public static FerryMovementInstruction ParseInputLine(string inputLine)
{
var match = Regex.Match(inputLine, @"^(E|N|W|S|L|R|F)(\d+)$");
if (!match.Success)
{
throw new Exception($"Unrecognized input line pattern: {inputLine}");
}
var rawDirection = match.Groups[1].Value;
var ferryMovementDirection = FerryMovementDirection.East;
if ("E".Equals(rawDirection))
{
ferryMovementDirection = FerryMovementDirection.East;
}
else if ("N".Equals(rawDirection))
{
ferryMovementDirection = FerryMovementDirection.North;
}
else if ("W".Equals(rawDirection))
{
ferryMovementDirection = FerryMovementDirection.West;
}
else if ("S".Equals(rawDirection))
{
ferryMovementDirection = FerryMovementDirection.South;
}
else if ("L".Equals(rawDirection))
{
ferryMovementDirection = FerryMovementDirection.Left;
}
else if ("R".Equals(rawDirection))
{
ferryMovementDirection = FerryMovementDirection.Right;
}
else if ("F".Equals(rawDirection))
{
ferryMovementDirection = FerryMovementDirection.Forward;
}
else
{
throw new Exception($"Unrecognized raw direction: {rawDirection}");
}
var value = int.Parse(match.Groups[2].Value);
var result = new FerryMovementInstruction(ferryMovementDirection, value);
return(result);
}
public static FerryState ApplyFerryMovementInstruction(
FerryState currentState,
FerryMovementInstruction ferryMovementInstruction)
{
var nextPosition = currentState.Position;
var nextHeading = currentState.Heading;
if (FerryMovementDirection.East.Equals(ferryMovementInstruction.MovementDirection))
{
nextPosition = nextPosition.MoveRight(ferryMovementInstruction.Value);
}
else if (FerryMovementDirection.North.Equals(ferryMovementInstruction.MovementDirection))
{
nextPosition = nextPosition.MoveUp(ferryMovementInstruction.Value);
}
else if (FerryMovementDirection.West.Equals(ferryMovementInstruction.MovementDirection))
{
nextPosition = nextPosition.MoveLeft(ferryMovementInstruction.Value);
}
else if (FerryMovementDirection.South.Equals(ferryMovementInstruction.MovementDirection))
{
nextPosition = nextPosition.MoveDown(ferryMovementInstruction.Value);
}
else if (FerryMovementDirection.Left.Equals(ferryMovementInstruction.MovementDirection))
{
var direction = GetMovementDirectionFromHeading(nextHeading);
var nextDirection = MovementDirectionHelper.Rotate(direction, ferryMovementInstruction.Value, true);
nextHeading = GetHeadingFromMovementDirection(nextDirection);
}
else if (FerryMovementDirection.Right.Equals(ferryMovementInstruction.MovementDirection))
{
var direction = GetMovementDirectionFromHeading(nextHeading);
var nextDirection = MovementDirectionHelper.Rotate(direction, ferryMovementInstruction.Value, false);
nextHeading = GetHeadingFromMovementDirection(nextDirection);
}
else if (FerryMovementDirection.Forward.Equals(ferryMovementInstruction.MovementDirection))
{
var direction = GetMovementDirectionFromHeading(nextHeading);
nextPosition = nextPosition.Move(direction, ferryMovementInstruction.Value);
}
else
{
throw new Exception($"Unknown direction: {ferryMovementInstruction.MovementDirection}");
}
var nextState = new FerryState(nextPosition, nextHeading);
return(nextState);
}
public static FerryState ApplyFerryMovementInstructionWithWaypoint(
FerryState currentState,
FerryMovementInstruction ferryMovementInstruction)
{
var nextPosition = currentState.Position;
var nextWaypointPosition = currentState.WaypointPosition;
if (FerryMovementDirection.East.Equals(ferryMovementInstruction.MovementDirection))
{
nextWaypointPosition = nextWaypointPosition.MoveRight(ferryMovementInstruction.Value);
}
else if (FerryMovementDirection.North.Equals(ferryMovementInstruction.MovementDirection))
{
nextWaypointPosition = nextWaypointPosition.MoveUp(ferryMovementInstruction.Value);
}
else if (FerryMovementDirection.West.Equals(ferryMovementInstruction.MovementDirection))
{
nextWaypointPosition = nextWaypointPosition.MoveLeft(ferryMovementInstruction.Value);
}
else if (FerryMovementDirection.South.Equals(ferryMovementInstruction.MovementDirection))
{
nextWaypointPosition = nextWaypointPosition.MoveDown(ferryMovementInstruction.Value);
}
else if (FerryMovementDirection.Left.Equals(ferryMovementInstruction.MovementDirection))
{
// https://stackoverflow.com/questions/786472/rotate-a-point-by-another-point-in-2d
// If you rotate point (px, py) around point (ox, oy) by angle theta you'll get:
// p'x = cos(theta) * (px-ox) - sin(theta) * (py-oy) + ox
// p'y = sin(theta) * (px-ox) + cos(theta) * (py-oy) + oy
var oX = nextPosition.X;
var oY = nextPosition.Y;
var pX = nextWaypointPosition.X;
var pY = nextWaypointPosition.Y;
var dX = pX - oX;
var dY = pY - oY;
var theta = (Math.PI / 180) * ferryMovementInstruction.Value;
var sinTheta = Math.Sin(theta);
var cosTheta = Math.Cos(theta);
var newPX = (int)Math.Round((dX * cosTheta) - (dY * sinTheta) + oX);
var newPY = (int)Math.Round((dX * sinTheta) + (dY * cosTheta) + oY);
nextWaypointPosition = new GridPoint(newPX, newPY);
}
else if (FerryMovementDirection.Right.Equals(ferryMovementInstruction.MovementDirection))
{
var oX = nextPosition.X;
var oY = nextPosition.Y;
var pX = nextWaypointPosition.X;
var pY = nextWaypointPosition.Y;
var dX = pX - oX;
var dY = pY - oY;
var theta = (Math.PI / 180) * (360 - ferryMovementInstruction.Value);
var sinTheta = Math.Sin(theta);
var cosTheta = Math.Cos(theta);
var newPX = (int)Math.Round((dX * cosTheta) - (dY * sinTheta) + oX);
var newPY = (int)Math.Round((dX * sinTheta) + (dY * cosTheta) + oY);
nextWaypointPosition = new GridPoint(newPX, newPY);
}
else if (FerryMovementDirection.Forward.Equals(ferryMovementInstruction.MovementDirection))
{
var dXSlope = nextWaypointPosition.X - nextPosition.X;
var dYSlope = nextWaypointPosition.Y - nextPosition.Y;
var dX = dXSlope * ferryMovementInstruction.Value;
var dY = dYSlope * ferryMovementInstruction.Value;
nextPosition = new GridPoint(nextPosition.X + dX, nextPosition.Y + dY);
nextWaypointPosition = new GridPoint(nextPosition.X + dXSlope, nextPosition.Y + dYSlope);
}
else
{
throw new Exception($"Unknown direction: {ferryMovementInstruction.MovementDirection}");
}
var nextState = new FerryState(nextPosition, nextWaypointPosition);
return(nextState);
}
