/*
     This file is part of GNUnet.
     Copyright (C) 2009, 2010, 2011, 2015, 2017, 2022 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 dht/gnunet-service-dht_datacache.c
 * @brief GNUnet DHT service's datacache integration
 * @author Christian Grothoff
 * @author Nathan Evans
 */
#include "platform.h"
#include "gnunet_datacache_lib.h"
#include "gnunet-service-dht_datacache.h"
#include "gnunet-service-dht_neighbours.h"
#include "gnunet-service-dht_routing.h"
#include "gnunet-service-dht.h"

#define LOG(kind, ...) GNUNET_log_from (kind, "dht-dhtcache", __VA_ARGS__)

/**
 * How many "closest" results to we return for migration when
 * asked (at most)?
 */
#define NUM_CLOSEST 42


/**
 * Handle to the datacache service (for inserting/retrieving data)
 */
static struct GNUNET_DATACACHE_Handle *datacache;


void
GDS_DATACACHE_handle_put (const struct GDS_DATACACHE_BlockData *bd)
{
  struct GNUNET_HashCode xor;
  enum GNUNET_GenericReturnValue r;

  if (NULL == datacache)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "PUT request received, but have no datacache!\n");
    return;
  }
  if (bd->data_size >= GNUNET_MAX_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    return;
  }
  /* Put size is actual data size plus struct overhead plus path length (if any) */
  GNUNET_STATISTICS_update (GDS_stats,
                            "# ITEMS stored in datacache",
                            1,
                            GNUNET_NO);
  GNUNET_CRYPTO_hash_xor (&bd->key,
                          &my_identity_hash,
                          &xor);
  r = GNUNET_DATACACHE_put (datacache,
                            &bd->key,
                            GNUNET_CRYPTO_hash_count_leading_zeros (&xor),
                            bd->data_size,
                            bd->data,
                            bd->type,
                            bd->expiration_time,
                            bd->put_path_length,
                            bd->put_path);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "DATACACHE PUT for key %s [%lu] completed (%d) after %u hops\n",
       GNUNET_h2s (&bd->key),
       (unsigned long) bd->data_size,
       r,
       bd->put_path_length);
}


/**
 * Context containing information about a GET request.
 */
struct GetRequestContext
{
  /**
   * extended query (see gnunet_block_lib.h).
   */
  const void *xquery;

  /**
   * The key this request was about
   */
  struct GNUNET_HashCode key;

  /**
   * Block group to use to evaluate replies (updated)
   */
  struct GNUNET_BLOCK_Group *bg;

  /**
   * Function to call on results.
   */
  GDS_DATACACHE_GetCallback gc;

  /**
   * Closure for @e gc.
   */
  void *gc_cls;

  /**
   * Number of bytes in xquery.
   */
  size_t xquery_size;

  /**
   * Return value to give back.
   */
  enum GNUNET_BLOCK_EvaluationResult eval;
};


/**
 * Iterator for local get request results,
 *
 * @param cls closure for iterator, a `struct GetRequestContext`
 * @param exp when does this value expire?
 * @param key the key this data is stored under
 * @param data_size the size of the data identified by key
 * @param data the actual data
 * @param type the type of the @a data
 * @param put_path_length number of peers in @a put_path
 * @param put_path path the reply took on put
 * @return #GNUNET_OK to continue iteration, anything else
 * to stop iteration.
 */
static enum GNUNET_GenericReturnValue
datacache_get_iterator (void *cls,
                        const struct GNUNET_HashCode *key,
                        size_t data_size,
                        const char *data,
                        enum GNUNET_BLOCK_Type type,
                        struct GNUNET_TIME_Absolute exp,
                        unsigned int put_path_length,
                        const struct GNUNET_DHT_PathElement *put_path)
{
  struct GetRequestContext *ctx = cls;
  enum GNUNET_BLOCK_ReplyEvaluationResult eval;
  struct GDS_DATACACHE_BlockData bd = {
    .key = *key,
    .expiration_time = exp,
    .put_path = put_path,
    .data = data,
    .data_size = data_size,
    .put_path_length = put_path_length,
    .type = type
  };

