/*
 *
 * Copyright 2015 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 <grpc/support/port_platform.h>

#include "src/core/lib/iomgr/port.h"

#ifdef GRPC_WINSOCK_SOCKET

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

#include <inttypes.h>
#include <io.h>

#include <vector>

#include "absl/strings/str_cat.h"

#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include <grpc/support/log_windows.h>
#include <grpc/support/string_util.h>
#include <grpc/support/sync.h>
#include <grpc/support/time.h>

#include "src/core/lib/channel/channel_args.h"
#include "src/core/lib/iomgr/iocp_windows.h"
#include "src/core/lib/iomgr/pollset_windows.h"
#include "src/core/lib/iomgr/resolve_address.h"
#include "src/core/lib/iomgr/sockaddr_utils.h"
#include "src/core/lib/iomgr/socket_windows.h"
#include "src/core/lib/iomgr/tcp_server.h"
#include "src/core/lib/iomgr/tcp_windows.h"
#include "src/core/lib/slice/slice_internal.h"

#define MIN_SAFE_ACCEPT_QUEUE_SIZE 100

/* one listening port */
typedef struct grpc_tcp_listener grpc_tcp_listener;
struct grpc_tcp_listener {
  /* This seemingly magic number comes from AcceptEx's documentation. each
     address buffer needs to have at least 16 more bytes at their end. */
  uint8_t addresses[(sizeof(grpc_sockaddr_in6) + 16) * 2];
  /* This will hold the socket for the next accept. */
  SOCKET new_socket;
  /* The listener winsocket. */
  grpc_winsocket* socket;
  /* The actual TCP port number. */
  int port;
  unsigned port_index;
  grpc_tcp_server* server;
  /* The cached AcceptEx for that port. */
  LPFN_ACCEPTEX AcceptEx;
  int shutting_down;
  int outstanding_calls;
  /* closure for socket notification of accept being ready */
  grpc_closure on_accept;
  /* linked list */
  struct grpc_tcp_listener* next;
};

/* the overall server */
struct grpc_tcp_server {
  gpr_refcount refs;
  /* Called whenever accept() succeeds on a server port. */
  grpc_tcp_server_cb on_accept_cb;
  void* on_accept_cb_arg;

  gpr_mu mu;

  /* active port count: how many ports are actually still listening */
  int active_ports;

  /* linked list of server ports */
  grpc_tcp_listener* head;
  grpc_tcp_listener* tail;

  /* List of closures passed to shutdown_starting_add(). */
  grpc_closure_list shutdown_starting;

  /* shutdown callback */
  grpc_closure* shutdown_complete;

  grpc_channel_args* channel_args;
};

/* Public function. Allocates the proper data structures to hold a
   grpc_tcp_server. */
static grpc_error* tcp_server_create(grpc_closure* shutdown_complete,
                                     const grpc_channel_args* args,
                                     grpc_tcp_server** server) {
  grpc_tcp_server* s = (grpc_tcp_server*)gpr_malloc(sizeof(grpc_tcp_server));
  s->channel_args = grpc_channel_args_copy(args);
  gpr_ref_init(&s->refs, 1);
  gpr_mu_init(&s->mu);
  s->active_ports = 0;
  s->on_accept_cb = NULL;
  s->on_accept_cb_arg = NULL;
  s->head = NULL;
  s->tail = NULL;
  s->shutdown_starting.head = NULL;
  s->shutdown_starting.tail = NULL;
  s->shutdown_complete = shutdown_complete;
  *server = s;
  return GRPC_ERROR_NONE;
}

static void destroy_server(void* arg, grpc_error* error) {
  grpc_tcp_server* s = (grpc_tcp_server*)arg;

