/*  hash.c -- type-general hashing                            */
/*  Copyright (c) 2009-2011 Alex Shinn.  All rights reserved. */
/*  BSD-style license: http://synthcode.com/license.txt       */

#include <chibi/eval.h>

#define HASH_DEPTH 5
#define HASH_BOUND sexp_make_fixnum(SEXP_MAX_FIXNUM)

#define FNV_PRIME 16777619
#define FNV_OFFSET_BASIS 2166136261uL

#define sexp_hash_table_buckets(x)  sexp_slot_ref(x, 0)
#define sexp_hash_table_size(x)     sexp_slot_ref(x, 1)
#define sexp_hash_table_hash_fn(x)  sexp_slot_ref(x, 2)
#define sexp_hash_table_eq_fn(x)    sexp_slot_ref(x, 3)

#define sexp_hash_resize_check(n, len) (((n)*3) > ((len)>>2))

static sexp_uint_t string_hash (char *str, sexp_uint_t bound) {
  sexp_uint_t acc = FNV_OFFSET_BASIS;
  while (*str) {acc *= FNV_PRIME; acc ^= *str++;}
  return acc % bound;
}

static sexp sexp_string_hash (sexp ctx, sexp self, sexp_sint_t n, sexp str, sexp bound) {
  if (! sexp_stringp(str))
    return sexp_type_exception(ctx, self, SEXP_STRING, str);
  else if (! sexp_fixnump(bound))
    return sexp_type_exception(ctx, self, SEXP_FIXNUM, bound);
  return sexp_make_fixnum(string_hash(sexp_string_data(str),
                                      sexp_unbox_fixnum(bound)));
}

static sexp_uint_t string_ci_hash (char *str, sexp_uint_t bound) {
  sexp_uint_t acc = FNV_OFFSET_BASIS;
  while (*str) {acc *= FNV_PRIME; acc ^= sexp_tolower(*str++);}
  return acc % bound;
}

static sexp sexp_string_ci_hash (sexp ctx, sexp self, sexp_sint_t n, sexp str, sexp bound) {
  if (! sexp_stringp(str))
    return sexp_type_exception(ctx, self, SEXP_STRING, str);
  else if (! sexp_fixnump(bound))
    return sexp_type_exception(ctx, self, SEXP_FIXNUM, bound);
  return sexp_make_fixnum(string_ci_hash(sexp_string_data(str),
                                         sexp_unbox_fixnum(bound)));
}

static sexp_uint_t hash_one (sexp ctx, sexp obj, sexp_uint_t bound, sexp_sint_t depth) {
  sexp_uint_t acc = FNV_OFFSET_BASIS, size;
  sexp_sint_t i, len;
  sexp t, *p;
  char *p0;
 loop:
  if (obj) {
#if SEXP_USE_FLONUMS
    if (sexp_flonump(obj))
      acc ^= (sexp_sint_t) sexp_flonum_value(obj);
    else
#endif
    if (sexp_pointerp(obj)) {
      if (depth > 0) {
        t = sexp_object_type(ctx, obj);
        p = (sexp*) (((char*)obj) + sexp_type_field_base(t));
        p0 = ((char*)obj) + offsetof(struct sexp_struct, value);
        if ((sexp)p == obj) p=(sexp*)p0;
        /* hash trailing non-object data */
        size = sexp_type_size_of_object(t, obj)-offsetof(struct sexp_struct, value);
        p0 = ((char*)p + sexp_type_num_slots_of_object(t,obj)*sizeof(sexp));
        if (((char*)obj + size) > p0)
          for (i=0; i<size; i++) {acc *= FNV_PRIME; acc ^= p0[i];}
        /* hash eq-object slots */
        len = sexp_type_num_eq_slots_of_object(t, obj);
        if (len > 0) {
          depth--;
          for (i=0; i<len-1; i++) {
            acc *= FNV_PRIME;
            acc ^= hash_one(ctx, p[i], 0, depth);
          }
          /* tail-recurse on the last value */
          obj = p[len-1]; goto loop;
        }
      } else {
        acc ^= sexp_pointer_tag(obj);
      }
    } else {
      acc ^= (sexp_uint_t)obj;
    }
  }
  return (bound ? acc % bound : acc);
}

