/*
 * Copyright (c) 2022 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <http/http.h>
#include <vnet/session/session.h>
#include <http/http_timer.h>

static http_main_t http_main;

#define HTTP_FIFO_THRESH (16 << 10)
#define CONTENT_LEN_STR	 "Content-Length: "

/* HTTP state machine result */
typedef enum http_sm_result_t_
{
  HTTP_SM_STOP = 0,
  HTTP_SM_CONTINUE = 1,
  HTTP_SM_ERROR = -1,
} http_sm_result_t;

const char *http_status_code_str[] = {
#define _(c, s, str) str,
  foreach_http_status_code
#undef _
};

const char *http_content_type_str[] = {
#define _(s, ext, str) str,
  foreach_http_content_type
#undef _
};

const http_buffer_type_t msg_to_buf_type[] = {
  [HTTP_MSG_DATA_INLINE] = HTTP_BUFFER_FIFO,
  [HTTP_MSG_DATA_PTR] = HTTP_BUFFER_PTR,
};

u8 *
format_http_state (u8 *s, va_list *va)
{
  http_state_t state = va_arg (*va, http_state_t);

  switch (state)
    {
    case HTTP_STATE_IDLE:
      return format (s, "idle");
    case HTTP_STATE_WAIT_APP_METHOD:
      return format (s, "wait app method");
    case HTTP_STATE_WAIT_SERVER_REPLY:
      return format (s, "wait server reply");
    case HTTP_STATE_CLIENT_IO_MORE_DATA:
      return format (s, "client io more data");
    case HTTP_STATE_WAIT_CLIENT_METHOD:
      return format (s, "wait client method");
    case HTTP_STATE_WAIT_APP_REPLY:
      return format (s, "wait app reply");
    case HTTP_STATE_APP_IO_MORE_DATA:
      return format (s, "app io more data");
    default:
      break;
    }
  return format (s, "unknown");
}

#define http_state_change(_hc, _state)                                        \
  do                                                                          \
    {                                                                         \
      HTTP_DBG (1, "changing http state %U -> %U", format_http_state,         \
		(_hc)->http_state, format_http_state, _state);                \
      (_hc)->http_state = _state;                                             \
    }                                                                         \
  while (0)

static inline http_worker_t *
http_worker_get (u32 thread_index)
{
  return &http_main.wrk[thread_index];
}

static inline u32
http_conn_alloc_w_thread (u32 thread_index)
{
  http_worker_t *wrk = http_worker_get (thread_index);
  http_conn_t *hc;

  pool_get_aligned_safe (wrk->conn_pool, hc, CLIB_CACHE_LINE_BYTES);
  clib_memset (hc, 0, sizeof (*hc));
  hc->c_thread_index = thread_index;
  hc->h_hc_index = hc - wrk->conn_pool;
  hc->h_pa_session_handle = SESSION_INVALID_HANDLE;
  hc->h_tc_session_handle = SESSION_INVALID_HANDLE;
  return hc->h_hc_index;
}

static inline http_conn_t *
http_conn_get_w_thread (u32 hc_index, u32 thread_index)
{
  http_worker_t *wrk = http_worker_get (thread_index);
  return pool_elt_at_index (wrk->conn_pool, hc_index);
}

void
http_conn_free (http_conn_t *hc)
{
  http_worker_t *wrk = http_worker_get (hc->c_thread_index);
  pool_put (wrk->conn_pool, hc);
}

static u32
http_listener_alloc (void)
{
  http_main_t *hm = &http_main;
  http_conn_t *lhc;

  pool_get_zero (hm->listener_pool, lhc);
  lhc->c_c_index = lhc - hm->listener_pool;
  return lhc->c_c_index;
}

http_conn_t *
http_listener_get (u32 lhc_index)
{
  return pool_elt_at_index (http_main.listener_pool, lhc_index);
}

void
http_listener_free (http_conn_t *lhc)
{
  http_main_t *hm = &http_main;

  vec_free (lhc->app_name);
  if (CLIB_DEBUG)
    memset (lhc, 0xfc, sizeof (*lhc));
  pool_put (hm->listener_pool, lhc);
}

void
http_disconnect_transport (http_conn_t *hc)
{
  vnet_disconnect_args_t a = {
    .handle = hc->h_tc_session_handle,
    .app_index = http_main.app_index,
  };

  hc->state = HTTP_CONN_STATE_CLOSED;

  if (vnet_disconnect_session (&a))
    clib_warning ("disconnect returned");
}

static void
http_conn_timeout_cb (void *hc_handlep)
{
  http_conn_t *hc;
  uword hs_handle;

  hs_handle = pointer_to_uword (hc_handlep);
  hc = http_conn_get_w_thread (hs_handle & 0x00FFFFFF, hs_handle >> 24);

  HTTP_DBG (1, "terminate thread %d index %d hs %llx", hs_handle >> 24,
	    hs_handle & 0x00FFFFFF, hc);
  if (!hc)
    return;

  hc->timer_handle = ~0;
  session_transport_closing_notify (&hc->connection);
  http_disconnect_transport (hc);
}

int
http_ts_accept_callback (session_t *ts)
{
  session_t *ts_listener, *as, *asl;
  app_worker_t *app_wrk;
  http_conn_t *lhc, *hc;
  u32 hc_index, thresh;
  int rv;

  ts_listener = listen_session_get_from_handle (ts->listener_handle);
  lhc = http_listener_get (ts_listener->opaque);

  hc_index = http_conn_alloc_w_thread (ts->thread_index);
  hc = http_conn_get_w_thread (hc_index, ts->thread_index);
  clib_memcpy_fast (hc, lhc, sizeof (*lhc));
  hc->c_thread_index = ts->thread_index;
  hc->h_hc_index = hc_index;

  hc->h_tc_session_handle = session_handle (ts);
  hc->c_flags |= TRANSPORT_CONNECTION_F_NO_LOOKUP;

  hc->state = HTTP_CONN_STATE_ESTABLISHED;
  http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);

  ts->session_state = SESSION_STATE_READY;
  ts->opaque = hc_index;

