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+/*
+     This file is part of GNUnet.
+     Copyright (C) 2013 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 Gabor X Toth
+ * @author Christian Grothoff
+ *
+ * @file
+ * Social service; implements social interactions through the PSYC service.
+ */
+
+/** @defgroup social Social service
+Social interactions through the PSYC service.
+
+# Overview
+
+The social service provides an API for social interactions based on a one-to-many messaging model.
+It manages subscriptions of applications to places, provides messaging functionality in places,
+allows access to the local message history and manages the GNS zone of _egos_ (user identities).
+
+The service stores private and public keys of subscribed places, as well as files received in subscribed places.
+
+# Concepts and terminology
+
+## Ego, Nym
+
+An _ego_ is an identity of a user, a private-public key pair.
+A _nym_ is an identity of another user in the network, identified by its public key.
+Each user can have multiple identities.
+
+struct GNUNET_SOCIAL_Ego and struct GNUNET_SOCIAL_Nym represents one of these identities.
+
+## Place, Host, Guest
+
+A _place_ is where social interactions happen.  It is owned and created by an _ego_.
+Creating a new place happens by an _ego_ entering a new place as a _host_,
+where _guests_ can enter later to receive messages sent to the place.
+
+A place is identified by its public key.
+
+- struct GNUNET_SOCIAL_Host represents a place entered as host,
+- struct GNUNET_SOCIAL_Guest is used for a place entered as guest.
+- A struct GNUNET_SOCIAL_Place can be obtained for both a host and guest place
+  using GNUNET_SOCIAL_host_get_place() and GNUNET_SOCIAL_guest_get_place()
+  and can be used with API functions common to hosts and guests.
+
+## History
+
+Messages sent to places are stored locally by the PSYCstore service, and can be queried any time.
+GNUNET_SOCIAL_history_replay_latest() retrieves the latest N messages sent to the place,
+while GNUNET_SOCIAL_history_replay() is used to query a given message ID range.
+
+## GNU Name System
+
+The GNU Name System is used for assigning human-readable names to nyms and places.
+There's a _GNS zone_ corresponding to each _nym_.
+An _ego_ can publish PKEY and PLACE records in its own zone, pointing to nyms and places, respectively.
+
+## Announcement, talk request
+
+The host can _announce_ messages to the place, using GNUNET_SOCIAL_host_announce().
+Guests can send _talk_ requests to the host, using GNUNET_SOCIAL_guest_talk().
+The host receives talk requests of guests and can _relay_ them to the place,
+or process it using a message handler function.
+
+# Using the API
+
+## Connecting to the service
+
+A client first establishes an _application connection_ to the service using
+GNUNET_SOCIAL_app_connect() providing its _application ID_, then receives the
+public keys of subscribed places and available egos in response.
+
+## Reconnecting to places
+
+Then the application can reconnect to its subscribed places by establishing
+_place connections_ with GNUNET_SOCIAL_host_enter_reconnect() and
+GNUNET_SOCIAL_guest_enter_reconnect().
+
+## Subscribing to a place
+
+Entering and subscribing a new host or guest place is done using
+GNUNET_SOCIAL_host_enter() and GNUNET_SOCIAL_guest_enter().
+
+## Disconnecting from a place
+
+An application can disconnect from a place while the social service keeps its
+network connection active, using GNUNET_SOCIAL_host_disconnect() and
+GNUNET_SOCIAL_guest_disconnect().
+
+## Leaving a place
+
+To permanently leave a place, see GNUNET_SOCIAL_host_leave() and GNUNET_SOCIAL_guest_leave().
+When leaving a place its network connections are closed and all applications are unsubscribed from the place.
+
+# Message methods
+
+## _converse
+
+Human conversation in a private or public place.
+
+### Environment
+
+#### _id_reply
+Message ID this message is in reply to.
+
+#### _id_thread
+Thread ID, the first message ID in the thread.
+
+#### _nym_author
+Nym of the author.
+
+FIXME: Are nyms a different data type from egos and person entities?
+Do they have a different format than any other entity address?
+Questions and thoughts on how to fix this in "questions.org"
+
+#### _sig_author
+Signature of the message body and its variables by the author.
+
+### Data
+
+Message body.
+
+## _notice_place
+
+Notification about a place.
+
+TODO: Applications can decide to auto-subscribe to certain places,
+e.g. files under a given size.
+
+### Environment
+
+#### Using GNS
+
+##### _gns_place
+GNS name of the place in a globally unique .zkey zone
+
+FIXME: A custom _gns PSYC data type should be avoidable by parsing
+and interpreting PSYC uniforms appropriately.
+Thoughts on this in "questions.org"
+
+#### Without GNS
+
+##### _key_pub_place
+Public key of place
+
+FIXME: _key_pub can't be the data type for GNUnet-specific cryptographic
+addressing. Questions and thoughts on how to fix this in "questions.org"
+
+##### _peer_origin
+Peer ID of origin
+
+##### _list_peer_relays
+List of peer IDs of relays
+
+## _notice_place_file
+
+Notification about a place hosting a file.
