#ifndef cmsg_sexp_h
#define cmsg_sexp_h

typedef struct sexp_data_t_ {
  refcount_t refcount;
  cmsg_bytes_t data;
} sexp_data_t;

typedef enum sexp_type_t_ {
  SEXP_BYTES,
  SEXP_SLICE,
  SEXP_DISPLAY_HINT,
  SEXP_PAIR
} sexp_type_t;

typedef struct sexp_t_ {
  refcount_t refcount;
  sexp_type_t kind;
  union {
    cmsg_bytes_t bytes;
    struct {
      sexp_data_t *data;
      size_t offset;
      size_t length;
    } slice;
    struct {
      struct sexp_t_ *head;
      struct sexp_t_ *tail;
    } pair; /* and display-hint */
  } data;
} sexp_t;

extern void release_sexp_cache(void);

extern void sexp_data_destructor(sexp_data_t *data);
extern void sexp_destructor(sexp_t *x);

extern sexp_data_t *sexp_data_copy(cmsg_bytes_t body, size_t offset, size_t length);
extern sexp_data_t *sexp_data_alias(cmsg_bytes_t body);

extern sexp_t *sexp_bytes(cmsg_bytes_t bytes);
extern sexp_t *sexp_slice(sexp_data_t *data, size_t offset, size_t length);
extern sexp_t *sexp_display_hint(sexp_t *hint, sexp_t *body);
extern sexp_t *sexp_cons(sexp_t *head, sexp_t *tail);

#define sexp_simple_stringp(x)	({					\
      sexp_t *__x = (x);						\
      (__x != NULL) && ((__x->kind == SEXP_BYTES) || (__x->kind == SEXP_SLICE)); \
    })

#define sexp_stringp(x) ({						\
      sexp_t *__x = (x);						\
      sexp_simple_stringp(__x) || ((__x != NULL) && (__x->kind == SEXP_DISPLAY_HINT)); \
    })

#define sexp_pairp(x) ({				\
      sexp_t *__x = (x);				\
      (__x != NULL) && (__x->kind == SEXP_PAIR);	\
    })

extern cmsg_bytes_t sexp_data(sexp_t *x);
#define sexp_head(x)	({sexp_t *__x = (x); assert(__x->kind == SEXP_PAIR); __x->data.pair.head;})
#define sexp_tail(x)	({sexp_t *__x = (x); assert(__x->kind == SEXP_PAIR); __x->data.pair.tail;})
#define sexp_hint(x)	({sexp_t *__x = (x); assert(__x->kind == SEXP_DISPLAY_HINT); __x->data.pair.head;})
#define sexp_body(x)	({sexp_t *__x = (x); assert(__x->kind == SEXP_DISPLAY_HINT); __x->data.pair.tail;})

#define sexp_setter_(x,y,fieldname)		\
  ({						\
    sexp_t *__x = (x);				\
    sexp_t *__y = (y);				\
    sexp_t *__old;				\
    assert(__x->kind == SEXP_PAIR);		\
    INCREF(__y);				\
    __old = __x->data.pair.fieldname;		\
    __x->data.pair.fieldname = __y;		\
    DECREF(__old, sexp_destructor);		\
    __x;					\
  })

#define sexp_sethead(x,y) sexp_setter_(x,y,head)
#define sexp_settail(x,y) sexp_setter_(x,y,tail)

#define sexp_push(stackvar,val)				\
  ({							\
    sexp_t *__oldstack = stackvar;			\
    stackvar = INCREF(sexp_cons((val), stackvar));	\
    DECREF(__oldstack, sexp_destructor);		\
    stackvar;						\
  })

#define sexp_pop(stackvar)				\
  ({							\
    sexp_t *__nextstack = INCREF(sexp_tail(stackvar));	\
    sexp_t *__val = INCREF(sexp_head(stackvar));	\
    DECREF(stackvar, sexp_destructor);			\
    stackvar = __nextstack;				\
    UNGRAB(__val);					\
    __val;						\
  })

extern sexp_t *sexp_assoc(sexp_t *list, cmsg_bytes_t key);

#endif