/*
     This file is part of GNUnet.
     Copyright (C) 2009-2013, 2016, 2018 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 gns/gns_tld_api.c
 * @brief library to access the GNS service, including TLD lookup
 * @author Martin Schanzenbach
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_constants.h"
#include "gnunet_arm_service.h"
#include "gnunet_identity_service.h"
#include "gnunet_hello_lib.h"
#include "gnunet_protocols.h"
#include "gnunet_dht_service.h"
#include "gns.h"
#include "gns_api.h"


#define LOG(kind, ...) GNUNET_log_from (kind, "gns-tld-api", __VA_ARGS__)


/**
 * Handle to a lookup request
 */
struct GNUNET_GNS_LookupWithTldRequest
{

  /**
   * handle to gns
   */
  struct GNUNET_GNS_Handle *gns_handle;

  /**
   * processor to call on lookup result
   */
  GNUNET_GNS_LookupResultProcessor2 lookup_proc;

  /**
   * Domain name we are resolving.
   */
  char *name;

  /**
   * @e lookup_proc closure
   */
  void *lookup_proc_cls;

  /**
   * Underlying GNS lookup.
   */
  struct GNUNET_GNS_LookupRequest *lr;

  /**
   * Lookup an ego with the identity service.
   */
  struct GNUNET_IDENTITY_Handle *id_co;

  /**
   * Name of the longest matching ego found so far.
   * Must be freed on termination.
   */
  char *longest_match;

  /**
   * Ego corresponding to @e longest_match.
   */
  struct GNUNET_IDENTITY_Ego *longest_match_ego;

  /**
   * Desired result record type.
   */
  uint32_t type;

  /**
   * Lookup options.
   */
  enum GNUNET_GNS_LocalOptions options;
};


/**
 * Obtain the TLD of the given @a name.
 *
 * @param name a name
 * @return the part of @a name after the last ".",
 *         or @a name if @a name does not contain a "."
 */
static const char *
get_tld (const char *name)
{
  const char *tld;

  tld = strrchr (name, (unsigned char) '.');
  if (NULL == tld)
    tld = name;
  else
    tld++; /* skip the '.' */
  return tld;
}


/**
 * Eat the "TLD" (last bit) of the given @a name.
 *
 * @param[in,out] name a name
 * @param tld what to eat (can be more than just the tld)
 */
static void
eat_tld (char *name, const char *tld)
{
  GNUNET_assert (0 < strlen (name));
  if ((NULL == tld) || (strlen (name) == strlen (tld)))
  {
    strcpy (name, GNUNET_GNS_EMPTY_LABEL_AT);
  }
  else
  {
    GNUNET_assert (strlen (tld) < strlen (name));
    name[strlen (name) - strlen (tld) - 1] = '\0';
  }
}


/**
 * Function called with the result of a GNS lookup.
 *
 * @param cls a `struct GNUNET_GNS_LookupWithTldRequest *`
 * @param rd_count number of records returned
 * @param rd array of @a rd_count records with the results
 */
static void
process_lookup_result (void *cls,
                       uint32_t rd_count,
                       const struct GNUNET_GNSRECORD_Data *rd)
{
  struct GNUNET_GNS_LookupWithTldRequest *ltr = cls;

  ltr->lr = NULL;
  ltr->lookup_proc (ltr->lookup_proc_cls, GNUNET_YES, rd_count, rd);
  GNUNET_GNS_lookup_with_tld_cancel (ltr);
}


/**
 * Perform the actual resolution, starting with the zone
 * identified by the given public key.
 *
 * @param pkey public key to use for the zone, can be NULL
 */
static void
lookup_with_public_key (struct GNUNET_GNS_LookupWithTldRequest *ltr,
                        const struct GNUNET_CRYPTO_EcdsaPublicKey *pkey)
{
  ltr->lr = GNUNET_GNS_lookup (ltr->gns_handle,
                               ltr->name,
                               pkey,
                               ltr->type,
                               ltr->options,
                               &process_lookup_result,
                               ltr);
}


/**
 * Method called to with the ego we are to use for the lookup,
 * when the ego is determined by a name.
 *
 * @param cls a `struct GNUNET_GNS_LookupWithTldRequest *`
 * @param ego ego handle, NULL at the end of the iteration
 * @param ctx context we could store data to associate with @e ego
 * @param name name of the ego
 */
static void
identity_zone_cb (void *cls,
                  struct GNUNET_IDENTITY_Ego *ego,
                  void **ctx,
                  const char *name)
{
  struct GNUNET_GNS_LookupWithTldRequest *ltr = cls;
  struct GNUNET_CRYPTO_EcdsaPublicKey pkey;

  if (NULL == ego)
  {
    if (NULL != ltr->longest_match)
    {
      /* Final case: TLD matches one of our egos */
      // FIXME: eat all of the match (not just TLD!)
      if (0 == strcmp (ltr->name, ltr->longest_match))
      {
        /* name matches ego name perfectly, only "@" remains */
        strcpy (ltr->name, GNUNET_GNS_EMPTY_LABEL_AT);
      }
      else
      {
        GNUNET_assert (strlen (ltr->longest_match) < strlen (ltr->name));
        ltr->name[strlen (ltr->name) - strlen (ltr->longest_match) - 1] = '\0';
      }

      /* if the name is of the form 'label' (and not 'label.SUBDOMAIN'), never go to the DHT */
      GNUNET_free (ltr->longest_match);
      ltr->longest_match = NULL;
      if (NULL == strchr (ltr->name, (unsigned char) '.'))
        ltr->options = GNUNET_GNS_LO_NO_DHT;
      else
        ltr->options = GNUNET_GNS_LO_LOCAL_MASTER;