  /*
   * Alloc session and initialize
   */
  as = session_alloc (hc->c_thread_index);
  hc->c_s_index = as->session_index;

  as->app_wrk_index = hc->h_pa_wrk_index;
  as->connection_index = hc->c_c_index;
  as->session_state = SESSION_STATE_ACCEPTING;

  asl = listen_session_get_from_handle (lhc->h_pa_session_handle);
  as->session_type = asl->session_type;
  as->listener_handle = lhc->h_pa_session_handle;

  /*
   * Init session fifos and notify app
   */
  if ((rv = app_worker_init_accepted (as)))
    {
      HTTP_DBG (1, "failed to allocate fifos");
      session_free (as);
      return rv;
    }

  hc->h_pa_session_handle = session_handle (as);
  hc->h_pa_wrk_index = as->app_wrk_index;
  app_wrk = app_worker_get (as->app_wrk_index);

  HTTP_DBG (1, "Accepted on listener %u new connection [%u]%x",
	    ts_listener->opaque, vlib_get_thread_index (), hc_index);

  if ((rv = app_worker_accept_notify (app_wrk, as)))
    {
      HTTP_DBG (0, "app accept returned");
      session_free (as);
      return rv;
    }

  /* Avoid enqueuing small chunks of data on transport tx notifications. If
   * the fifo is small (under 16K) we set the threshold to it's size, meaning
   * a notification will be given when the fifo empties.
   */
  ts = session_get_from_handle (hc->h_tc_session_handle);
  thresh = clib_min (svm_fifo_size (ts->tx_fifo), HTTP_FIFO_THRESH);
  svm_fifo_set_deq_thresh (ts->tx_fifo, thresh);

  http_conn_timer_start (hc);

  return 0;
}

static int
http_ts_connected_callback (u32 http_app_index, u32 ho_hc_index, session_t *ts,
			    session_error_t err)
{
  u32 new_hc_index;
  session_t *as;
  http_conn_t *hc, *ho_hc;
  app_worker_t *app_wrk;
  int rv;

  if (err)
    {
      clib_warning ("ERROR: %d", err);
      return 0;
    }

  new_hc_index = http_conn_alloc_w_thread (ts->thread_index);
  hc = http_conn_get_w_thread (new_hc_index, ts->thread_index);
  ho_hc = http_conn_get_w_thread (ho_hc_index, 0);

  ASSERT (ho_hc->state == HTTP_CONN_STATE_CONNECTING);

  clib_memcpy_fast (hc, ho_hc, sizeof (*hc));

  hc->c_thread_index = ts->thread_index;
  hc->h_tc_session_handle = session_handle (ts);
  hc->c_c_index = new_hc_index;
  hc->c_flags |= TRANSPORT_CONNECTION_F_NO_LOOKUP;
  hc->state = HTTP_CONN_STATE_ESTABLISHED;
  http_state_change (hc, HTTP_STATE_WAIT_APP_METHOD);

  ts->session_state = SESSION_STATE_READY;
  ts->opaque = new_hc_index;

  /* allocate app session and initialize */

  as = session_alloc (hc->c_thread_index);
  hc->c_s_index = as->session_index;
  as->connection_index = hc->c_c_index;
  as->app_wrk_index = hc->h_pa_wrk_index;
  as->session_state = SESSION_STATE_READY;
  as->opaque = hc->h_pa_app_api_ctx;
  as->session_type = session_type_from_proto_and_ip (
    TRANSPORT_PROTO_HTTP, session_type_is_ip4 (ts->session_type));

  HTTP_DBG (1, "half-open hc index %d,  hc index %d", ho_hc_index,
	    new_hc_index);

  app_wrk = app_worker_get (hc->h_pa_wrk_index);
  if (!app_wrk)
    {
      clib_warning ("no app worker");
      return -1;
    }

  if ((rv = app_worker_init_connected (app_wrk, as)))
    {
      HTTP_DBG (1, "failed to allocate fifos");
      session_free (as);
      return rv;
    }
  app_worker_connect_notify (app_wrk, as, err, hc->h_pa_app_api_ctx);
  hc->h_pa_session_handle = session_handle (as);
  http_conn_timer_start (hc);

  return 0;
}

static void
http_ts_disconnect_callback (session_t *ts)
{
  http_conn_t *hc;

  hc = http_conn_get_w_thread (ts->opaque, ts->thread_index);

  if (hc->state < HTTP_CONN_STATE_TRANSPORT_CLOSED)
    hc->state = HTTP_CONN_STATE_TRANSPORT_CLOSED;

  /* Nothing more to rx, propagate to app */
  if (!svm_fifo_max_dequeue_cons (ts->rx_fifo))
    session_transport_closing_notify (&hc->connection);
}

static void
http_ts_reset_callback (session_t *ts)
{
  http_conn_t *hc;

  hc = http_conn_get_w_thread (ts->opaque, ts->thread_index);

  hc->state = HTTP_CONN_STATE_CLOSED;
  http_buffer_free (&hc->tx_buf);
  http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
  session_transport_reset_notify (&hc->connection);

  http_disconnect_transport (hc);
}

/**
 * http error boilerplate
 */
static const char *http_error_template = "HTTP/1.1 %s\r\n"
					 "Date: %U GMT\r\n"
					 "Content-Type: text/html\r\n"
					 "Connection: close\r\n"
					 "Pragma: no-cache\r\n"
					 "Content-Length: 0\r\n\r\n";

static const char *http_redirect_template = "HTTP/1.1 %s\r\n";

/**
 * http response boilerplate
 */
static const char *http_response_template = "HTTP/1.1 %s\r\n"
					    "Date: %U GMT\r\n"
					    "Expires: %U GMT\r\n"
					    "Server: %s\r\n"
					    "Content-Type: %s\r\n"
					    "Content-Length: %lu\r\n\r\n";

static const char *http_request_template = "GET %s HTTP/1.1\r\n"
					   "User-Agent: VPP HTTP client\r\n"
					   "Accept: */*\r\n";

static u32
http_send_data (http_conn_t *hc, u8 *data, u32 length, u32 offset)
{
  const u32 max_burst = 64 << 10;
  session_t *ts;
  u32 to_send;
  int sent;

  ts = session_get_from_handle (hc->h_tc_session_handle);

  to_send = clib_min (length - offset, max_burst);
  sent = svm_fifo_enqueue (ts->tx_fifo, to_send, data + offset);

  if (sent <= 0)
    return offset;

  if (svm_fifo_set_event (ts->tx_fifo))
    session_send_io_evt_to_thread (ts->tx_fifo, SESSION_IO_EVT_TX);

  return (offset + sent);
}

static void
http_send_error (http_conn_t *hc, http_status_code_t ec)
{
  http_main_t *hm = &http_main;
  u8 *data;
  f64 now;

  if (ec >= HTTP_N_STATUS)
    ec = HTTP_STATUS_INTERNAL_ERROR;

  now = clib_timebase_now (&hm->timebase);
  data = format (0, http_error_template, http_status_code_str[ec],
		 format_clib_timebase_time, now);
  http_send_data (hc, data, vec_len (data), 0);
  vec_free (data);
}

static int
http_read_message (http_conn_t *hc)
{
  u32 max_deq, cursize;
  session_t *ts;
  int n_read;

  ts = session_get_from_handle (hc->h_tc_session_handle);

  cursize = vec_len (hc->rx_buf);
  max_deq = svm_fifo_max_dequeue (ts->rx_fifo);
  if (PREDICT_FALSE (max_deq == 0))
    return -1;

  vec_validate (hc->rx_buf, cursize + max_deq - 1);
  n_read = svm_fifo_dequeue (ts->rx_fifo, max_deq, hc->rx_buf + cursize);
  ASSERT (n_read == max_deq);

  if (svm_fifo_is_empty (ts->rx_fifo))
    svm_fifo_unset_event (ts->rx_fifo);

  vec_set_len (hc->rx_buf, cursize + n_read);
  return 0;
}

static int
v_find_index (u8 *vec, u32 offset, char *str)
{
  int start_index = offset;
  u32 slen = (u32) strnlen_s_inline (str, 16);
  u32 vlen = vec_len (vec);

  ASSERT (slen > 0);

  if (vlen <= slen)
    return -1;

  for (; start_index < (vlen - slen); start_index++)
    {
      if (!memcmp (vec + start_index, str, slen))
	return start_index;
    }

  return -1;
}

static int
http_parse_header (http_conn_t *hc, int *content_length)
{
  unformat_input_t input;
  int i, len;
  u8 *line;

  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, CONTENT_LEN_STR);
  if (i < 0)
    {
      clib_warning ("cannot find '%s' in the header!", CONTENT_LEN_STR);
      return -1;
    }

  hc->rx_buf_offset = i;

  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, "\n");
  if (i < 0)
    {
      clib_warning ("end of line missing; incomplete data");
      return -1;
    }

  len = i - hc->rx_buf_offset;
  line = vec_new (u8, len);
  clib_memcpy (line, hc->rx_buf + hc->rx_buf_offset, len);

  unformat_init_vector (&input, line);
  if (!unformat (&input, CONTENT_LEN_STR "%d", content_length))
    {
      clib_warning ("failed to unformat content length!");
      return -1;
    }
  unformat_free (&input);

  /* skip rest of the header */
  hc->rx_buf_offset += len;
  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, "<html>");
  if (i < 0)
    {
      clib_warning ("<html> tag not found");
      return -1;
    }
  hc->rx_buf_offset = i;

  return 0;
}

static http_sm_result_t
http_state_wait_server_reply (http_conn_t *hc, transport_send_params_t *sp)
{
  int i, rv, content_length;
  http_msg_t msg = {};
  app_worker_t *app_wrk;
  session_t *as;
  http_status_code_t ec;

  rv = http_read_message (hc);

  /* Nothing yet, wait for data or timer expire */
  if (rv)
    return HTTP_SM_STOP;

  if (vec_len (hc->rx_buf) < 8)
    {
      ec = HTTP_STATUS_BAD_REQUEST;
      goto error;
    }

  if ((i = v_find_index (hc->rx_buf, 0, "200 OK")) >= 0)
    {
      msg.type = HTTP_MSG_REPLY;
      msg.content_type = HTTP_CONTENT_TEXT_HTML;
      msg.code = HTTP_STATUS_OK;
      msg.data.type = HTTP_MSG_DATA_INLINE;
      msg.data.len = 0;

      rv = http_parse_header (hc, &content_length);
      if (rv)
	{
	  clib_warning ("failed to parse http reply");
	  session_transport_closing_notify (&hc->connection);
	  http_disconnect_transport (hc);
	  return -1;
	}
      msg.data.len = content_length;
      u32 dlen = vec_len (hc->rx_buf) - hc->rx_buf_offset;
      as = session_get_from_handle (hc->h_pa_session_handle);
      svm_fifo_seg_t segs[2] = { { (u8 *) &msg, sizeof (msg) },
				 { &hc->rx_buf[hc->rx_buf_offset], dlen } };

      rv = svm_fifo_enqueue_segments (as->rx_fifo, segs, 2,
				      0 /* allow partial */);
      if (rv < 0)
	{
	  clib_warning ("error enqueue");
	  return HTTP_SM_ERROR;
	}

      hc->rx_buf_offset += dlen;
      hc->to_recv = content_length - dlen;

      if (hc->rx_buf_offset == vec_len (hc->rx_buf))
	{
	  vec_reset_length (hc->rx_buf);
	  hc->rx_buf_offset = 0;
	}

      if (hc->to_recv == 0)
	{
	  hc->rx_buf_offset = 0;
	  vec_reset_length (hc->rx_buf);
	  http_state_change (hc, HTTP_STATE_WAIT_APP_METHOD);
	}
      else
	{
	  http_state_change (hc, HTTP_STATE_CLIENT_IO_MORE_DATA);
	}

      app_wrk = app_worker_get_if_valid (as->app_wrk_index);
      if (app_wrk)
	app_worker_rx_notify (app_wrk, as);
      return HTTP_SM_STOP;
    }
  else
    {
      HTTP_DBG (0, "Unknown http method %v", hc->rx_buf);
      ec = HTTP_STATUS_METHOD_NOT_ALLOWED;
      goto error;
    }

error:
  http_send_error (hc, ec);
  session_transport_closing_notify (&hc->connection);
  http_disconnect_transport (hc);

  return HTTP_SM_ERROR;
}

static http_sm_result_t
http_state_wait_client_method (http_conn_t *hc, transport_send_params_t *sp)
{
  http_status_code_t ec;
  app_worker_t *app_wrk;
  http_msg_t msg;
  session_t *as;
  int i, rv;
  u32 len;
  u8 *buf;

  rv = http_read_message (hc);

  /* Nothing yet, wait for data or timer expire */
  if (rv)
    return HTTP_SM_STOP;

  if (vec_len (hc->rx_buf) < 8)
    {
      ec = HTTP_STATUS_BAD_REQUEST;
      goto error;
    }

  if ((i = v_find_index (hc->rx_buf, 0, "GET ")) >= 0)
    {
      hc->method = HTTP_REQ_GET;
      hc->rx_buf_offset = i + 5;

      i = v_find_index (hc->rx_buf, hc->rx_buf_offset, "HTTP");
      if (i < 0)
	{
	  ec = HTTP_STATUS_BAD_REQUEST;
	  goto error;
	}

      HTTP_DBG (0, "GET method %v", hc->rx_buf);
      len = i - hc->rx_buf_offset - 1;
    }
  else if ((i = v_find_index (hc->rx_buf, 0, "POST ")) >= 0)
    {
      hc->method = HTTP_REQ_POST;
      hc->rx_buf_offset = i + 6;
      len = vec_len (hc->rx_buf) - hc->rx_buf_offset - 1;
      HTTP_DBG (0, "POST method %v", hc->rx_buf);
    }
  else
    {
      HTTP_DBG (0, "Unknown http method %v", hc->rx_buf);
      ec = HTTP_STATUS_METHOD_NOT_ALLOWED;
      goto error;
    }

  buf = &hc->rx_buf[hc->rx_buf_offset];

  msg.type = HTTP_MSG_REQUEST;
  msg.method_type = hc->method;
  msg.content_type = HTTP_CONTENT_TEXT_HTML;
  msg.data.type = HTTP_MSG_DATA_INLINE;
  msg.data.len = len;

  svm_fifo_seg_t segs[2] = { { (u8 *) &msg, sizeof (msg) }, { buf, len } };

  as = session_get_from_handle (hc->h_pa_session_handle);
  rv = svm_fifo_enqueue_segments (as->rx_fifo, segs, 2, 0 /* allow partial */);
  if (rv < 0 || rv != sizeof (msg) + len)
    {
      clib_warning ("failed app enqueue");
      /* This should not happen as we only handle 1 request per session,
       * and fifo is allocated, but going forward we should consider
       * rescheduling */
      return HTTP_SM_ERROR;
    }

  vec_free (hc->rx_buf);
  http_state_change (hc, HTTP_STATE_WAIT_APP_REPLY);

  app_wrk = app_worker_get_if_valid (as->app_wrk_index);
  if (app_wrk)
    app_worker_rx_notify (app_wrk, as);

  return HTTP_SM_STOP;

error:

  http_send_error (hc, ec);
  session_transport_closing_notify (&hc->connection);
  http_disconnect_transport (hc);

  return HTTP_SM_ERROR;
}

static http_sm_result_t
http_state_wait_app_reply (http_conn_t *hc, transport_send_params_t *sp)
{
  http_main_t *hm = &http_main;
  u8 *header;
  u32 offset;
  f64 now;
  session_t *as;
  http_status_code_t sc;
  http_msg_t msg;
  int rv;

  as = session_get_from_handle (hc->h_pa_session_handle);

  rv = svm_fifo_dequeue (as->tx_fifo, sizeof (msg), (u8 *) &msg);
  ASSERT (rv == sizeof (msg));

  if (msg.data.type > HTTP_MSG_DATA_PTR)
    {
      clib_warning ("no data");
      sc = HTTP_STATUS_INTERNAL_ERROR;
      goto error;
    }

  if (msg.type != HTTP_MSG_REPLY)
    {
      clib_warning ("unexpected message type %d", msg.type);
      sc = HTTP_STATUS_INTERNAL_ERROR;
      goto error;
    }

  http_buffer_init (&hc->tx_buf, msg_to_buf_type[msg.data.type], as->tx_fifo,
		    msg.data.len);

  /*
   * Add headers. For now:
   * - current time
   * - expiration time
   * - server name
   * - content type
   * - data length
   */
  now = clib_timebase_now (&hm->timebase);

  switch (msg.code)
    {
    case HTTP_STATUS_OK:
      header =
	format (0, http_response_template, http_status_code_str[msg.code],
		/* Date */
		format_clib_timebase_time, now,
		/* Expires */
		format_clib_timebase_time, now + 600.0,
		/* Server */
		hc->app_name,
		/* Content type */
		http_content_type_str[msg.content_type],
		/* Length */
		msg.data.len);
      break;
    case HTTP_STATUS_MOVED:
      header =
	format (0, http_redirect_template, http_status_code_str[msg.code]);
      /* Location: http(s)://new-place already queued up as data */
      break;
    default:
      return HTTP_SM_ERROR;
    }

  offset = http_send_data (hc, header, vec_len (header), 0);
  if (offset != vec_len (header))
    {
      clib_warning ("couldn't send response header!");
      sc = HTTP_STATUS_INTERNAL_ERROR;
      vec_free (header);
      goto error;
    }
  vec_free (header);

  /* Start sending the actual data */
  http_state_change (hc, HTTP_STATE_APP_IO_MORE_DATA);

  ASSERT (sp->max_burst_size >= offset);
  sp->max_burst_size -= offset;
  return HTTP_SM_CONTINUE;

error:
  clib_warning ("unexpected msg type from app %u", msg.type);
  http_send_error (hc, sc);
  http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
  session_transport_closing_notify (&hc->connection);
  http_disconnect_transport (hc);
  return HTTP_SM_STOP;
}

static http_sm_result_t
http_state_wait_app_method (http_conn_t *hc, transport_send_params_t *sp)
{
  http_msg_t msg;
  session_t *as;
  u8 *buf = 0, *request;
  u32 offset;
  int rv;

  as = session_get_from_handle (hc->h_pa_session_handle);

  rv = svm_fifo_dequeue (as->tx_fifo, sizeof (msg), (u8 *) &msg);
  ASSERT (rv == sizeof (msg));

  if (msg.data.type > HTTP_MSG_DATA_PTR)
    {
      clib_warning ("no data");
      goto error;
    }

  if (msg.type != HTTP_MSG_REQUEST)
    {
      clib_warning ("unexpected message type %d", msg.type);
      goto error;
    }

  vec_validate (buf, msg.data.len - 1);
  rv = svm_fifo_dequeue (as->tx_fifo, msg.data.len, buf);
  ASSERT (rv == msg.data.len);

  request = format (0, http_request_template, buf);
  offset = http_send_data (hc, request, vec_len (request), 0);
  if (offset != vec_len (request))
    {
      clib_warning ("sending request failed!");
      goto error;
    }

  http_state_change (hc, HTTP_STATE_WAIT_SERVER_REPLY);

  vec_free (buf);
  vec_free (request);

  return HTTP_SM_STOP;

error:
  svm_fifo_dequeue_drop_all (as->tx_fifo);
  session_transport_closing_notify (&hc->connection);
  session_transport_closed_notify (&hc->connection);
  http_disconnect_transport (hc);
  return HTTP_SM_ERROR;
}

static http_sm_result_t
http_state_client_io_more_data (http_conn_t *hc, transport_send_params_t *sp)
{
  session_t *as, *ts;
  app_worker_t *app_wrk;
  svm_fifo_seg_t _seg, *seg = &_seg;
  u32 max_len, max_deq, max_enq, n_segs = 1;
  int rv, len;

  as = session_get_from_handle (hc->h_pa_session_handle);
  ts = session_get_from_handle (hc->h_tc_session_handle);

  max_deq = svm_fifo_max_dequeue (ts->rx_fifo);
  if (max_deq == 0)
    {
      HTTP_DBG (1, "no data to deq");
      return HTTP_SM_STOP;
    }

  max_enq = svm_fifo_max_enqueue (as->rx_fifo);
  if (max_enq == 0)
    {
      HTTP_DBG (1, "app's rx fifo full");
      svm_fifo_add_want_deq_ntf (as->rx_fifo, SVM_FIFO_WANT_DEQ_NOTIF);
      return HTTP_SM_STOP;
    }

  max_len = clib_min (max_enq, max_deq);
  len = svm_fifo_segments (ts->rx_fifo, 0, seg, &n_segs, max_len);
  if (len < 0)
    {
      HTTP_DBG (1, "svm_fifo_segments() len %d", len);
      return HTTP_SM_STOP;
    }

  rv = svm_fifo_enqueue_segments (as->rx_fifo, seg, 1, 0 /* allow partial */);
  if (rv < 0)
    {
      clib_warning ("data enqueue failed, rv: %d", rv);
      return HTTP_SM_ERROR;
    }

  svm_fifo_dequeue_drop (ts->rx_fifo, rv);
  if (rv > hc->to_recv)
    {
      clib_warning ("http protocol error: received more data than expected");
      session_transport_closing_notify (&hc->connection);
      http_disconnect_transport (hc);
      http_state_change (hc, HTTP_STATE_WAIT_APP_METHOD);
      return HTTP_SM_ERROR;
    }
  hc->to_recv -= rv;
  HTTP_DBG (1, "drained %d from ts; remains %d", rv, hc->to_recv);

  app_wrk = app_worker_get_if_valid (as->app_wrk_index);
  if (app_wrk)
    app_worker_rx_notify (app_wrk, as);

  if (svm_fifo_max_dequeue_cons (ts->rx_fifo))
    session_enqueue_notify (ts);

  return HTTP_SM_STOP;
}

static http_sm_result_t
http_state_app_io_more_data (http_conn_t *hc, transport_send_params_t *sp)
{
  u32 max_send = 64 << 10, n_segs;
  http_buffer_t *hb = &hc->tx_buf;
  svm_fifo_seg_t *seg;
  session_t *ts;
  int sent = 0;

  max_send = clib_min (max_send, sp->max_burst_size);
  ts = session_get_from_handle (hc->h_tc_session_handle);
  if ((seg = http_buffer_get_segs (hb, max_send, &n_segs)))
    sent = svm_fifo_enqueue_segments (ts->tx_fifo, seg, n_segs,
				      1 /* allow partial */);

  if (sent > 0)
    {
      /* Ask scheduler to notify app of deq event if needed */
      sp->bytes_dequeued += http_buffer_drain (hb, sent);
      sp->max_burst_size -= sent;
    }

  /* Not finished sending all data */
  if (!http_buffer_is_drained (hb))
    {
      if (sent && svm_fifo_set_event (ts->tx_fifo))
	session_send_io_evt_to_thread (ts->tx_fifo, SESSION_IO_EVT_TX);

      if (svm_fifo_max_enqueue (ts->tx_fifo) < HTTP_FIFO_THRESH)
	{
	  /* Deschedule http session and wait for deq notification if
	   * underlying ts tx fifo almost full */
	  svm_fifo_add_want_deq_ntf (ts->tx_fifo, SVM_FIFO_WANT_DEQ_NOTIF);
	  transport_connection_deschedule (&hc->connection);
	  sp->flags |= TRANSPORT_SND_F_DESCHED;
	}
    }
  else
    {
      if (sent && svm_fifo_set_event (ts->tx_fifo))
	session_send_io_evt_to_thread (ts->tx_fifo, SESSION_IO_EVT_TX_FLUSH);

      /* Finished transaction, back to HTTP_STATE_WAIT_METHOD */
      http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
      http_buffer_free (&hc->tx_buf);
    }

  return HTTP_SM_STOP;
}

typedef http_sm_result_t (*http_sm_handler) (http_conn_t *,
					     transport_send_params_t *sp);

static http_sm_handler state_funcs[HTTP_N_STATES] = {
  0, /* idle state */
  http_state_wait_app_method,
  http_state_wait_client_method,
  http_state_wait_server_reply,
  http_state_wait_app_reply,
  http_state_client_io_more_data,
  http_state_app_io_more_data,
};

static void
http_req_run_state_machine (http_conn_t *hc, transport_send_params_t *sp)
{
  http_sm_result_t res;

  do
    {
      res = state_funcs[hc->http_state](hc, sp);
      if (res == HTTP_SM_ERROR)
	{
	  HTTP_DBG (1, "error in state machine %d", res);
	  return;
	}
    }
  while (res == HTTP_SM_CONTINUE);

  /* Reset the session expiration timer */
  http_conn_timer_update (hc);
}

static int
http_ts_rx_callback (session_t *ts)
{
  http_conn_t *hc;

  hc = http_conn_get_w_thread (ts->opaque, ts->thread_index);
  if (!hc)
    {
      clib_warning ("http connection not found (ts %d)", ts->opaque);
      return -1;
    }

  if (hc->state == HTTP_CONN_STATE_CLOSED)
    {
      svm_fifo_dequeue_drop_all (ts->tx_fifo);
      return 0;
    }

  http_req_run_state_machine (hc, 0);

  if (hc->state == HTTP_CONN_STATE_TRANSPORT_CLOSED)
    {
      if (!svm_fifo_max_dequeue_cons (ts->rx_fifo))
	session_transport_closing_notify (&hc->connection);
    }
  return 0;
}

int
http_ts_builtin_tx_callback (session_t *ts)
{
  http_conn_t *hc;

  hc = http_conn_get_w_thread (ts->opaque, ts->thread_index);
  transport_connection_reschedule (&hc->connection);

  return 0;
}

static void
http_ts_cleanup_callback (session_t *ts, session_cleanup_ntf_t ntf)
{
  http_conn_t *hc;

  if (ntf == SESSION_CLEANUP_TRANSPORT)
    return;

  hc = http_conn_get_w_thread (ts->opaque, ts->thread_index);
  if (!hc)
    {
      clib_warning ("no http connection for %u", ts->session_index);
      return;
    }

  vec_free (hc->rx_buf);

  http_buffer_free (&hc->tx_buf);
  http_conn_timer_stop (hc);

  session_transport_delete_notify (&hc->connection);
  http_conn_free (hc);
}

int
http_add_segment_callback (u32 client_index, u64 segment_handle)
{
  /* No-op for builtin */
  return 0;
}

int
http_del_segment_callback (u32 client_index, u64 segment_handle)
{
  return 0;
}

static session_cb_vft_t http_app_cb_vft = {
  .session_accept_callback = http_ts_accept_callback,
  .session_disconnect_callback = http_ts_disconnect_callback,
  .session_connected_callback = http_ts_connected_callback,
  .session_reset_callback = http_ts_reset_callback,
  .session_cleanup_callback = http_ts_cleanup_callback,
  .add_segment_callback = http_add_segment_callback,
  .del_segment_callback = http_del_segment_callback,
  .builtin_app_rx_callback = http_ts_rx_callback,
  .builtin_app_tx_callback = http_ts_builtin_tx_callback,
};

static clib_error_t *
http_transport_enable (vlib_main_t *vm, u8 is_en)
{
  vnet_app_detach_args_t _da, *da = &_da;
  vnet_app_attach_args_t _a, *a = &_a;
  u64 options[APP_OPTIONS_N_OPTIONS];
  http_main_t *hm = &http_main;

  if (!is_en)
    {
      da->app_index = hm->app_index;
      da->api_client_index = APP_INVALID_INDEX;
      vnet_application_detach (da);
      return 0;
    }

  vec_validate (hm->wrk, vlib_num_workers ());

  clib_memset (a, 0, sizeof (*a));
  clib_memset (options, 0, sizeof (options));

  a->session_cb_vft = &http_app_cb_vft;
  a->api_client_index = APP_INVALID_INDEX;
  a->options = options;
  a->name = format (0, "http");
  a->options[APP_OPTIONS_SEGMENT_SIZE] = hm->first_seg_size;
  a->options[APP_OPTIONS_ADD_SEGMENT_SIZE] = hm->add_seg_size;
  a->options[APP_OPTIONS_RX_FIFO_SIZE] = hm->fifo_size;
  a->options[APP_OPTIONS_TX_FIFO_SIZE] = hm->fifo_size;
  a->options[APP_OPTIONS_FLAGS] = APP_OPTIONS_FLAGS_IS_BUILTIN;
  a->options[APP_OPTIONS_FLAGS] |= APP_OPTIONS_FLAGS_USE_GLOBAL_SCOPE;
  a->options[APP_OPTIONS_FLAGS] |= APP_OPTIONS_FLAGS_IS_TRANSPORT_APP;

  if (vnet_application_attach (a))
    return clib_error_return (0, "failed to attach http app");

  hm->app_index = a->app_index;
  vec_free (a->name);

  clib_timebase_init (&hm->timebase, 0 /* GMT */, CLIB_TIMEBASE_DAYLIGHT_NONE,
		      &vm->clib_time /* share the system clock */);

  http_timers_init (vm, http_conn_timeout_cb);

  return 0;
}

static int
http_transport_connect (transport_endpoint_cfg_t *tep)
{
  vnet_connect_args_t _cargs, *cargs = &_cargs;
  http_main_t *hm = &http_main;
  session_endpoint_cfg_t *sep = (session_endpoint_cfg_t *) tep;
  application_t *app;
  http_conn_t *hc;
  int error;
  u32 hc_index;
  app_worker_t *app_wrk = app_worker_get (sep->app_wrk_index);

  clib_memset (cargs, 0, sizeof (*cargs));
  clib_memcpy (&cargs->sep_ext, sep, sizeof (session_endpoint_cfg_t));
  cargs->sep.transport_proto = TRANSPORT_PROTO_TCP;
  cargs->app_index = hm->app_index;
  app = application_get (app_wrk->app_index);
  cargs->sep_ext.ns_index = app->ns_index;

  hc_index = http_conn_alloc_w_thread (0 /* ts->thread_index */);
  hc = http_conn_get_w_thread (hc_index, 0);
  hc->h_pa_wrk_index = sep->app_wrk_index;
  hc->h_pa_app_api_ctx = sep->opaque;
  hc->state = HTTP_CONN_STATE_CONNECTING;
  cargs->api_context = hc_index;

  HTTP_DBG (1, "hc ho_index %x", hc_index);

  if ((error = vnet_connect (cargs)))
    return error;

  return 0;
}

static u32
http_start_listen (u32 app_listener_index, transport_endpoint_cfg_t *tep)
{
  vnet_listen_args_t _args = {}, *args = &_args;
  session_t *ts_listener, *app_listener;
  http_main_t *hm = &http_main;
  session_endpoint_cfg_t *sep;
  app_worker_t *app_wrk;
  transport_proto_t tp;
  app_listener_t *al;
  application_t *app;
  http_conn_t *lhc;
  u32 lhc_index;

  sep = (session_endpoint_cfg_t *) tep;

  app_wrk = app_worker_get (sep->app_wrk_index);
  app = application_get (app_wrk->app_index);

  args->app_index = hm->app_index;
  args->sep_ext = *sep;
  args->sep_ext.ns_index = app->ns_index;
  tp = sep->ext_cfg ? TRANSPORT_PROTO_TLS : TRANSPORT_PROTO_TCP;
  args->sep_ext.transport_proto = tp;

  if (vnet_listen (args))
    return SESSION_INVALID_INDEX;

  lhc_index = http_listener_alloc ();
  lhc = http_listener_get (lhc_index);

  /* Grab transport connection listener and link to http listener */
  lhc->h_tc_session_handle = args->handle;
  al = app_listener_get_w_handle (lhc->h_tc_session_handle);
  ts_listener = app_listener_get_session (al);
  ts_listener->opaque = lhc_index;

  /* Grab application listener and link to http listener */
  app_listener = listen_session_get (app_listener_index);
  lhc->h_pa_wrk_index = sep->app_wrk_index;
  lhc->h_pa_session_handle = listen_session_get_handle (app_listener);
  lhc->c_s_index = app_listener_index;
  lhc->c_flags |= TRANSPORT_CONNECTION_F_NO_LOOKUP;

  if (vec_len (app->name))
    lhc->app_name = vec_dup (app->name);
  else
    lhc->app_name = format (0, "VPP server app");

  return lhc_index;
}

static u32
http_stop_listen (u32 listener_index)
{
  http_conn_t *lhc;
  int rv;

  lhc = http_listener_get (listener_index);

  vnet_unlisten_args_t a = {
    .handle = lhc->h_tc_session_handle,
    .app_index = http_main.app_index,
    .wrk_map_index = 0 /* default wrk */
  };

  if ((rv = vnet_unlisten (&a)))
    clib_warning ("unlisten returned %d", rv);

  http_listener_free (lhc);

  return 0;
}

static void
http_transport_close (u32 hc_index, u32 thread_index)
{
  session_t *as;
  http_conn_t *hc;

  HTTP_DBG (1, "App disconnecting %x", hc_index);

  hc = http_conn_get_w_thread (hc_index, thread_index);
  if (hc->state == HTTP_CONN_STATE_CONNECTING)
    {
      hc->state = HTTP_CONN_STATE_APP_CLOSED;
      http_disconnect_transport (hc);
      return;
    }
  else if (hc->state == HTTP_CONN_STATE_CLOSED)
    {
      HTTP_DBG (1, "nothing to do, already closed");
      return;
    }
  as = session_get_from_handle (hc->h_pa_session_handle);

  /* Nothing more to send, confirm close */
  if (!svm_fifo_max_dequeue_cons (as->tx_fifo))
    {
      session_transport_closed_notify (&hc->connection);
      http_disconnect_transport (hc);
    }
  else
    {
      /* Wait for all data to be written to ts */
      hc->state = HTTP_CONN_STATE_APP_CLOSED;
    }
}

static transport_connection_t *
http_transport_get_connection (u32 hc_index, u32 thread_index)
{
  http_conn_t *hc = http_conn_get_w_thread (hc_index, thread_index);
  return &hc->connection;
}

static transport_connection_t *
http_transport_get_listener (u32 listener_index)
{
  http_conn_t *lhc = http_listener_get (listener_index);
  return &lhc->connection;
}

static int
http_app_tx_callback (void *session, transport_send_params_t *sp)
{
  session_t *as = (session_t *) session;
  u32 max_burst_sz, sent;
  http_conn_t *hc;

  HTTP_DBG (1, "app session conn index %x", as->connection_index);

  hc = http_conn_get_w_thread (as->connection_index, as->thread_index);
  if (!http_state_is_tx_valid (hc))
    {
      if (hc->state != HTTP_CONN_STATE_CLOSED)
	clib_warning ("app data req state '%U' session state %u",
		      format_http_state, hc->http_state, hc->state);
      svm_fifo_dequeue_drop_all (as->tx_fifo);
      return 0;
    }

  max_burst_sz = sp->max_burst_size * TRANSPORT_PACER_MIN_MSS;
  sp->max_burst_size = max_burst_sz;

  http_req_run_state_machine (hc, sp);

  if (hc->state == HTTP_CONN_STATE_APP_CLOSED)
    {
      if (!svm_fifo_max_dequeue_cons (as->tx_fifo))
	http_disconnect_transport (hc);
    }

  sent = max_burst_sz - sp->max_burst_size;

  return sent > 0 ? clib_max (sent / TRANSPORT_PACER_MIN_MSS, 1) : 0;
}

static void
http_transport_get_endpoint (u32 hc_index, u32 thread_index,
			     transport_endpoint_t *tep, u8 is_lcl)
{
  http_conn_t *hc = http_conn_get_w_thread (hc_index, thread_index);
  session_t *ts;

  ts = session_get_from_handle (hc->h_tc_session_handle);
  session_get_endpoint (ts, tep, is_lcl);
}

static u8 *
format_http_connection (u8 *s, va_list *args)
{
  http_conn_t *hc = va_arg (*args, http_conn_t *);
  session_t *ts;

  ts = session_get_from_handle (hc->h_tc_session_handle);
  s = format (s, "[%d:%d][H] app_wrk %u ts %d:%d", hc->c_thread_index,
	      hc->c_s_index, hc->h_pa_wrk_index, ts->thread_index,
	      ts->session_index);

  return s;
}

static u8 *
format_http_listener (u8 *s, va_list *args)
{
  http_conn_t *lhc = va_arg (*args, http_conn_t *);
  app_listener_t *al;
  session_t *lts;

  al = app_listener_get_w_handle (lhc->h_tc_session_handle);
  lts = app_listener_get_session (al);
  s = format (s, "[%d:%d][H] app_wrk %u ts %d:%d", lhc->c_thread_index,
	      lhc->c_s_index, lhc->h_pa_wrk_index, lts->thread_index,
	      lts->session_index);

  return s;
}

static u8 *
format_http_conn_state (u8 *s, va_list *args)
{
  http_conn_t *hc = va_arg (*args, http_conn_t *);

  switch (hc->state)
    {
    case HTTP_CONN_STATE_LISTEN:
      s = format (s, "LISTEN");
      break;
    case HTTP_CONN_STATE_CONNECTING:
      s = format (s, "CONNECTING");
      break;
    case HTTP_CONN_STATE_ESTABLISHED:
      s = format (s, "ESTABLISHED");
      break;
    case HTTP_CONN_STATE_TRANSPORT_CLOSED:
      s = format (s, "TRANSPORT_CLOSED");
      break;
    case HTTP_CONN_STATE_APP_CLOSED:
      s = format (s, "APP_CLOSED");
      break;
    case HTTP_CONN_STATE_CLOSED:
      s = format (s, "CLOSED");
      break;
    }

  return s;
}

static u8 *
format_http_transport_connection (u8 *s, va_list *args)
{
  u32 tc_index = va_arg (*args, u32);
  u32 thread_index = va_arg (*args, u32);
  u32 verbose = va_arg (*args, u32);
  http_conn_t *hc;

  hc = http_conn_get_w_thread (tc_index, thread_index);

  s = format (s, "%-" SESSION_CLI_ID_LEN "U", format_http_connection, hc);
  if (verbose)
    {
      s =
	format (s, "%-" SESSION_CLI_STATE_LEN "U", format_http_conn_state, hc);
      if (verbose > 1)
	s = format (s, "\n");
    }

  return s;
}

static u8 *
format_http_transport_listener (u8 *s, va_list *args)
{
  u32 tc_index = va_arg (*args, u32);
  u32 __clib_unused thread_index = va_arg (*args, u32);
  u32 __clib_unused verbose = va_arg (*args, u32);
  http_conn_t *lhc = http_listener_get (tc_index);

  s = format (s, "%-" SESSION_CLI_ID_LEN "U", format_http_listener, lhc);
  if (verbose)
    s =
      format (s, "%-" SESSION_CLI_STATE_LEN "U", format_http_conn_state, lhc);
  return s;
}

static const transport_proto_vft_t http_proto = {
  .enable = http_transport_enable,
  .connect = http_transport_connect,
  .start_listen = http_start_listen,
  .stop_listen = http_stop_listen,
  .close = http_transport_close,
  .custom_tx = http_app_tx_callback,
  .get_connection = http_transport_get_connection,
  .get_listener = http_transport_get_listener,
  .get_transport_endpoint = http_transport_get_endpoint,
  .format_connection = format_http_transport_connection,
  .format_listener = format_http_transport_listener,
  .transport_options = {
    .name = "http",
    .short_name = "H",
    .tx_type = TRANSPORT_TX_INTERNAL,
    .service_type = TRANSPORT_SERVICE_APP,
  },
};

static clib_error_t *
http_transport_init (vlib_main_t *vm)
{
  http_main_t *hm = &http_main;

  transport_register_protocol (TRANSPORT_PROTO_HTTP, &http_proto,
			       FIB_PROTOCOL_IP4, ~0);
  transport_register_protocol (TRANSPORT_PROTO_HTTP, &http_proto,
			       FIB_PROTOCOL_IP6, ~0);

  /* Default values, configurable via startup conf */
  hm->add_seg_size = 256 << 20;
  hm->first_seg_size = 32 << 20;
  hm->fifo_size = 512 << 10;

  return 0;
}

VLIB_INIT_FUNCTION (http_transport_init);

static clib_error_t *
http_config_fn (vlib_main_t *vm, unformat_input_t *input)
{
  http_main_t *hm = &http_main;
  uword mem_sz;

  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
    {
      if (unformat (input, "first-segment-size %U", unformat_memory_size,
		    &mem_sz))
	{
	  hm->first_seg_size = clib_max (mem_sz, 1 << 20);
	  if (hm->first_seg_size != mem_sz)
	    clib_warning ("first seg size too small %u", mem_sz);
	}
      else if (unformat (input, "add-segment-size %U", unformat_memory_size,
			 &mem_sz))
	{
	  hm->add_seg_size = clib_max (mem_sz, 1 << 20);
	  if (hm->add_seg_size != mem_sz)
	    clib_warning ("add seg size too small %u", mem_sz);
	}
      else if (unformat (input, "fifo-size %U", unformat_memory_size, &mem_sz))
	{
	  hm->fifo_size = clib_clamp (mem_sz, 4 << 10, 2 << 30);
	  if (hm->fifo_size != mem_sz)
	    clib_warning ("invalid fifo size %lu", mem_sz);
	}
      else
	return clib_error_return (0, "unknown input `%U'",
				  format_unformat_error, input);
    }
  return 0;
}

VLIB_CONFIG_FUNCTION (http_config_fn, "http");

VLIB_PLUGIN_REGISTER () = {
  .version = VPP_BUILD_VER,
  .description = "Hypertext Transfer Protocol (HTTP)",
  .default_disabled = 0,
};

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */