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+/*
+ * libEtPan! -- a mail stuff library
+ *
+ * Copyright (C) 2001, 2002 - DINH Viet Hoa
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the libEtPan! project nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * $Id$
+ */
+
+#ifndef MAILDRIVER_TYPES_H
+
+#define MAILDRIVER_TYPES_H
+
+#include <inttypes.h>
+#include <sys/types.h>
+
+#include <libetpan/mailstream.h>
+#include <libetpan/mailimf.h>
+#include <libetpan/mailmime.h>
+#include <libetpan/carray.h>
+
+#include <libetpan/mailthread_types.h>
+#include <libetpan/maildriver_errors.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct mailsession_driver mailsession_driver;
+
+typedef struct mailsession mailsession;
+
+typedef struct mailmessage_driver mailmessage_driver;
+
+typedef struct mailmessage mailmessage;
+
+
+/*
+  mailmessage_list is a list of mailmessage
+  
+  - tab is an array of mailmessage structures
+*/
+
+struct mailmessage_list {
+  carray * msg_tab; /* elements are (mailmessage *) */
+};
+
+struct mailmessage_list * mailmessage_list_new(carray * msg_tab);
+void mailmessage_list_free(struct mailmessage_list * env_list);
+
+/*
+  mail_list is a list of mailbox names
+
+  - list is a list of mailbox names
+*/
+
+struct mail_list {
+  clist * mb_list; /* elements are (char *) */
+};
+
+struct mail_list * mail_list_new(clist * mb_list);
+void mail_list_free(struct mail_list * resp);
+
+/*
+  This is a flag value.
+  Flags can be combined with OR operation
+*/
+
+enum {
+  MAIL_FLAG_NEW       = 1 << 0,
+  MAIL_FLAG_SEEN      = 1 << 1,
+  MAIL_FLAG_FLAGGED   = 1 << 2,
+  MAIL_FLAG_DELETED   = 1 << 3,
+  MAIL_FLAG_ANSWERED  = 1 << 4,
+  MAIL_FLAG_FORWARDED = 1 << 5,
+  MAIL_FLAG_CANCELLED = 1 << 6,
+};
+
+/*
+  mail_flags is the value of a flag related to a message.
+  
+  - flags is the standard flags value
+
+  - extension is a list of unknown flags for libEtPan!
+*/
+
+struct mail_flags {
+  uint32_t fl_flags;
+  clist * fl_extension; /* elements are (char *) */
+};
+
+struct mail_flags * mail_flags_new(uint32_t fl_flags, clist * fl_ext);
+void mail_flags_free(struct mail_flags * flags);
+
+/*
+  This function creates a flag for a new message
+*/
+
+struct mail_flags * mail_flags_new_empty(void);
+
+
+/*
+  mailimf_date_time_comp compares two dates
+  
+  
+*/
+
+int32_t mailimf_date_time_comp(struct mailimf_date_time * date1,
+    struct mailimf_date_time * date2);
+
+/*
+  this is type type of the search criteria
+*/
+
+enum {
+  MAIL_SEARCH_KEY_ALL,        /* all messages correspond */
+  MAIL_SEARCH_KEY_ANSWERED,   /* messages with flag \Answered */
+  MAIL_SEARCH_KEY_BCC,        /* messages which Bcc field contains
+                                 a given string */
+  MAIL_SEARCH_KEY_BEFORE,     /* messages which internal date is earlier
+                                 than the specified date */
+  MAIL_SEARCH_KEY_BODY,       /* message that contains the given string
+                                 (in header and text parts) */
+  MAIL_SEARCH_KEY_CC,         /* messages whose Cc field contains the
+                                 given string */
+  MAIL_SEARCH_KEY_DELETED,    /* messages with the flag \Deleted */
+  MAIL_SEARCH_KEY_FLAGGED,    /* messages with the flag \Flagged */ 
+  MAIL_SEARCH_KEY_FROM,       /* messages whose From field contains the
+                                 given string */
+  MAIL_SEARCH_KEY_NEW,        /* messages with the flag \Recent and not
+                                 the \Seen flag */
+  MAIL_SEARCH_KEY_OLD,        /* messages that do not have the
+                                 \Recent flag set */
+  MAIL_SEARCH_KEY_ON,         /* messages whose internal date is the
+                                 specified date */
+  MAIL_SEARCH_KEY_RECENT,     /* messages with the flag \Recent */
+  MAIL_SEARCH_KEY_SEEN,       /* messages with the flag \Seen */
+  MAIL_SEARCH_KEY_SINCE,      /* messages whose internal date is later
+                                 than specified date */
+  MAIL_SEARCH_KEY_SUBJECT,    /* messages whose Subject field contains the
+                                 given string */
