/*
 * This file is part of GNUnet
 * Copyright (C) 2009-2015 GNUnet e.V.
 *
 * GNUnet is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Affero General Public License as published
 * by the Free Software Foundation, either version 3 of the License,
 * or (at your option) any later version.
 *
 * GNUnet 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
 * Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

    SPDX-License-Identifier: AGPL3.0-or-later
 */

/**
 * @file namecache/plugin_namecache_flat.c
 * @brief flat file-based namecache backend
 * @author Martin Schanzenbach
 */

#include "platform.h"
#include "gnunet_namecache_plugin.h"
#include "gnunet_namecache_service.h"
#include "gnunet_gnsrecord_lib.h"
#include "namecache.h"

/**
 * Context for all functions in this plugin.
 */
struct Plugin
{
  const struct GNUNET_CONFIGURATION_Handle *cfg;

  /**
   * Database filename.
   */
  char *fn;

  /**
   * HashMap
   */
  struct GNUNET_CONTAINER_MultiHashMap *hm;
};

struct FlatFileEntry
{
  /**
   * Block
   */
  struct GNUNET_GNSRECORD_Block *block;

  /**
   * query
   */
  struct GNUNET_HashCode query;
};

/**
 * Initialize the database connections and associated
 * data structures (create tables and indices
 * as needed as well).
 *
 * @param plugin the plugin context (state for this module)
 * @return #GNUNET_OK on success
 */
static int
database_setup (struct Plugin *plugin)
{
  char *afsdir;
  char*block_buffer;
  char*buffer;
  char*line;
  char*query;
  char*block;
  uint64_t size;
  struct FlatFileEntry *entry;
  struct GNUNET_DISK_FileHandle *fh;

  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_filename (plugin->cfg,
                                               "namecache-flat",
                                               "FILENAME",
                                               &afsdir))
  {
    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                               "namecache-flat", "FILENAME");
    return GNUNET_SYSERR;
  }
  if (GNUNET_OK != GNUNET_DISK_file_test (afsdir))
  {
    if (GNUNET_OK != GNUNET_DISK_directory_create_for_file (afsdir))
    {
      GNUNET_break (0);
      GNUNET_free (afsdir);
      return GNUNET_SYSERR;
    }
  }
  /* afsdir should be UTF-8-encoded. If it isn't, it's a bug */
  plugin->fn = afsdir;

  /* Load data from file into hashmap */
  plugin->hm = GNUNET_CONTAINER_multihashmap_create (10,
                                                     GNUNET_NO);
  fh = GNUNET_DISK_file_open (afsdir,
                              GNUNET_DISK_OPEN_CREATE
                              | GNUNET_DISK_OPEN_READWRITE,
                              GNUNET_DISK_PERM_USER_WRITE
                              | GNUNET_DISK_PERM_USER_READ);
  if (NULL == fh)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("Unable to initialize file: %s.\n"),
                afsdir);
    return GNUNET_SYSERR;
  }

  if (GNUNET_SYSERR == GNUNET_DISK_file_size (afsdir,
                                              &size,
                                              GNUNET_YES,
                                              GNUNET_YES))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("Unable to get filesize: %s.\n"),
                afsdir);
    GNUNET_DISK_file_close (fh);
    return GNUNET_SYSERR;
  }

  if (0 == size)
  {
    GNUNET_DISK_file_close (fh);
    return GNUNET_OK;
  }

  buffer = GNUNET_malloc (size + 1);

  if (GNUNET_SYSERR == GNUNET_DISK_file_read (fh,
                                              buffer,
                                              size))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("Unable to read file: %s.\n"),
                afsdir);
    GNUNET_free (buffer);
    GNUNET_DISK_file_close (fh);
    return GNUNET_SYSERR;
  }
  buffer[size] = '\0';