+
+### Environment
+
+The environment of _notice_place above, plus the following:
+
+#### _size_file
+Size of file
+
+#### _type_file
+MIME type of file
+
+#### _name_file
+Name of file
+
+#### _description_file
+Description of file
+
+## _file
+
+Messages with a _file method contain a file,
+which is saved to disk upon reception at the following location:
+$GNUNET_DATA_HOME/social/files/<H(place_pub)>/<H(message_id)>
+
+### Environment
+
+#### _size_file
+Size of file
+
+#### _type_file
+MIME type of file
+
+#### _name_file
+Name of file
+
+#### _description_file
+Description of file
+
+@{
+*/
+
+
+#ifndef GNUNET_SOCIAL_SERVICE_H
+#define GNUNET_SOCIAL_SERVICE_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+#include <stdint.h>
+#include "gnunet_util_lib.h"
+#include "gnunet_psyc_util_lib.h"
+#include "gnunet_identity_service.h"
+#include "gnunet_namestore_service.h"
+#include "gnunet_psyc_service.h"
+
+
+/**
+ * Version number of GNUnet Social API.
+ */
+#define GNUNET_SOCIAL_VERSION 0x00000000
+
+/**
+ * Maximum size of client ID including '\0' terminator.
+ */
+#define GNUNET_SOCIAL_APP_MAX_ID_SIZE 256
+
+enum GNUNET_SOCIAL_MsgProcFlags {
+  GNUNET_SOCIAL_MSG_PROC_NONE = 0,
+  GNUNET_SOCIAL_MSG_PROC_RELAY = 1,
+  GNUNET_SOCIAL_MSG_PROC_SAVE= 2,
+};
+
+/**
+ * Handle for an application.
+ */
+struct GNUNET_SOCIAL_App;
+
+/**
+ * Handle for an ego (own identity)
+ */
+struct GNUNET_SOCIAL_Ego;
+
+/**
+ * Handle for a pseudonym of another user in the network.
+ */
+struct GNUNET_SOCIAL_Nym;
+
+/**
+ * Handle for a place where social interactions happen.
+ */
+struct GNUNET_SOCIAL_Place;
+
+/**
+ * Host handle for a place that we entered.
+ */
+struct GNUNET_SOCIAL_Host;
+
+/**
+ * Guest handle for place that we entered.
+ */
+struct GNUNET_SOCIAL_Guest;
+
+/**
+ * Handle that can be used to reconnect to a place as host.
+ */
+struct GNUNET_SOCIAL_HostConnection;
+
+/**
+ * Handle that can be used to reconnect to a place as guest.
+ */
+struct GNUNET_SOCIAL_GuestConnection;
+
+/**
+ * Notification about an available identity.
+ *
+ * @param cls
+ *        Closure.
+ * @param pub_key
+ *        Public key of ego.
+ * @param name
+ *        Name of ego.
+ */
+typedef void
+(*GNUNET_SOCIAL_AppEgoCallback) (void *cls,
+                                 struct GNUNET_SOCIAL_Ego *ego,
+                                 const struct GNUNET_CRYPTO_EcdsaPublicKey *ego_pub_key,
+                                 const char *name);
+
+
+/**
+ * Entry status of a place per application.
+ */
+enum GNUNET_SOCIAL_AppPlaceState
+{
+  /**
+   * The place was once entered by the ego, but left since.
+   * It's possible to establish a local connection to the place
+   * without re-entering to fetch history from the PSYCstore.
+   * @see enum GNUNET_PSYC_SlaveJoinFlags and GNUNET_SOCIAL_guest_enter()
+   */
+  GNUNET_SOCIAL_PLACE_STATE_ARCHIVED = 0,
+
+  /**
+   * The place is entered by the ego,
+   * but this application is not subscribed to it.
+   */
+  GNUNET_SOCIAL_PLACE_STATE_ENTERED = 1,
+
+  /**
+   * The place is entered by the ego and
+   * and this application is subscribed to it.
+   */
+  GNUNET_SOCIAL_PLACE_STATE_SUBSCRIBED = 2,
+};
+
+
+/**
+ * Called after receiving initial list of egos and places.
+ */
+typedef void
+(*GNUNET_SOCIAL_AppConnectedCallback) (void *cls);
+
+
+/**
+ * Notification about a home.
+ *
+ * @param cls
+ *        Closure.
+ * @param hconn
+ *        Host connection, to be used with GNUNET_SOCIAL_host_enter_reconnect()
+ * @param ego
+ *        Ego used to enter the place.
+ * @param place_pub_key
+ *        Public key of the place.
+ * @param place_state
+ *        @see enum GNUNET_SOCIAL_AppPlaceState
+ */
+typedef void
+(*GNUNET_SOCIAL_AppHostPlaceCallback) (void *cls,
+                                       struct GNUNET_SOCIAL_HostConnection *hconn,
+                                       struct GNUNET_SOCIAL_Ego *ego,
+                                       const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                                       enum GNUNET_SOCIAL_AppPlaceState place_state);
+
+/**
+ * Notification about a place.
+ *
+ * @param cls
+ *        Closure.
+ * @param gconn
+ *        Guest connection, to be used with GNUNET_SOCIAL_guest_enter_reconnect()
+ * @param ego
+ *        Ego used to enter the place.
+ * @param place_pub_key
+ *        Public key of the place.
+ * @param place_state
+ *        @see enum GNUNET_SOCIAL_AppPlaceState
+ */
+typedef void
+(*GNUNET_SOCIAL_AppGuestPlaceCallback) (void *cls,
+                                        struct GNUNET_SOCIAL_GuestConnection *gconn,
+                                        struct GNUNET_SOCIAL_Ego *ego,
+                                        const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                                        enum GNUNET_SOCIAL_AppPlaceState place_state);
+
+
+/**
+ * Establish application connection to the social service.
+ *
+ * The @host_cb and @guest_cb functions are
+ * initially called for each entered places,
+ * then later each time a new place is entered with the current app ID.
+ *
+ * @param cfg
+ *        Configuration.
+ * @param ego_cb
+ *        Function to notify about an available ego.
+ * @param host_cb
+ *        Function to notify about a place entered as host.
+ * @param guest_cb
+ *        Function to notify about a place entered as guest.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to stop listening.
+ */
+struct GNUNET_SOCIAL_App *
+GNUNET_SOCIAL_app_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
+                           const char *id,
+                           GNUNET_SOCIAL_AppEgoCallback ego_cb,
+                           GNUNET_SOCIAL_AppHostPlaceCallback host_cb,
+                           GNUNET_SOCIAL_AppGuestPlaceCallback guest_cb,
+                           GNUNET_SOCIAL_AppConnectedCallback connected_cb,
+                           void *cls);
+
+
+/**
+ * Disconnect app.
+ *
+ * @param app
+ *        Application handle.
+ * @param disconnect_cb
+ *        Disconnect callback.
+ * @param disconnect_cls
+ *        Disconnect closure.
+ */
+void
+GNUNET_SOCIAL_app_disconnect (struct GNUNET_SOCIAL_App *app,
+                              GNUNET_ContinuationCallback disconnect_cb,
+                              void *disconnect_cls);
+
+
+/**
+ * Get the public key of @a ego.
+ *
+ * @param ego
+ *        Ego.
+ *
+ * @return Public key of ego.
+ */
+const struct GNUNET_CRYPTO_EcdsaPublicKey *
+GNUNET_SOCIAL_ego_get_pub_key (const struct GNUNET_SOCIAL_Ego *ego);
+
+
+/**
+ * Get the name of @a ego.
+ *
+ * @param ego
+ *        Ego.
+ *
+ * @return Public key of @a ego.
+ */
+const char *
+GNUNET_SOCIAL_ego_get_name (const struct GNUNET_SOCIAL_Ego *ego);
+
+
+/**
+ * Get the public key of a @a nym.
+ *
+ * Suitable, for example, to be used with GNUNET_SOCIAL_zone_add_nym().
+ *
+ * @param nym
+ *        Pseudonym to map to a cryptographic identifier.
+ *
+ * @return Public key of nym.
+ */
+const struct GNUNET_CRYPTO_EcdsaPublicKey *
+GNUNET_SOCIAL_nym_get_pub_key (const struct GNUNET_SOCIAL_Nym *nym);
+
+
+/**
+ * Get the hash of the public key of a @a nym.
+ *
+ * @param nym
+ *        Pseudonym to map to a cryptographic identifier.
+ *
+ * @return Hash of the public key of nym.
+ */
+const struct GNUNET_HashCode *
+GNUNET_SOCIAL_nym_get_pub_key_hash (const struct GNUNET_SOCIAL_Nym *nym);
+
+
+/**
+ * Function called asking for nym to be admitted to the place.
+ *
+ * Should call either GNUNET_SOCIAL_host_admit() or
+ * GNUNET_SOCIAL_host_reject_entry() (possibly asynchronously).  If this host
+ * cannot decide, it is fine to call neither function, in which case hopefully
+ * some other host of the place exists that will make the decision.  The @a nym
+ * reference remains valid until the #GNUNET_SOCIAL_FarewellCallback is invoked
+ * for it.
+ *
+ * @param cls
+ *        Closure.
+ * @param nym
+ *        Handle for the user who wants to enter.
+ * @param method_name
+ *        Method name in the entry request.
+ * @param variable_count
+ *        Number of elements in the @a variables array.
+ * @param variables
+ *        Variables present in the message.
+ * @param data
+ *        Payload given on enter (e.g. a password).
+ * @param data_size
+ *        Number of bytes in @a data.
+ */
+typedef void
+(*GNUNET_SOCIAL_AnswerDoorCallback) (void *cls,
+                                     struct GNUNET_SOCIAL_Nym *nym,
+                                     const char *method_name,
+                                     struct GNUNET_PSYC_Environment *env,
+                                     const void *data,
+                                     size_t data_size);
+
+
+/**
+ * Function called when a @a nym leaves the place.
+ *
+ * This is also called if the @a nym was never given permission to enter
+ * (i.e. the @a nym stopped asking to get in).
+ *
+ * @param cls
+ *        Closure.
+ * @param nym
+ *        Handle for the user who left.
+ */
+typedef void
+(*GNUNET_SOCIAL_FarewellCallback) (void *cls,
+                                   const struct GNUNET_SOCIAL_Nym *nym,
+                                   struct GNUNET_PSYC_Environment *env);
+
+
+/**
+ * Function called after the host entered a home.
+ *
+ * @param cls
+ *        Closure.
+ * @param result
+ *        #GNUNET_OK on success, or
+ *        #GNUNET_SYSERR on error.
+ * @param place_pub_key
+ *        Public key of home.
+ * @param max_message_id
+ *        Last message ID sent to the channel.
+ *        Or 0 if no messages have been sent to the place yet.