+  MAIL_SEARCH_KEY_TEXT,       /* messages whose text part contains the
+                                 given string */
+  MAIL_SEARCH_KEY_TO,         /* messages whose To field contains the
+                                 given string */
+  MAIL_SEARCH_KEY_UNANSWERED, /* messages with no flag \Answered */
+  MAIL_SEARCH_KEY_UNDELETED,  /* messages with no flag \Deleted */
+  MAIL_SEARCH_KEY_UNFLAGGED,  /* messages with no flag \Flagged */
+  MAIL_SEARCH_KEY_UNSEEN,     /* messages with no flag \Seen */
+  MAIL_SEARCH_KEY_HEADER,     /* messages whose given field 
+                                 contains the given string */
+  MAIL_SEARCH_KEY_LARGER,     /* messages whose size is larger then
+                                 the given size */
+  MAIL_SEARCH_KEY_NOT,        /* not operation of the condition */
+  MAIL_SEARCH_KEY_OR,         /* or operation between two conditions */
+  MAIL_SEARCH_KEY_SMALLER,    /* messages whose size is smaller than
+                                 the given size */
+  MAIL_SEARCH_KEY_MULTIPLE    /* the boolean operator between the
+                                 conditions is AND */
+};
+
+/*
+  mail_search_key is the condition on the messages to return
+  
+  - type is the type of the condition
+
+  - bcc is the text to search in the Bcc field when type is
+    MAIL_SEARCH_KEY_BCC, should be allocated with malloc()
+
+  - before is a date when type is MAIL_SEARCH_KEY_BEFORE
+
+  - body is the text to search in the message when type is
+    MAIL_SEARCH_KEY_BODY, should be allocated with malloc()
+
+  - cc is the text to search in the Cc field when type is
+    MAIL_SEARCH_KEY_CC, should be allocated with malloc()
+  
+  - from is the text to search in the From field when type is
+    MAIL_SEARCH_KEY_FROM, should be allocated with malloc()
+
+  - on is a date when type is MAIL_SEARCH_KEY_ON
+
+  - since is a date when type is MAIL_SEARCH_KEY_SINCE
+  
+  - subject is the text to search in the Subject field when type is
+    MAILIMAP_SEARCH_KEY_SUBJECT, should be allocated with malloc()
+
+  - text is the text to search in the text part of the message when
+    type is MAILIMAP_SEARCH_KEY_TEXT, should be allocated with malloc()
+
+  - to is the text to search in the To field when type is
+    MAILIMAP_SEARCH_KEY_TO, should be allocated with malloc()
+
+  - header_name is the header name when type is MAILIMAP_SEARCH_KEY_HEADER,
+    should be allocated with malloc()
+
+  - header_value is the text to search in the given header when type is
+    MAILIMAP_SEARCH_KEY_HEADER, should be allocated with malloc()
+
+  - larger is a size when type is MAILIMAP_SEARCH_KEY_LARGER
+
+  - not is a condition when type is MAILIMAP_SEARCH_KEY_NOT
+
+  - or1 is a condition when type is MAILIMAP_SEARCH_KEY_OR
+
+  - or2 is a condition when type is MAILIMAP_SEARCH_KEY_OR
+  
+  - sentbefore is a date when type is MAILIMAP_SEARCH_KEY_SENTBEFORE
+
+  - senton is a date when type is MAILIMAP_SEARCH_KEY_SENTON
+
+  - sentsince is a date when type is MAILIMAP_SEARCH_KEY_SENTSINCE
+
+  - smaller is a size when type is MAILIMAP_SEARCH_KEY_SMALLER
+
+  - multiple is a set of message when type is MAILIMAP_SEARCH_KEY_MULTIPLE
+*/
+
+#if 0
+struct mail_search_key {
+  int sk_type;
+  union {
+    char * sk_bcc;
+    struct mailimf_date_time * sk_before;
+    char * sk_body;
+    char * sk_cc;
+    char * sk_from;
+    struct mailimf_date_time * sk_on;
+    struct mailimf_date_time * sk_since;
+    char * sk_subject;
+    char * sk_text;
+    char * sk_to;
+    char * sk_header_name;
+    char * sk_header_value;
+    size_t sk_larger;
+    struct mail_search_key * sk_not;
+    struct mail_search_key * sk_or1;
+    struct mail_search_key * sk_or2;
+    size_t sk_smaller;
+    clist * sk_multiple; /* list of (struct mailimap_search_key *) */
+  } sk_data;
+};
+
+
+struct mail_search_key *
+mail_search_key_new(int sk_type,
+    char * sk_bcc, struct mailimf_date_time * sk_before,
+    char * sk_body, char * sk_cc, char * sk_from,
+    struct mailimf_date_time * sk_on, struct mailimf_date_time * sk_since,
+    char * sk_subject, char * sk_text, char * sk_to,
