/*
 *
 * Copyright 2016 gRPC authors.
 *
 * 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 "test/core/util/passthru_endpoint.h"

#include <inttypes.h>
#include <string.h>

#include <string>

#include "absl/strings/str_format.h"

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

#include "src/core/lib/iomgr/sockaddr.h"
#include "src/core/lib/slice/slice_internal.h"

typedef struct passthru_endpoint passthru_endpoint;

typedef struct {
  grpc_endpoint base;
  passthru_endpoint* parent;
  grpc_slice_buffer read_buffer;
  grpc_slice_buffer* on_read_out;
  grpc_closure* on_read;
} half;

struct passthru_endpoint {
  gpr_mu mu;
  int halves;
  grpc_passthru_endpoint_stats* stats;
  bool shutdown;
  half client;
  half server;
};

static void me_read(grpc_endpoint* ep, grpc_slice_buffer* slices,
                    grpc_closure* cb, bool /*urgent*/) {
  half* m = reinterpret_cast<half*>(ep);
  gpr_mu_lock(&m->parent->mu);
  if (m->parent->shutdown) {
    grpc_core::ExecCtx::Run(
        DEBUG_LOCATION, cb,
        GRPC_ERROR_CREATE_FROM_STATIC_STRING("Already shutdown"));
  } else if (m->read_buffer.count > 0) {
    grpc_slice_buffer_swap(&m->read_buffer, slices);
    grpc_core::ExecCtx::Run(DEBUG_LOCATION, cb, GRPC_ERROR_NONE);
  } else {
    m->on_read = cb;
    m->on_read_out = slices;
  }
  gpr_mu_unlock(&m->parent->mu);
}

static half* other_half(half* h) {
  if (h == &h->parent->client) return &h->parent->server;
  return &h->parent->client;
}

static void me_write(grpc_endpoint* ep, grpc_slice_buffer* slices,
                     grpc_closure* cb, void* /*arg*/) {
  half* m = other_half(reinterpret_cast<half*>(ep));
  gpr_mu_lock(&m->parent->mu);
  grpc_error_handle error = GRPC_ERROR_NONE;
  gpr_atm_no_barrier_fetch_add(&m->parent->stats->num_writes, (gpr_atm)1);
  if (m->parent->shutdown) {
    error = GRPC_ERROR_CREATE_FROM_STATIC_STRING("Endpoint already shutdown");
  } else if (m->on_read != nullptr) {
    for (size_t i = 0; i < slices->count; i++) {
      grpc_slice_buffer_add(m->on_read_out, grpc_slice_copy(slices->slices[i]));
    }
    grpc_core::ExecCtx::Run(DEBUG_LOCATION, m->on_read, GRPC_ERROR_NONE);
    m->on_read = nullptr;
  } else {
    for (size_t i = 0; i < slices->count; i++) {
      grpc_slice_buffer_add(&m->read_buffer,
                            grpc_slice_copy(slices->slices[i]));
    }
  }
  gpr_mu_unlock(&m->parent->mu);
  grpc_core::ExecCtx::Run(DEBUG_LOCATION, cb, error);
}

static void me_add_to_pollset(grpc_endpoint* /*ep*/,
                              grpc_pollset* /*pollset*/) {}

static void me_add_to_pollset_set(grpc_endpoint* /*ep*/,
                                  grpc_pollset_set* /*pollset*/) {}

static void me_delete_from_pollset_set(grpc_endpoint* /*ep*/,
                                       grpc_pollset_set* /*pollset*/) {}

static void me_shutdown(grpc_endpoint* ep, grpc_error_handle why) {
  half* m = reinterpret_cast<half*>(ep);
  gpr_mu_lock(&m->parent->mu);
  m->parent->shutdown = true;
  if (m->on_read) {
    grpc_core::ExecCtx::Run(
        DEBUG_LOCATION, m->on_read,
        GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING("Shutdown", &why, 1));
    m->on_read = nullptr;
  }
  m = other_half(m);
  if (m->on_read) {
    grpc_core::ExecCtx::Run(
        DEBUG_LOCATION, m->on_read,
        GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING("Shutdown", &why, 1));
    m->on_read = nullptr;
  }
  gpr_mu_unlock(&m->parent->mu);
  GRPC_ERROR_UNREF(why);
}

static void me_destroy(grpc_endpoint* ep) {
  passthru_endpoint* p = (reinterpret_cast<half*>(ep))->parent;
  gpr_mu_lock(&p->mu);
  if (0 == --p->halves) {
    gpr_mu_unlock(&p->mu);
    gpr_mu_destroy(&p->mu);
    grpc_passthru_endpoint_stats_destroy(p->stats);
    grpc_slice_buffer_destroy_internal(&p->client.read_buffer);
    grpc_slice_buffer_destroy_internal(&p->server.read_buffer);
    gpr_free(p);
  } else {
    gpr_mu_unlock(&p->mu);
  }
}

static absl::string_view me_get_peer(grpc_endpoint* ep) {
  passthru_endpoint* p = (reinterpret_cast<half*>(ep))->parent;
  return (reinterpret_cast<half*>(ep)) == &p->client
             ? "fake:mock_client_endpoint"
             : "fake:mock_server_endpoint";
}

static absl::string_view me_get_local_address(grpc_endpoint* ep) {
  passthru_endpoint* p = (reinterpret_cast<half*>(ep))->parent;
  return (reinterpret_cast<half*>(ep)) == &p->client
             ? "fake:mock_client_endpoint"
             : "fake:mock_server_endpoint";
}

static int me_get_fd(grpc_endpoint* /*ep*/) { return -1; }

static bool me_can_track_err(grpc_endpoint* /*ep*/) { return false; }

static const grpc_endpoint_vtable vtable = {
    me_read,
    me_write,
    me_add_to_pollset,
    me_add_to_pollset_set,
    me_delete_from_pollset_set,
    me_shutdown,
    me_destroy,
    me_get_peer,
    me_get_local_address,
    me_get_fd,
    me_can_track_err,
};

static void half_init(half* m, passthru_endpoint* parent,
                      const char* half_name) {
  m->base.vtable = &vtable;
  m->parent = parent;
  grpc_slice_buffer_init(&m->read_buffer);
  m->on_read = nullptr;
  std::string name =
      absl::StrFormat("passthru_endpoint_%s_%p", half_name, parent);
}

void grpc_passthru_endpoint_create(grpc_endpoint** client,
                                   grpc_endpoint** server,
                                   grpc_passthru_endpoint_stats* stats) {
  passthru_endpoint* m =
      static_cast<passthru_endpoint*>(gpr_malloc(sizeof(*m)));
  m->halves = 2;
  m->shutdown = false;
  if (stats == nullptr) {
    m->stats = grpc_passthru_endpoint_stats_create();
  } else {
    gpr_ref(&stats->refs);
    m->stats = stats;
  }
  half_init(&m->client, m, "client");
  half_init(&m->server, m, "server");
  gpr_mu_init(&m->mu);
  *client = &m->client.base;
  *server = &m->server.base;
}

grpc_passthru_endpoint_stats* grpc_passthru_endpoint_stats_create() {
  grpc_passthru_endpoint_stats* stats =
      static_cast<grpc_passthru_endpoint_stats*>(
          gpr_malloc(sizeof(grpc_passthru_endpoint_stats)));
  memset(stats, 0, sizeof(*stats));
  gpr_ref_init(&stats->refs, 1);
  return stats;
}

void grpc_passthru_endpoint_stats_destroy(grpc_passthru_endpoint_stats* stats) {
  if (gpr_unref(&stats->refs)) {
    gpr_free(stats);
  }
}