  /* Now that the accepts have been aborted, we can destroy the sockets.
     The IOCP won't get notified on these, so we can flag them as already
     closed by the system. */
  while (s->head) {
    grpc_tcp_listener* sp = s->head;
    s->head = sp->next;
    sp->next = NULL;
    grpc_winsocket_destroy(sp->socket);
    gpr_free(sp);
  }
  grpc_channel_args_destroy(s->channel_args);
  gpr_mu_destroy(&s->mu);
  gpr_free(s);
}

static void finish_shutdown_locked(grpc_tcp_server* s) {
  if (s->shutdown_complete != NULL) {
    grpc_core::ExecCtx::Run(DEBUG_LOCATION, s->shutdown_complete,
                            GRPC_ERROR_NONE);
  }

  grpc_core::ExecCtx::Run(
      DEBUG_LOCATION,
      GRPC_CLOSURE_CREATE(destroy_server, s, grpc_schedule_on_exec_ctx),
      GRPC_ERROR_NONE);
}

static grpc_tcp_server* tcp_server_ref(grpc_tcp_server* s) {
  gpr_ref_non_zero(&s->refs);
  return s;
}

static void tcp_server_shutdown_starting_add(grpc_tcp_server* s,
                                             grpc_closure* shutdown_starting) {
  gpr_mu_lock(&s->mu);
  grpc_closure_list_append(&s->shutdown_starting, shutdown_starting,
                           GRPC_ERROR_NONE);
  gpr_mu_unlock(&s->mu);
}

static void tcp_server_destroy(grpc_tcp_server* s) {
  grpc_tcp_listener* sp;
  gpr_mu_lock(&s->mu);

  /* First, shutdown all fd's. This will queue abortion calls for all
     of the pending accepts due to the normal operation mechanism. */
  if (s->active_ports == 0) {
    finish_shutdown_locked(s);
  } else {
    for (sp = s->head; sp; sp = sp->next) {
      sp->shutting_down = 1;
      grpc_winsocket_shutdown(sp->socket);
    }
  }
  gpr_mu_unlock(&s->mu);
}

static void tcp_server_unref(grpc_tcp_server* s) {
  if (gpr_unref(&s->refs)) {
    grpc_tcp_server_shutdown_listeners(s);
    gpr_mu_lock(&s->mu);
    grpc_core::ExecCtx::RunList(DEBUG_LOCATION, &s->shutdown_starting);
    gpr_mu_unlock(&s->mu);
    tcp_server_destroy(s);
  }
}

/* Prepare (bind) a recently-created socket for listening. */
static grpc_error* prepare_socket(SOCKET sock,
                                  const grpc_resolved_address* addr,
                                  int* port) {
  grpc_resolved_address sockname_temp;
  grpc_error* error = GRPC_ERROR_NONE;
  int sockname_temp_len;

  error = grpc_tcp_prepare_socket(sock);
  if (error != GRPC_ERROR_NONE) {
    goto failure;
  }

  if (bind(sock, (const grpc_sockaddr*)addr->addr, (int)addr->len) ==
      SOCKET_ERROR) {
    error = GRPC_WSA_ERROR(WSAGetLastError(), "bind");
    goto failure;
  }

  if (listen(sock, SOMAXCONN) == SOCKET_ERROR) {
    error = GRPC_WSA_ERROR(WSAGetLastError(), "listen");
    goto failure;
  }

  sockname_temp_len = sizeof(struct sockaddr_storage);
  if (getsockname(sock, (grpc_sockaddr*)sockname_temp.addr,
                  &sockname_temp_len) == SOCKET_ERROR) {
    error = GRPC_WSA_ERROR(WSAGetLastError(), "getsockname");
    goto failure;
  }
  sockname_temp.len = (size_t)sockname_temp_len;

  *port = grpc_sockaddr_get_port(&sockname_temp);
  return GRPC_ERROR_NONE;

failure:
  GPR_ASSERT(error != GRPC_ERROR_NONE);
  grpc_error_set_int(
      grpc_error_set_str(
          GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
              "Failed to prepare server socket", &error, 1),
          GRPC_ERROR_STR_TARGET_ADDRESS,
          grpc_slice_from_cpp_string(grpc_sockaddr_to_uri(addr))),
      GRPC_ERROR_INT_FD, (intptr_t)sock);
  GRPC_ERROR_UNREF(error);
  if (sock != INVALID_SOCKET) closesocket(sock);
  return error;
}

static void decrement_active_ports_and_notify_locked(grpc_tcp_listener* sp) {
  sp->shutting_down = 0;
  GPR_ASSERT(sp->server->active_ports > 0);
  if (0 == --sp->server->active_ports) {
    finish_shutdown_locked(sp->server);
  }
}

