/*
   This file is part of GNUnet.
   Copyright (C) 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
 */
/**
 * @author Tobias Frisch
 * @file src/messenger/gnunet-service-messenger_member_session.c
 * @brief GNUnet MESSENGER service
 */

#include "gnunet-service-messenger_member_session.h"

#include "gnunet-service-messenger_room.h"
#include "gnunet-service-messenger_message_store.h"

#include "messenger_api_contact_store.h"

struct GNUNET_MESSENGER_MemberSession*
create_member_session (struct GNUNET_MESSENGER_Member *member,
                       const struct GNUNET_IDENTITY_PublicKey *pubkey)
{
  if ((!member) || (!pubkey) || (!(member->store)))
    return NULL;

  struct GNUNET_MESSENGER_MemberSession *session = GNUNET_new(struct GNUNET_MESSENGER_MemberSession);
  session->member = member;

  GNUNET_memcpy(&(session->public_key), pubkey, sizeof(session->public_key));

  get_context_from_member (
      get_member_session_key (session),
      get_member_session_id (session),
      &(session->context)
  );

  struct GNUNET_MESSENGER_ContactStore *store = get_member_contact_store(session->member->store);

  session->contact = get_store_contact(
      store,
      get_member_session_context (session),
      get_member_session_public_key (session)
  );

  if (!(session->contact))
  {
    GNUNET_free(session);
    return NULL;
  }

  increase_contact_rc (session->contact);

  session->history = GNUNET_CONTAINER_multihashmap_create(8, GNUNET_NO);

  init_list_messages(&(session->messages));

  session->prev = NULL;
  session->next = NULL;

  session->start = GNUNET_TIME_absolute_get();

  session->closed = GNUNET_NO;
  session->completed = GNUNET_NO;

  return session;
}

static void
check_member_session_completion (struct GNUNET_MESSENGER_MemberSession *session)
{
  GNUNET_assert (session);

  if (!session->messages.tail)
  {
    session->completed = GNUNET_YES;
    goto completion;
  }

  const struct GNUNET_HashCode* start = &(session->messages.head->hash);
  const struct GNUNET_HashCode* end = &(session->messages.tail->hash);

  struct GNUNET_MESSENGER_ListMessages level;
  init_list_messages(&level);

  add_to_list_messages(&level, end);

  struct GNUNET_MESSENGER_MessageStore *store = get_room_message_store(session->member->store->room);

  struct GNUNET_MESSENGER_ListMessages list;
  init_list_messages(&list);

  while (level.head)
  {
    struct GNUNET_MESSENGER_ListMessage *element;

    for (element = level.head; element; element = element->next)
    {
      const struct GNUNET_MESSENGER_MessageLink *link = get_store_message_link(
          store, &(element->hash), GNUNET_NO
      );

      if (!link)
        continue;

      add_to_list_messages(&list, &(link->first));

      if (GNUNET_YES == link->multiple)
        add_to_list_messages(&list, &(link->second));
    }

    clear_list_messages(&level);

    for (element = list.head; element; element = element->next)
      if (GNUNET_YES == check_member_session_history(session, &(element->hash), GNUNET_YES))
        break;

    if (element)
      if (0 != GNUNET_CRYPTO_hash_cmp(&(element->hash), start))
        add_to_list_messages(&level, &(element->hash));
      else
        session->completed = GNUNET_YES;
    else
      copy_list_messages(&level, &list);

    clear_list_messages(&list);
  }

completion:
  if (GNUNET_YES == is_member_session_completed(session))
  {
    GNUNET_CONTAINER_multihashmap_destroy (session->history);

    struct GNUNET_MESSENGER_ContactStore *store = get_member_contact_store(session->member->store);

    if ((session->contact) && (GNUNET_YES == decrease_contact_rc (session->contact)))
      remove_store_contact (
          store,
          session->contact,
          get_member_session_context(session)
      );

    session->contact = NULL;
  }
}

static int
iterate_copy_history (void *cls, const struct GNUNET_HashCode *key, void *value)
{
  struct GNUNET_MESSENGER_MemberSession *next = cls;

  GNUNET_CONTAINER_multihashmap_put(next->history, key, (value? next : NULL),
                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST);

  return GNUNET_YES;
}

struct GNUNET_MESSENGER_MemberSession*
switch_member_session (struct GNUNET_MESSENGER_MemberSession *session,
                       const struct GNUNET_MESSENGER_Message *message,
                       const struct GNUNET_HashCode *hash)
{
  if ((!session) || (!message) || (!hash))
    return NULL;

