizing, check the external pressure and only depressurize to that value.
            // TODO: test this for floating point errors
            if (airVent.Depressurize && airSensor != null)
            {
                targetOxygenLevel = airSensor.GetOxygenLevel();
                _p.Echo($"Set depressurization target to {targetOxygenLevel}");
            }
        }

        // Open the appropriate door based on pressure state.
        private void openDoor()
        {
            _p.Echo("DEBUG: Opening Door");

            if (airVent.Status == VentStatus.Pressurized)
            {
                innerDoor.Enabled = true;
                innerDoor.OpenDoor();
            }
            else
            {
                outerDoor.Enabled = true;
                outerDoor.OpenDoor();
            }
        }

        // TODO: blinkenlights are unsatisfying right now...
        private void setLights(AirlockLightState lightState)
        {
            float blinkLength = 1.0F;
            float blinkInterval = 0.0F;
            Color color = Color.Red;

            switch (lightState)
            {
                case AirlockLightState.Off:
                    color = Color.Green;
                    break;
                case AirlockLightState.Cycling:
                    blinkInterval = 1.0F;
                    blinkLength = 0.75F;
                    break;
                case AirlockLightState.Cooldown:
                    color = Color.Yellow;
                    break;
                case AirlockLightState.Error:
                    // the defaults already set this correctly
                    break;
            }

            foreach (IMyLightingBlock light in lights)
            {
                light.Enabled = true;
                light.BlinkIntervalSeconds = blinkInterval;
                light.BlinkLength = blinkLength;
                light.Color = color;
            }
        }

        private void lockDoors()
        {
            innerDoor.Enabled = false;
            outerDoor.Enabled = false;
        }

        private void error(string error)
        {
            _p.Echo(error);
            setLights(AirlockLightState.Error);
        }
    }
}