/* In order to do an async accept, we need to create a socket first which
   will be the one assigned to the new incoming connection. */
static grpc_error* start_accept_locked(grpc_tcp_listener* port) {
  SOCKET sock = INVALID_SOCKET;
  BOOL success;
  DWORD addrlen = sizeof(grpc_sockaddr_in6) + 16;
  DWORD bytes_received = 0;
  grpc_error* error = GRPC_ERROR_NONE;

  if (port->shutting_down) {
    return GRPC_ERROR_NONE;
  }

  sock = WSASocket(AF_INET6, SOCK_STREAM, IPPROTO_TCP, NULL, 0,
                   grpc_get_default_wsa_socket_flags());
  if (sock == INVALID_SOCKET) {
    error = GRPC_WSA_ERROR(WSAGetLastError(), "WSASocket");
    goto failure;
  }

  error = grpc_tcp_prepare_socket(sock);
  if (error != GRPC_ERROR_NONE) goto failure;

  /* Start the "accept" asynchronously. */
  success = port->AcceptEx(port->socket->socket, sock, port->addresses, 0,
                           addrlen, addrlen, &bytes_received,
                           &port->socket->read_info.overlapped);

  /* It is possible to get an accept immediately without delay. However, we
     will still get an IOCP notification for it. So let's just ignore it. */
  if (!success) {
    int last_error = WSAGetLastError();
    if (last_error != ERROR_IO_PENDING) {
      error = GRPC_WSA_ERROR(last_error, "AcceptEx");
      goto failure;
    }
  }

  /* We're ready to do the accept. Calling grpc_socket_notify_on_read may
     immediately process an accept that happened in the meantime. */
  port->new_socket = sock;
  grpc_socket_notify_on_read(port->socket, &port->on_accept);
  port->outstanding_calls++;
  return error;

failure:
  GPR_ASSERT(error != GRPC_ERROR_NONE);
  if (sock != INVALID_SOCKET) closesocket(sock);
  return error;
}

/* Event manager callback when reads are ready. */
static void on_accept(void* arg, grpc_error* error) {
  grpc_tcp_listener* sp = (grpc_tcp_listener*)arg;
  SOCKET sock = sp->new_socket;
  grpc_winsocket_callback_info* info = &sp->socket->read_info;
  grpc_endpoint* ep = NULL;
  grpc_resolved_address peer_name;
  DWORD transfered_bytes;
  DWORD flags;
  BOOL wsa_success;
  int err;

  gpr_mu_lock(&sp->server->mu);

  peer_name.len = sizeof(struct sockaddr_storage);

  /* The general mechanism for shutting down is to queue abortion calls. While
     this is necessary in the read/write case, it's useless for the accept
     case. We only need to adjust the pending callback count */
  if (error != GRPC_ERROR_NONE) {
    const char* msg = grpc_error_string(error);
    gpr_log(GPR_INFO, "Skipping on_accept due to error: %s", msg);

    gpr_mu_unlock(&sp->server->mu);
    return;
  }

  /* The IOCP notified us of a completed operation. Let's grab the results,
     and act accordingly. */
  transfered_bytes = 0;
  wsa_success = WSAGetOverlappedResult(sock, &info->overlapped,
                                       &transfered_bytes, FALSE, &flags);
  if (!wsa_success) {
    if (!sp->shutting_down) {
      char* utf8_message = gpr_format_message(WSAGetLastError());
      gpr_log(GPR_ERROR, "on_accept error: %s", utf8_message);
      gpr_free(utf8_message);
    }
    closesocket(sock);
  } else {
    if (!sp->shutting_down) {
      err = setsockopt(sock, SOL_SOCKET, SO_UPDATE_ACCEPT_CONTEXT,
                       (char*)&sp->socket->socket, sizeof(sp->socket->socket));
      if (err) {
        char* utf8_message = gpr_format_message(WSAGetLastError());
        gpr_log(GPR_ERROR, "setsockopt error: %s", utf8_message);
        gpr_free(utf8_message);
      }
      int peer_name_len = (int)peer_name.len;
      err = getpeername(sock, (grpc_sockaddr*)peer_name.addr, &peer_name_len);
      peer_name.len = (size_t)peer_name_len;
      std::string peer_name_string;
      if (!err) {
        peer_name_string = grpc_sockaddr_to_uri(&peer_name);
      } else {
        char* utf8_message = gpr_format_message(WSAGetLastError());
        gpr_log(GPR_ERROR, "getpeername error: %s", utf8_message);
        gpr_free(utf8_message);
      }
      std::string fd_name = absl::StrCat("tcp_server:", peer_name_string);
      ep = grpc_tcp_create(grpc_winsocket_create(sock, fd_name.c_str()),
                           sp->server->channel_args, peer_name_string.c_str());
    } else {
      closesocket(sock);
    }
  }

