/*
 * eset_rtp (ESET Real-time file system protection module)
 * Copyright (C) 1992-2023 ESET, spol. s r.o.
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * In case of any questions, you can contact us at ESET, spol. s r.o., Einsteinova 24, 851 01 Bratislava, Slovakia.
 */

#include "ertp_cache_container.h"
#include "ertp_logs.h"

#include <linux/slab.h>

static struct kmem_cache *ertp_cache_allocator = NULL;

int ertp_cache_item_allocator_init(void) {
  ertp_cache_allocator = kmem_cache_create(
      "ertp_cache_allocator", sizeof(struct ertp_cache_item),
      __alignof__(struct ertp_cache_item), SLAB_RECLAIM_ACCOUNT, NULL);

  if (!ertp_cache_allocator) {
    return -ENOMEM;
  }

  return 0;
}

void ertp_cache_item_allocator_deinit(void) {
  kmem_cache_destroy(ertp_cache_allocator);
}

static struct ertp_cache_item *ertp_cache_item_new(struct ertp_cache_key key,
                                                   ertp_timespec_t ctime,
                                                   unsigned type) {
  struct ertp_cache_item *item =
      kmem_cache_zalloc(ertp_cache_allocator, GFP_KERNEL);
  if (!item) {
    return ERR_PTR(-ENOMEM);
  }

  INIT_LIST_HEAD(&item->time_list);

  item->key = key;
  item->ctime = ctime;
  item->event_type = type;
  return item;
}

static void ertp_cache_item_free(struct ertp_cache_item *item) {
  kmem_cache_free(ertp_cache_allocator, item);
}

static inline int ertp_cache_key_cmp(const struct ertp_cache_key *key1,
                                     const struct ertp_cache_key *key2) {
  if (key1->ino < key2->ino) {
    return -1;
  }

  if (key1->ino > key2->ino) {
    return 1;
  }

  if (key1->dev < key2->dev) {
    return -1;
  }

  if (key1->dev > key2->dev) {
    return 1;
  }

  return 0;
}

struct ertp_cache_item *ertp_cache_container_find(
    struct rb_root *root, const struct ertp_cache_key *key,
    struct rb_node **parent) {
  struct rb_node *p = NULL;
  struct rb_node *node = root->rb_node;
  struct ertp_cache_item *result = NULL;

  while (node) {
    struct rb_node *child;
    struct ertp_cache_item *entry =
        rb_entry(node, struct ertp_cache_item, node);
    int cmp = ertp_cache_key_cmp(key, &entry->key);

    if (cmp < 0) {
      child = node->rb_left;
    } else if (cmp > 0) {
      child = node->rb_right;
    } else {
      result = entry;
      break;
    }

    p = node;
    node = child;
  }

  if (parent) {
    *parent = p;
  }

  return result;
}

static void ertp_cache_container_insert(struct rb_root *root,
                                        struct ertp_cache_item *item,
                                        struct rb_node *parent) {
  struct rb_node **link;

  if (RB_EMPTY_ROOT(root)) {
    link = &root->rb_node;
  } else {
    struct ertp_cache_item *parent_entry;
    int cmp;

    if (unlikely(parent == NULL)) {
      BUG();
    }

    parent_entry = rb_entry(parent, struct ertp_cache_item, node);
    cmp = ertp_cache_key_cmp(&item->key, &parent_entry->key);

    if (cmp < 0) {
      link = &parent->rb_left;
    } else if (cmp > 0) {
      link = &parent->rb_right;
    } else {
      BUG();
    }
  }

  rb_link_node(&item->node, parent, link);
  rb_insert_color(&item->node, root);
}

struct ertp_cache_item *ertp_cache_container_add(
    struct rb_root *root, const struct ertp_cache_key *key,
    ertp_timespec_t ctime, unsigned type) {
  struct rb_node *parent = NULL;

  struct ertp_cache_item *item = ertp_cache_container_find(root, key, &parent);
  if (item) {
    if (ertp_timespec_equal(item->ctime, ctime)) {
      item->event_type |= type;
    } else {
      item->ctime = ctime;
      item->event_type = type;
    }
  } else {
    item = ertp_cache_item_new(*key, ctime, type);
    if (unlikely(IS_ERR(item))) {
      return NULL;
    }
    ertp_cache_container_insert(root, item, parent);
  }

  return item;
}

void ertp_cache_container_erase(struct rb_root *root,
                                struct ertp_cache_item *item) {
  rb_erase(&item->node, root);
  ertp_cache_item_free(item);
}

void ertp_cache_container_clear(struct rb_root *root) {
  struct ertp_cache_item *item;
  struct ertp_cache_item *tmp;

  rbtree_postorder_for_each_entry_safe(item, tmp, root, node) {
    ertp_pr_log(ERTP_LOG_CACHE,
                "deleting item from cache with ino %lld and dev %lld",
                item->key.ino, item->key.dev);
    ertp_cache_item_free(item);
  }
}