public void UnitIjkToDigit()
{
var zero = new CoordIjk();
var i = new CoordIjk(1, 0, 0);
var outOfRange = new CoordIjk(2, 0, 0);
var unNormalizedZero = new CoordIjk(2, 2, 2);
Assert.AreEqual(zero.ToDirection(), Direction.CENTER_DIGIT);
Assert.AreEqual(i.ToDirection(), Direction.I_AXES_DIGIT);
Assert.AreEqual(outOfRange.ToDirection(), Direction.INVALID_DIGIT);
Assert.AreEqual(unNormalizedZero.ToDirection(), Direction.CENTER_DIGIT);
}
/// <summary>
/// Produces an index for ijk+ coordinates anchored by an origin.
///
/// The coordinate space used by this function may have deleted
/// regions or warping due to pentagonal distortion.
///
/// Failure may occur if the coordinates are too far away from the origin
/// or if the index is on the other side of a pentagon.
/// </summary>
/// <param name="origin">An anchoring index for the ijk+ coordinate system.</param>
/// <param name="ijk">IJK+ Coordinates to find the index of</param>
/// <returns>0 on success, or another value on failure</returns>
/// <!--
/// localij.c
/// int localIjkToH3
/// -->
public static (int, H3Index) LocalIjkToH3(this CoordIjk ijk, H3Index origin)
{
int res = origin.Resolution;
int originBaseCell = origin.BaseCell;
bool originOnPent = originBaseCell.IsBaseCellPentagon();
// This logic is very similar to faceIjkToH3
// initialize the index
var outH3 = new H3Index(Constants.H3Index.H3_INIT);
outH3 = outH3.SetMode(H3Mode.Hexagon).SetResolution(res);
// check for res 0/base cell
if (res == 0)
{
if (ijk.I > 1 || ijk.J > 1 || ijk.K > 1)
{
return(1, outH3);
}
Direction dir = ijk.ToDirection();
int newBaseCell = originBaseCell.GetNeighbor(dir);
if (newBaseCell == Constants.BaseCells.InvalidBaseCell)
{
// Moving in an invalid direction off a pentagon.
return(1, new H3Index());
}
return(0, outH3.SetBaseCell(newBaseCell));
}
// we need to find the correct base cell offset (if any) for this H3 index;
// start with the passed in base cell and resolution res ijk coordinates
// in that base cell's coordinate system
var ijkCopy = new CoordIjk(ijk);
// build the H3Index from finest res up
// adjust r for the fact that the res 0 base cell offsets the indexing
// digits
for (int r = res - 1; r >= 0; r--)
{
var lastIJK = new CoordIjk(ijkCopy);
CoordIjk lastCenter;
if ((r + 1).IsResClassIii())
{
// rotate ccw
ijkCopy = ijkCopy.UpAp7();
lastCenter = new CoordIjk(ijkCopy);
lastCenter = lastCenter.DownAp7();
}
else
{
// rotate cw
ijkCopy = ijkCopy.UpAp7R();
lastCenter = new CoordIjk(ijkCopy);
lastCenter = lastCenter.DownAp7R();
}
var diff = (lastIJK - lastCenter).Normalized();
outH3 = outH3.SetIndexDigit(r + 1, (ulong)diff.ToDirection());
}
// ijkCopy should now hold the IJK of the base cell in the
// coordinate system of the current base cell
if (ijkCopy.I > 1 || ijkCopy.J > 1 || ijkCopy.K > 1)
{
// out of range input
return(2, new H3Index());
}
// lookup the correct base cell
var dir2 = ijkCopy.ToDirection();
int baseCell = originBaseCell.GetNeighbor(dir2);
// If baseCell is invalid, it must be because the origin base cell is a
// pentagon, and because pentagon base cells do not border each other,
// baseCell must not be a pentagon.
int indexOnPent =
baseCell == Constants.BaseCells.InvalidBaseCell
? 0
: baseCell.IsBaseCellPentagon()
? 1
: 0;
if (dir2 != Direction.CENTER_DIGIT)
{
// If the index is in a warped direction, we need to un-warp the base
// cell direction. There may be further need to rotate the index digits.