  /* The only time we should call our callback, is where we successfully
     managed to accept a connection, and created an endpoint. */
  if (ep) {
    // Create acceptor.
    grpc_tcp_server_acceptor* acceptor =
        (grpc_tcp_server_acceptor*)gpr_malloc(sizeof(*acceptor));
    acceptor->from_server = sp->server;
    acceptor->port_index = sp->port_index;
    acceptor->fd_index = 0;
    acceptor->external_connection = false;
    sp->server->on_accept_cb(sp->server->on_accept_cb_arg, ep, NULL, acceptor);
  }
  /* As we were notified from the IOCP of one and exactly one accept,
     the former socked we created has now either been destroy or assigned
     to the new connection. We need to create a new one for the next
     connection. */
  GPR_ASSERT(GRPC_LOG_IF_ERROR("start_accept", start_accept_locked(sp)));
  if (0 == --sp->outstanding_calls) {
    decrement_active_ports_and_notify_locked(sp);
  }
  gpr_mu_unlock(&sp->server->mu);
}

static grpc_error* add_socket_to_server(grpc_tcp_server* s, SOCKET sock,
                                        const grpc_resolved_address* addr,
                                        unsigned port_index,
                                        grpc_tcp_listener** listener) {
  grpc_tcp_listener* sp = NULL;
  int port = -1;
  int status;
  GUID guid = WSAID_ACCEPTEX;
  DWORD ioctl_num_bytes;
  LPFN_ACCEPTEX AcceptEx;
  grpc_error* error = GRPC_ERROR_NONE;

  /* We need to grab the AcceptEx pointer for that port, as it may be
     interface-dependent. We'll cache it to avoid doing that again. */
  status =
      WSAIoctl(sock, SIO_GET_EXTENSION_FUNCTION_POINTER, &guid, sizeof(guid),
               &AcceptEx, sizeof(AcceptEx), &ioctl_num_bytes, NULL, NULL);

  if (status != 0) {
    char* utf8_message = gpr_format_message(WSAGetLastError());
    gpr_log(GPR_ERROR, "on_connect error: %s", utf8_message);
    gpr_free(utf8_message);
    closesocket(sock);
    return GRPC_ERROR_NONE;
  }

  error = prepare_socket(sock, addr, &port);
  if (error != GRPC_ERROR_NONE) {
    return error;
  }

  GPR_ASSERT(port >= 0);
  gpr_mu_lock(&s->mu);
  GPR_ASSERT(!s->on_accept_cb && "must add ports before starting server");
  sp = (grpc_tcp_listener*)gpr_malloc(sizeof(grpc_tcp_listener));
  sp->next = NULL;
  if (s->head == NULL) {
    s->head = sp;
  } else {
    s->tail->next = sp;
  }
  s->tail = sp;
  sp->server = s;
  sp->socket = grpc_winsocket_create(sock, "listener");
  sp->shutting_down = 0;
  sp->outstanding_calls = 0;
  sp->AcceptEx = AcceptEx;
  sp->new_socket = INVALID_SOCKET;
  sp->port = port;
  sp->port_index = port_index;
  GRPC_CLOSURE_INIT(&sp->on_accept, on_accept, sp, grpc_schedule_on_exec_ctx);
  GPR_ASSERT(sp->socket);
  gpr_mu_unlock(&s->mu);
  *listener = sp;

  return GRPC_ERROR_NONE;
}

static grpc_error* tcp_server_add_port(grpc_tcp_server* s,
                                       const grpc_resolved_address* addr,
                                       int* port) {
  grpc_tcp_listener* sp = NULL;
  SOCKET sock;
  grpc_resolved_address addr6_v4mapped;
  grpc_resolved_address wildcard;
  grpc_resolved_address* allocated_addr = NULL;
  grpc_resolved_address sockname_temp;
  unsigned port_index = 0;
  grpc_error* error = GRPC_ERROR_NONE;

