/*
 *
 * Copyright 2014, 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/server.h"

#include <stdlib.h>
#include <string.h>

#include "src/core/channel/census_filter.h"
#include "src/core/channel/channel_args.h"
#include "src/core/channel/connected_channel.h"
#include "src/core/surface/call.h"
#include "src/core/surface/channel.h"
#include "src/core/surface/completion_queue.h"
#include "src/core/surface/surface_em.h"
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include <grpc/support/string.h>
#include <grpc/support/useful.h>

typedef enum { PENDING_START, ALL_CALLS, CALL_LIST_COUNT } call_list;

typedef struct listener {
  void *arg;
  void (*start)(grpc_server *server, void *arg);
  void (*destroy)(grpc_server *server, void *arg);
  struct listener *next;
} listener;

typedef struct call_data call_data;
typedef struct channel_data channel_data;

struct channel_data {
  grpc_server *server;
  grpc_channel *channel;
  /* linked list of all channels on a server */
  channel_data *next;
  channel_data *prev;
};

struct grpc_server {
  size_t channel_filter_count;
  const grpc_channel_filter **channel_filters;
  grpc_channel_args *channel_args;
  grpc_completion_queue *cq;
  grpc_em *em;

  gpr_mu mu;

  void **tags;
  size_t ntags;
  size_t tag_cap;

  gpr_uint8 shutdown;

  call_data *lists[CALL_LIST_COUNT];
  channel_data root_channel_data;

  listener *listeners;
  gpr_refcount internal_refcount;
};

typedef struct {
  call_data *next;
  call_data *prev;
} call_link;

typedef enum {
  /* waiting for metadata */
  NOT_STARTED,
  /* inital metadata read, not flow controlled in yet */
  PENDING,
  /* flow controlled in, on completion queue */
  ACTIVATED,
  /* cancelled before being queued */
  ZOMBIED
} call_state;

struct call_data {
  grpc_call *call;

  call_state state;
  gpr_timespec deadline;

  gpr_uint8 included[CALL_LIST_COUNT];
  call_link links[CALL_LIST_COUNT];
};

#define SERVER_FROM_CALL_ELEM(elem) \
  (((channel_data *)(elem)->channel_data)->server)

static void do_nothing(void *unused, grpc_op_error ignored) {}

static int call_list_join(grpc_server *server, call_data *call,
                          call_list list) {
  if (call->included[list]) return 0;
  call->included[list] = 1;
  if (!server->lists[list]) {
    server->lists[list] = call;
    call->links[list].next = call->links[list].prev = call;
  } else {
    call->links[list].next = server->lists[list];
    call->links[list].prev = server->lists[list]->links[list].prev;
    call->links[list].next->links[list].prev =
        call->links[list].prev->links[list].next = call;
  }
  return 1;
}

static call_data *call_list_remove_head(grpc_server *server, call_list list) {
  call_data *out = server->lists[list];
  if (out) {
    out->included[list] = 0;
    if (out->links[list].next == out) {
      server->lists[list] = NULL;
    } else {
      server->lists[list] = out->links[list].next;
      out->links[list].next->links[list].prev = out->links[list].prev;
      out->links[list].prev->links[list].next = out->links[list].next;
    }
  }
  return out;
}

static int call_list_remove(grpc_server *server, call_data *call,
                            call_list list) {
  if (!call->included[list]) return 0;
  call->included[list] = 0;
  if (server->lists[list] == call) {
    server->lists[list] = call->links[list].next;
    if (server->lists[list] == call) {
      server->lists[list] = NULL;
      return 1;
    }
  }
  GPR_ASSERT(server->lists[list] != call);
  call->links[list].next->links[list].prev = call->links[list].prev;
  call->links[list].prev->links[list].next = call->links[list].next;
  return 1;
}

static void server_ref(grpc_server *server) {
  gpr_ref(&server->internal_refcount);
}

static void server_unref(grpc_server *server) {
  if (gpr_unref(&server->internal_refcount)) {
    grpc_channel_args_destroy(server->channel_args);
    gpr_mu_destroy(&server->mu);
    gpr_free(server->channel_filters);
    gpr_free(server->tags);
    gpr_free(server);
  }
}

static int is_channel_orphaned(channel_data *chand) {
  return chand->next == chand;
}

