#ifndef TUMBLER_H
#define TUMBLER_H

#include <stddef.h>
#include <stdint.h>

typedef struct {
    uint64_t *digits;
    size_t count;
} tumbler_t;

typedef enum {
    TUMBLER_OK = 0,
    TUMBLER_ERR_NULL,
    TUMBLER_ERR_INVALID,
    TUMBLER_ERR_NOMEM,
    TUMBLER_ERR_OVERFLOW,
    TUMBLER_ERR_UNDERFLOW
} tumbler_error_t;

typedef struct {
    tumbler_error_t code;
    const char *msg;
} tumbler_result_t;

/* Parse the dotted decimal representation into a heap-owned tumbler.
 * On success, caller owns out->digits and must call tumbler_free(). */
tumbler_result_t tumbler_parse(const char *text, tumbler_t *out);
void tumbler_free(tumbler_t *t);

/* Format a tumbler as a newly allocated dotted decimal string.
 * Caller frees the returned string. */
tumbler_result_t tumbler_to_string(const tumbler_t *t, char **out);

/* Whole-tumbler numeric ordering. Missing fields compare as zero, so
 * 1 < 1.1 < 1.1.1 and trailing zero fields do not affect ordering. */
int tumbler_compare(const tumbler_t *a, const tumbler_t *b);

/* Xanadu tumbler addition: position + offset. */
tumbler_result_t tumbler_add(const tumbler_t *position,
                             const tumbler_t *offset,
                             tumbler_t *out);

/* Strong and weak tumbler subtraction, as described in the historical
 * Xanadu material. Both require non-negative results at their first
 * differing field. */
tumbler_result_t tumbler_subtract_strong(const tumbler_t *position,
                                         const tumbler_t *offset,
                                         tumbler_t *out);
tumbler_result_t tumbler_subtract_weak(const tumbler_t *position,
                                       const tumbler_t *offset,
                                       tumbler_t *out);

/* Generalized tumbler difference used by the Xanadu system:
 * if a > b, strong-subtract b from a; otherwise weak-subtract a from b. */
tumbler_result_t tumbler_subtract(const tumbler_t *a,
                                  const tumbler_t *b,
                                  tumbler_t *out);

#endif /* TUMBLER_H */