  GNUNET_assert((GNUNET_MESSENGER_KIND_ID == message->header.kind) ||
                (GNUNET_MESSENGER_KIND_KEY == message->header.kind));

  struct GNUNET_MESSENGER_MemberSession *next = GNUNET_new(struct GNUNET_MESSENGER_MemberSession);

  if (GNUNET_MESSENGER_KIND_ID == message->header.kind)
    next->member = add_store_member(session->member->store, &(message->body.id.id));
  else
    next->member = session->member;

  if (GNUNET_MESSENGER_KIND_KEY == message->header.kind)
    GNUNET_memcpy(&(next->public_key), &(message->body.key.key), sizeof(next->public_key));
  else
    GNUNET_memcpy(&(next->public_key), get_member_session_public_key(session), sizeof(next->public_key));

  get_context_from_member (
      get_member_session_key (next),
      get_member_session_id (next),
      &(next->context)
  );

  update_store_contact(
      get_member_contact_store(next->member->store),
      get_member_session_contact(session),
      get_member_session_context(session),
      get_member_session_context(next),
      get_member_session_public_key(next)
  );

  next->contact = get_member_session_contact(session);

  if (!(next->contact))
  {
    GNUNET_free(next);
    return NULL;
  }

  increase_contact_rc (next->contact);

  next->history = GNUNET_CONTAINER_multihashmap_create(
      GNUNET_CONTAINER_multihashmap_size(session->history), GNUNET_NO
  );

  GNUNET_CONTAINER_multihashmap_iterate(session->history, iterate_copy_history, next);

  init_list_messages(&(next->messages));
  copy_list_messages(&(next->messages), &(session->messages));

  session->next = next;
  next->prev = session;
  next->next = NULL;

  next->start = GNUNET_TIME_absolute_get();

  session->closed = GNUNET_YES;
  next->closed = GNUNET_NO;
  next->completed = GNUNET_NO;

  check_member_session_completion (session);

  return next;
}

void
destroy_member_session(struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert (session);

  GNUNET_CONTAINER_multihashmap_destroy (session->history);

  clear_list_messages (&(session->messages));

  struct GNUNET_MESSENGER_Contact *contact = get_member_session_contact (session);

  if ((contact) && (GNUNET_YES == decrease_contact_rc (contact)))
    remove_store_contact (
        get_member_contact_store(session->member->store),
        contact,
        get_member_session_context(session)
    );

  GNUNET_free(session);
}

int
reset_member_session (struct GNUNET_MESSENGER_MemberSession* session,
                      const struct GNUNET_HashCode *hash)
{
  GNUNET_assert ((session) && (hash));

  struct GNUNET_MESSENGER_ContactStore *store = get_member_contact_store(session->member->store);
  struct GNUNET_MESSENGER_Contact *contact = get_store_contact(
      store,
      get_member_session_context (session),
      get_member_session_public_key (session)
  );

  if (!contact)
    return GNUNET_SYSERR;

  if (contact == session->contact)
    goto clear_messages;

  session->contact = contact;
  increase_contact_rc (session->contact);

clear_messages:
  clear_list_messages(&(session->messages));
  add_to_list_messages(&(session->messages), hash);

  session->next = NULL;
  session->closed = GNUNET_NO;
  session->completed = GNUNET_NO;

  return GNUNET_OK;
}

void
close_member_session (struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert (session);

  session->closed = GNUNET_YES;
  check_member_session_completion (session);
}

int
is_member_session_closed (const struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert(session);

  return session->closed;
}

int
is_member_session_completed (const struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert(session);

  return session->completed;
}

struct GNUNET_TIME_Absolute
get_member_session_start (const struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert(session);

  if (session->prev)
    return get_member_session_start(session->prev);

  return session->start;
}

const struct GNUNET_HashCode*
get_member_session_key (const struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert((session) && (session->member));

  return get_member_store_key(session->member->store);
}

const struct GNUNET_ShortHashCode*
get_member_session_id (const struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert(session);

  return get_member_id(session->member);
}

const struct GNUNET_IDENTITY_PublicKey*
get_member_session_public_key (const struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert(session);