+ */
+typedef void
+(*GNUNET_SOCIAL_HostEnterCallback) (void *cls, int result,
+                                    const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                                    uint64_t max_message_id);
+
+
+/**
+ * Enter a place as host.
+ *
+ * A place is created upon first entering, and it is active until permanently
+ * left using GNUNET_SOCIAL_host_leave().
+ *
+ * @param cfg
+ *        Configuration to contact the social service.
+ * @param ego
+ *        Identity of the host.
+ * @param place_key
+ *        Private-public key pair of the place.
+ *        NULL for ephemeral places.
+ * @param policy
+ *        Policy specifying entry and history restrictions for the place.
+ * @param slicer
+ *        Slicer to handle incoming messages.
+ * @param enter_cb
+ *        Function called when the place is entered and ready to use.
+ * @param answer_door_cb
+ *        Function to handle new nyms that want to enter.
+ * @param farewell_cb
+ *        Function to handle departing nyms.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle for the host.
+ */
+struct GNUNET_SOCIAL_Host *
+GNUNET_SOCIAL_host_enter (const struct GNUNET_SOCIAL_App *app,
+                          const struct GNUNET_SOCIAL_Ego *ego,
+                          enum GNUNET_PSYC_Policy policy,
+                          struct GNUNET_PSYC_Slicer *slicer,
+                          GNUNET_SOCIAL_HostEnterCallback enter_cb,
+                          GNUNET_SOCIAL_AnswerDoorCallback answer_door_cb,
+                          GNUNET_SOCIAL_FarewellCallback farewell_cb,
+                          void *cls);
+
+
+/**
+ * Reconnect to an already entered place as host.
+ *
+ * @param hconn
+ *        Host connection handle.
+ *        @see GNUNET_SOCIAL_app_connect() & GNUNET_SOCIAL_AppHostPlaceCallback()
+ * @param slicer
+ *        Slicer to handle incoming messages.
+ * @param enter_cb
+ *        Function called when the place is entered and ready to use.
+ * @param answer_door_cb
+ *        Function to handle new nyms that want to enter.
+ * @param farewell_cb
+ *        Function to handle departing nyms.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle for the host.
+ */
+struct GNUNET_SOCIAL_Host *
+GNUNET_SOCIAL_host_enter_reconnect (struct GNUNET_SOCIAL_HostConnection *hconn,
+                                    struct GNUNET_PSYC_Slicer *slicer,
+                                    GNUNET_SOCIAL_HostEnterCallback enter_cb,
+                                    GNUNET_SOCIAL_AnswerDoorCallback answer_door_cb,
+                                    GNUNET_SOCIAL_FarewellCallback farewell_cb,
+                                    void *cls);
+
+
+/**
+ * Decision whether to admit @a nym into the place or refuse entry.
+ *
+ * @param hst
+ *        Host of the place.
+ * @param nym
+ *        Handle for the entity that wanted to enter.
+ * @param is_admitted
+ *        #GNUNET_YES    if @a nym is admitted,
+ *        #GNUNET_NO     if @a nym is refused entry,
+ *        #GNUNET_SYSERR if we cannot answer the request.
+ * @param entry_resp
+ *        Entry response message, or NULL.
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_SYSERR if the message is too large.
+ */
+int
+GNUNET_SOCIAL_host_entry_decision (struct GNUNET_SOCIAL_Host *hst,
+                                   struct GNUNET_SOCIAL_Nym *nym,
+                                   int is_admitted,
+                                   const struct GNUNET_PSYC_Message *entry_resp);
+
+
+/**
+ * Throw @a nym out of the place.
+ *
+ * Sends a _notice_place_leave announcement to the home.
+ *
+ * The @a nym reference will remain valid until the
+ * #GNUNET_SOCIAL_FarewellCallback is invoked,
+ * which should be very soon after this call.
+ *
+ * @param host
+ *        Host of the place.
+ * @param nym
+ *        Handle for the entity to be ejected.
+ * @param env
+ *        Environment for the message or NULL.
+ *        _nym is set to @e nym regardless whether an @e env is provided.
+ */
+void
+GNUNET_SOCIAL_host_eject (struct GNUNET_SOCIAL_Host *host,
+                          const struct GNUNET_SOCIAL_Nym *nym,
+                          struct GNUNET_PSYC_Environment *env);
+
+
+/**
+ * Flags for announcements by a host.
+ */
+enum GNUNET_SOCIAL_AnnounceFlags
+{
+  GNUNET_SOCIAL_ANNOUNCE_NONE = 0,
+
+  /**
+   * Whether this announcement removes all objects from the place.
+   *
+   * New objects can be still added to the now empty place using the @e env
+   * parameter of the same announcement.
+   */
+  GNUNET_SOCIAL_ANNOUNCE_CLEAR_OBJECTS = 1 << 0
+};
+
+
+/**
+ * Handle for an announcement request.
+ */
+struct GNUNET_SOCIAL_Announcement;
+
+
+/**
+ * Send a message to all nyms that are present in the place.
+ *
+ * This function is restricted to the host.  Nyms can only send requests
+ * to the host who can decide to relay it to everyone in the place.
+ *
+ * @param host
+ *        Host of the place.
+ * @param method_name
+ *        Method to use for the announcement.
+ * @param env
+ *        Environment containing variables for the message and operations
+ *        on objects of the place.
+ *        Has to remain available until the first call to @a notify_data.
