/*
Serval DNA MeshMS HTTP RESTful interface
Copyright (C) 2013,2014 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.
*/

#include "serval.h"
#include "conf.h"
#include "httpd.h"
#include "str.h"
#include "numeric_str.h"
#include "base64.h"
#include "strbuf_helpers.h"
#include "debug.h"

DEFINE_FEATURE(http_rest_meshms);

DECLARE_HANDLER("/restful/meshms/", restful_meshms_);

static void on_rhizome_bundle_added(httpd_request *r, rhizome_manifest *m);

static void finalise_union_meshms_conversationlist(httpd_request *r)
{
  meshms_free_conversations(r->u.mclist.conv);
  r->u.mclist.conv = NULL;
}

static void finalise_union_meshms_messagelist(httpd_request *r)
{
  meshms_message_iterator_close(&r->u.msglist.iter);
}

static void finalise_union_meshms_sendmessage(httpd_request *r)
{
  form_buf_malloc_release(&r->u.sendmsg.message);
}

#define MAX_TOKEN_LEN 21
#define MESHMS_TOKEN_STRLEN (BASE64_ENCODED_LEN(MAX_TOKEN_LEN))
#define alloca_meshms_token(pos) meshms_token_to_str(alloca(MESHMS_TOKEN_STRLEN + 1), (pos))

static char *meshms_token_to_str(char *buf, struct meshms_position *pos)
{
  uint8_t tmp[MAX_TOKEN_LEN];
  int ofs = 0;
  tmp[ofs++]=pos->which_ply;
  ofs += pack_uint(tmp + ofs, pos->offset);
  ofs += pack_uint(tmp + ofs, pos->their_ack);
  assert(ofs <= MAX_TOKEN_LEN);
  size_t n = base64url_encode(buf, tmp, ofs);
  assert(n <= MESHMS_TOKEN_STRLEN);
  buf[n] = '\0';
  return buf;
}

static int strn_to_meshms_token(const char *str, struct meshms_position *pos, const char **afterp)
{
  uint8_t token[MAX_TOKEN_LEN];
  size_t token_len = base64url_decode(token, sizeof token, str, 0, afterp, 0, NULL);
  if (token_len < 3)
    goto blank;

  size_t ofs=0;
  pos->which_ply = token[ofs++];
  int unpacked;
  if ((unpacked = unpack_uint(token + ofs, token_len - ofs, &pos->offset))==-1)
    goto blank;

  ofs += unpacked;
  if ((unpacked = unpack_uint(token + ofs, token_len - ofs, &pos->their_ack))==-1)
    goto blank;

  (*afterp)++;
  return 1;

blank:
  // don't skip the token
  *afterp=str;
  pos->which_ply = MY_PLY;
  pos->offset = 0;
  pos->their_ack = 0;
  return 1;
}

static int http_request_meshms_response(struct httpd_request *r, uint16_t result, const char *message, enum meshms_status status)
{
  uint16_t meshms_result = 0;
  const char *meshms_message = NULL;
  switch (status) {
    case MESHMS_STATUS_OK:
      meshms_result = 200;
      break;
    case MESHMS_STATUS_UPDATED:
      meshms_result = 201; // Created
      meshms_message = "Updated";
      break;
    case MESHMS_STATUS_SID_LOCKED:
      meshms_result = 419; // Authentication Timeout
      meshms_message = "Identity locked";
      break;
    case MESHMS_STATUS_PROTOCOL_FAULT:
      meshms_result = 500;
      meshms_message = "MeshMS protocol fault";
      break;
    case MESHMS_STATUS_ERROR:
      meshms_result = 500;
      break;
  }
  if (meshms_result == 0) {
    WHYF("Invalid MeshMS status code %d", status);
    meshms_result = 500;
  }
  r->http.response.result_extra[0].label = "meshms_status_code";
  r->http.response.result_extra[0].value.type = JSON_INTEGER;
  r->http.response.result_extra[0].value.u.integer = status;
  const char *status_message = meshms_status_message(status);
  if (status_message) {
    r->http.response.result_extra[1].label = "meshms_status_message";
    r->http.response.result_extra[1].value.type = JSON_STRING_NULTERM;
    r->http.response.result_extra[1].value.u.string.content = status_message;
  }
  if (meshms_result > result) {
    result = meshms_result;
    message = meshms_message;
  }
  assert(result != 0);
  http_request_simple_response(&r->http, result, message);
  return result;
}