  GNUNET_DISK_file_close (fh);
  if (0 < size)
  {
    line = strtok (buffer, "\n");
    while (line != NULL)
    {
      query = strtok (line, ",");
      if (NULL == query)
        break;
      block = strtok (NULL, ",");
      if (NULL == block)
        break;
      line = strtok (NULL, "\n");
      entry = GNUNET_malloc (sizeof(struct FlatFileEntry));
      GNUNET_assert (GNUNET_OK == GNUNET_CRYPTO_hash_from_string (query,
                                                                  &entry->query));
      GNUNET_STRINGS_base64_decode (block,
                                    strlen (block),
                                    (void **) &block_buffer);
      entry->block = (struct GNUNET_GNSRECORD_Block *) block_buffer;
      if (GNUNET_OK !=
          GNUNET_CONTAINER_multihashmap_put (plugin->hm,
                                             &entry->query,
                                             entry,
                                             GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
      {
        GNUNET_free (entry);
        GNUNET_break (0);
      }
    }
  }
  GNUNET_free (buffer);
  return GNUNET_OK;
}


/**
 * Store values in hashmap in file and free data
 *
 * @param plugin the plugin context
 */
static int
store_and_free_entries (void *cls,
                        const struct GNUNET_HashCode *key,
                        void *value)
{
  struct GNUNET_DISK_FileHandle *fh = cls;
  struct FlatFileEntry *entry = value;

  char *line;
  char *block_b64;
  struct GNUNET_CRYPTO_HashAsciiEncoded query;
  size_t block_size;

  block_size = GNUNET_GNSRECORD_block_get_size (entry->block);
  GNUNET_STRINGS_base64_encode ((char *) entry->block,
                                block_size,
                                &block_b64);
  GNUNET_CRYPTO_hash_to_enc (&entry->query,
                             &query);
  GNUNET_asprintf (&line,
                   "%s,%s\n",
                   (char *) &query,
                   block_b64);

  GNUNET_free (block_b64);

  GNUNET_DISK_file_write (fh,
                          line,
                          strlen (line));

  GNUNET_free (entry->block);
  GNUNET_free (entry);
  GNUNET_free (line);
  return GNUNET_YES;
}


/**
 * Shutdown database connection and associate data
 * structures.
 * @param plugin the plugin context (state for this module)
 */
static void
database_shutdown (struct Plugin *plugin)
{
  struct GNUNET_DISK_FileHandle *fh;

  fh = GNUNET_DISK_file_open (plugin->fn,
                              GNUNET_DISK_OPEN_CREATE
                              | GNUNET_DISK_OPEN_TRUNCATE
                              | GNUNET_DISK_OPEN_READWRITE,
                              GNUNET_DISK_PERM_USER_WRITE
                              | GNUNET_DISK_PERM_USER_READ);
  if (NULL == fh)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("Unable to initialize file: %s.\n"),
                plugin->fn);
    return;
  }

  GNUNET_CONTAINER_multihashmap_iterate (plugin->hm,
                                         &store_and_free_entries,
                                         fh);
  GNUNET_CONTAINER_multihashmap_destroy (plugin->hm);
  GNUNET_DISK_file_close (fh);
}


static int
expire_blocks (void *cls,
               const struct GNUNET_HashCode *key,
               void *value)
{
  struct Plugin *plugin = cls;
  struct FlatFileEntry *entry = value;
  struct GNUNET_TIME_Absolute now;
  struct GNUNET_TIME_Absolute expiration;

  now = GNUNET_TIME_absolute_get ();
  expiration = GNUNET_GNSRECORD_block_get_expiration (entry->block);

  if (0 == GNUNET_TIME_absolute_get_difference (now,
                                                expiration).rel_value_us)
  {
    GNUNET_CONTAINER_multihashmap_remove_all (plugin->hm, key);
  }
  return GNUNET_YES;
}


/**
 * Removes any expired block.
 *
 * @param plugin the plugin
 */
static void
namecache_expire_blocks (struct Plugin *plugin)
{
  GNUNET_CONTAINER_multihashmap_iterate (plugin->hm,
                                         &expire_blocks,
                                         plugin);
}