+    char * sk_header_name, char * sk_header_value, size_t sk_larger,
+    struct mail_search_key * sk_not, struct mail_search_key * sk_or1,
+    struct mail_search_key * sk_or2, size_t sk_smaller,
+    clist * sk_multiple);
+
+void mail_search_key_free(struct mail_search_key * key);
+#endif
+
+/*
+  mail_search_result is a list of message numbers that is returned
+  by the mailsession_search_messages function()
+*/
+
+#if 0
+struct mail_search_result {
+  clist * sr_list; /* list of (uint32_t *) */
+};
+
+struct mail_search_result * mail_search_result_new(clist * sr_list);
+
+void mail_search_result_free(struct mail_search_result * search_result);
+#endif
+
+
+/*
+  There is three kinds of identities :
+  - storage
+  - folders
+  - session
+
+  A storage (struct mailstorage) represents whether a server or
+  a main path,
+
+  A storage can be an IMAP server, the root path of a MH or a mbox file.
+
+  Folders (struct mailfolder) are the mailboxes we can
+  choose in the server or as sub-folder of the main path.
+
+  Folders for IMAP are the IMAP mailboxes, for MH this is one of the
+  folder of the MH storage, for mbox, there is only one folder, the
+  mbox file content;
+
+  A mail session (struct mailsession) is whether a connection to a server
+  or a path that is open. It is the abstraction lower folders and storage.
+  It allow us to send commands.
+
+  We have a session driver for mail session for each kind of storage.
+
+  From a session, we can get a message (struct mailmessage) to read.
+  We have a message driver for each kind of storage.
+*/
+
+/*
+  maildriver is the driver structure for mail sessions
+
+  - name is the name of the driver
+  
+  - initialize() is the function that will initializes a data structure
+      specific to the driver, it returns a value that will be stored
+      in the field data of the session.
+      The field data of the session is the state of the session,
+      the internal data structure used by the driver.
+      It is called when creating the mailsession structure with
+      mailsession_new().
+  
+  - uninitialize() frees the structure created with initialize()
+
+  - parameters() implements functions specific to the given mail access
+  
+  - connect_stream() connects a stream to the session
+
+  - connect_path() notify a main path to the session
+
+  - starttls() changes the current stream to a TLS stream
+  
+  - login() notifies the user and the password to authenticate to the
+      session
+
+  - logout() exits the session and closes the stream
+
+  - noop() does no operation on the session, but it can be
+      used to poll for the status of the connection.
+
+  - build_folder_name() will return an allocated string with
+      that contains the complete path of the folder to create
+
+  - create_folder() creates the folder that corresponds to the
+      given name
+
+  - delete_folder() deletes the folder that corresponds to the
+      given name
+
+  - rename_folder() change the name of the folder
+
+  - check_folder() makes a checkpoint of the session
+
+  - examine_folder() selects a mailbox as readonly
+
+  - select_folder() selects a mailbox
+
+  - expunge_folder() deletes all messages marked \Deleted
+
+  - status_folder() queries the status of the folder
+      (number of messages, number of recent messages, number of
+      unseen messages)
+
+  - messages_number() queries the number of messages in the folder
+
+  - recent_number() queries the number of recent messages in the folder
+
+  - unseen_number() queries the number of unseen messages in the folder
+
+  - list_folders() returns the list of all sub-mailboxes
+      of the given mailbox
+
+  - lsub_folders() returns the list of subscribed
+      sub-mailboxes of the given mailbox
+
+  - subscribe_folder() subscribes to the given mailbox
+
+  - unsubscribe_folder() unsubscribes to the given mailbox
+
+  - append_message() adds a RFC 2822 message to the current
+      given mailbox
+
+  - copy_message() copies a message whose number is given to
+       a given mailbox. The mailbox must be accessible from
+       the same session.