static HTTP_HANDLER restful_meshms_conversationlist_json;
static HTTP_HANDLER restful_meshms_messagelist_json;
static HTTP_HANDLER restful_meshms_newsince_messagelist_json;
static HTTP_HANDLER restful_meshms_sendmessage;
static HTTP_HANDLER restful_meshms_read_all_conversations;
static HTTP_HANDLER restful_meshms_read_all_messages;
static HTTP_HANDLER restful_meshms_read_to_offset;

static int restful_meshms_(httpd_request *r, const char *remainder)
{
  r->http.response.header.content_type = &CONTENT_TYPE_JSON;
  if (!is_rhizome_http_enabled())
    return 404;
  int ret = authorize_restful(&r->http);
  if (ret)
    return ret;
  const char *verb = HTTP_VERB_GET;
  http_size_t content_length = CONTENT_LENGTH_UNKNOWN;
  HTTP_HANDLER *handler = NULL;
  const char *end;
  if (parse_sid_t(&r->sid1, remainder, -1, &end) != -1) {
    remainder = end;
    if (strcmp(remainder, "/conversationlist.json") == 0) {
      handler = restful_meshms_conversationlist_json;
      remainder = "";
    }
    else if (strcmp(remainder, "/readall") == 0) {
      handler = restful_meshms_read_all_conversations;
      verb = HTTP_VERB_POST;
      content_length = 0;
      remainder = "";
    }
    else if (*remainder == '/' && parse_sid_t(&r->sid2, remainder + 1, -1, &end) != -1) {
      remainder = end;
      if (strcmp(remainder, "/messagelist.json") == 0) {
	handler = restful_meshms_messagelist_json;
	remainder = "";
      }
      else if (strcmp(remainder, "/newsince/messagelist.json") == 0){
	handler = restful_meshms_newsince_messagelist_json;
	remainder = "";
	r->u.msglist.token.which_ply = MY_PLY;
	r->u.msglist.token.offset = 0;
	r->u.msglist.token.their_ack = 0;
      }
      else if (   str_startswith(remainder, "/newsince/", &end)
	       && strn_to_meshms_token(end, &r->u.msglist.token, &end)
	       && strcmp(end, "messagelist.json") == 0
      ) {
	handler = restful_meshms_newsince_messagelist_json;
	remainder = "";
      }
      else if (strcmp(remainder, "/sendmessage") == 0) {
	handler = restful_meshms_sendmessage;
	verb = HTTP_VERB_POST;
	remainder = "";
      }
      else if (strcmp(remainder, "/readall") == 0) {
	handler = restful_meshms_read_all_messages;
	verb = HTTP_VERB_POST;
	content_length = 0;
	remainder = "";
      }
      else if (str_startswith(remainder, "/recv/", &end)) {
	remainder = end;
	if (str_to_uint64(remainder, 10, &r->ui64, &end)) {
	  remainder = end;
	  if (strcmp(remainder, "/read") == 0) {
	    handler = restful_meshms_read_to_offset;
	    verb = HTTP_VERB_POST;
	    content_length = 0;
	    remainder = "";
	  }
	}
      }
    }
  }
  if (handler == NULL)
    return 404;
  if (	 content_length != CONTENT_LENGTH_UNKNOWN
      && r->http.request_header.content_length != CONTENT_LENGTH_UNKNOWN
      && r->http.request_header.content_length != content_length) {
    http_request_simple_response(&r->http, 400, "Bad content length");
    return 400;
  }
  if (r->http.verb != verb)
    return 405;
  return handler(r, remainder);
}

