/*
     This file is part of GNUnet
     Copyright (C) 2017, 2021 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 consensus/plugin_block_consensus.c
 * @brief consensus block, either nested block or marker
 * @author Christian Grothoff
 */

#include "platform.h"
#include "consensus_protocol.h"
#include "gnunet_block_plugin.h"
#include "gnunet_block_group_lib.h"


/**
 * Our closure.
 */
struct BlockContext
{
  /**
   * Configuration to use.
   */
  const struct GNUNET_CONFIGURATION_Handle *cfg;

  /**
   * Lazily initialized block context.
   */
  struct GNUNET_BLOCK_Context *bc;
};


/**
 * Function called to validate a reply or a request.  For
 * request evaluation, simply pass "NULL" for the reply_block.
 *
 * @param cls closure
 * @param ctx context
 * @param type block type
 * @param group block group to use
 * @param eo control flags
 * @param query original query (hash)
 * @param xquery extrended query data (can be NULL, depending on type)
 * @param xquery_size number of bytes in xquery
 * @param reply_block response to validate
 * @param reply_block_size number of bytes in reply block
 * @return characterization of result
 */
static enum GNUNET_BLOCK_EvaluationResult
block_plugin_consensus_evaluate (void *cls,
                                 struct GNUNET_BLOCK_Context *ctx,
                                 enum GNUNET_BLOCK_Type type,
                                 struct GNUNET_BLOCK_Group *group,
                                 enum GNUNET_BLOCK_EvaluationOptions eo,
                                 const struct GNUNET_HashCode *query,
                                 const void *xquery,
                                 size_t xquery_size,
                                 const void *reply_block,
                                 size_t reply_block_size)
{
  struct BlockContext *bctx = cls;
  const struct ConsensusElement *ce = reply_block;

  if (reply_block_size < sizeof(struct ConsensusElement))
    return GNUNET_BLOCK_EVALUATION_RESULT_INVALID;
  if ( (0 != ce->marker) ||
       (0 == ce->payload_type) )
    return GNUNET_BLOCK_EVALUATION_OK_MORE;

  if (NULL == bctx->bc)
    bctx->bc = GNUNET_BLOCK_context_create (bctx->cfg);
  return GNUNET_BLOCK_evaluate (bctx->bc,
                                type,
                                group,
                                eo,
                                query,
                                xquery,
                                xquery_size,
                                &ce[1],
                                reply_block_size
                                - sizeof(struct ConsensusElement));
}


/**
 * Function called to validate a query.
 *
 * @param cls closure
 * @param ctx block context
 * @param type block type
 * @param query original query (hash)
 * @param xquery extrended query data (can be NULL, depending on type)
 * @param xquery_size number of bytes in @a xquery
 * @return #GNUNET_OK if the query is fine, #GNUNET_NO if not
 */
static enum GNUNET_GenericReturnValue
block_plugin_consensus_check_query (void *cls,
                                    enum GNUNET_BLOCK_Type type,
                                    const struct GNUNET_HashCode *query,
                                    const void *xquery,
                                    size_t xquery_size)
{
  /* consensus does not use queries/DHT */
  GNUNET_break (0);
  return GNUNET_SYSERR;
}


/**
 * Function called to validate a block for storage.
 *
 * @param cls closure
 * @param type block type
 * @param query key for the block (hash), must match exactly
 * @param block block data to validate
 * @param block_size number of bytes in @a block
 * @return #GNUNET_OK if the block is fine, #GNUNET_NO if not
 */
static enum GNUNET_GenericReturnValue
block_plugin_consensus_check_block (void *cls,
                                    enum GNUNET_BLOCK_Type type,
                                    const struct GNUNET_HashCode *query,
                                    const void *block,
                                    size_t block_size)
{
  struct BlockContext *ctx = cls;
  const struct ConsensusElement *ce = block;

  if (block_size < sizeof(*ce))
    return GNUNET_NO;
  if ( (0 != ce->marker) ||
       (0 == ce->payload_type) )
    return GNUNET_OK;
  if (NULL == ctx->bc)
    ctx->bc = GNUNET_BLOCK_context_create (ctx->cfg);
  return GNUNET_BLOCK_check_block (ctx->bc,
                                   ntohl (ce->payload_type),
                                   query,
                                   &ce[1],
                                   block_size - sizeof(*ce));
}