  return &(session->public_key);
}

const struct GNUNET_HashCode*
get_member_session_context (const struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert(session);

  return &(session->context);
}

struct GNUNET_MESSENGER_Contact*
get_member_session_contact (struct GNUNET_MESSENGER_MemberSession* session)
{
  GNUNET_assert (session);

  return session->contact;
}

int verify_member_session_as_sender (const struct GNUNET_MESSENGER_MemberSession *session,
                                     const struct GNUNET_MESSENGER_Message *message,
                                     const struct GNUNET_HashCode *hash)
{
  GNUNET_assert((session) && (message) && (hash));

  if (GNUNET_YES == is_member_session_completed(session))
    return GNUNET_SYSERR;

  if (0 != GNUNET_memcmp(get_member_session_id(session), &(message->header.sender_id)))
    return GNUNET_SYSERR;

  return verify_message(message, hash, get_member_session_public_key(session));
}

int
check_member_session_history (const struct GNUNET_MESSENGER_MemberSession *session,
                              const struct GNUNET_HashCode *hash, int ownership)
{
  GNUNET_assert((session) && (hash));

  if (GNUNET_YES == ownership)
    return (NULL != GNUNET_CONTAINER_multihashmap_get(session->history, hash)? GNUNET_YES : GNUNET_NO);
  else
    return GNUNET_CONTAINER_multihashmap_contains(session->history, hash);
}

static void
update_member_chain_history (struct GNUNET_MESSENGER_MemberSession *session,
                             const struct GNUNET_HashCode *hash, int ownership)
{
  GNUNET_assert ((session) && (hash));

  if ((GNUNET_OK == GNUNET_CONTAINER_multihashmap_put(session->history, hash, (GNUNET_YES == ownership? session : NULL),
                                                      GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST)) && (session->next))
    update_member_chain_history (session->next, hash, ownership);
}

void
update_member_session_history (struct GNUNET_MESSENGER_MemberSession *session,
                               const struct GNUNET_MESSENGER_Message *message,
                               const struct GNUNET_HashCode *hash)
{
  GNUNET_assert((session) && (message) && (hash));

  if (GNUNET_YES == is_member_session_completed(session))
    return;

  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Updating sessions history (%s) += (%s)\n",
             GNUNET_sh2s(get_member_session_id(session)), GNUNET_h2s(hash));

  if (GNUNET_OK == verify_member_session_as_sender (session, message, hash))
  {
    if (GNUNET_YES == is_message_session_bound (message))
      add_to_list_messages(&(session->messages), hash);

    update_member_chain_history (session, hash, GNUNET_YES);
  }
  else
    update_member_chain_history (session, hash, GNUNET_NO);

  if (GNUNET_YES == session->closed)
    check_member_session_completion(session);
}

static void
clear_member_chain_history (struct GNUNET_MESSENGER_MemberSession *session,
                            const struct GNUNET_HashCode *hash)
{
  GNUNET_assert ((session) && (hash));

  if ((0 < GNUNET_CONTAINER_multihashmap_remove_all(session->history, hash)) && (session->next))
    clear_member_session_history(session->next, hash);
}

void
clear_member_session_history (struct GNUNET_MESSENGER_MemberSession *session,
                              const struct GNUNET_HashCode *hash)
{
  GNUNET_assert((session) && (hash));

  clear_member_chain_history (session, hash);
}

struct GNUNET_MESSENGER_MemberSessionHistoryEntry
{
  struct GNUNET_HashCode hash;
  unsigned char ownership;
};

static void
load_member_session_history (struct GNUNET_MESSENGER_MemberSession *session, const char *path)
{
  GNUNET_assert((session) && (path));

  if (GNUNET_YES != GNUNET_DISK_file_test (path))
    return;

  enum GNUNET_DISK_AccessPermissions permission = (GNUNET_DISK_PERM_USER_READ | GNUNET_DISK_PERM_USER_WRITE);

  struct GNUNET_DISK_FileHandle *handle = GNUNET_DISK_file_open(
      path, GNUNET_DISK_OPEN_READ, permission
  );

  if (!handle)
    return;