static HTTP_CONTENT_GENERATOR restful_meshms_conversationlist_json_content;

static int restful_meshms_conversationlist_json(httpd_request *r, const char *remainder)
{
  if (*remainder)
    return 404;
  assert(r->finalise_union == NULL);
  r->finalise_union = finalise_union_meshms_conversationlist;
  r->u.mclist.phase = LIST_HEADER;
  r->u.mclist.rowcount = 0;
  r->u.mclist.conv = NULL;
  enum meshms_status status;
  if (meshms_failed(status = meshms_conversations_list(NULL, &r->sid1, &r->u.mclist.conv)))
    return http_request_meshms_response(r, 0, NULL, status);
  if (r->u.mclist.conv != NULL)
    meshms_conversation_iterator_start(&r->u.mclist.iter, r->u.mclist.conv);
  http_request_response_generated(&r->http, 200, &CONTENT_TYPE_JSON, restful_meshms_conversationlist_json_content);
  return 1;
}

static HTTP_CONTENT_GENERATOR_STRBUF_CHUNKER restful_meshms_conversationlist_json_content_chunk;

static int restful_meshms_conversationlist_json_content(struct http_request *hr, unsigned char *buf, size_t bufsz, struct http_content_generator_result *result)
{
  return generate_http_content_from_strbuf_chunks(hr, (char *)buf, bufsz, result, restful_meshms_conversationlist_json_content_chunk);
}

static int restful_meshms_conversationlist_json_content_chunk(struct http_request *hr, strbuf b)
{
  httpd_request *r = (httpd_request *) hr;
  // The "my_sid" and "their_sid" per-conversation fields allow the same JSON structure to be used
  // in a future, non-SID-specific request, eg, to list all conversations for all currently open
  // identities.
  const char *headers[] = {
    "_id",
    "my_sid",
    "their_sid",
    "read",
    "last_message",
    "read_offset"
  };
  switch (r->u.mclist.phase) {
    case LIST_HEADER:
      strbuf_puts(b, "{\n\"header\":[");
      unsigned i;
      for (i = 0; i != NELS(headers); ++i) {
	if (i)
	  strbuf_putc(b, ',');
	strbuf_json_string(b, headers[i]);
      }
      strbuf_puts(b, "],\n\"rows\":[");
      if (!strbuf_overrun(b))
	r->u.mclist.phase = LIST_FIRST;
      return 1;

    case LIST_ROWS:
    case LIST_FIRST:
      if (r->u.mclist.conv == NULL || r->u.mclist.iter.current == NULL) {
	r->u.mclist.phase = LIST_END;
	// fall through...
      } else {
	if (r->u.mclist.rowcount!=0)
	  strbuf_putc(b, ',');
	strbuf_puts(b, "\n[");
	strbuf_sprintf(b, "%zu", r->u.mclist.rowcount);
	strbuf_putc(b, ',');
	strbuf_json_hex(b, r->sid1.binary, sizeof r->sid1.binary);
	strbuf_putc(b, ',');
	strbuf_json_hex(b, r->u.mclist.iter.current->them.binary, sizeof r->u.mclist.iter.current->them.binary);
	strbuf_putc(b, ',');
	strbuf_json_boolean(b, r->u.mclist.iter.current->metadata.read_offset >= r->u.mclist.iter.current->metadata.their_last_message);
	strbuf_putc(b, ',');
	strbuf_sprintf(b, "%"PRIu64, r->u.mclist.iter.current->metadata.their_last_message);
	strbuf_putc(b, ',');
	strbuf_sprintf(b, "%"PRIu64, r->u.mclist.iter.current->metadata.read_offset);
	strbuf_puts(b, "]");
	if (!strbuf_overrun(b)) {
	  r->u.mclist.phase=LIST_ROWS;
	  meshms_conversation_iterator_advance(&r->u.mclist.iter);
	  ++r->u.mclist.rowcount;
	}
	return 1;
      }
      // fall through...
    case LIST_END:
      strbuf_puts(b, "\n]\n}\n");
      if (!strbuf_overrun(b))
	r->u.mclist.phase = LIST_DONE;
      // fall through...
    case LIST_DONE:
      return 0;
  }
  abort();
  return 0;
}

