Thruster_Safety.txt

//Configuration
//--------------------
const string
    nameController = "Remote Control";

const double
    //angle between gravity and thrust direction that causes it to disable
    angleSafetyCutoff = 120.0 * (Math.PI / 180.0);


//Definitions
//--------------------

//Opcodes for use as arguments
//-commands may be issued directly
const string
    command_Initialise = "Init";   //args: <none>

//Utility definitions
static Vector3D GridToWorld(Vector3I gridVector, IMyCubeGrid grid){
    //convert a grid vector for the specified grid into a world direction vector
    return Vector3D.Subtract (
        grid.GridIntegerToWorld (gridVector),
        grid.GridIntegerToWorld (Vector3I.Zero) );
}

static readonly double
    safetyCutoff = Math.Cos(angleSafetyCutoff);


//Internal Types
//--------------------
public struct Status
{
    //program data not persistent across restarts
    public bool
        initialised;

    //configuration constants
    private const char
        delimiter = ';';

    //Operations

    public void Initialise(){   //data setup
        //no data persistent across restarts
    }

    public string Store()
    {
        return "";
    }

    public bool TryRestore(string storage)
    {
        string[] elements = storage.Split(delimiter);
        return
            (elements.Length == 1)
            && elements[0] == "";
    }
}


//Global variables
//--------------------
bool restarted = true;
Status status;

IMyShipController controller;

List<IMyTerminalBlock> temp = new List<IMyTerminalBlock>();


//Program
//--------------------
public void Main(string argument)
{
    //First ensure the system is able to process commands
    //-if necessary, perform first time setup
    //-if necessary or requested, initialise the system
    //  >otherwise, check that the setup is still valid
    if (restarted) {
        //script has been reloaded
        //-may be first time running
        //-world may have been reloaded (or script recompiled)
        if (Storage == null) {
            //use default values
            status.Initialise();
        } else {
            //attempt to restore saved values
            //  -otherwise use defaults
            Echo ("restoring saved state...");
            if ( !status.TryRestore(Storage) ){
                Echo ("restoration failed.");
                status.Initialise();
            }
        }
        status.initialised = false; //we are not initialised after restart
        Storage = null; //will be resaved iff initialisation is successful
        restarted = false;
    }
    if ( !status.initialised || argument == command_Initialise) {
        //if we cannot initialise, end here
        if ( !Initialise() )
            return;
    }
    else if ( !Validate() ) {
        //if saved state is not valid, try re-initialising
        //if we cannot initialise, end here
        if ( !Initialise() )
            return;
    }

    //Perform main processing
    Update ();


    //Save current status
    Storage = status.Store();
    Echo (Storage);
}


private void Update(){
    //-Prepare data
    //  >get local gravity vector
    //  >normalise vector to simplify angle calculation
    Vector3D
        worldGravity = controller.GetNaturalGravity ();
    worldGravity.Normalize();

    //Check each thruster to see if it is safe to enable
    //-only check thrusters on our grid
    //-check that we have access to the thruster
    //-disable any that are pointing down
    //  >(with safetyCutoff tolerance)
    //  >enable any others
    GridTerminalSystem.GetBlocksOfType<IMyThrust>(temp);
    int count = 0;
    for (int i=0; i<temp.Count; i++) {
        IMyThrust thruster = (IMyThrust)temp[i];

        if (thruster.CubeGrid != controller.CubeGrid)
            continue;

        count++;
        //Check if we can actually use the thruster
        if ( ValidateBlock (thruster, callbackRequired: false) ) {
            Vector3D
                worldThruster = GridToWorld (
                        Base6Directions.GetIntVector(thruster.Orientation.Forward),
                        thruster.CubeGrid);
            //Compare the dot product of gravity and thrust direction (normalised)
            // 1.0 => 0 degrees
            // 0.0 => 90 degrees
            //-1.0 => 180 degrees
            //safe iff angle <= safetyCutoffAngle
            //=> safe iff dot product >= cos(safetyCutoffAngle)
            bool
                safe = Vector3D.Dot(worldGravity, worldThruster) >= safetyCutoff * worldThruster.Length();
            if (thruster.Enabled != safe)
                thruster.RequestEnable (safe);
        }
    } //end for

    Echo(temp.Count.ToString() +" thrusters found.");
    Echo(count.ToString() +" processed.");
}


private bool Initialise()
{
    status.initialised = false;
    Echo ("initialising...");

    //Find Controller
    controller = null;
    GridTerminalSystem.GetBlocksOfType<IMyShipController> (temp);
    for (int i=0; i < temp.Count; i++){
        if (temp[i].CustomName == nameController) {
            if (controller == null) {
                controller = (IMyShipController)temp[i];
            } else {
                Echo ("ERROR: duplicate name \"" +nameController +"\"");
                return false;
            }
        }
    }
    //verify that the Controller was found
    if (controller == null) {
        Echo ("ERROR: block not found \"" +nameController +"\"");
        return false;
    }
    //validate that the Controller is operable
    if ( ! ValidateBlock (controller, callbackRequired:false) ) return false;


    status.initialised = true;
    Echo ("Initialisation completed with no errors.");
    return true;
}


private bool ValidateBlock(IMyTerminalBlock block, bool callbackRequired=true)
{
    //check for block deletion?

    //check that we have required permissions to control the block
    if ( ! Me.HasPlayerAccess(block.OwnerId) ) {
        Echo ("ERROR: no permissions for \"" +block.CustomName +"\"");
        return false;
    }

    //check that the block has required permissions to make callbacks
    if ( callbackRequired && !block.HasPlayerAccess(Me.OwnerId) ) {
        Echo ("ERROR: no permissions on \"" +block.CustomName +"\"");
        return false;
    }

    //check that block is functional
    if (!block.IsFunctional) {
        Echo ("ERROR: non-functional block \"" +block.CustomName +"\"");
        return false;
    }

    return true;
}


private bool Validate(){
    bool valid =
        ValidateBlock (controller, callbackRequired: false);

    if ( !valid ) {
        Echo ("Validation of saved blocks failed.");
    }
    return valid;
}