+ *        Can be NULL.
+ * @param notify_data
+ *        Function to call to get the payload of the announcement.
+ * @param notify_data_cls
+ *        Closure for @a notify.
+ * @param flags
+ *        Flags for this announcement.
+ *
+ * @return NULL on error (another announcement already in progress?).
+ */
+struct GNUNET_SOCIAL_Announcement *
+GNUNET_SOCIAL_host_announce (struct GNUNET_SOCIAL_Host *host,
+                             const char *method_name,
+                             const struct GNUNET_PSYC_Environment *env,
+                             GNUNET_PSYC_TransmitNotifyData notify_data,
+                             void *notify_data_cls,
+                             enum GNUNET_SOCIAL_AnnounceFlags flags);
+
+
+/**
+ * Resume transmitting announcement.
+ *
+ * @param a
+ *        The announcement to resume.
+ */
+void
+GNUNET_SOCIAL_host_announce_resume (struct GNUNET_SOCIAL_Announcement *a);
+
+
+/**
+ * Cancel announcement.
+ *
+ * @param a
+ *        The announcement to cancel.
+ */
+void
+GNUNET_SOCIAL_host_announce_cancel (struct GNUNET_SOCIAL_Announcement *a);
+
+
+/**
+ * Allow relaying messages from guests matching a given @a method_prefix.
+ *
+ * @param host
+ *        The host.
+ * @param method_prefix
+ *        Method prefix to allow.
+ */
+void
+GNUNET_SOCIAL_host_relay_allow_method (struct GNUNET_SOCIAL_Host *host,
+                                       const char *method_prefix);
+
+
+/**
+ * Allow relaying changes to objects of the place.
+ *
+ * Only applies to messages with an allowed method name.
+ * @see GNUNET_SCOIAL_host_relay_allow_method()
+ *
+ * @param host
+ *        The host.
+ * @param object_prefix
+ *        Object prefix to allow modifying.
+ */
+void
+GNUNET_SOCIAL_host_relay_allow_method (struct GNUNET_SOCIAL_Host *host,
+                                       const char *object_prefix);
+
+
+/**
+ * Stop relaying messages from guests.
+ *
+ * Remove all allowed relay rules.
+ *
+ *
+ *
+ */
+void
+GNUNET_SOCIAL_host_relay_stop (struct GNUNET_SOCIAL_Host *host);
+
+
+/**
+ * Obtain handle for a hosted place.
+ *
+ * The returned handle can be used to access the place API.
+ *
+ * @param host
+ *        Handle for the host.
+ *
+ * @return Handle for the hosted place, valid as long as @a host is valid.
+ */
+struct GNUNET_SOCIAL_Place *
+GNUNET_SOCIAL_host_get_place (struct GNUNET_SOCIAL_Host *host);
+
+
+/**
+ * Disconnect from a home.
+ *
+ * Invalidates host handle.
+ *
+ * @param hst
+ *        The host to disconnect.
+ * @param disconnect_cb
+ *        Function called after disconnected from the service.
+ * @param cls
+ *        Closure for @a disconnect_cb.
+ */
+void
+GNUNET_SOCIAL_host_disconnect (struct GNUNET_SOCIAL_Host *hst,
+                               GNUNET_ContinuationCallback disconnect_cb,
+                               void *cls);
+
+
+/**
+ * Stop hosting a home.
+ *
+ * Sends a _notice_place_closing announcement to the home.
+ * Invalidates host handle.
+ *
+ * @param hst
+ *        Host leaving.
+ * @param env
+ *        Environment for the message or NULL.
+ * @param disconnect_cb
+ *        Function called after the host left the place
+ *        and disconnected from the service.
+ * @param cls
+ *        Closure for @a disconnect_cb.
+ */
+void
+GNUNET_SOCIAL_host_leave (struct GNUNET_SOCIAL_Host *hst,
+                          const struct GNUNET_PSYC_Environment *env,
+                          GNUNET_ContinuationCallback disconnect_cb,
+                          void *cls);
+
+
+/**
+ * Function called after the guest entered the local copy of the place.
+ *
+ * History and object query functions can be used after this call,
+ * but new messages can't be sent or received.
+ *
+ * @param cls
+ *        Closure.
+ * @param result
+ *        #GNUNET_OK on success, or
+ *        #GNUNET_SYSERR on error, e.g. could not connect to the service, or
+ *        could not resolve GNS name.
+ * @param place_pub_key
+ *        Public key of place.
+ * @param max_message_id
+ *        Last message ID sent to the place.
+ *        Or 0 if no messages have been sent to the place yet.
+ */
+typedef void
+(*GNUNET_SOCIAL_GuestEnterCallback) (void *cls, int result,
+                                     const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                                     uint64_t max_message_id);
+
+
+/**
+ * Function called upon a guest receives a decision about entry to the place.
+ *
+ * @param is_admitted
+ *        Is the guest admitted to the place?
+ *        #GNUNET_YES    if admitted,
+ *        #GNUNET_NO     if refused entry,
+ *        #GNUNET_SYSERR if the request could not be answered.
+ * @param data
+ *        Entry response message.
+ */
+typedef void
+(*GNUNET_SOCIAL_EntryDecisionCallback) (void *cls,
+                                        int is_admitted,
+                                        const struct GNUNET_PSYC_Message *entry_resp);
+
+
+/**
+ * Request entry to a place as a guest.