static HTTP_CONTENT_GENERATOR restful_meshms_messagelist_json_content;

static enum meshms_status reopen_meshms_message_iterator(httpd_request *r)
{
  if (r->u.msglist.dirty) {
    meshms_message_iterator_close(&r->u.msglist.iter);
    r->u.msglist.dirty = 0;
    enum meshms_status status;
    if (   meshms_failed(status = meshms_message_iterator_open(&r->u.msglist.iter, &r->sid1, &r->sid2))
	|| meshms_failed(status = meshms_message_iterator_prev(&r->u.msglist.iter))
    )
      return status;
    r->u.msglist.finished = status != MESHMS_STATUS_UPDATED;
    if (!r->u.msglist.finished) {
      r->u.msglist.latest.which_ply = r->u.msglist.iter.which_ply;
      r->u.msglist.latest.offset = r->u.msglist.iter.which_ply == MY_PLY ? r->u.msglist.iter.my_offset : r->u.msglist.iter.their_offset;
      r->u.msglist.current.their_ack = r->u.msglist.latest.their_ack = r->u.msglist.iter.metadata.their_last_ack;
    }
  }
  return MESHMS_STATUS_OK;
}

static int restful_meshms_messagelist_json(httpd_request *r, const char *remainder)
{
  if (*remainder)
    return 404;
  assert(r->finalise_union == NULL);
  r->finalise_union = finalise_union_meshms_messagelist;
  r->u.msglist.rowcount = 0;
  r->u.msglist.phase = LIST_HEADER;
  r->u.msglist.token.which_ply = NEITHER_PLY;
  r->u.msglist.token.offset = 0;
  r->u.msglist.end_time = 0;
  r->u.msglist.dirty = 1;
  enum meshms_status status;
  if (meshms_failed(status = reopen_meshms_message_iterator(r)))
    return http_request_meshms_response(r, 0, NULL, status);
  http_request_response_generated(&r->http, 200, &CONTENT_TYPE_JSON, restful_meshms_messagelist_json_content);
  return 1;
}

static int restful_meshms_newsince_messagelist_json(httpd_request *r, const char *remainder)
{
  if (*remainder)
    return 404;
  assert(r->finalise_union == NULL);
  r->finalise_union = finalise_union_meshms_messagelist;
  r->trigger_rhizome_bundle_added = on_rhizome_bundle_added;
  r->u.msglist.rowcount = 0;
  r->u.msglist.phase = LIST_HEADER;
  r->u.msglist.dirty = 1;
  enum meshms_status status;
  if (meshms_failed(status = reopen_meshms_message_iterator(r)))
    return http_request_meshms_response(r, 0, NULL, status);
  r->u.msglist.end_time = gettime_ms() + config.api.restful.newsince_timeout * 1000;
  http_request_response_generated(&r->http, 200, &CONTENT_TYPE_JSON, restful_meshms_messagelist_json_content);
  return 1;
}

static void on_rhizome_bundle_added(httpd_request *r, rhizome_manifest *m)
{
  if (strcmp(m->service, RHIZOME_SERVICE_MESHMS2) == 0) {
    if (   (cmp_sid_t(&m->sender, &r->sid1) == 0 && cmp_sid_t(&m->recipient, &r->sid2) == 0)
	|| (cmp_sid_t(&m->sender, &r->sid2) == 0 && cmp_sid_t(&m->recipient, &r->sid1) == 0)
    ) {
      r->u.msglist.dirty = 1;
      http_request_resume_response(&r->http);
    }
  }
}

static HTTP_CONTENT_GENERATOR_STRBUF_CHUNKER restful_meshms_messagelist_json_content_chunk;

