/*

 * Copyright 2020 Google LLC

 *

 * Use of this source code is governed by a BSD-style

 * license that can be found in the LICENSE file or at

 * https://developers.google.com/open-source/licenses/bsd

 */

#include "pq.h"

#include "reftable-error.h"

#include "reftable-record.h"

#include "system.h"

#include "basics.h"

int pq_less(struct pq_entry *a, struct pq_entry *b)

{

  int cmp, err;

  err = reftable_record_cmp(a->rec, b->rec, &cmp);

  if (err < 0)

    return err;

  if (cmp == 0)

    return a->index > b->index;

  return cmp < 0;

}

int merged_iter_pqueue_remove(struct merged_iter_pqueue *pq, struct pq_entry *out)

{

  size_t i = 0;

  struct pq_entry e = pq->heap[0];

  pq->heap[0] = pq->heap[pq->len - 1];

  pq->len--;

  while (i < pq->len) {

    size_t min = i;

    size_t j = 2 * i + 1;

    size_t k = 2 * i + 2;

    int cmp;

    if (j < pq->len) {

      cmp = pq_less(&pq->heap[j], &pq->heap[i]);

      if (cmp < 0)

        return -1;

      else if (cmp)

        min = j;

    }

    if (k < pq->len) {

      cmp = pq_less(&pq->heap[k], &pq->heap[min]);

      if (cmp < 0)

        return -1;

      else if (cmp)

        min = k;

    }

    if (min == i)

      break;

    REFTABLE_SWAP(pq->heap[i], pq->heap[min]);

    i = min;

  }

  if (out)

    *out = e;

  return 0;

}

int merged_iter_pqueue_add(struct merged_iter_pqueue *pq, const struct pq_entry *e)

{

  size_t i = 0;

  REFTABLE_ALLOC_GROW_OR_NULL(pq->heap, pq->len + 1, pq->cap);

  if (!pq->heap)

    return REFTABLE_OUT_OF_MEMORY_ERROR;

  pq->heap[pq->len++] = *e;

  i = pq->len - 1;

  while (i > 0) {

    size_t j = (i - 1) / 2;

    if (pq_less(&pq->heap[j], &pq->heap[i]))

      break;

    REFTABLE_SWAP(pq->heap[j], pq->heap[i]);

    i = j;

  }

  return 0;

}

void merged_iter_pqueue_release(struct merged_iter_pqueue *pq)

{

  REFTABLE_FREE_AND_NULL(pq->heap);

  memset(pq, 0, sizeof(*pq));

}