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

// common types
typedef void V;

typedef uintptr_t U;
typedef intptr_t I;

typedef uint8_t U8;
typedef uint32_t U32;
typedef int32_t I32;
typedef size_t Z;

// objects
typedef uintptr_t O;

// cons pair
typedef struct C C;
struct C {
  O car, cdr;
};

// lambda
typedef struct L L;
struct L {
  O args, body, env;
};

// symbol
typedef struct S S;
struct S {
  U8 *data;
  U32 hash;
  Z len;
};

// symbol table
typedef struct St St;
struct St {
  I count;
  Z capacity;
  S **data;
};

#define TYPE_MASK 7

enum {
  TAG_GC = 0,   // GC-managed object
  TAG_NUM = 1,  // Immediate number
  TAG_SYM = 2,  // Pointer to symbol
  TAG_PRIM = 4, // Pointer to primitive
};

enum {
  KIND_NIL = 0,
  KIND_NUM = 1,
  KIND_SYM = 2,
  KIND_PRIM = 4,
  KIND_CONS = 5,
  KIND_CLOS = 6,
  KIND__MAX,
};

#define TYPE(x) (((U)(x)) & TYPE_MASK)
#define UNTAG(x) (((U)(x)) & ~TYPE_MASK)
#define TAG(x, t) (void *)(((U)(x)) | t)

enum { OBJ_CONS = 5, OBJ_CLOS = 6, OBJ_FWD = 7 };

// gc header
typedef struct H H;
struct H {
  I type;
  Z size;
};

// heap
typedef struct E E;
struct E {
  struct {
    U8 *start, *end;
    U8 *free;
  } from, to;

  I root_count;
  Z root_capacity;
  O **roots;
};

// primitive
typedef struct P P;
struct P {
  const char *name;
  O (*fn)(O, O);
};

extern E heap;
extern St syms;

#define ALIGN(n) (((n) + 7) & ~7)
#define INFROM(x)                                                              \
  (((const U8 *)x) >= heap.from.start && ((const U8 *)x) < heap.from.end)

#define IMM(x) ((x) & 1)
#define NUM(x) (((O)((I)(x) << 1)) | (O)1)
#define ORD(x) ((I)(x) >> 1)
#define BOX(x) ((O)(x))
#define UNBOX(x) ((H *)(x))

#define SYM(s) BOX(TAG(intern(s, -1), TAG_SYM))

#define NIL ((O)0)
#define GC_HEAP_BYTES (1024 * 1024)

// GC
void addroot(O *ptr);
I rootmark(void);
void rootreset(I mark);
void collect(void);
H *alloc(Z sz);
void gcinit(void);
void gcfinalize(void);

I kind(O obj);
const char *kindname(I k);

S *intern(const char *str, I len);
O mksym(const char *str);

O cons(O head, O tail);
C *uncons(O obj);

V setupenv(O *env);
O eval(O obj, O env);

void print(O obj);
void println(O obj);