      GNUNET_IDENTITY_ego_get_public_key (ltr->longest_match_ego, &pkey);
      GNUNET_IDENTITY_disconnect (ltr->id_co);
      ltr->id_co = NULL;
      lookup_with_public_key (ltr, &pkey);
    }
    else
    {
      /* no matching ego found */
      GNUNET_IDENTITY_disconnect (ltr->id_co);
      ltr->id_co = NULL;
      ltr->lookup_proc (ltr->lookup_proc_cls, GNUNET_NO, 0, NULL);
      GNUNET_GNS_lookup_with_tld_cancel (ltr);
    }
    return;
  }
  else if (NULL != name)
  {
    if ((strlen (name) <= strlen (ltr->name)) &&
        (0 == strcmp (name, &ltr->name[strlen (ltr->name) - strlen (name)])) &&
        ((strlen (name) == strlen (ltr->name)) ||
         ('.' == ltr->name[strlen (ltr->name) - strlen (name) - 1])) &&
        ((NULL == ltr->longest_match) ||
         (strlen (name) > strlen (ltr->longest_match))))
    {
      /* found better match, update! */
      GNUNET_free_non_null (ltr->longest_match);
      ltr->longest_match = GNUNET_strdup (name);
      ltr->longest_match_ego = ego;
    }
  }
}


/**
 * Perform an asynchronous lookup operation on the GNS,
 * determining the zone using the TLD of the given name
 * and the current configuration to resolve TLDs to zones.
 *
 * @param handle handle to the GNS service
 * @param name the name to look up, including TLD
 * @param type the record type to look up
 * @param options local options for the lookup
 * @param proc processor to call on result
 * @param proc_cls closure for @a proc
 * @return handle to the get request, NULL on error (i.e. bad configuration)
 */
struct GNUNET_GNS_LookupWithTldRequest *
GNUNET_GNS_lookup_with_tld (struct GNUNET_GNS_Handle *handle,
                            const char *name,
                            uint32_t type,
                            enum GNUNET_GNS_LocalOptions options,
                            GNUNET_GNS_LookupResultProcessor2 proc,
                            void *proc_cls)
{
  struct GNUNET_GNS_LookupWithTldRequest *ltr;
  const char *tld;
  char *dot_tld;
  char *zonestr;
  struct GNUNET_CRYPTO_EcdsaPublicKey pkey;

  ltr = GNUNET_new (struct GNUNET_GNS_LookupWithTldRequest);
  ltr->gns_handle = handle;
  ltr->name = GNUNET_strdup (name);
  ltr->type = type;
  ltr->options = options;
  ltr->lookup_proc = proc;
  ltr->lookup_proc_cls = proc_cls;
  /* start with trivial case: TLD is zkey */
  tld = get_tld (ltr->name);
  if (GNUNET_OK ==
      GNUNET_CRYPTO_ecdsa_public_key_from_string (tld, strlen (tld), &pkey))
  {
    eat_tld (ltr->name, tld);
    lookup_with_public_key (ltr, &pkey);
    return ltr;
  }

  /* second case: domain is mapped in our configuration file */
  for (const char *domain = name; NULL != domain;
       domain = strchr (domain, (unsigned char) '.'))
  {
    if ('.' == domain[0])
      domain++;
    GNUNET_asprintf (&dot_tld, ".%s", domain);
    if (GNUNET_OK == GNUNET_CONFIGURATION_get_value_string (handle->cfg,
                                                            "gns",
                                                            dot_tld,
                                                            &zonestr))
    {
      if (GNUNET_OK !=
          GNUNET_CRYPTO_ecdsa_public_key_from_string (zonestr,
                                                      strlen (zonestr),
                                                      &pkey))
      {
        GNUNET_log_config_invalid (
          GNUNET_ERROR_TYPE_ERROR,
          "gns",
          dot_tld,
          _ ("Expected a base32-encoded public zone key\n"));
        GNUNET_free (zonestr);
        GNUNET_free (dot_tld);
        GNUNET_free (ltr->name);
        GNUNET_free (ltr);
        return NULL;
      }
      eat_tld (ltr->name, &dot_tld[1]);
      GNUNET_free (zonestr);
      GNUNET_free (dot_tld);
      lookup_with_public_key (ltr, &pkey);
      return ltr;
    }
    GNUNET_free (dot_tld);
  }
  /* FIXME: this call is still shitty slow to do the longest
     suffix if we have thousands of egos. We should modify
     the IDENTITY API to do the longest suffix matching
     inside of the identity service and not do an O(n) IPC! */
  ltr->id_co =
    GNUNET_IDENTITY_connect (ltr->gns_handle->cfg, &identity_zone_cb, ltr);
  if (NULL == ltr->id_co)
  {
    GNUNET_free (ltr->name);
    GNUNET_free (ltr);
    return NULL;
  }
  return ltr;
}


/**
 * Cancel pending lookup request
 *
 * @param ltr the lookup request to cancel
 * @return closure from the lookup result processor
 */
void *
GNUNET_GNS_lookup_with_tld_cancel (struct GNUNET_GNS_LookupWithTldRequest *ltr)
{
  void *ret = ltr->lookup_proc_cls;

  if (NULL != ltr->id_co)
  {
    GNUNET_IDENTITY_disconnect (ltr->id_co);
    ltr->id_co = NULL;
  }
  if (NULL != ltr->lr)
  {
    GNUNET_GNS_lookup_cancel (ltr->lr);
    ltr->lr = NULL;
  }
  GNUNET_free_non_null (ltr->longest_match);
  GNUNET_free (ltr->name);
  GNUNET_free (ltr);
  return ret;
}

/* end of gns_tld_api.c */