static int restful_meshms_messagelist_json_content(struct http_request *hr, unsigned char *buf, size_t bufsz, struct http_content_generator_result *result)
{
  httpd_request *r = (httpd_request *) hr;
  if (meshms_failed(reopen_meshms_message_iterator(r)))
    return -1;
  return generate_http_content_from_strbuf_chunks(hr, (char *)buf, bufsz, result, restful_meshms_messagelist_json_content_chunk);
}

static void _messagelist_json_ack(struct httpd_request *r, strbuf b);

static int restful_meshms_messagelist_json_content_chunk(struct http_request *hr, strbuf b)
{
  httpd_request *r = (httpd_request *) hr;
  // Include "my_sid" and "their_sid" per-message, so that the same JSON structure can be used by a
  // future, non-SID-specific request (eg, to get all messages for all currently open identities).
  const char *headers[] = {
    "type",
    "my_sid",
    "their_sid",
    "my_offset",
    "their_offset",
    "token",
    "text",
    "delivered",
    "read",
    "timestamp",
    "ack_offset"
  };
  switch (r->u.msglist.phase) {
    case LIST_HEADER:
      strbuf_puts(b, "{\n");
      if (!r->u.msglist.end_time) {
	strbuf_sprintf(b, "\"read_offset\":%"PRIu64",\n\"latest_ack_offset\":%"PRIu64",\n",
	    r->u.msglist.iter.metadata.read_offset,
	    r->u.msglist.iter.metadata.their_last_ack
	  );
      }
      strbuf_puts(b, "\"header\":[");
      unsigned i;
      for (i = 0; i != NELS(headers); ++i) {
	if (i)
	  strbuf_putc(b, ',');
	strbuf_json_string(b, headers[i]);
      }
      strbuf_puts(b, "],\n\"rows\":[");
      if (!strbuf_overrun(b))
	r->u.msglist.phase = LIST_ROWS;
      return 1;
    case LIST_FIRST:
    case LIST_ROWS:
      {
	r->u.msglist.current.which_ply = r->u.msglist.iter.which_ply;
	r->u.msglist.current.offset = (r->u.msglist.iter.which_ply == MY_PLY) ? r->u.msglist.iter.my_offset : r->u.msglist.iter.their_offset;
	if (   r->u.msglist.finished
	    || (r->u.msglist.token.which_ply == r->u.msglist.current.which_ply && r->u.msglist.current.offset <= r->u.msglist.token.offset)
	) {
	  time_ms_t now;
	  if (r->u.msglist.end_time && (now = gettime_ms()) < r->u.msglist.end_time) {
	    // If messages before the requested token have now been acked, add an extra ack record to the end
	    if (r->u.msglist.token.their_ack != r->u.msglist.latest.their_ack){
		r->u.msglist.current.their_ack = r->u.msglist.latest.their_ack;
	      _messagelist_json_ack(r, b);
	      if (strbuf_overrun(b))
		return 1;
	      ++r->u.msglist.rowcount;
	    }
	    r->u.msglist.token = r->u.msglist.latest;
	    meshms_message_iterator_close(&r->u.msglist.iter);
	    r->u.msglist.dirty = 1;
	    http_request_pause_response(&r->http, r->u.msglist.end_time);
	    return 0;
	  }
	  r->u.msglist.phase = LIST_END;
	} else {
	  int rows=0;

