/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * 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.
 *     * Neither the name of Google Inc. 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 COPYRIGHT HOLDERS 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 COPYRIGHT
 * OWNER 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.
 *
 */

#include "src/core/surface/channel.h"

#include <grpc/support/alloc.h>
#include <grpc/support/log.h>

#include "src/core/channel/client_channel.h"
#include "src/core/iomgr/alarm.h"
#include "src/core/surface/completion_queue.h"

grpc_connectivity_state
grpc_channel_check_connectivity_state (grpc_channel * channel, int try_to_connect)
{
  /* forward through to the underlying client channel */
  grpc_channel_element *client_channel_elem = grpc_channel_stack_last_element (grpc_channel_get_channel_stack (channel));
  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
  grpc_connectivity_state state;
  if (client_channel_elem->filter != &grpc_client_channel_filter)
    {
      gpr_log (GPR_ERROR, "grpc_channel_check_connectivity_state called on something that is " "not a client channel, but '%s'", client_channel_elem->filter->name);
      return GRPC_CHANNEL_FATAL_FAILURE;
    }
  state = grpc_client_channel_check_connectivity_state (client_channel_elem, try_to_connect, &closure_list);
  grpc_exec_ctx_finish (&exec_ctx);
  return state;
}

typedef enum
{
  WAITING,
  CALLING_BACK,
  CALLING_BACK_AND_FINISHED,
  CALLED_BACK
} callback_phase;

typedef struct
{
  gpr_mu mu;
  callback_phase phase;
  int success;
  int removed;
  grpc_closure on_complete;
  grpc_alarm alarm;
  grpc_connectivity_state state;
  grpc_completion_queue *cq;
  grpc_cq_completion completion_storage;
  grpc_channel *channel;
  void *tag;
} state_watcher;

static void
delete_state_watcher (grpc_exec_ctx * exec_ctx, state_watcher * w)
{
  GRPC_CHANNEL_INTERNAL_UNREF (exec_ctx, w->channel, "watch_connectivity");
  gpr_mu_destroy (&w->mu);
  gpr_free (w);
}

static void
finished_completion (grpc_exec_ctx * exec_ctx, void *pw, grpc_cq_completion * ignored)
{
  int delete = 0;
  state_watcher *w = pw;
  gpr_mu_lock (&w->mu);
  switch (w->phase)
    {
    case WAITING:
    case CALLED_BACK:
      gpr_log (GPR_ERROR, "should never reach here");
      abort ();
      break;
    case CALLING_BACK:
      w->phase = CALLED_BACK;
      break;
    case CALLING_BACK_AND_FINISHED:
      delete = 1;
      break;
    }
  gpr_mu_unlock (&w->mu);

  if (delete)
    {
      delete_state_watcher (exec_ctx, w);
    }
}

static void
partly_done (grpc_exec_ctx * exec_ctx, state_watcher * w, int due_to_completion)
{
  int delete = 0;
  grpc_channel_element *client_channel_elem = NULL;

  gpr_mu_lock (&w->mu);
  if (w->removed == 0)
    {
      w->removed = 1;
      client_channel_elem = grpc_channel_stack_last_element (grpc_channel_get_channel_stack (w->channel));
      grpc_client_channel_del_interested_party (client_channel_elem, grpc_cq_pollset (exec_ctx, w->cq));
    }
  gpr_mu_unlock (&w->mu);
  if (due_to_completion)
    {
      gpr_mu_lock (&w->mu);
      w->success = 1;
      gpr_mu_unlock (&w->mu);
      grpc_alarm_cancel (exec_ctx, &w->alarm);
    }

  gpr_mu_lock (&w->mu);
  switch (w->phase)
    {
    case WAITING:
      w->phase = CALLING_BACK;
      grpc_cq_end_op (exec_ctx, w->cq, w->tag, w->success, finished_completion, w, &w->completion_storage);
      break;
    case CALLING_BACK:
      w->phase = CALLING_BACK_AND_FINISHED;
      break;
    case CALLING_BACK_AND_FINISHED:
      gpr_log (GPR_ERROR, "should never reach here");
      abort ();
      break;
    case CALLED_BACK:
      delete = 1;
      break;
    }
  gpr_mu_unlock (&w->mu);

  if (delete)
    {
      delete_state_watcher (exec_ctx, w);
    }
}

static void
watch_complete (grpc_exec_ctx * exec_ctx, void *pw, int success)
{
  partly_done (exec_ctx, pw, 1);
}

static void
timeout_complete (grpc_exec_ctx * exec_ctx, void *pw, int success)
{
  partly_done (exec_ctx, pw, 0);
}

void
grpc_channel_watch_connectivity_state (grpc_channel * channel, grpc_connectivity_state last_observed_state, gpr_timespec deadline, grpc_completion_queue * cq, void *tag)
{
  grpc_channel_element *client_channel_elem = grpc_channel_stack_last_element (grpc_channel_get_channel_stack (channel));
  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
  state_watcher *w = gpr_malloc (sizeof (*w));

  grpc_cq_begin_op (cq);

  gpr_mu_init (&w->mu);
  grpc_closure_init (&w->on_complete, watch_complete, w);
  w->phase = WAITING;
  w->state = last_observed_state;
  w->success = 0;
  w->removed = 0;
  w->cq = cq;
  w->tag = tag;
  w->channel = channel;

  grpc_alarm_init (&w->alarm, gpr_convert_clock_type (deadline, GPR_CLOCK_MONOTONIC), timeout_complete, w, gpr_now (GPR_CLOCK_MONOTONIC), &closure_list);

  if (client_channel_elem->filter != &grpc_client_channel_filter)
    {
      gpr_log (GPR_ERROR, "grpc_channel_watch_connectivity_state called on something that is " "not a client channel, but '%s'", client_channel_elem->filter->name);
      grpc_closure_list_add (&closure_list, &w->on_complete, 1);
    }
  else
    {
      GRPC_CHANNEL_INTERNAL_REF (channel, "watch_connectivity");
      grpc_client_channel_add_interested_party (client_channel_elem, grpc_cq_pollset (cq), &closure_list);
      grpc_client_channel_watch_connectivity_state (client_channel_elem, &w->state, &w->on_complete, &closure_list);
    }

  grpc_exec_ctx_finish (&exec_ctx);
}