/*
Serval DNA MeshMS
Copyright (C) 2014 Serval Project Inc.
 
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
 
This program 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 General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

#ifndef __SERVAL_DNA__MESHMS_H
#define __SERVAL_DNA__MESHMS_H

#ifndef __MESHMS_INLINE
# if __GNUC__ && !__GNUC_STDC_INLINE__
#  define __MESHMS_INLINE extern inline
# else
#  define __MESHMS_INLINE inline
# endif
#endif

#include "rhizome.h"

#define MESHMS_MESSAGE_MAX_LEN  4095

/* The result of a MeshMS operation.  Negative indicates failure, zero or
 * positive success.
 */
enum meshms_status {
    MESHMS_STATUS_ERROR = -1, // unexpected error (underlying failure)
    MESHMS_STATUS_OK = 0, // operation succeeded, no bundle changed
    MESHMS_STATUS_UPDATED = 1, // operation succeeded, bundle updated
    MESHMS_STATUS_SID_LOCKED = 2, // cannot decode or send messages for that SID
    MESHMS_STATUS_PROTOCOL_FAULT = 3, // missing or faulty ply bundle
};

__MESHMS_INLINE int meshms_failed(enum meshms_status status) {
    return status != MESHMS_STATUS_OK && status != MESHMS_STATUS_UPDATED;
}

const char *meshms_status_message(enum meshms_status);

// the manifest details for one half of a conversation
struct meshms_ply {
  rhizome_bid_t bundle_id;
  uint64_t version;
  uint64_t tail;
  uint64_t size;
};

struct meshms_conversations {
  // binary tree
  struct meshms_conversations *_left;
  struct meshms_conversations *_right;
  // keeping a pointer to parent node here means the traversal iterator does not need a stack, so
  // there is no fixed limit on the tree depth
  struct meshms_conversations *_parent;
  
  // who are we talking to?
  sid_t them;
  
  char found_my_ply;
  struct meshms_ply my_ply;
  
  char found_their_ply;
  struct meshms_ply their_ply;
  
  // what is the offset of their last message
  uint64_t their_last_message;
  // what is the last message we marked as read
  uint64_t read_offset;
  // our cached value for the last known size of their ply
  uint64_t their_size;
};

// cursor state for reading one half of a conversation
struct meshms_ply_read {
  // rhizome payload
  struct rhizome_read read;
  // block buffer
  struct rhizome_read_buffer buff;
  // details of the current record
  uint64_t record_end_offset;
  uint16_t record_length;
  size_t record_size;
  char type;
  // raw record data
  unsigned char *record;
};

/* Fetch the list of all MeshMS conversations into a binary tree whose nodes
 * are all allocated by malloc(3).
 */
enum meshms_status meshms_conversations_list(const sid_t *my_sid, const sid_t *their_sid, struct meshms_conversations **conv);
void meshms_free_conversations(struct meshms_conversations *conv);

/* For iterating over a binary tree of all MeshMS conversations, as created by
 * meshms_conversations_list().
 *
 *      struct meshms_conversation_iterator it;
 *      meshms_conversation_iterator_start(&it, conv);
 *      while (it.current) {
 *          ...
 *          meshms_conversation_iterator_advance(&it);
 *      }
 */
struct meshms_conversation_iterator {
  struct meshms_conversations *current;
};
void meshms_conversation_iterator_start(struct meshms_conversation_iterator *, struct meshms_conversations *);
void meshms_conversation_iterator_advance(struct meshms_conversation_iterator *);

/* For iterating through the messages in a single MeshMS conversation; both
 * plys threaded (interleaved) in the order as seen by the sender.  The
 * meshms_message_iterator_prev() function returns MESHMS_STATUS_UPDATED if it
 * advances the iterator to a message, or MESHMS_STATUS_OK if there are no more
 * messages.  Any other return value indicates failure.
 *
 *      struct meshms_message_iterator it;
 *      enum meshms_status status;
 *      if (meshms_failed(status = meshms_message_iterator_open(&it, &sender_sid, &recip_sid)))
 *          return -1;
 *      while ((status = meshms_message_iterator_prev(&it)) == MESHMS_STATUS_UPDATED) {
 *          ...
 *      }
 *      meshms_message_iterator_close(&it);
 *      if (meshms_failed(status))
 *          return -1;
 *      ...
 */
struct meshms_message_iterator {
  // Public fields that remain fixed for the life of the iterator:
  const sid_t *my_sid;
  const sid_t *their_sid;
  const rhizome_bid_t *my_ply_bid;
  const rhizome_bid_t *their_ply_bid;
  uint64_t latest_ack_offset; // offset in remote (their) ply of most recent ACK
  uint64_t latest_ack_my_offset; // offset in my ply of most recent message ACKed by them
  uint64_t read_offset; // offset in remote (their) ply of most recent message read by me
  // The following public fields change per message:
  enum meshms_which_ply { MY_PLY, THEIR_PLY } which_ply;
  enum { MESSAGE_SENT, MESSAGE_RECEIVED, ACK_RECEIVED } type;
  // For MESSAGE_SENT 'offset' is the byte position within the local ply
  // (mine).  For MESSAGE_RECEIVED and ACK_RECEIVED, it is the byte position
  // within the remote ply (theirs).
  time_s_t timestamp;
  uint64_t offset;
  const char *text; // text of UTF8 message (NUL terminated)
  size_t text_length; // excluding terminating NUL
  union {
    bool_t delivered; // for MESSAGE_SENT
    bool_t read; // for MESSAGE_RECEIVED
    uint64_t ack_offset; // for ACK_RECEIVED
  };
  // Private implementation -- could change, so don't use them.
  sid_t _my_sid;
  struct meshms_conversations *_conv;
  rhizome_manifest *_my_manifest;
  rhizome_manifest *_their_manifest;
  struct meshms_ply_read _my_reader;
  struct meshms_ply_read _their_reader;
  uint64_t _end_range;
  bool_t _in_ack;
};
enum meshms_status meshms_message_iterator_open(struct meshms_message_iterator *, const sid_t *me, const sid_t *them);
int meshms_message_iterator_is_open(const struct meshms_message_iterator *);
void meshms_message_iterator_close(struct meshms_message_iterator *);
enum meshms_status meshms_message_iterator_prev(struct meshms_message_iterator *);

/* Append a message ('message_len' bytes of UTF8 at 'message') to the sender's
 * ply in the conversation between 'sender' and 'recipient'.  If no
 * conversation (ply bundle) exists, then create it.  Returns
 * MESHMS_STATUS_UPDATED on success, any other value indicates a failure or
 * error (which is already logged).
 */
enum meshms_status meshms_send_message(const sid_t *sender, const sid_t *recipient, const char *message, size_t message_len);

/* Update the read offset for one or more conversations.  Returns
 * MESHMS_STATUS_UPDATED on success, any other value indicates a failure or
 * error (which is already logged).
 *
 * If 'offset' is greater than a conversation's last-received offset, then it
 * is clamped to the last-received offset.  This means that passing an offset
 * of UINT64_MAX will mark the conversation as fully read, and an offset of
 * zero will have no effect.
 *
 * If 'recipient' is NULL then all of the sender's conversations are marked
 * with the given read offset.  In this case it only makes sense to pass an
 * offest of UINT64_MAX.
 */
enum meshms_status meshms_mark_read(const sid_t *sender, const sid_t *recipient, uint64_t offset);

#endif // __SERVAL_DNA__MESHMS_H