/// <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>
/// <param name="out_h3">The index will be placed here on success</param>
/// <returns>0 on success, or another value on failure</returns>
/// <!-- Based off 3.2.0 -->
internal static int localIjkToH3(H3Index origin, CoordIJK ijk, ref H3Index out_h3)
{
int res = H3Index.H3_GET_RESOLUTION(origin);
int originBaseCell = H3Index.H3_GET_BASE_CELL(origin);
int originOnPent = BaseCells._isBaseCellPentagon(originBaseCell)
? 1
: 0;
// This logic is very similar to faceIjkToH3
// initialize the index
out_h3 = H3Index.H3_INIT;
H3Index.H3_SET_MODE(ref out_h3, Constants.H3_HEXAGON_MODE);
H3Index.H3_SET_RESOLUTION(ref out_h3, res);
Direction dir;
// check for res 0/base cell
if (res == 0)
{
if (ijk.i > 1 || ijk.j > 1 || ijk.k > 1)
{
// out of range input
return(1);
}
dir = CoordIJK._unitIjkToDigit(ref ijk);
int newBaseCell = BaseCells._getBaseCellNeighbor(originBaseCell, dir);
if (newBaseCell == BaseCells.INVALID_BASE_CELL)
{
// Moving in an invalid direction off a pentagon.
return(1);
}
H3Index.H3_SET_BASE_CELL(ref out_h3, newBaseCell);
return(0);
}
// 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
CoordIJK ijkCopy = new CoordIJK(ijk.i, ijk.j, ijk.k);
// 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--)
{
CoordIJK lastIJK = ijkCopy;
CoordIJK lastCenter;
if (H3Index.isResClassIII(r + 1))
{
// rotate ccw
CoordIJK._upAp7(ref ijkCopy);
lastCenter = ijkCopy;
CoordIJK._downAp7(ref lastCenter);
}
else
{
// rotate cw
CoordIJK._upAp7r(ref ijkCopy);
lastCenter = ijkCopy;
CoordIJK._downAp7r(ref lastCenter);
}
CoordIJK diff = new CoordIJK();
CoordIJK._ijkSub(ref lastIJK, ref lastCenter, ref diff);
CoordIJK._ijkNormalize(ref diff);
H3Index.H3_SET_INDEX_DIGIT(ref out_h3, r + 1, (ulong)CoordIJK._unitIjkToDigit(ref diff));
}
// 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);
}
// lookup the correct base cell
dir = CoordIJK._unitIjkToDigit(ref ijkCopy);
int baseCell = BaseCells._getBaseCellNeighbor(originBaseCell, dir);
// 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 == BaseCells.INVALID_BASE_CELL
? 0
: BaseCells._isBaseCellPentagon(baseCell)
? 1
: 0);
if (dir != (int)Direction.CENTER_DIGIT)
{
// If the index is in a warped direction, we need to unwarp the base
// cell direction. There may be further need to rotate the index digits.
int pentagonRotations = 0;
if (originOnPent != 0)
{
Direction originLeadingDigit = H3Index._h3LeadingNonZeroDigit(origin);
pentagonRotations =
PENTAGON_ROTATIONS_REVERSE[(int)originLeadingDigit, (int)dir];
for (int i = 0; i < pentagonRotations; i++)
{
dir = CoordIJK._rotate60ccw(dir);
}
// 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 (dir == Direction.K_AXES_DIGIT)
{
return(3);
}
baseCell = BaseCells._getBaseCellNeighbor(originBaseCell, dir);
// indexOnPent does not need to be checked again since no pentagon
// base cells border each other.
if (baseCell == BaseCells.INVALID_BASE_CELL)
{
throw new Exception("assert(baseCell != BaseCells.INVALID_BASE_CELL);");
}
if (BaseCells._isBaseCellPolarPentagon(baseCell))
{
throw new Exception("assert(!BaseCells._isBaseCellPentagon(baseCell));");
}
}
// Now we can determine the relation between the origin and target base
// cell.