+
+  - move_message() copies a message whose number is given to
+       a given mailbox. The mailbox must be accessible from the
+       same session.
+
+  - get_messages_list() returns the list of message numbers
+      of the current mailbox.
+
+  - get_envelopes_list() fills the parsed fields in the
+      mailmessage structures of the mailmessage_list.
+
+  - remove_message() removes the given message from the mailbox.
+      The message is permanently deleted.
+
+  - search_message() returns a list of message numbers that
+      corresponds to the given criteria.
+
+  - get_message returns a mailmessage structure that corresponds
+      to the given message number.
+
+  - get_message_by_uid returns a mailmessage structure that corresponds
+      to the given message unique identifier.
+
+  * mandatory functions are the following :
+
+  - connect_stream() of connect_path()
+  - logout()
+  - get_messages_list()
+  - get_envelopes_list()
+
+  * we advise you to implement these functions :
+
+  - select_folder() (in case a session can access several folders)
+  - noop() (to check if the server is responding)
+  - check_folder() (to make a checkpoint of the session)
+  - status_folder(), messages_number(), recent_number(), unseen_number()
+      (to get stat of the folder)
+  - append_message() (but can't be done in the case of POP3 at least)
+  - login() in a case of an authenticated driver.
+  - starttls() in a case of a stream driver, if the procotol supports
+      STARTTLS.
+  - get_message_by_uid() so that the application can remember the message
+      by UID and build its own list of messages.
+
+  * drivers' specific :
+
+  Everything that is specific to the driver will be implemented in this
+  function :
+
+  - parameters()
+*/
+
+struct mailsession_driver {
+  char * sess_name;
+
+  int (* sess_initialize)(mailsession * session);
+  void (* sess_uninitialize)(mailsession * session);
+
+  int (* sess_parameters)(mailsession * session,
+      int id, void * value);
+
+  int (* sess_connect_stream)(mailsession * session, mailstream * s);
+  int (* sess_connect_path)(mailsession * session, char * path);
+
+  int (* sess_starttls)(mailsession * session);
+
+  int (* sess_login)(mailsession * session, char * userid, char * password);
+  int (* sess_logout)(mailsession * session);
+  int (* sess_noop)(mailsession * session);
+
+  /* folders operations */
+
+  int (* sess_build_folder_name)(mailsession * session, char * mb,
+      char * name, char ** result);
+
+  int (* sess_create_folder)(mailsession * session, char * mb);
+  int (* sess_delete_folder)(mailsession * session, char * mb);
+  int (* sess_rename_folder)(mailsession * session, char * mb,
+      char * new_name);
+  int (* sess_check_folder)(mailsession * session);
+  int (* sess_examine_folder)(mailsession * session, char * mb);
+  int (* sess_select_folder)(mailsession * session, char * mb);
+  int (* sess_expunge_folder)(mailsession * session);
+  int (* sess_status_folder)(mailsession * session, char * mb,
+      uint32_t * result_num, uint32_t * result_recent,
+      uint32_t * result_unseen);
+  int (* sess_messages_number)(mailsession * session, char * mb,
+      uint32_t * result);
+  int (* sess_recent_number)(mailsession * session, char * mb,
+      uint32_t * result);
+  int (* sess_unseen_number)(mailsession * session, char * mb,
+      uint32_t * result);
+
+  int (* sess_list_folders)(mailsession * session, char * mb,
+      struct mail_list ** result);
+  int (* sess_lsub_folders)(mailsession * session, char * mb,
+      struct mail_list ** result);
+
+  int (* sess_subscribe_folder)(mailsession * session, char * mb);
+  int (* sess_unsubscribe_folder)(mailsession * session, char * mb);
+
+  /* messages operations */
+
+  int (* sess_append_message)(mailsession * session,
+      char * message, size_t size);
+  int (* sess_copy_message)(mailsession * session,
+      uint32_t num, char * mb);
+  int (* sess_move_message)(mailsession * session,
+      uint32_t num, char * mb);
+
+  int (* sess_get_message)(mailsession * session,
+      uint32_t num, mailmessage ** result);
+
+  int (* sess_get_message_by_uid)(mailsession * session,
+      const char * uid, mailmessage ** result);
+  
+  int (* sess_get_messages_list)(mailsession * session,
+      struct mailmessage_list ** result);
+  int (* sess_get_envelopes_list)(mailsession * session,
+      struct mailmessage_list * env_list);
+  int (* sess_remove_message)(mailsession * session, uint32_t num);
+#if 0
+  int (* sess_search_messages)(mailsession * session, char * charset,
+      struct mail_search_key * key,
+      struct mail_search_result ** result);
+#endif
+};
+
+
+/*
+  session is the data structure for a mail session.
