/**
 * See Copyright Notice in picrin.h
 */

#include "picrin.h"

KHASH_DECLARE(m, void *, int)
KHASH_DEFINE2(m, void *, int, 0, kh_ptr_hash_func, kh_ptr_hash_equal)

static bool
internal_equal_p(pic_state *pic, pic_value x, pic_value y, int depth, khash_t(m) *h)
{
  pic_value localx = pic_nil_value();
  pic_value localy = pic_nil_value();
  int cx = 0;
  int cy = 0;

  if (depth > 10) {
    if (depth > 200) {
      pic_errorf(pic, "Stack overflow in equal\n");
    }
    if (pic_pair_p(x) || pic_vec_p(x)) {
      int ret;
      kh_put(m, h, pic_obj_ptr(x), &ret);
      if (ret != 0) {
        return true;            /* `x' was seen already.  */
      }
    }
  }

 LOOP:

  if (pic_eqv_p(x, y)) {
    return true;
  }
  if (pic_type(x) != pic_type(y)) {
    return false;
  }

  switch (pic_type(x)) {
  case PIC_TT_ID: {
    struct pic_id *id1, *id2;
    pic_sym *s1, *s2;

    id1 = pic_id_ptr(x);
    id2 = pic_id_ptr(y);

    s1 = pic_lookup_identifier(pic, id1->u.id.id, id1->u.id.env);
    s2 = pic_lookup_identifier(pic, id2->u.id.id, id2->u.id.env);

    return s1 == s2;
  }
  case PIC_TT_STRING: {
    return pic_str_cmp(pic, pic_str_ptr(x), pic_str_ptr(y)) == 0;
  }
  case PIC_TT_BLOB: {
    pic_blob *blob1, *blob2;
    int i;

    blob1 = pic_blob_ptr(x);
    blob2 = pic_blob_ptr(y);

    if (blob1->len != blob2->len) {
      return false;
    }
    for (i = 0; i < blob1->len; ++i) {
      if (blob1->data[i] != blob2->data[i])
        return false;
    }
    return true;
  }
  case PIC_TT_PAIR: {
    if (! internal_equal_p(pic, pic_car(pic, x), pic_car(pic, y), depth + 1, h))
      return false;

    /* Floyd's cycle-finding algorithm */
    if (pic_nil_p(localx)) {
      localx = x;
    }
    x = pic_cdr(pic, x);
    cx++;
    if (pic_nil_p(localy)) {
      localy = y;
    }
    y = pic_cdr(pic, y);
    cy++;
    if (cx == 2) {
      cx = 0;
      localx = pic_cdr(pic, localx);
      if (pic_eq_p(localx, x)) {
        if (cy < 0 ) return true; /* both lists circular */
        cx = INT_MIN; /* found a cycle on x */
      }
    }
    if (cy == 2) {
      cy = 0;
      localy = pic_cdr(pic, localy);
      if (pic_eq_p(localy, y)) {
        if (cx < 0 ) return true; /* both lists circular */
        cy = INT_MIN; /* found a cycle on y */
      }
    }
    goto LOOP;                  /* tail-call optimization */
  }
  case PIC_TT_VECTOR: {
    int i;
    struct pic_vector *u, *v;

    u = pic_vec_ptr(x);
    v = pic_vec_ptr(y);

    if (u->len != v->len) {
      return false;
    }
    for (i = 0; i < u->len; ++i) {
      if (! internal_equal_p(pic, u->data[i], v->data[i], depth + 1, h))
        return false;
    }
    return true;
  }
  default:
    return false;
  }
}

bool
pic_equal_p(pic_state *pic, pic_value x, pic_value y)
{
  khash_t(m) h;

  kh_init(m, &h);

  return internal_equal_p(pic, x, y, 0, &h);
}

static pic_value
pic_bool_eq_p(pic_state *pic)
{
  pic_value x, y;

  pic_get_args(pic, "oo", &x, &y);

  return pic_bool_value(pic_eq_p(x, y));
}

static pic_value
pic_bool_eqv_p(pic_state *pic)
{
  pic_value x, y;

  pic_get_args(pic, "oo", &x, &y);

  return pic_bool_value(pic_eqv_p(x, y));
}

static pic_value
pic_bool_equal_p(pic_state *pic)
{
  pic_value x, y;

  pic_get_args(pic, "oo", &x, &y);

  return pic_bool_value(pic_equal_p(pic, x, y));
}

static pic_value
pic_bool_not(pic_state *pic)
{
  pic_value v;

  pic_get_args(pic, "o", &v);

  return pic_false_p(v) ? pic_true_value() : pic_false_value();
}

static pic_value
pic_bool_boolean_p(pic_state *pic)
{
  pic_value v;

  pic_get_args(pic, "o", &v);

  return (pic_true_p(v) || pic_false_p(v)) ? pic_true_value() : pic_false_value();
}

static pic_value
pic_bool_boolean_eq_p(pic_state *pic)
{
  int argc, i;
  pic_value *argv;

  pic_get_args(pic, "*", &argc, &argv);

  for (i = 0; i < argc; ++i) {
    if (! (pic_true_p(argv[i]) || pic_false_p(argv[i]))) {
      return pic_false_value();
    }
    if (! pic_eq_p(argv[i], argv[0])) {
      return pic_false_value();
    }
  }
  return pic_true_value();
}

void
pic_init_bool(pic_state *pic)
{
  pic_defun(pic, "eq?", pic_bool_eq_p);
  pic_defun(pic, "eqv?", pic_bool_eqv_p);
  pic_defun(pic, "equal?", pic_bool_equal_p);

  pic_defun(pic, "not", pic_bool_not);

  pic_defun(pic, "boolean?", pic_bool_boolean_p);
  pic_defun(pic, "boolean=?", pic_bool_boolean_eq_p);
}