/**
 * Function called to validate a reply to a request.  Note that it is assumed
 * that the reply has already been matched to the key (and signatures checked)
 * as it would be done with the GetKeyFunction and the
 * BlockEvaluationFunction.
 *
 * @param cls closure
 * @param type block type
 * @param group which block group to use for evaluation
 * @param query original query (hash)
 * @param xquery extrended query data (can be NULL, depending on type)
 * @param xquery_size number of bytes in @a xquery
 * @param reply_block response to validate
 * @param reply_block_size number of bytes in @a reply_block
 * @return characterization of result
 */
static enum GNUNET_BLOCK_ReplyEvaluationResult
block_plugin_consensus_check_reply (
  void *cls,
  enum GNUNET_BLOCK_Type type,
  struct GNUNET_BLOCK_Group *group,
  const struct GNUNET_HashCode *query,
  const void *xquery,
  size_t xquery_size,
  const void *reply_block,
  size_t reply_block_size)
{
  struct BlockContext *ctx = cls;
  const struct ConsensusElement *ce = reply_block;

  if (reply_block_size < sizeof(struct ConsensusElement))
    return GNUNET_NO;
  if ( (0 != ce->marker) ||
       (0 == ce->payload_type) )
    return GNUNET_BLOCK_REPLY_OK_MORE;
  if (NULL == ctx->bc)
    ctx->bc = GNUNET_BLOCK_context_create (ctx->cfg);
  return GNUNET_BLOCK_check_reply (ctx->bc,
                                   ntohl (ce->payload_type),
                                   group,
                                   query,
                                   xquery,
                                   xquery_size,
                                   &ce[1],
                                   reply_block_size - sizeof(*ce));
}


/**
 * Function called to obtain the key for a block.
 *
 * @param cls closure
 * @param type block type
 * @param block block to get the key for
 * @param block_size number of bytes in block
 * @param key set to the key (query) for the given block
 * @return #GNUNET_OK on success, #GNUNET_SYSERR if type not supported
 *         (or if extracting a key from a block of this type does not work)
 */
static enum GNUNET_GenericReturnValue
block_plugin_consensus_get_key (void *cls,
                                enum GNUNET_BLOCK_Type type,
                                const void *block,
                                size_t block_size,
                                struct GNUNET_HashCode *key)
{
  return GNUNET_SYSERR;
}


/**
 * Entry point for the plugin.
 */
void *
libgnunet_plugin_block_consensus_init (void *cls)
{
  static const enum GNUNET_BLOCK_Type types[] = {
    GNUNET_BLOCK_TYPE_CONSENSUS_ELEMENT,
    GNUNET_BLOCK_TYPE_ANY       /* end of list */
  };
  const struct GNUNET_CONFIGURATION_Handle *cfg = cls;
  struct BlockContext *ctx;
  struct GNUNET_BLOCK_PluginFunctions *api;

  ctx = GNUNET_new (struct BlockContext);
  ctx->cfg = cfg;
  api = GNUNET_new (struct GNUNET_BLOCK_PluginFunctions);
  api->cls = ctx;
  api->evaluate = &block_plugin_consensus_evaluate;
  api->get_key = &block_plugin_consensus_get_key;
  api->check_query = &block_plugin_consensus_check_query;
  api->check_block = &block_plugin_consensus_check_block;
  api->check_reply = &block_plugin_consensus_check_reply;
  api->types = types;
  return api;
}


/**
 * Exit point from the plugin.
 */
void *
libgnunet_plugin_block_consensus_done (void *cls)
{
  struct GNUNET_BLOCK_PluginFunctions *api = cls;
  struct BlockContext *ctx = api->cls;

  if (NULL != ctx->bc)
    GNUNET_BLOCK_context_destroy (ctx->bc);
  GNUNET_free (ctx);
  GNUNET_free (api);
  return NULL;
}


/* end of plugin_block_consensus.c */