int baseCellRotations =
BaseCells.baseCellNeighbor60CCWRots[originBaseCell, (int)dir];
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)
{
Direction revDir =
BaseCells._getBaseCellDirection(baseCell, originBaseCell);
if (revDir == Direction.INVALID_DIGIT)
{
throw new Exception("assert(revDir != Direction.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 (int i = 0; i < baseCellRotations; i++)
{
out_h3 = H3Index._h3Rotate60ccw(ref out_h3);
}
Direction indexLeadingDigit = H3Index._h3LeadingNonZeroDigit(out_h3);
if (BaseCells._isBaseCellPolarPentagon(baseCell))
{
pentagonRotations =
PENTAGON_ROTATIONS_REVERSE_POLAR[(int)revDir, (int)indexLeadingDigit];
}
else
{
pentagonRotations =
PENTAGON_ROTATIONS_REVERSE_NONPOLAR[(int)revDir, (int)indexLeadingDigit];
}
if (pentagonRotations < 0)
{
throw new Exception("assert(pentagonRotations >= 0);");
}
for (int i = 0; i < pentagonRotations; i++)
{
out_h3 = H3Index._h3RotatePent60ccw(ref out_h3);
}
}
else
{
if (pentagonRotations < 0)
{
throw new Exception("assert(pentagonRotations >= 0);");
}
for (int i = 0; i < pentagonRotations; i++)
{
out_h3 = H3Index._h3Rotate60ccw(ref out_h3);
}
// Adjust for the different coordinate space in the two base cells.
for (int i = 0; i < baseCellRotations; i++)
{
out_h3 = H3Index._h3Rotate60ccw(ref out_h3);
}
}
}
else if (originOnPent != 0 && indexOnPent != 0)
{
int originLeadingDigit = (int)H3Index._h3LeadingNonZeroDigit(origin);
int indexLeadingDigit = (int)H3Index._h3LeadingNonZeroDigit(out_h3);
int withinPentagonRotations =
PENTAGON_ROTATIONS_REVERSE[originLeadingDigit, indexLeadingDigit];
if (withinPentagonRotations < 0)
{
throw new Exception("assert(withinPentagonRotations >= 0);");
}
for (int i = 0; i < withinPentagonRotations; i++)
{
out_h3 = H3Index._h3Rotate60ccw(ref out_h3);
}
}
if (indexOnPent != 0)
{
// TODO: There are cases in h3ToLocalIjk which are failed but not
// accounted for here - instead just fail if the recovered index is
// invalid.
if (H3Index._h3LeadingNonZeroDigit(out_h3) == Direction.K_AXES_DIGIT)
{
return(4);
}
}
H3Index.H3_SET_BASE_CELL(ref out_h3, baseCell);
return(0);
}
/// <summary>
/// Returns the hexagon index neighboring the origin, in the direction dir.
///
/// Implementation note: The only reachable case where this returns 0 is if the
/// origin is a pentagon and the translation is in the k direction. Thus,
/// 0 can only be returned if origin is a pentagon.
/// </summary>
/// <param name="origin">Origin index</param>
/// <param name="dir">Direction to move in</param>
/// <param name="rotations">
/// Number of ccw rotations to perform to reorient the translation vector.
/// Will be modified to the new number of rotations to perform (such as
/// when crossing a face edge.)
/// </param>
/// <returns>H3Index of the specified neighbor or 0 if deleted k-subsequence distortion is encountered.</returns>
/// <!-- Based off 3.2.0 -->
internal static ulong h3NeighborRotations(H3Index origin, Direction dir, ref int rotations)
{
H3Index out_hex = origin;
for (int i = 0; i < rotations; i++)
{
dir = CoordIJK._rotate60ccw(dir);
}
int newRotations = 0;
int oldBaseCell = H3Index.H3_GET_BASE_CELL(out_hex);
Direction oldLeadingDigit = H3Index._h3LeadingNonZeroDigit(out_hex);
// Adjust the indexing digits and, if needed, the base cell.
int r = H3Index.H3_GET_RESOLUTION(out_hex) - 1;
while (true)
{
if (r == -1)
{
H3Index.H3_SET_BASE_CELL(ref out_hex, BaseCells.baseCellNeighbors[oldBaseCell, (int)dir]);
newRotations = BaseCells.baseCellNeighbor60CCWRots[oldBaseCell, (int)dir];
if (H3Index.H3_GET_BASE_CELL(out_hex) == BaseCells.INVALID_BASE_CELL)
{
// Adjust for the deleted k vertex at the base cell level.
// This edge actually borders a different neighbor.
H3Index.H3_SET_BASE_CELL(ref out_hex,
BaseCells.baseCellNeighbors[oldBaseCell, (int)Direction.IK_AXES_DIGIT]);
newRotations =
BaseCells.baseCellNeighbor60CCWRots[oldBaseCell, (int)Direction.IK_AXES_DIGIT];
// perform the adjustment for the k-subsequence we're skipping
// over.
out_hex = H3Index._h3Rotate60ccw(ref out_hex);
rotations++;
}
break;
}
Direction oldDigit = H3Index.H3_GET_INDEX_DIGIT(out_hex, r + 1);
Direction nextDir;
if (H3Index.isResClassIII(r + 1))
{
H3Index.H3_SET_INDEX_DIGIT(ref out_hex, r + 1, (ulong)NEW_DIGIT_II[(int)oldDigit, (int)dir]);
nextDir = NEW_ADJUSTMENT_II[(int)oldDigit, (int)dir];
}
else
{
H3Index.H3_SET_INDEX_DIGIT(ref out_hex, r + 1,
(ulong)NEW_DIGIT_III[(int)oldDigit, (int)dir]);
nextDir = NEW_ADJUSTMENT_III[(int)oldDigit, (int)dir];
}
if (nextDir != Direction.CENTER_DIGIT)
{
dir = nextDir;
r--;
}
else
{
// No more adjustment to perform
break;
}
}
int newBaseCell = H3Index.H3_GET_BASE_CELL(out_hex);
if (BaseCells._isBaseCellPentagon(newBaseCell))
{
int alreadyAdjustedKSubsequence = 0;
// force rotation out of missing k-axes sub-sequence
if (H3Index._h3LeadingNonZeroDigit(out_hex) == Direction.K_AXES_DIGIT)
{
if (oldBaseCell != newBaseCell)
{
// in this case, we traversed into the deleted
// k subsequence of a pentagon base cell.
// We need to rotate out of that case depending
// on how we got here.
// check for a cw/ccw offset face; default is ccw
if (BaseCells._baseCellIsCwOffset(
newBaseCell, BaseCells.baseCellData[oldBaseCell].homeFijk.face))
{
out_hex = H3Index._h3Rotate60cw(ref out_hex);
}
else
{
out_hex = H3Index._h3Rotate60ccw(ref out_hex); // LCOV_EXCL_LINE
}
// See cwOffsetPent in testKRing.c for why this is
// unreachable.
alreadyAdjustedKSubsequence = 1;
}
else
{
// In this case, we traversed into the deleted
// k subsequence from within the same pentagon
// base cell.
if (oldLeadingDigit == Direction.CENTER_DIGIT)
{
// Undefined: the k direction is deleted from here
return(H3Index.H3_INVALID_INDEX);
}
switch (oldLeadingDigit)
{
case Direction.JK_AXES_DIGIT:
// Rotate out of the deleted k subsequence
// We also need an additional change to the direction we're
// moving in
out_hex = H3Index._h3Rotate60ccw(ref out_hex);
rotations++;
break;
case Direction.IK_AXES_DIGIT:
// Rotate out of the deleted k subsequence
// We also need an additional change to the direction we're
// moving in
out_hex = H3Index._h3Rotate60cw(ref out_hex);
rotations += 5;
break;
default:
// Should never occur
return(H3Index.H3_INVALID_INDEX); // LCOV_EXCL_LINE
}
}
}
for (int i = 0; i < newRotations; i++)
{
out_hex = H3Index._h3RotatePent60ccw(ref out_hex);
}
// Account for differing orientation of the base cells (this edge
// might not follow properties of some other edges.)
if (oldBaseCell != newBaseCell)
{
if (BaseCells._isBaseCellPolarPentagon(newBaseCell))
{
// 'polar' base cells behave differently because they have all
// i neighbors.
if (oldBaseCell != 118 && oldBaseCell != 8 &&
H3Index._h3LeadingNonZeroDigit(out_hex) != Direction.JK_AXES_DIGIT)
{
rotations++;
}
}
else if (H3Index._h3LeadingNonZeroDigit(out_hex) == Direction.IK_AXES_DIGIT &&
alreadyAdjustedKSubsequence == 0)
{
// account for distortion introduced to the 5 neighbor by the
// deleted k subsequence.
rotations++;
}
}
}
else
{
for (int i = 0; i < newRotations; i++)
{
out_hex = H3Index._h3Rotate60ccw(ref out_hex);
}
}
rotations = (rotations + newRotations) % 6;
return(out_hex);
}