+ *
+ * @param app
+ *        Application handle.
+ * @param ego
+ *        Identity of the guest.
+ * @param place_pub_key
+ *        Public key of the place to enter.
+ * @param flags
+ *        Flags for the entry.
+ * @param origin
+ *        Peer identity of the origin of the underlying multicast group.
+ * @param relay_count
+ *        Number of elements in the @a relays array.
+ * @param relays
+ *        Relays for the underlying multicast group.
+ * @param entry_msg
+ *        Entry message.
+ * @param slicer
+ *        Slicer to use for processing incoming requests from guests.
+ *
+ * @return NULL on errors, otherwise handle for the guest.
+ */
+struct GNUNET_SOCIAL_Guest *
+GNUNET_SOCIAL_guest_enter (const struct GNUNET_SOCIAL_App *app,
+                           const struct GNUNET_SOCIAL_Ego *ego,
+                           const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                           enum GNUNET_PSYC_SlaveJoinFlags flags,
+                           const struct GNUNET_PeerIdentity *origin,
+                           uint32_t relay_count,
+                           const struct GNUNET_PeerIdentity *relays,
+                           const struct GNUNET_PSYC_Message *entry_msg,
+                           struct GNUNET_PSYC_Slicer *slicer,
+                           GNUNET_SOCIAL_GuestEnterCallback local_enter_cb,
+                           GNUNET_SOCIAL_EntryDecisionCallback entry_dcsn_cb,
+                           void *cls);
+
+
+/**
+ * Request entry to a place by name as a guest.
+ *
+ * @param app
+ *        Application handle.
+ * @param ego
+ *        Identity of the guest.
+ * @param gns_name
+ *        GNS name of the place to enter.  Either in the form of
+ *        'room.friend.gnu', or 'NYMPUBKEY.zkey'.  This latter case refers to
+ *        the 'PLACE' record of the empty label ("+") in the GNS zone with the
+ *        nym's public key 'NYMPUBKEY', and can be used to request entry to a
+ *        pseudonym's place directly.
+ * @param password
+ *        Password to decrypt the record, or NULL for cleartext records.
+ * @param join_msg
+ *        Entry request message.
+ * @param slicer
+ *        Slicer to use for processing incoming requests from guests.
+ * @param local_enter_cb
+ *        Called upon connection established to the social service.
+ * @param entry_decision_cb
+ *        Called upon receiving entry decision.
+ *
+ * @return NULL on errors, otherwise handle for the guest.
+ */
+struct GNUNET_SOCIAL_Guest *
+GNUNET_SOCIAL_guest_enter_by_name (const struct GNUNET_SOCIAL_App *app,
+                                   const struct GNUNET_SOCIAL_Ego *ego,
+                                   const char *gns_name,
+                                   const char *password,
+                                   const struct GNUNET_PSYC_Message *join_msg,
+                                   struct GNUNET_PSYC_Slicer *slicer,
+                                   GNUNET_SOCIAL_GuestEnterCallback local_enter_cb,
+                                   GNUNET_SOCIAL_EntryDecisionCallback entry_decision_cb,
+                                   void *cls);
+
+
+/**
+ * Reconnect to an already entered place as guest.
+ *
+ * @param gconn
+ *        Guest connection handle.
+ *        @see GNUNET_SOCIAL_app_connect() & GNUNET_SOCIAL_AppGuestPlaceCallback()
+ * @param flags
+ *        Flags for the entry.
+ * @param slicer
+ *        Slicer to use for processing incoming requests from guests.
+ * @param local_enter_cb
+ *        Called upon connection established to the social service.
+ * @param entry_decision_cb
+ *        Called upon receiving entry decision.
+ *
+ * @return NULL on errors, otherwise handle for the guest.
+ */
+struct GNUNET_SOCIAL_Guest *
+GNUNET_SOCIAL_guest_enter_reconnect (struct GNUNET_SOCIAL_GuestConnection *gconn,
+                                     enum GNUNET_PSYC_SlaveJoinFlags flags,
+                                     struct GNUNET_PSYC_Slicer *slicer,
+                                     GNUNET_SOCIAL_GuestEnterCallback local_enter_cb,
+                                     void *cls);
+
+
+/**
+ * Flags for talking to the host of a place.
+ */
+enum GNUNET_SOCIAL_TalkFlags
+{
+  GNUNET_SOCIAL_TALK_NONE = 0
+};
+
+
+/**
+ * A talk request.
+ */
+struct GNUNET_SOCIAL_TalkRequest;
+
+
+/**
+ * Talk to the host of the place.
+ *
+ * @param place
+ *        Place where we want to talk to the host.
+ * @param method_name
+ *        Method to invoke on the host.
+ * @param env
+ *        Environment containing variables for the message, or NULL.
+ * @param notify_data
+ *        Function to use to get the payload for the method.
+ * @param notify_data_cls
+ *        Closure for @a notify_data.
+ * @param flags
+ *        Flags for the message being sent.
+ *
+ * @return NULL if we are already trying to talk to the host,
+ *         otherwise handle to cancel the request.