	  switch (r->u.msglist.iter.type) {
	    case MESSAGE_SENT:
	      // if you haven't seen the current ack && this is the message that was acked.
	      // output the ack now
	      if (r->u.msglist.token.their_ack != r->u.msglist.latest.their_ack &&
		r->u.msglist.current.offset <= r->u.msglist.latest.their_ack){
		_messagelist_json_ack(r, b);
		if (!strbuf_overrun(b)){
		  ++r->u.msglist.rowcount;
		  r->u.msglist.token.their_ack = r->u.msglist.latest.their_ack;
		  r->u.msglist.current.their_ack = 0;
		}
		return 1;
	      }
	      if (r->u.msglist.rowcount != 0)
		strbuf_putc(b, ',');
	      strbuf_puts(b, "\n[");
	      strbuf_json_string(b, ">");
	      strbuf_putc(b, ',');
	      strbuf_json_hex(b, r->u.msglist.iter.my_sid.binary, sizeof r->u.msglist.iter.my_sid.binary);
	      strbuf_putc(b, ',');
	      strbuf_json_hex(b, r->u.msglist.iter.their_sid.binary, sizeof r->u.msglist.iter.their_sid.binary);
	      strbuf_putc(b, ',');
	      strbuf_sprintf(b, "%"PRIu64, r->u.msglist.iter.my_offset);
	      strbuf_putc(b, ',');
	      strbuf_sprintf(b, "%"PRIu64, r->u.msglist.iter.their_offset);
	      strbuf_putc(b, ',');
	      strbuf_json_string(b, alloca_meshms_token(&r->u.msglist.current));
	      strbuf_putc(b, ',');
	      strbuf_json_string(b, r->u.msglist.iter.text);
	      strbuf_putc(b, ',');
	      strbuf_json_boolean(b, r->u.msglist.iter.delivered);
	      strbuf_putc(b, ',');
	      strbuf_json_boolean(b, 0);
	      strbuf_putc(b, ',');
	      strbuf_sprintf(b, "%d", r->u.msglist.iter.timestamp);
	      strbuf_putc(b, ',');
	      strbuf_json_null(b);
	      strbuf_puts(b, "]");
	      rows++;
	      break;
	    case MESSAGE_RECEIVED:
	      if (r->u.msglist.rowcount != 0)
		strbuf_putc(b, ',');
	      strbuf_puts(b, "\n[");
	      strbuf_json_string(b, "<");
	      strbuf_putc(b, ',');
	      strbuf_json_hex(b, r->u.msglist.iter.my_sid.binary, sizeof r->u.msglist.iter.my_sid.binary);
	      strbuf_putc(b, ',');
	      strbuf_json_hex(b, r->u.msglist.iter.their_sid.binary, sizeof r->u.msglist.iter.their_sid.binary);
	      strbuf_putc(b, ',');
	      strbuf_sprintf(b, "%"PRIu64, r->u.msglist.iter.my_offset);
	      strbuf_putc(b, ',');
	      strbuf_sprintf(b, "%"PRIu64, r->u.msglist.iter.their_offset);
	      strbuf_putc(b, ',');
	      strbuf_json_string(b, alloca_meshms_token(&r->u.msglist.current));
	      strbuf_putc(b, ',');
	      strbuf_json_string(b, r->u.msglist.iter.text);
	      strbuf_putc(b, ',');
	      strbuf_json_boolean(b, 1);
	      strbuf_putc(b, ',');
	      strbuf_json_boolean(b, r->u.msglist.iter.read);
	      strbuf_putc(b, ',');
	      strbuf_sprintf(b, "%d", r->u.msglist.iter.timestamp);
	      strbuf_putc(b, ',');
	      strbuf_json_null(b);
	      strbuf_puts(b, "]");
	      rows++;
	      break;
	    case ACK_RECEIVED:
	      break;
	  }
	  if (!strbuf_overrun(b)) {
	    r->u.msglist.rowcount+=rows;
	    enum meshms_status status;
	    if (meshms_failed(status = meshms_message_iterator_prev(&r->u.msglist.iter)))
	      return http_request_meshms_response(r, 0, NULL, status);
	    r->u.msglist.finished = status != MESHMS_STATUS_UPDATED;
	  }
	  return 1;
	}
	r->u.msglist.phase = LIST_END;
      }
      // fall through...
    case LIST_END:
      strbuf_puts(b, "\n]\n}\n");
      if (!strbuf_overrun(b))
	r->u.msglist.phase = LIST_DONE;
      // fall through...
    case LIST_DONE:
      return 0;
  }
  abort();
  return 0;
}

