#ifndef IMB3_VALUE_H
#define IMB3_VALUE_H

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

/**
 * Declared "for real" in gc.h.
 */
struct object;

struct value {
  uintptr_t bits;
};

enum value_tag {
  /**
   * A big integer or the nil constant.
   */
  TAG_BIGINT_OR_NIL = 0b000,

  /**
   * Fixnums, i.e. integers that are stored directly in the value rather than
   * being pointed to. This is a two-bit tag rather than a three-bit tag...
   */
  TAG_FIXNUM = 0b01,

  /**
   * A builtin-object.
   */
  TAG_BUILTIN_OBJECT = 0b010,

  /**
   * A simple-array, i.e. an array of values without a fill-pointer.
   */
  TAG_SIMPLE_ARRAY = 0b100,

  /**
   * A standard-object, effectively a pair of a class and a slot array.
   */
  TAG_STANDARD_OBJECT = 0b110,

  /**
   * An tag that is _invalid_ for values, but may be used by the internals of
   * the garbage collector.
   */
  TAG_GC_INTERNAL = 0b111,
};

/**
 * The nil constant.
 */
static const struct value NIL = {.bits = 0};

/**
 * Allocates a builtin-object with the given class and slot count.
 */
struct value alloc_builtin_object(struct value class, size_t value_slot_count,
                                  size_t untraced_slot_count);

/**
 * Stores an intptr_t as a fixnum or a bignum.
 */
struct value integer_of_int(intptr_t);

/**
 * Returns the tag of a value.
 */
enum value_tag get_tag(struct value);

/**
 * Returns whether a value is a pointer.
 */
bool is_ptr(struct value);

/**
 * Tags a pointer.
 */
struct value tag_ptr(struct object *, enum value_tag);

/**
 * Untags a fixnum.
 */
intptr_t untag_fixnum(struct value);

/**
 * Untags a pointer.
 */
struct object *untag_ptr(struct value);

/**
 * Bootstraps the class heirarchy. This should only be called once.
 */
void bootstrap(void);

#endif // IMB3_VALUE_H