+ */
+struct GNUNET_SOCIAL_TalkRequest *
+GNUNET_SOCIAL_guest_talk (struct GNUNET_SOCIAL_Guest *guest,
+                          const char *method_name,
+                          const struct GNUNET_PSYC_Environment *env,
+                          GNUNET_PSYC_TransmitNotifyData notify_data,
+                          void *notify_data_cls,
+                          enum GNUNET_SOCIAL_TalkFlags flags);
+
+
+/**
+ * Resume talking to the host of the place.
+ *
+ * @param tr
+ *        Talk request to resume.
+ */
+void
+GNUNET_SOCIAL_guest_talk_resume (struct GNUNET_SOCIAL_TalkRequest *tr);
+
+
+/**
+ * Cancel talking to the host of the place.
+ *
+ * @param tr
+ *        Talk request to cancel.
+ */
+void
+GNUNET_SOCIAL_guest_talk_cancel (struct GNUNET_SOCIAL_TalkRequest *tr);
+
+
+/**
+ * Disconnect from a place.
+ *
+ * Invalidates guest handle.
+ *
+ * @param gst
+ *        The guest to disconnect.
+ * @param disconnect_cb
+ *        Function called after disconnected from the service.
+ * @param cls
+ *        Closure for @a disconnect_cb.
+ */
+void
+GNUNET_SOCIAL_guest_disconnect (struct GNUNET_SOCIAL_Guest *gst,
+                                GNUNET_ContinuationCallback disconnect_cb,
+                                void *cls);
+
+
+/**
+ * Leave a place temporarily or permanently.
+ *
+ * Notifies the owner of the place about leaving, and destroys the place handle.
+ *
+ * @param place
+ *        Place to leave.
+ * @param env
+ *        Optional environment for the leave message if @a keep_active
+ *        is #GNUNET_NO.  NULL if not needed.
+ * @param disconnect_cb
+ *        Called upon disconnecting from the social service.
+ */
+void
+GNUNET_SOCIAL_guest_leave (struct GNUNET_SOCIAL_Guest *gst,
+                           struct GNUNET_PSYC_Environment *env,
+                           GNUNET_ContinuationCallback disconnect_cb,
+                           void *leave_cls);
+
+
+/**
+ * Obtain handle for a place entered as guest.
+ *
+ * The returned handle can be used to access the place API.
+ *
+ * @param guest  Handle for the guest.
+ *
+ * @return Handle for the place, valid as long as @a guest is valid.
+ */
+struct GNUNET_SOCIAL_Place *
+GNUNET_SOCIAL_guest_get_place (struct GNUNET_SOCIAL_Guest *guest);
+
+
+/**
+ * A history request.
+ */
+struct GNUNET_SOCIAL_HistoryRequest;
+
+
+/**
+ * Get the public key of a place.
+ *
+ * @param plc
+ *        Place.
+ *
+ * @return Public key of the place.
+ */
+const struct GNUNET_CRYPTO_EddsaPublicKey *
+GNUNET_SOCIAL_place_get_pub_key (const struct GNUNET_SOCIAL_Place *plc);
+
+
+/**
+ * Set message processing @a flags for a @a method_prefix.
+ *
+ * @param plc
+ *        Place.
+ * @param method_prefix
+ *        Method prefix @a flags apply to.
+ * @param flags
+ *        The flags that apply to a matching @a method_prefix.
+ */
+void
+GNUNET_SOCIAL_place_msg_proc_set (struct GNUNET_SOCIAL_Place *plc,
+                                  const char *method_prefix,
+                                  enum GNUNET_SOCIAL_MsgProcFlags flags);
+
+/**
+ * Clear all message processing flags previously set for this place.
+ */
+void
+GNUNET_SOCIAL_place_msg_proc_clear (struct GNUNET_SOCIAL_Place *plc);
+
+
+/**
+ * Learn about the history of a place.
+ *
+ * Messages are returned through the @a slicer function
+ * and have the #GNUNET_PSYC_MESSAGE_HISTORIC flag set.
+ *
+ * @param place
+ *        Place we want to learn more about.
+ * @param start_message_id
+ *        First historic message we are interested in.
+ * @param end_message_id
+ *        Last historic message we are interested in (inclusive).
+ * @param method_prefix
+ *        Only retrieve messages with this method prefix.
+ * @param flags
+ *        OR'ed GNUNET_PSYC_HistoryReplayFlags
+ * @param slicer
+ *        Slicer to use for retrieved messages.
+ *        Can be the same as the slicer of the place.
+ * @param result_cb
+ *        Function called after all messages retrieved.
+ *        NULL if not needed.
+ * @param cls Closure for @a result_cb.
+ */
+struct GNUNET_SOCIAL_HistoryRequest *
+GNUNET_SOCIAL_place_history_replay (struct GNUNET_SOCIAL_Place *plc,
+                                    uint64_t start_message_id,
+                                    uint64_t end_message_id,
+                                    const char *method_prefix,
+                                    uint32_t flags,
+                                    struct GNUNET_PSYC_Slicer *slicer,
+                                    GNUNET_ResultCallback result_cb,
+                                    void *cls);
+
+
+/**
+ * Learn about the history of a place.
+ *
+ * Sends messages through the slicer function of the place where
+ * start_message_id <= message_id <= end_message_id.
+ * The messages will have the #GNUNET_PSYC_MESSAGE_HISTORIC flag set.
+ *
+ * To get the latest message, use 0 for both the start and end message ID.
+ *
+ * @param place
+ *        Place we want to learn more about.