var pentagonRotations = 0;
if (originOnPent)
{
Direction originLeadingDigit = origin.LeadingNonZeroDigit;
pentagonRotations =
Constants.LocalIJ.PENTAGON_ROTATIONS_REVERSE[(int)originLeadingDigit, (int)dir2];
for (var i = 0; i < pentagonRotations; i++)
{
dir2 = dir2.Rotate60CounterClockwise();
}
// The pentagon rotations are being chosen so that dir is not the
// deleted direction. If it still happens, it means we're moving
// into a deleted subsequence, so there is no index here.
if (dir2 == Direction.K_AXES_DIGIT)
{
return(3, new H3Index());
}
baseCell = Constants.BaseCells.BaseCellNeighbors[originBaseCell, (int)dir2];
// indexOnPent does not need to be checked again since no pentagon
// base cells border each other.
if (baseCell == Constants.BaseCells.InvalidBaseCell)
{
throw new Exception("baseCell != INVALID_BASE_CELL");
}
if (baseCell.IsBaseCellPentagon())
{
throw new Exception("!_isBaseCellPentagon(baseCell)");
}
}
// Now we can determine the relation between the origin and target base
// cell.
int baseCellRotations =
Constants.BaseCells.BaseCellNeighbor60CounterClockwiseRotation[originBaseCell, (int)dir2];
if (baseCellRotations < 0)
{
throw new Exception("assert(baseCellRotations >= 0)");
}
// Adjust for pentagon warping within the base cell. The base cell
// should be in the right location, so now we need to rotate the index
// back. We might not need to check for errors since we would just be
// double mapping.
if (indexOnPent != 0)
{
var revDir = baseCell.GetBaseCellDirection(originBaseCell);
if (revDir == Direction.INVALID_DIGIT)
{
throw new Exception("assert(revDir != INVALID_DIGIT)");
}
// Adjust for the different coordinate space in the two base cells.
// This is done first because we need to do the pentagon rotations
// based on the leading digit in the pentagon's coordinate system.
for (var i = 0; i < baseCellRotations; i++)
{
outH3 = outH3.Rotate60CounterClockwise();
}
var indexLeadingDigit = outH3.LeadingNonZeroDigit;
pentagonRotations =
baseCell.IsBaseCellPolarPentagon()
? Constants.LocalIJ.PENTAGON_ROTATIONS_REVERSE_POLAR[(int)revDir, (int)indexLeadingDigit]
: Constants.LocalIJ.PENTAGON_ROTATIONS_REVERSE_NONPOLAR[(int)revDir, (int)indexLeadingDigit];
if (pentagonRotations < 0)
{
throw new Exception("pentagonRotations >= 0");
}
for (int i = 0; i < pentagonRotations; i++)
{
outH3 = outH3.RotatePent60CounterClockwise();
}
}
else
{
if (pentagonRotations < 0)
{
throw new Exception("pentagonRotations >= 0");
}
for (var i = 0; i < pentagonRotations; i++)
{
outH3 = outH3.Rotate60CounterClockwise();
}
// Adjust for the different coordinate space in the two base cells.
for (var i = 0; i < baseCellRotations; i++)
{
outH3 = outH3.Rotate60CounterClockwise();
}
}
}
else if (originOnPent && indexOnPent != 0)
{
var originLeadingDigit = (int)origin.LeadingNonZeroDigit;
var indexLeadingDigit = (int)outH3.LeadingNonZeroDigit;
int withinPentagonRotations =
Constants.LocalIJ.PENTAGON_ROTATIONS_REVERSE[originLeadingDigit, indexLeadingDigit];
if (withinPentagonRotations < 0)
{
throw new Exception("withinPentagonRotations >= 0");
}
for (var i = 0; i < withinPentagonRotations; i++)
{
outH3 = outH3.Rotate60CounterClockwise();
}
}
if (indexOnPent == 0)
{
return(0, outH3.SetBaseCell(baseCell));
}
// TODO: There are cases in h3ToLocalIjk which are failed but not
// accounted for here - instead just fail if the recovered index is
// invalid.
return(outH3.LeadingNonZeroDigit == Direction.K_AXES_DIGIT
? (4, new H3Index())
: (0, outH3.SetBaseCell(baseCell)));
}