  if (s->tail != NULL) {
    port_index = s->tail->port_index + 1;
  }

  /* Check if this is a wildcard port, and if so, try to keep the port the same
     as some previously created listener. */
  if (grpc_sockaddr_get_port(addr) == 0) {
    for (sp = s->head; sp; sp = sp->next) {
      int sockname_temp_len = sizeof(struct sockaddr_storage);
      if (0 == getsockname(sp->socket->socket,
                           (grpc_sockaddr*)sockname_temp.addr,
                           &sockname_temp_len)) {
        sockname_temp.len = (size_t)sockname_temp_len;
        *port = grpc_sockaddr_get_port(&sockname_temp);
        if (*port > 0) {
          allocated_addr =
              (grpc_resolved_address*)gpr_malloc(sizeof(grpc_resolved_address));
          memcpy(allocated_addr, addr, sizeof(grpc_resolved_address));
          grpc_sockaddr_set_port(allocated_addr, *port);
          addr = allocated_addr;
          break;
        }
      }
    }
  }

  if (grpc_sockaddr_to_v4mapped(addr, &addr6_v4mapped)) {
    addr = &addr6_v4mapped;
  }

  /* Treat :: or 0.0.0.0 as a family-agnostic wildcard. */
  if (grpc_sockaddr_is_wildcard(addr, port)) {
    grpc_sockaddr_make_wildcard6(*port, &wildcard);

    addr = &wildcard;
  }

  sock = WSASocket(AF_INET6, SOCK_STREAM, IPPROTO_TCP, NULL, 0,
                   grpc_get_default_wsa_socket_flags());
  if (sock == INVALID_SOCKET) {
    error = GRPC_WSA_ERROR(WSAGetLastError(), "WSASocket");
    goto done;
  }

  error = add_socket_to_server(s, sock, addr, port_index, &sp);

done:
  gpr_free(allocated_addr);

  if (error != GRPC_ERROR_NONE) {
    grpc_error* error_out = GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
        "Failed to add port to server", &error, 1);
    GRPC_ERROR_UNREF(error);
    error = error_out;
    *port = -1;
  } else {
    GPR_ASSERT(sp != NULL);
    *port = sp->port;
  }
  return error;
}

static void tcp_server_start(grpc_tcp_server* s,
                             const std::vector<grpc_pollset*>* /*pollsets*/,
                             grpc_tcp_server_cb on_accept_cb,
                             void* on_accept_cb_arg) {
  grpc_tcp_listener* sp;
  GPR_ASSERT(on_accept_cb);
  gpr_mu_lock(&s->mu);
  GPR_ASSERT(!s->on_accept_cb);
  GPR_ASSERT(s->active_ports == 0);
  s->on_accept_cb = on_accept_cb;
  s->on_accept_cb_arg = on_accept_cb_arg;
  for (sp = s->head; sp; sp = sp->next) {
    GPR_ASSERT(GRPC_LOG_IF_ERROR("start_accept", start_accept_locked(sp)));
    s->active_ports++;
  }
  gpr_mu_unlock(&s->mu);
}

static unsigned tcp_server_port_fd_count(grpc_tcp_server* s,
                                         unsigned port_index) {
  return 0;
}

static int tcp_server_port_fd(grpc_tcp_server* s, unsigned port_index,
                              unsigned fd_index) {
  return -1;
}

static grpc_core::TcpServerFdHandler* tcp_server_create_fd_handler(
    grpc_tcp_server* s) {
  return nullptr;
}

static void tcp_server_shutdown_listeners(grpc_tcp_server* s) {}

grpc_tcp_server_vtable grpc_windows_tcp_server_vtable = {
    tcp_server_create,        tcp_server_start,
    tcp_server_add_port,      tcp_server_create_fd_handler,
    tcp_server_port_fd_count, tcp_server_port_fd,
    tcp_server_ref,           tcp_server_shutdown_starting_add,
    tcp_server_unref,         tcp_server_shutdown_listeners};
#endif /* GRPC_WINSOCK_SOCKET */