+ * @param message_limit
+ *        Maximum number of historic messages we are interested in.
+ * @param result_cb
+ *        Function called after all messages retrieved.
+ *        NULL if not needed.
+ * @param cls Closure for @a result_cb.
+ */
+struct GNUNET_SOCIAL_HistoryRequest *
+GNUNET_SOCIAL_place_history_replay_latest (struct GNUNET_SOCIAL_Place *plc,
+                                           uint64_t message_limit,
+                                           const char *method_prefix,
+                                           uint32_t flags,
+                                           struct GNUNET_PSYC_Slicer *slicer,
+                                           GNUNET_ResultCallback result_cb,
+                                           void *cls);
+
+/**
+ * Cancel learning about the history of a place.
+ *
+ * @param hist
+ *        History lesson to cancel.
+ */
+void
+GNUNET_SOCIAL_place_history_replay_cancel (struct GNUNET_SOCIAL_HistoryRequest *hist);
+
+
+struct GNUNET_SOCIAL_LookHandle;
+
+
+/**
+ * Look at a particular object in the place.
+ *
+ * The best matching object is returned (its name might be less specific than
+ * what was requested).
+ *
+ * @param place
+ *        The place to look the object at.
+ * @param full_name
+ *        Full name of the object.
+ *
+ * @return NULL if there is no such object at this place.
+ */
+struct GNUNET_SOCIAL_LookHandle *
+GNUNET_SOCIAL_place_look_at (struct GNUNET_SOCIAL_Place *plc,
+                             const char *full_name,
+                             GNUNET_PSYC_StateVarCallback var_cb,
+                             GNUNET_ResultCallback result_cb,
+                             void *cls);
+
+/**
+ * Look for objects in the place with a matching name prefix.
+ *
+ * @param place
+ *        The place to look its objects at.
+ * @param name_prefix
+ *        Look at objects with names beginning with this value.
+ * @param var_cb
+ *        Function to call for each object found.
+ * @param cls
+ *        Closure for callback function.
+ *
+ * @return Handle that can be used to stop looking at objects.
+ */
+struct GNUNET_SOCIAL_LookHandle *
+GNUNET_SOCIAL_place_look_for (struct GNUNET_SOCIAL_Place *plc,
+                              const char *name_prefix,
+                              GNUNET_PSYC_StateVarCallback var_cb,
+                              GNUNET_ResultCallback result_cb,
+                              void *cls);
+
+
+/**
+ * Stop looking at objects.
+ *
+ * @param lh Look handle to stop.
+ */
+void
+GNUNET_SOCIAL_place_look_cancel (struct GNUNET_SOCIAL_LookHandle *lh);
+
+
+/**
+ * Advertise a @e place in the GNS zone of @a ego.
+ *
+ * @param app
+ *        Application handle.
+ * @param ego
+ *        Ego.
+ * @param place_pub_key
+ *        Public key of place to add.
+ * @param name
+ *        The name for the PLACE record to put in the zone.
+ * @param password
+ *        Password used to encrypt the record or NULL to keep it cleartext.
+ * @param relay_count
+ *        Number of elements in the @a relays array.
+ * @param relays
+ *        List of relays to put in the PLACE record to advertise
+ *        as entry points to the place in addition to the origin.
+ * @param expiration_time
+ *        Expiration time of the record, use 0 to remove the record.
+ * @param result_cb
+ *        Function called with the result of the operation.
+ * @param result_cls
+ *        Closure for @a result_cb
+ *
+ * @return #GNUNET_OK if the request was sent,
+ *         #GNUNET_SYSERR on error, e.g. the name/password is too long.
+ */
+int
+GNUNET_SOCIAL_zone_add_place (const struct GNUNET_SOCIAL_App *app,
+                              const struct GNUNET_SOCIAL_Ego *ego,
+                              const char *name,
+                              const char *password,
+                              const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                              const struct GNUNET_PeerIdentity *origin,
+                              uint32_t relay_count,
+                              const struct GNUNET_PeerIdentity *relays,
+                              struct GNUNET_TIME_Absolute expiration_time,
+                              GNUNET_ResultCallback result_cb,
+                              void *result_cls);
+
+
+/**
+ * Add public key to the GNS zone of the @e ego.
+ *
+ * @param cfg
+ *        Configuration.
+ * @param ego
+ *        Ego.
+ * @param name
+ *        The name for the PKEY record to put in the zone.
+ * @param nym_pub_key
+ *        Public key of nym to add.
+ * @param expiration_time
+ *        Expiration time of the record, use 0 to remove the record.
+ * @param result_cb
+ *        Function called with the result of the operation.
+ * @param result_cls
+ *        Closure for @a result_cb
+ *
+ * @return #GNUNET_OK if the request was sent,
+ *         #GNUNET_SYSERR on error, e.g. the name is too long.
+ */
+int
+GNUNET_SOCIAL_zone_add_nym (const struct GNUNET_SOCIAL_App *app,
+                            const struct GNUNET_SOCIAL_Ego *ego,
+                            const char *name,
+                            const struct GNUNET_CRYPTO_EcdsaPublicKey *nym_pub_key,
+                            struct GNUNET_TIME_Absolute expiration_time,
+                            GNUNET_ResultCallback result_cb,
+                            void *result_cls);
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_SOCIAL_SERVICE_H */
+#endif
+
+/** @} */  /* end of group */