/*

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 "system.h"

int pq_less(struct pq_entry a, struct pq_entry b)

{

  struct slice ak = { 0 };

  struct slice bk = { 0 };

  int cmp = 0;

  record_key(a.rec, &ak);

  record_key(b.rec, &bk);

  cmp = slice_compare(ak, bk);

  slice_clear(&ak);

  slice_clear(&bk);

  if (cmp == 0) {

    return a.index > b.index;

  }

  return cmp < 0;

}

struct pq_entry merged_iter_pqueue_top(struct merged_iter_pqueue pq)

{

  return pq.heap[0];

}

bool merged_iter_pqueue_is_empty(struct merged_iter_pqueue pq)

{

  return pq.len == 0;

}

void merged_iter_pqueue_check(struct merged_iter_pqueue pq)

{

  int i = 0;

  for (i = 1; i < pq.len; i++) {

    int parent = (i - 1) / 2;

    assert(pq_less(pq.heap[parent], pq.heap[i]));

  }

}

struct pq_entry merged_iter_pqueue_remove(struct merged_iter_pqueue *pq)

{

  int i = 0;

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

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

  pq->len--;

  i = 0;

  while (i < pq->len) {

    int min = i;

    int j = 2 * i + 1;

    int k = 2 * i + 2;

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

      min = j;

    }

    if (k < pq->len && pq_less(pq->heap[k], pq->heap[min])) {

      min = k;

    }

    if (min == i) {

      break;

    }

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

    i = min;

  }

  return e;

}

void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, struct pq_entry e)

{

  int i = 0;

  if (pq->len == pq->cap) {

    pq->cap = 2 * pq->cap + 1;

    pq->heap = reftable_realloc(pq->heap,

              pq->cap * sizeof(struct pq_entry));

  }

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

  i = pq->len - 1;

  while (i > 0) {

    int j = (i - 1) / 2;

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

      break;

    }

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

    i = j;

  }

}

void merged_iter_pqueue_clear(struct merged_iter_pqueue *pq)

{

  int i = 0;

  for (i = 0; i < pq->len; i++) {

    record_destroy(&pq->heap[i].rec);

  }

  FREE_AND_NULL(pq->heap);

  pq->len = pq->cap = 0;

}