/**
 * Cache a block in the datastore.
 *
 * @param cls closure (internal context for the plugin)
 * @param block block to cache
 * @return #GNUNET_OK on success, else #GNUNET_SYSERR
 */
static int
namecache_cache_block (void *cls,
                       const struct GNUNET_GNSRECORD_Block *block)
{
  struct Plugin *plugin = cls;
  struct GNUNET_HashCode query;
  struct FlatFileEntry *entry;
  size_t block_size;

  namecache_expire_blocks (plugin);
  GNUNET_GNSRECORD_query_from_block (block,
                                     &query);
  block_size = GNUNET_GNSRECORD_block_get_size (block);
  if (block_size > 64 * 65536)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  entry = GNUNET_malloc (sizeof(struct FlatFileEntry));
  entry->block = GNUNET_malloc (block_size);
  GNUNET_memcpy (entry->block, block, block_size);
  GNUNET_CONTAINER_multihashmap_remove_all (plugin->hm, &query);
  if (GNUNET_OK !=
      GNUNET_CONTAINER_multihashmap_put (plugin->hm,
                                         &query,
                                         entry,
                                         GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
  {
    GNUNET_free (entry);
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Caching block under derived key `%s'\n",
              GNUNET_h2s_full (&query));
  return GNUNET_OK;
}


/**
 * Get the block for a particular zone and label in the
 * datastore.  Will return at most one result to the iterator.
 *
 * @param cls closure (internal context for the plugin)
 * @param query hash of public key derived from the zone and the label
 * @param iter function to call with the result
 * @param iter_cls closure for @a iter
 * @return #GNUNET_OK on success, #GNUNET_NO if there were no results, #GNUNET_SYSERR on error
 */
static int
namecache_lookup_block (void *cls,
                        const struct GNUNET_HashCode *query,
                        GNUNET_NAMECACHE_BlockCallback iter, void *iter_cls)
{
  struct Plugin *plugin = cls;
  const struct GNUNET_GNSRECORD_Block *block;

  block = GNUNET_CONTAINER_multihashmap_get (plugin->hm, query);
  if (NULL == block)
    return GNUNET_NO;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Found block under derived key `%s'\n",
              GNUNET_h2s_full (query));
  iter (iter_cls, block);
  return GNUNET_YES;
}


/**
 * Entry point for the plugin.
 *
 * @param cls the "struct GNUNET_NAMECACHE_PluginEnvironment*"
 * @return NULL on error, otherwise the plugin context
 */
void *
libgnunet_plugin_namecache_flat_init (void *cls)
{
  static struct Plugin plugin;
  const struct GNUNET_CONFIGURATION_Handle *cfg = cls;
  struct GNUNET_NAMECACHE_PluginFunctions *api;

  if (NULL != plugin.cfg)
    return NULL;                /* can only initialize once! */
  memset (&plugin, 0, sizeof(struct Plugin));
  plugin.cfg = cfg;
  if (GNUNET_OK != database_setup (&plugin))
  {
    database_shutdown (&plugin);
    return NULL;
  }
  api = GNUNET_new (struct GNUNET_NAMECACHE_PluginFunctions);
  api->cls = &plugin;
  api->cache_block = &namecache_cache_block;
  api->lookup_block = &namecache_lookup_block;
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              _ ("flat plugin running\n"));
  return api;
}


/**
 * Exit point from the plugin.
 *
 * @param cls the plugin context (as returned by "init")
 * @return always NULL
 */
void *
libgnunet_plugin_namecache_flat_done (void *cls)
{
  struct GNUNET_NAMECACHE_PluginFunctions *api = cls;
  struct Plugin *plugin = api->cls;

  database_shutdown (plugin);
  plugin->cfg = NULL;
  GNUNET_free (api);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "flat plugin is finished\n");
  return NULL;
}


/* end of plugin_namecache_sqlite.c */