static void _messagelist_json_ack(struct httpd_request *r, strbuf b)
{
  if (r->u.msglist.rowcount != 0)
    strbuf_putc(b, ',');
  strbuf_puts(b, "\n[");
  strbuf_json_string(b, "ACK");
  strbuf_putc(b, ',');
  strbuf_json_hex(b, r->u.msglist.iter.my_sid.binary, sizeof r->u.msglist.iter.my_sid.binary);
  strbuf_putc(b, ',');
  strbuf_json_hex(b, r->u.msglist.iter.their_sid.binary, sizeof r->u.msglist.iter.their_sid.binary);
  strbuf_putc(b, ',');
  strbuf_sprintf(b, "%"PRIu64, r->u.msglist.iter.my_offset);
  strbuf_putc(b, ',');
  strbuf_sprintf(b, "%"PRIu64, r->u.msglist.iter.metadata.their_last_ack_offset);
  strbuf_putc(b, ',');
  strbuf_json_string(b, alloca_meshms_token(&r->u.msglist.current));
  strbuf_putc(b, ',');
  strbuf_json_null(b);
  strbuf_putc(b, ',');
  strbuf_json_boolean(b, 1);
  strbuf_putc(b, ',');
  strbuf_json_boolean(b, 0);
  strbuf_putc(b, ',');
  strbuf_json_null(b); // no timestamp on ACKs
  strbuf_putc(b, ',');
  strbuf_sprintf(b, "%"PRIu64, r->u.msglist.iter.metadata.their_last_ack);
  strbuf_puts(b, "]");
}

static HTTP_REQUEST_PARSER restful_meshms_sendmessage_end;
static int send_mime_part_start(struct http_request *);
static int send_mime_part_end(struct http_request *);
static int send_mime_part_header(struct http_request *, const struct mime_part_headers *);
static int send_mime_part_body(struct http_request *, char *, size_t);

static int restful_meshms_sendmessage(httpd_request *r, const char *remainder)
{
  if (*remainder)
    return 404;
  assert(r->finalise_union == NULL);
  r->finalise_union = finalise_union_meshms_sendmessage;
  // Parse the request body as multipart/form-data.
  assert(r->u.sendmsg.current_part == NULL);
  assert(!r->u.sendmsg.received_message);
  r->http.form_data.handle_mime_part_start = send_mime_part_start;
  r->http.form_data.handle_mime_part_end = send_mime_part_end;
  r->http.form_data.handle_mime_part_header = send_mime_part_header;
  r->http.form_data.handle_mime_body = send_mime_part_body;
  // Send the message once the body has arrived.
  r->http.handle_content_end = restful_meshms_sendmessage_end;
  return 1;
}

static char PART_MESSAGE[] = "message";

static int send_mime_part_start(struct http_request *hr)
{
  httpd_request *r = (httpd_request *) hr;
  assert(r->u.sendmsg.current_part == NULL);
  return 0;
}

static int send_mime_part_end(struct http_request *hr)
{
  httpd_request *r = (httpd_request *) hr;
  if (r->u.sendmsg.current_part == PART_MESSAGE) {
    if (r->u.sendmsg.message.length == 0)
      return http_response_form_part(r, 400, "Invalid (empty)", PART_MESSAGE, NULL, 0);
    r->u.sendmsg.received_message = 1;
    DEBUGF(httpd, "received %s = %s", PART_MESSAGE, alloca_toprint(-1, r->u.sendmsg.message.buffer, r->u.sendmsg.message.length));
  } else
    FATALF("current_part = %s", alloca_str_toprint(r->u.sendmsg.current_part));
  r->u.sendmsg.current_part = NULL;
  return 0;
}