  GNUNET_DISK_file_seek(handle, 0, GNUNET_DISK_SEEK_SET);

  struct GNUNET_MESSENGER_MemberSessionHistoryEntry entry;
  ssize_t len;

  int status;

  do {
    len = GNUNET_DISK_file_read(handle, &(entry.hash), sizeof(entry.hash));

    if (len != sizeof(entry.hash))
      break;

    len = GNUNET_DISK_file_read(handle, &(entry.ownership), sizeof(entry.ownership));

    if (len != sizeof(entry.ownership))
      break;

    status = GNUNET_CONTAINER_multihashmap_put(session->history, &(entry.hash), (entry.ownership? session : NULL),
                                               GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST);
  } while (status == GNUNET_OK);

  GNUNET_DISK_file_close(handle);
}

void
load_member_session (struct GNUNET_MESSENGER_Member *member, const char *directory)
{
  GNUNET_assert ((member) && (directory));

  char *config_file;
  GNUNET_asprintf (&config_file, "%s%s", directory, "session.cfg");

  struct GNUNET_MESSENGER_MemberSession *session = NULL;

  if (GNUNET_YES != GNUNET_DISK_file_test (config_file))
    goto free_config;

  struct GNUNET_CONFIGURATION_Handle *cfg = GNUNET_CONFIGURATION_create ();

  if (GNUNET_OK == GNUNET_CONFIGURATION_parse (cfg, config_file))
  {
    char *key_data;

    if (GNUNET_OK != GNUNET_CONFIGURATION_get_value_string(cfg, "session", "key", &key_data))
      goto destroy_config;

    struct GNUNET_IDENTITY_PublicKey key;

    enum GNUNET_GenericReturnValue key_return = GNUNET_IDENTITY_public_key_from_string(key_data, &key);

    GNUNET_free(key_data);

    if (GNUNET_OK != key_return)
      goto destroy_config;

    session = create_member_session(member, &key);

    unsigned long long numeric_value;

    if (GNUNET_OK == GNUNET_CONFIGURATION_get_value_number(cfg, "session", "start", &numeric_value))
      session->start.abs_value_us = numeric_value;

    if (GNUNET_OK == GNUNET_CONFIGURATION_get_value_number(cfg, "session", "closed", &numeric_value))
      session->closed = (GNUNET_YES == numeric_value? GNUNET_YES : GNUNET_NO);

    if (GNUNET_OK == GNUNET_CONFIGURATION_get_value_number(cfg, "session", "completed", &numeric_value))
      session->completed = (GNUNET_YES == numeric_value? GNUNET_YES : GNUNET_NO);
  }

destroy_config:
  GNUNET_CONFIGURATION_destroy (cfg);

free_config:
  GNUNET_free(config_file);

  if (!session)
    return;

  char *history_file;
  GNUNET_asprintf (&history_file, "%s%s", directory, "history.map");

  load_member_session_history (session, history_file);
  GNUNET_free(history_file);

  char *messages_file;
  GNUNET_asprintf (&messages_file, "%s%s", directory, "messages.list");

  load_list_messages(&(session->messages), messages_file);
  GNUNET_free(messages_file);

  add_member_session(member, session);
}

static struct GNUNET_MESSENGER_MemberSession*
get_cycle_safe_next_session (struct GNUNET_MESSENGER_MemberSession *session, struct GNUNET_MESSENGER_MemberSession *next)
{
  if (!next)
    return NULL;

  struct GNUNET_MESSENGER_MemberSession *check = next;

  do {
    if (check == session)
      return NULL;

    check = check->next;
  } while (check);

  return next;
}

void
load_member_session_next (struct GNUNET_MESSENGER_MemberSession *session, const char *directory)
{
  GNUNET_assert ((session) && (directory));

  char *config_file;
  GNUNET_asprintf (&config_file, "%s%s", directory, "session.cfg");

  if (GNUNET_YES != GNUNET_DISK_file_test (config_file))
    goto free_config;

  struct GNUNET_CONFIGURATION_Handle *cfg = GNUNET_CONFIGURATION_create ();

  if (GNUNET_OK == GNUNET_CONFIGURATION_parse (cfg, config_file))
  {
    char *key_data;

    if (GNUNET_OK != GNUNET_CONFIGURATION_get_value_string(cfg, "session", "next_key", &key_data))
      goto destroy_config;

    struct GNUNET_IDENTITY_PublicKey next_key;

    enum GNUNET_GenericReturnValue key_return = GNUNET_IDENTITY_public_key_from_string(key_data, &next_key);

    GNUNET_free(key_data);

    if (GNUNET_OK != key_return)
      goto destroy_config;

    struct GNUNET_ShortHashCode next_id;

    if (GNUNET_OK != GNUNET_CONFIGURATION_get_data (cfg, "session", "next_id", &next_id, sizeof(next_id)))
      goto destroy_config;

    struct GNUNET_MESSENGER_Member *member = get_store_member(session->member->store, &next_id);

    session->next = get_cycle_safe_next_session(
        session, member? get_member_session (member, &next_key) : NULL
    );

    if (session->next)
      session->next->prev = session;
  }

destroy_config:
  GNUNET_CONFIGURATION_destroy (cfg);

free_config:
  GNUNET_free(config_file);
}

static int
iterate_save_member_session_history_hentries (void *cls, const struct GNUNET_HashCode *key, void *value)
{
  struct GNUNET_DISK_FileHandle *handle = cls;
  unsigned char ownership = value? GNUNET_YES : GNUNET_NO;

  GNUNET_DISK_file_write(handle, key, sizeof(*key));
  GNUNET_DISK_file_write(handle, &ownership, sizeof(ownership));

  return GNUNET_YES;
}

static void
save_member_session_history (struct GNUNET_MESSENGER_MemberSession *session, const char *path)
{
  GNUNET_assert((session) && (path));

  enum GNUNET_DISK_AccessPermissions permission = (GNUNET_DISK_PERM_USER_READ | GNUNET_DISK_PERM_USER_WRITE);

  struct GNUNET_DISK_FileHandle *handle = GNUNET_DISK_file_open(
      path, GNUNET_DISK_OPEN_CREATE | GNUNET_DISK_OPEN_WRITE, permission
  );

  if (!handle)
    return;

  GNUNET_DISK_file_seek(handle, 0, GNUNET_DISK_SEEK_SET);

  GNUNET_CONTAINER_multihashmap_iterate(
      session->history,
      iterate_save_member_session_history_hentries,
      handle
  );

  GNUNET_DISK_file_sync(handle);
  GNUNET_DISK_file_close(handle);
}

void
save_member_session (struct GNUNET_MESSENGER_MemberSession *session, const char *directory)
{
  GNUNET_assert ((session) && (directory));

  char *config_file;
  GNUNET_asprintf (&config_file, "%s%s", directory, "session.cfg");

  struct GNUNET_CONFIGURATION_Handle *cfg = GNUNET_CONFIGURATION_create ();

  char *key_data = GNUNET_IDENTITY_public_key_to_string(get_member_session_public_key(session));

  if (key_data)
  {
    GNUNET_CONFIGURATION_set_value_string (cfg, "session", "key", key_data);

    GNUNET_free(key_data);
  }

  if (session->next)
  {
    const struct GNUNET_ShortHashCode *next_id = get_member_session_id(session->next);

    char *next_id_data = GNUNET_STRINGS_data_to_string_alloc (next_id, sizeof(*next_id));

    if (next_id_data)
    {
      GNUNET_CONFIGURATION_set_value_string (cfg, "session", "next_id", next_id_data);

      GNUNET_free(next_id_data);
    }

    key_data = GNUNET_IDENTITY_public_key_to_string(get_member_session_public_key(session->next));

    if (key_data)
    {
      GNUNET_CONFIGURATION_set_value_string (cfg, "session", "next_key", key_data);

      GNUNET_free(key_data);
    }
  }

  GNUNET_CONFIGURATION_set_value_number(cfg, "session", "start", session->start.abs_value_us);

  GNUNET_CONFIGURATION_set_value_number (cfg, "session", "closed", session->closed);
  GNUNET_CONFIGURATION_set_value_number (cfg, "session", "completed", session->completed);

  GNUNET_CONFIGURATION_write (cfg, config_file);
  GNUNET_CONFIGURATION_destroy (cfg);

  GNUNET_free(config_file);

  char *history_file;
  GNUNET_asprintf (&history_file, "%s%s", directory, "history.map");

  save_member_session_history (session, history_file);
  GNUNET_free(history_file);

  char *messages_file;
  GNUNET_asprintf (&messages_file, "%s%s", directory, "messages.list");

  save_list_messages(&(session->messages), messages_file);
  GNUNET_free(messages_file);
}