+
+  - data is the internal data structure used by the driver
+    It is called when initializing the mailsession structure.
+
+  - driver is the driver used for the session
+*/
+
+struct mailsession {
+  void * sess_data;
+  mailsession_driver * sess_driver;
+};
+
+
+
+
+/*
+  mailmessage_driver is the driver structure to get information from messages.
+  
+  - name is the name of the driver
+
+  - initialize() is the function that will initializes a data structure
+      specific to the driver, it returns a value that will be stored
+      in the field data of the mailsession.
+      The field data of the session is the state of the session,
+      the internal data structure used by the driver.
+      It is called when initializing the mailmessage structure with
+      mailmessage_init().
+  
+  - uninitialize() frees the structure created with initialize().
+      It will be called by mailmessage_free().
+
+  - flush() will free from memory all temporary structures of the message
+      (for example, the MIME structure of the message).
+
+  - fetch_result_free() will free all strings resulted by fetch() or
+      any fetch_xxx() functions that returns a string.
+
+  - fetch() returns the content of the message (headers and text).
+
+  - fetch_header() returns the content of the headers.
+
+  - fetch_body() returns the message text (message content without headers)
+
+  - fetch_size() returns the size of the message content.
+
+  - get_bodystructure() returns the MIME structure of the message.
+
+  - fetch_section() returns the content of a given MIME part
+
+  - fetch_section_header() returns the header of the message
+      contained by the given MIME part.
+
+  - fetch_section_mime() returns the MIME headers of the
+      given MIME part.
+
+  - fetch_section_body() returns the text (if this is a message, this is the
+      message content without headers) of the given MIME part.
+
+  - fetch_envelope() returns a mailimf_fields structure, with a list of
+      fields chosen by the driver.
+
+  - get_flags() returns a the flags related to the message.
+      When you want to get flags of a message, you have to make sure to
+      call get_flags() at least once before using directly message->flags.
+*/
+
+#define LIBETPAN_MAIL_MESSAGE_CHECK
+
+struct mailmessage_driver {
+  char * msg_name;
+
+  int (* msg_initialize)(mailmessage * msg_info);
+ 
+  void (* msg_uninitialize)(mailmessage * msg_info);
+  
+  void (* msg_flush)(mailmessage * msg_info);
+
+  void (* msg_check)(mailmessage * msg_info);
+
+  void (* msg_fetch_result_free)(mailmessage * msg_info,
+                             char * msg);
+
+  int (* msg_fetch)(mailmessage * msg_info,
+                char ** result,
+                size_t * result_len);
+       
+  int (* msg_fetch_header)(mailmessage * msg_info,
+                       char ** result,
+                       size_t * result_len);
+  
+  int (* msg_fetch_body)(mailmessage * msg_info,
+                     char ** result, size_t * result_len);
+
+  int (* msg_fetch_size)(mailmessage * msg_info,
+                     size_t * result);
+  
+  int (* msg_get_bodystructure)(mailmessage * msg_info,
+                            struct mailmime ** result);
+  
+  int (* msg_fetch_section)(mailmessage * msg_info,
+                        struct mailmime * mime,
+                        char ** result, size_t * result_len);
+  
+  int (* msg_fetch_section_header)(mailmessage * msg_info,
+                               struct mailmime * mime,
+                               char ** result,
+                               size_t * result_len);
+  
+  int (* msg_fetch_section_mime)(mailmessage * msg_info,
+                             struct mailmime * mime,
+                             char ** result,
+                             size_t * result_len);
+  
+  int (* msg_fetch_section_body)(mailmessage * msg_info,
+                             struct mailmime * mime,
+                             char ** result,
+                             size_t * result_len);
+
+  int (* msg_fetch_envelope)(mailmessage * msg_info,
+                         struct mailimf_fields ** result);
+
+  int (* msg_get_flags)(mailmessage * msg_info,
+                    struct mail_flags ** result);
+};
+
+
+/*
+  mailmessage is a data structure to get information from messages
+
+  - session is the session linked to the given message, it can be NULL
+
+  - driver is the message driver
+  
+  - index is the message number
+
+  - uid, when it is not NULL, it means that the folder 
+      the folder has persistant message numbers, the string is
+      the unique message number in the folder.