static int send_mime_part_header(struct http_request *hr, const struct mime_part_headers *h)
{
  httpd_request *r = (httpd_request *) hr;
  if (!h->content_disposition.type[0])
    return http_response_content_disposition(r, 415, "Missing", h->content_disposition.type);
  if (strcmp(h->content_disposition.type, "form-data") != 0)
    return http_response_content_disposition(r, 415, "Unsupported", h->content_disposition.type);
  if (strcmp(h->content_disposition.name, PART_MESSAGE) == 0) {
    if (r->u.sendmsg.received_message)
      return http_response_form_part(r, 400, "Duplicate", PART_MESSAGE, NULL, 0);
    r->u.sendmsg.current_part = PART_MESSAGE;
    form_buf_malloc_init(&r->u.sendmsg.message, MESSAGE_PLY_MAX_LEN);
  }
  else
    return http_response_form_part(r, 415, "Unsupported", h->content_disposition.name, NULL, 0);
  if (!h->content_type.type[0] || !h->content_type.subtype[0])
    return http_response_content_type(r, 400, "Missing", &h->content_type);
  if (strcmp(h->content_type.type, "text") != 0 || strcmp(h->content_type.subtype, "plain") != 0)
    return http_response_content_type(r, 415, "Unsupported", &h->content_type);
  if (!h->content_type.charset[0])
    return http_response_content_type(r, 400, "Missing charset", &h->content_type);
  if (strcmp(h->content_type.charset, "utf-8") != 0)
    return http_response_content_type(r, 415, "Unsupported charset", &h->content_type);
  return 0;
}

static int send_mime_part_body(struct http_request *hr, char *buf, size_t len)
{
  httpd_request *r = (httpd_request *) hr;
  if (r->u.sendmsg.current_part == PART_MESSAGE) {
    form_buf_malloc_accumulate(r, PART_MESSAGE, &r->u.sendmsg.message, buf, len);
  } else
    FATALF("current_part = %s", alloca_str_toprint(r->u.sendmsg.current_part));
  return 0;
}

static int restful_meshms_sendmessage_end(struct http_request *hr)
{
  httpd_request *r = (httpd_request *) hr;
  if (!r->u.sendmsg.received_message)
    return http_response_form_part(r, 400, "Missing", PART_MESSAGE, NULL, 0);
  assert(r->u.sendmsg.message.length > 0);
  assert(r->u.sendmsg.message.length <= MESSAGE_PLY_MAX_LEN);
  enum meshms_status status;
  if (meshms_failed(status = meshms_send_message(&r->sid1, &r->sid2, r->u.sendmsg.message.buffer, r->u.sendmsg.message.length)))
    return http_request_meshms_response(r, 0, NULL, status);
  return http_request_meshms_response(r, 201, "Message sent", status);
}

static int restful_meshms_read_all_conversations(httpd_request *r, const char *remainder)
{
  if (*remainder)
    return 404;
  assert(r->finalise_union == NULL);
  enum meshms_status status;
  if (meshms_failed(status = meshms_mark_read(&r->sid1, NULL, UINT64_MAX)))
    return http_request_meshms_response(r, 0, NULL, status);
  if (status == MESHMS_STATUS_UPDATED)
    return http_request_meshms_response(r, 201, "Read offsets updated", status);
  return http_request_meshms_response(r, 200, "Read offsets unchanged", status);
}

static int restful_meshms_read_all_messages(httpd_request *r, const char *remainder)
{
  if (*remainder)
    return 404;
  assert(r->finalise_union == NULL);
  enum meshms_status status;
  if (meshms_failed(status = meshms_mark_read(&r->sid1, &r->sid2, UINT64_MAX)))
    return http_request_meshms_response(r, 0, NULL, status);
  if (status == MESHMS_STATUS_UPDATED)
    return http_request_meshms_response(r, 201, "Read offset updated", status);
  return http_request_meshms_response(r, 200, "Read offset unchanged", status);
}

static int restful_meshms_read_to_offset(httpd_request *r, const char *remainder)
{
  if (*remainder)
    return 404;
  assert(r->finalise_union == NULL);
  enum meshms_status status;
  if (meshms_failed(status = meshms_mark_read(&r->sid1, &r->sid2, r->ui64)))
    return http_request_meshms_response(r, 0, NULL, status);
  if (status == MESHMS_STATUS_UPDATED)
    return http_request_meshms_response(r, 201, "Read offset updated", status);
  return http_request_meshms_response(r, 200, "Read offset unchanged", status);
}