  if (GNUNET_TIME_absolute_is_past (exp))
  {
    GNUNET_break (0);  /* why does datacache return expired values? */
    return GNUNET_OK;   /* skip expired record */
  }
  eval
    = GNUNET_BLOCK_check_reply (GDS_block_context,
                                bd.type,
                                ctx->bg,
                                &bd.key,
                                ctx->xquery,
                                ctx->xquery_size,
                                bd.data,
                                bd.data_size);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Evaluated reply for query %s in datacache, result is %d\n",
       GNUNET_h2s (key),
       (int) eval);
  ctx->eval = eval;
  switch (eval)
  {
  case GNUNET_BLOCK_REPLY_OK_MORE:
  case GNUNET_BLOCK_REPLY_OK_LAST:
  case GNUNET_BLOCK_REPLY_TYPE_NOT_SUPPORTED:
    /* forward to initiator */
    GNUNET_STATISTICS_update (GDS_stats,
                              "# Good RESULTS found in datacache",
                              1,
                              GNUNET_NO);
    ctx->gc (ctx->gc_cls,
             &bd);
    break;
  case GNUNET_BLOCK_REPLY_OK_DUPLICATE:
    GNUNET_STATISTICS_update (GDS_stats,
                              "# Duplicate RESULTS found in datacache",
                              1,
                              GNUNET_NO);
    break;
  case GNUNET_BLOCK_REPLY_INVALID:
    /* maybe it expired? */
    GNUNET_STATISTICS_update (GDS_stats,
                              "# Invalid RESULTS found in datacache",
                              1,
                              GNUNET_NO);
    break;
  case GNUNET_BLOCK_REPLY_IRRELEVANT:
    GNUNET_STATISTICS_update (GDS_stats,
                              "# Irrelevant RESULTS found in datacache",
                              1,
                              GNUNET_NO);
    break;
  }
  return (eval == GNUNET_BLOCK_REPLY_OK_LAST) ? GNUNET_NO : GNUNET_OK;
}


enum GNUNET_BLOCK_EvaluationResult
GDS_DATACACHE_handle_get (const struct GNUNET_HashCode *key,
                          enum GNUNET_BLOCK_Type type,
                          const void *xquery,
                          size_t xquery_size,
                          struct GNUNET_BLOCK_Group *bg,
                          GDS_DATACACHE_GetCallback gc,
                          void *gc_cls)
{
  struct GetRequestContext ctx;
  unsigned int r;

  if (NULL == datacache)
    return GNUNET_BLOCK_EVALUATION_REQUEST_VALID;
  GNUNET_STATISTICS_update (GDS_stats,
                            "# GET requests given to datacache",
                            1,
                            GNUNET_NO);
  ctx.eval = GNUNET_BLOCK_EVALUATION_REQUEST_VALID;
  ctx.key = *key;
  ctx.xquery = xquery;
  ctx.xquery_size = xquery_size;
  ctx.bg = bg;
  ctx.gc = gc;
  ctx.gc_cls = gc_cls;
  r = GNUNET_DATACACHE_get (datacache,
                            key,
                            type,
                            &datacache_get_iterator,
                            &ctx);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "DATACACHE GET for key %s completed (%d). %u results found.\n",
       GNUNET_h2s (key),
       ctx.eval,
       r);
  return ctx.eval;
}


/**
 * Closure for #datacache_get_successors_iterator().
 */
struct SuccContext
{
  /**
   * Function to call on the result
   */
  GDS_DATACACHE_GetCallback cb;

  /**
   * Closure for @e cb.
   */
  void *cb_cls;

};


/**
 * Iterator for local get request results,
 *
 * @param cls closure with the `struct GNUNET_HashCode *` with the trail ID
 * @param key the key this data is stored under
 * @param size the size of the data identified by key
 * @param data the actual data
 * @param type the type of the data
 * @param exp when does this value expire?
 * @param put_path_length number of peers in @a put_path
 * @param put_path path the reply took on put
 * @return #GNUNET_OK to continue iteration, anything else
 * to stop iteration.
 */
static enum GNUNET_GenericReturnValue
datacache_get_successors_iterator (void *cls,
                                   const struct GNUNET_HashCode *key,
                                   size_t size,
                                   const char *data,
                                   enum GNUNET_BLOCK_Type type,
                                   struct GNUNET_TIME_Absolute exp,
                                   unsigned int put_path_length,
                                   const struct
                                   GNUNET_DHT_PathElement *put_path)
{
  const struct SuccContext *sc = cls;
  struct GDS_DATACACHE_BlockData bd = {
    .key = *key,
    .expiration_time = exp,
    .put_path = put_path,
    .data = data,
    .data_size = size,
    .put_path_length = put_path_length,
    .type = type
  };

  /* NOTE: The datacache currently does not store the RO from
     the original 'put', so we don't know the 'correct' option
     at this point anymore.  Thus, we conservatively assume
     that recording is desired (for now). */
  sc->cb (sc->cb_cls,
          &bd);
  return GNUNET_OK;
}


void
GDS_DATACACHE_get_closest (const struct GNUNET_HashCode *key,
                           GDS_DATACACHE_GetCallback cb,
                           void *cb_cls)
{
  struct SuccContext sc = {
    .cb = cb,
    .cb_cls = cb_cls
  };

  (void) GNUNET_DATACACHE_get_closest (datacache,
                                       key,
                                       NUM_CLOSEST,
                                       &datacache_get_successors_iterator,
                                       &sc);
}


void
GDS_DATACACHE_init ()
{
  datacache = GNUNET_DATACACHE_create (GDS_cfg,
                                       "dhtcache");
}


void
GDS_DATACACHE_done ()
{
  if (NULL != datacache)
  {
    GNUNET_DATACACHE_destroy (datacache);
    datacache = NULL;
  }
}


/* end of gnunet-service-dht_datacache.c */