+      uid should be implemented if possible.
+      for drivers where we cannot generate real uid,
+      a suggestion is "AAAA-IIII" where AAAA is some
+      random session number and IIII the content of index field.
+
+  - size, when it is not 0, is the size of the message content.
+  
+  - fields, when it is not NULL, are the header fields of the message.
+
+  - flags, when it is not NULL, are the flags related to the message.
+
+  - single_fields, when resolved != 0, is filled with the data of fields.
+
+  - mime, when it is not NULL
+
+  - cached is != 0 when the header fields were read from the cache.
+  
+  - data is data specific to the driver, this is internal data structure,
+      some state of the message.
+*/
+
+struct mailmessage {
+  mailsession * msg_session;
+  mailmessage_driver * msg_driver;
+  uint32_t msg_index;
+  char * msg_uid;
+
+  size_t msg_size;
+  struct mailimf_fields * msg_fields;
+  struct mail_flags * msg_flags;
+
+  int msg_resolved;
+  struct mailimf_single_fields msg_single_fields;
+  struct mailmime * msg_mime;
+
+  /* internal data */
+
+  int msg_cached;
+  void * msg_data;
+  
+ /*
+   msg_folder field :
+   used to reference the mailfolder, this is a workaround due
+   to the problem with initial conception, where folder notion
+   did not exist.
+ */
+  void * msg_folder;
+  /* user data */
+  void * msg_user_data;
+};
+
+
+/*
+  mailmessage_tree is a node in the messages tree (thread)
+  
+  - parent is the parent of the message, it is NULL if the message
+      is the root of the message tree.
+
+  - date is the date of the message in number of second elapsed
+      since 00:00:00 on January 1, 1970, Coordinated Universal Time (UTC).
+
+  - msg is the message structure that is stored referenced by the node.
+      is msg is NULL, this is a dummy node.
+
+  - children is an array that contains all the children of the node.
+      children are mailmessage_tree structures.
+
+  - is_reply is != 0 when the message is a reply or a forward
+
+  - base_subject is the extracted subject of the message.
+
+  - index is the message number.
+*/
+
+struct mailmessage_tree {
+  struct mailmessage_tree * node_parent;
+  char * node_msgid;
+  time_t node_date;
+  mailmessage * node_msg;
+  carray * node_children; /* array of (struct mailmessage_tree *) */
+
+  /* private, used for threading */
+  int node_is_reply;
+  char * node_base_subject;
+};
+
+
+struct mailmessage_tree *
+mailmessage_tree_new(char * node_msgid, time_t node_date,
+    mailmessage * node_msg);
+
+void mailmessage_tree_free(struct mailmessage_tree * tree);
+
+/*
+  mailmessage_tree_free_recursive
+
+  if you want to release memory of the given tree and all the sub-trees,
+  you can use this function.
+*/
+
+void mailmessage_tree_free_recursive(struct mailmessage_tree * tree);
+
+
+struct generic_message_t {
+  int (* msg_prefetch)(mailmessage * msg_info);
+  void (* msg_prefetch_free)(struct generic_message_t * msg);
+  int msg_fetched;
+  char * msg_message;
+  size_t msg_length;
+  void * msg_data;
+};
+
+
+const char * maildriver_strerror(int err);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif