/* -*-comment-start: "//";comment-end:""-*-
 * GNU Mes --- Maxwell Equations of Software
 * Copyright © 2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
 * Copyright © 2019 Jeremiah Orians <jeremiah@pdp10.guru>
 *
 * This file is part of GNU Mes.
 *
 * GNU Mes is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 *
 * GNU Mes is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "mes/lib.h"
#include "mes/mes.h"

#include <string.h>

SCM
hash_cstring (char *s, SCM size)
{
  int h = s[0] * 37;

  if (s[0] && s[1])
    {
      h = h + s[1] * 43;
    }

  require (0 != size, "src/hash.c: hash_cstring must not be zero");
  h = h % size;
  return h;
}

SCM
hashq_ (struct scm *x, SCM size)
{
  struct scm *y = x;
  if (y->type == TSPECIAL || y->type == TSYMBOL)
    {
      char *p = y->cdr->string;
      return hash_cstring (p, size);    /* FIXME: hash x directly */
    }

  error (cell_symbol_system_error, cons (make_string_ ("hashq_: not a symbol"), x));
  exit (EXIT_FAILURE);
}

SCM
hash_ (struct scm *x, SCM size)
{
  struct scm *y = x;
  if (y->type == TSTRING)
    {
      char *p = y->cdr->string;
      return hash_cstring (p, size);
    }

  require (FALSE, "src/hash.c: hash_ impossible condition hit");
  return hashq_ (x, size);
}

struct scm *
hashq (struct scm *x, struct scm *size)
{
  require (FALSE, "src/hash.c: hashq impossible condition hit");
  return make_number (hashq_ (x, size->value));
}

struct scm *
hash (struct scm *x, struct scm *size)
{
  require (FALSE, "src/hash.c: hash impossible condition hit");
  return make_number (hash_ (x, size->value));
}

struct scm *
hashq_get_handle (struct scm *table, struct scm *key, struct scm *dflt)
{
  struct scm *ydflt = dflt;
  if (ydflt->type == TPAIR)
    {
      return ydflt->car;
    }

  struct scm *ybucket = vector_ref_ (struct_ref_ (table, 4), hashq_ (key, struct_ref_ (table, 3)->value));
  if (ybucket->type == TPAIR)
    {
      return assq (key, ybucket);
    }

  return cell_f;
}

struct scm *
hashq_ref (struct scm *table, struct scm *key, struct scm *dflt)
{
  struct scm *x = hashq_get_handle (table, key, dflt);

  if (x == cell_f)
    {
      return x;
    }

  return x->cdr;
}

struct scm *
hash_ref (struct scm *table, struct scm *key, struct scm *dflt) /* External */
{
  struct scm *bucket = vector_ref_ (struct_ref_ (table, 4), hash_ (key, struct_ref_ (table, 3)->value));
  if (bucket->type == TPAIR)
    {
      struct scm *y = assoc (key, bucket);
      if (y != cell_f)
        {
          return y->cdr;
        }
    }

  return cell_f;
}

struct scm *
hashq_set_x (struct scm *table, struct scm *key, struct scm *value)
{
  SCM size = struct_ref_ (table, 3)->value;
  struct scm *buckets = struct_ref_ (table, 4);

  struct scm *ybucket = vector_ref_ (buckets, hashq_ (key, size));
  if (ybucket->type != TPAIR)
    {
      vector_set_x_ (buckets, hashq_ (key, size), acons (key, value, cell_nil));
    }
  else
    {
      vector_set_x_ (buckets, hashq_ (key, size),
                     acons (key, value, vector_ref_ (buckets, hashq_ (key, size))));
    }
  return value;
}

struct scm *
hash_set_x (struct scm *table, struct scm *key, struct scm *value)
{
  SCM size = struct_ref_ (table, 3)->value;
  unsigned h = hash_ (key, size);
  struct scm *buckets = struct_ref_ (table, 4);
  struct scm *bucket = vector_ref_ (buckets, h);

  struct scm *ybucket = bucket;
  if (ybucket->type != TPAIR)
    {
      bucket = cell_nil;
    }

  bucket = acons (key, value, bucket);
  vector_set_x_ (buckets, h, bucket);
  return value;
}

struct scm *
make_hashq_type ()              /* ((internal)) */
{
  struct scm *record_type = cell_symbol_record_type;    /* FIXME */
  struct scm *fields = cell_nil;
  fields = cons (cell_symbol_buckets, fields);
  fields = cons (cell_symbol_size, fields);
  fields = cons (fields, cell_nil);
  fields = cons (cell_symbol_hashq_table, fields);
  return make_struct (record_type, fields, cell_unspecified);
}

struct scm *
make_hash_table_ (SCM size)
{
  if (!size)
    {
      size = 100;
    }

  struct scm *hashq_type = make_hashq_type ();
  struct scm *buckets = make_vector__ (size);
  struct scm *values = cell_nil;
  values = cons (buckets, values);
  values = cons (make_number (size), values);
  values = cons (cell_symbol_hashq_table, values);
  /* FIXME: symbol/printer return make_struct (hashq_type, values, cstring_to_symbol ("hash-table-printer"); */
  return make_struct (hashq_type, values, cell_unspecified);
}

struct scm *
make_hash_table (struct scm *x)
{
  SCM size = 0;

  struct scm *y = x;
  if (y->type == TPAIR)
    {
      require (TNUMBER == y->type, "y->type must be TNUMBER\nsrc/hash.c: make_hash_table\n");
      size = y->value;
    }

  return make_hash_table_ (size);
}


/* Externally exposed */
struct scm *
hashq_set_x_ (struct scm *table, struct scm *key, struct scm *value)
{
  return hashq_set_x (table, key, value);
}

struct scm *
hash_ref_ (struct scm *table, struct scm *key, struct scm *dflt)
{
  return hash_ref (table, key, dflt);
}