static sexp sexp_hash (sexp ctx, sexp self, sexp_sint_t n, sexp obj, sexp bound) {
  if (! sexp_exact_integerp(bound))
    return sexp_type_exception(ctx, self, SEXP_FIXNUM, bound);
  return sexp_make_fixnum(hash_one(ctx, obj, sexp_unbox_fixnum(bound), HASH_DEPTH));
}

static sexp sexp_hash_by_identity (sexp ctx, sexp self, sexp_sint_t n, sexp obj, sexp bound) {
  if (! sexp_exact_integerp(bound))
    return sexp_type_exception(ctx, self, SEXP_FIXNUM, bound);
  return sexp_make_fixnum((sexp_uint_t)obj % sexp_unbox_fixnum(bound));
}

static sexp sexp_get_bucket (sexp ctx, sexp buckets, sexp hash_fn, sexp obj) {
  sexp_gc_var1(args);
  sexp res;
  sexp_uint_t len = sexp_vector_length(buckets);
  if (hash_fn == SEXP_ONE)
    res = sexp_hash_by_identity(ctx, NULL, 2, obj, sexp_make_fixnum(len));
  else if (hash_fn == SEXP_TWO)
    res = sexp_hash(ctx, NULL, 2, obj, sexp_make_fixnum(len));
  else {
    sexp_gc_preserve1(ctx, args);
    args = sexp_list2(ctx, obj, sexp_make_fixnum(len));
    res = sexp_apply(ctx, hash_fn, args);
    if (sexp_exceptionp(res)) {
      args = sexp_eval_string(ctx, "(current-error-port)", -1, sexp_context_env(ctx));
      sexp_print_exception(ctx, res, args);
      res = SEXP_ZERO;
    } else if (sexp_unbox_fixnum(res) >= len) {
      res = SEXP_ZERO;
    }
    sexp_gc_release1(ctx);
  }
  return res;
}

static sexp sexp_scan_bucket (sexp ctx, sexp ls, sexp obj, sexp eq_fn) {
  sexp_gc_var1(res);
  sexp p;
  res = SEXP_FALSE;
  if ((eq_fn == SEXP_ONE)
      || ((eq_fn == SEXP_TWO)
          && (sexp_pointerp(obj) ?
              (sexp_pointer_tag(obj) == SEXP_SYMBOL) : ! sexp_fixnump(obj)))) {
    for (p=ls; sexp_pairp(p); p=sexp_cdr(p)) {
      if (sexp_caar(p) == obj) {
        res = p;
        break;
      }
    }
  } else if (eq_fn == SEXP_TWO) {
    for (p=ls; sexp_pairp(p); p=sexp_cdr(p)) {
      if (sexp_truep(sexp_equalp(ctx, sexp_caar(p), obj))) {
        res = p;
        break;
      }
    }
  } else {
    sexp_gc_preserve1(ctx, res);
    for (p=ls; sexp_pairp(p); p=sexp_cdr(p)) {
      res = sexp_list2(ctx, sexp_caar(p), obj);
      if (sexp_truep(sexp_apply(ctx, eq_fn, res))) {
        res = p;
        break;
      } else {
        res = SEXP_FALSE;
      }
    }
    sexp_gc_release1(ctx);
  }
  return res;
}

static void sexp_regrow_hash_table (sexp ctx, sexp ht, sexp oldbuckets, sexp hash_fn) {
  sexp ls, *oldvec, *newvec;
  int i, j, oldsize=sexp_vector_length(oldbuckets), newsize=oldsize*2;
  sexp_gc_var1(newbuckets);
  sexp_gc_preserve1(ctx, newbuckets);
  newbuckets = sexp_make_vector(ctx, sexp_make_fixnum(newsize), SEXP_NULL);
  if (newbuckets) {
    oldvec = sexp_vector_data(oldbuckets);
    newvec = sexp_vector_data(newbuckets);
    for (i=0; i<oldsize; i++) {
      for (ls=oldvec[i]; sexp_pairp(ls); ls=sexp_cdr(ls)) {
        j = sexp_unbox_fixnum(sexp_get_bucket(ctx, newbuckets, hash_fn, sexp_caar(ls)));
        sexp_push(ctx, newvec[j], sexp_car(ls));
      }
    }
    sexp_hash_table_buckets(ht) = newbuckets;
  }
  sexp_gc_release1(ctx);
}

static sexp sexp_hash_table_cell (sexp ctx, sexp self, sexp_sint_t n, sexp ht, sexp obj, sexp createp) {
  sexp buckets, eq_fn, hash_fn, i;
  sexp_uint_t size;
  sexp_gc_var1(res);
  /* extra check - exact type should be checked by the calling procedure */
  if (! sexp_pointerp(ht))
    return sexp_xtype_exception(ctx, self, "not a Hash-Table", ht);
  buckets = sexp_hash_table_buckets(ht);
  eq_fn = sexp_hash_table_eq_fn(ht);
  hash_fn = sexp_hash_table_hash_fn(ht);
  i = sexp_get_bucket(ctx, buckets, hash_fn, obj);
  res = sexp_scan_bucket(ctx, sexp_vector_ref(buckets, i), obj, eq_fn);
  if (sexp_truep(res)) {
    res = sexp_car(res);
  } else if (sexp_truep(createp)) {
    sexp_gc_preserve1(ctx, res);
    size = sexp_unbox_fixnum(sexp_hash_table_size(ht));
    if (sexp_hash_resize_check(size, sexp_vector_length(buckets))) {
      sexp_regrow_hash_table(ctx, ht, buckets, hash_fn);
      buckets = sexp_hash_table_buckets(ht);
      i = sexp_get_bucket(ctx, buckets, hash_fn, obj);
    }
    res = sexp_cons(ctx, obj, createp);
    sexp_vector_set(buckets, i, sexp_cons(ctx, res, sexp_vector_ref(buckets, i)));
    sexp_hash_table_size(ht) = sexp_make_fixnum(size+1);
    sexp_gc_release1(ctx);
  }
  return res;
}

static sexp sexp_hash_table_delete (sexp ctx, sexp self, sexp_sint_t n, sexp ht, sexp obj) {
  sexp buckets, eq_fn, hash_fn, i, p, res;
  if (!(sexp_pointerp(ht) && strcmp(sexp_string_data(sexp_object_type_name(ctx, ht)), "Hash-Table") == 0))
    return sexp_xtype_exception(ctx, self, "not a Hash-Table", ht);
  buckets = sexp_hash_table_buckets(ht);
  eq_fn = sexp_hash_table_eq_fn(ht);
  hash_fn = sexp_hash_table_hash_fn(ht);
  i = sexp_get_bucket(ctx, buckets, hash_fn, obj);
  res = sexp_scan_bucket(ctx, sexp_vector_ref(buckets, i), obj, eq_fn);
  if (sexp_pairp(res)) {
    sexp_hash_table_size(ht) = sexp_fx_sub(sexp_hash_table_size(ht), SEXP_ONE);
    if (res == sexp_vector_ref(buckets, i)) {
      sexp_vector_set(buckets, i, sexp_cdr(res));
    } else {
      for (p=sexp_vector_ref(buckets, i); sexp_cdr(p)!=res; p=sexp_cdr(p))
        ;
      sexp_cdr(p) = sexp_cdr(res);
    }
  }
  return SEXP_VOID;
}

sexp sexp_init_library (sexp ctx, sexp self, sexp_sint_t n, sexp env, const char* version, sexp_abi_identifier_t abi) {
  if (!(sexp_version_compatible(ctx, version, sexp_version)
        && sexp_abi_compatible(ctx, abi, SEXP_ABI_IDENTIFIER)))
    return SEXP_ABI_ERROR;

  sexp_define_foreign_opt(ctx, env, "string-hash", 2, sexp_string_hash, HASH_BOUND);
  sexp_define_foreign_opt(ctx, env, "string-ci-hash", 2, sexp_string_ci_hash, HASH_BOUND);
  sexp_define_foreign_opt(ctx, env, "hash", 2, sexp_hash, HASH_BOUND);
  sexp_define_foreign_opt(ctx, env, "hash-by-identity", 2, sexp_hash_by_identity, HASH_BOUND);
  sexp_define_foreign(ctx, env, "hash-table-cell", 3, sexp_hash_table_cell);
  sexp_define_foreign(ctx, env, "hash-table-delete!", 2, sexp_hash_table_delete);

  return SEXP_VOID;
}