basic-computer-games/84_Super_Star_Trek/csharp/Space/Course.cs

using System;
using System.Collections.Generic;

namespace SuperStarTrek.Space;

// Implements the course calculations from the original code:
//     530 FORI=1TO9:C(I,1)=0:C(I,2)=0:NEXTI
//     540 C(3,1)=-1:C(2,1)=-1:C(4,1)=-1:C(4,2)=-1:C(5,2)=-1:C(6,2)=-1
//     600 C(1,2)=1:C(2,2)=1:C(6,1)=1:C(7,1)=1:C(8,1)=1:C(8,2)=1:C(9,2)=1
//
//     3110 X1=C(C1,1)+(C(C1+1,1)-C(C1,1))*(C1-INT(C1))
//     3140 X2=C(C1,2)+(C(C1+1,2)-C(C1,2))*(C1-INT(C1))
internal class Course
{
    private static readonly (int DeltaX, int DeltaY)[] cardinals = new[]
    {
        (0, 1),
        (-1, 1),
        (-1, 0),
        (-1, -1),
        (0, -1),
        (1, -1),
        (1, 0),
        (1, 1),
        (0, 1)
    };

    internal Course(float direction)
    {
        if (direction < 1 || direction > 9)
        {
            throw new ArgumentOutOfRangeException(
                nameof(direction),
                direction,
                "Must be between 1 and 9, inclusive.");
        }

        var cardinalDirection = (int)(direction - 1) % 8;
        var fractionalDirection = direction - (int)direction;

        var baseCardinal = cardinals[cardinalDirection];
        var nextCardinal = cardinals[cardinalDirection + 1];

        DeltaX = baseCardinal.DeltaX + (nextCardinal.DeltaX - baseCardinal.DeltaX) * fractionalDirection;
        DeltaY = baseCardinal.DeltaY + (nextCardinal.DeltaY - baseCardinal.DeltaY) * fractionalDirection;
    }

    internal float DeltaX { get; }

    internal float DeltaY { get; }

    internal IEnumerable<Coordinates> GetSectorsFrom(Coordinates start)
    {
        (float x, float y) = start;

        while(true)
        {
            x += DeltaX;
            y += DeltaY;

            if (!Coordinates.TryCreate(x, y, out var coordinates))
            {
                yield break;
            }

            yield return coordinates;
        }
    }

    internal (bool, Coordinates, Coordinates) GetDestination(Coordinates quadrant, Coordinates sector, int distance)
    {
        var (xComplete, quadrantX, sectorX) = GetNewCoordinate(quadrant.X, sector.X, DeltaX * distance);
        var (yComplete, quadrantY, sectorY) = GetNewCoordinate(quadrant.Y, sector.Y, DeltaY * distance);

        return (xComplete && yComplete, new Coordinates(quadrantX, quadrantY), new Coordinates(sectorX, sectorY));
    }

    private static (bool, int, int) GetNewCoordinate(int quadrant, int sector, float sectorsTravelled)
    {
        var galacticCoordinate = quadrant * 8 + sector + sectorsTravelled;
        var newQuadrant = (int)(galacticCoordinate / 8);
        var newSector = (int)(galacticCoordinate - newQuadrant * 8);

        if (newSector < 0)
        {
            newQuadrant -= 1;
            newSector += 8;
        }

        return newQuadrant switch
        {
            < 0 => (false, 0, 0),
            > 7 => (false, 7, 7),
            _ => (true, newQuadrant, newSector)
        };
    }
}