// Encodes datum at the end of key, using direction `dir` for the encoding.
// It takes in an inclusive key and returns an inclusive key if
// isLastEndConstraint is not set, and an exclusive key otherwise (the idea is
// that, for inclusive constraints, the value for the last column in the
// constraint needs to be adapted to an exclusive span.EndKey).
func encodeInclusiveEndValue(
	key roachpb.Key, datum parser.Datum, dir encoding.Direction, isLastEndConstraint bool,
) roachpb.Key {
	// Since the end of a span is exclusive, if the last constraint is an
	// inclusive one, we might need to make the key exclusive by applying a
	// PrefixEnd().  We normally avoid doing this by transforming "a = x" to
	// "a = x±1" for the last end constraint, depending on the encoding direction
	// (since this keeps the key nice and pretty-printable).
	// However, we might not be able to do the ±1.
	needExclusiveKey := false
	if isLastEndConstraint {
		if dir == encoding.Ascending {
			if datum.IsMax() || !datum.HasNext() {
				needExclusiveKey = true
			} else {
				datum = datum.Next()
			}
		} else {
			if datum.IsMin() || !datum.HasPrev() {
				needExclusiveKey = true
			} else {
				datum = datum.Prev()
			}
		}
	}
	key, err := sqlbase.EncodeTableKey(key, datum, dir)
	if err != nil {
		panic(err)
	}
	if needExclusiveKey {
		key = key.PrefixEnd()
	}
	return key
}