static void orphan_channel(channel_data *chand) {
  chand->next->prev = chand->prev;
  chand->prev->next = chand->next;
  chand->next = chand->prev = chand;
}

static void finish_destroy_channel(void *cd, grpc_em_cb_status status) {
  channel_data *chand = cd;
  grpc_server *server = chand->server;
  /*gpr_log(GPR_INFO, "destroy channel %p", chand->channel);*/
  grpc_channel_destroy(chand->channel);
  server_unref(server);
}

static void destroy_channel(channel_data *chand) {
  if (is_channel_orphaned(chand)) return;
  GPR_ASSERT(chand->server != NULL);
  orphan_channel(chand);
  server_ref(chand->server);
  grpc_em_add_callback(chand->server->em, finish_destroy_channel, chand);
}

static void queue_new_rpc(grpc_server *server, call_data *calld, void *tag) {
  grpc_call *call = calld->call;
  grpc_metadata_buffer *mdbuf = grpc_call_get_metadata_buffer(call);
  size_t count = grpc_metadata_buffer_count(mdbuf);
  grpc_metadata *elements = grpc_metadata_buffer_extract_elements(mdbuf);
  const char *host = NULL;
  const char *method = NULL;
  size_t i;
  grpc_metadata status_md;

  for (i = 0; i < count; i++) {
    if (0 == strcmp(elements[i].key, ":authority")) {
      host = elements[i].value;
    } else if (0 == strcmp(elements[i].key, ":path")) {
      method = elements[i].value;
    }
  }

  status_md.key = ":status";
  status_md.value = "200";
  status_md.value_length = 3;
  grpc_call_add_metadata(call, &status_md, GRPC_WRITE_BUFFER_HINT);

  grpc_call_internal_ref(call);
  grpc_cq_end_new_rpc(server->cq, tag, call,
                      grpc_metadata_buffer_cleanup_elements, elements, method,
                      host, calld->deadline, count, elements);
}

static void start_new_rpc(grpc_call_element *elem) {
  channel_data *chand = elem->channel_data;
  call_data *calld = elem->call_data;
  grpc_server *server = chand->server;

  gpr_mu_lock(&server->mu);
  if (server->ntags) {
    calld->state = ACTIVATED;
    queue_new_rpc(server, calld, server->tags[--server->ntags]);
  } else {
    calld->state = PENDING;
    call_list_join(server, calld, PENDING_START);
  }
  gpr_mu_unlock(&server->mu);
}

static void kill_zombie(void *elem, grpc_em_cb_status status) {
  grpc_call_destroy(grpc_call_from_top_element(elem));
}

static void finish_rpc(grpc_call_element *elem, int is_full_close) {
  call_data *calld = elem->call_data;
  channel_data *chand = elem->channel_data;
  gpr_mu_lock(&chand->server->mu);
  switch (calld->state) {
    case ACTIVATED:
      grpc_call_recv_finish(elem, is_full_close);
      break;
    case PENDING:
      if (!is_full_close) {
        grpc_call_recv_finish(elem, is_full_close);
        break;
      }
      call_list_remove(chand->server, calld, PENDING_START);
    /* fallthrough intended */
    case NOT_STARTED:
      calld->state = ZOMBIED;
      grpc_em_add_callback(chand->server->em, kill_zombie, elem);
      break;
    case ZOMBIED:
      break;
  }
  gpr_mu_unlock(&chand->server->mu);
}

static void call_op(grpc_call_element *elem, grpc_call_op *op) {
  GRPC_CALL_LOG_OP(GPR_INFO, elem, op);
  switch (op->type) {
    case GRPC_RECV_METADATA:
      grpc_call_recv_metadata(elem, op);
      break;
    case GRPC_RECV_END_OF_INITIAL_METADATA:
      start_new_rpc(elem);
      break;
    case GRPC_RECV_MESSAGE:
      grpc_call_recv_message(elem, op->data.message, op->done_cb,
                             op->user_data);
      break;
    case GRPC_RECV_HALF_CLOSE:
      finish_rpc(elem, 0);
      break;
    case GRPC_RECV_FINISH:
      finish_rpc(elem, 1);
      break;
    case GRPC_RECV_DEADLINE:
      grpc_call_set_deadline(elem, op->data.deadline);
      ((call_data *)elem->call_data)->deadline = op->data.deadline;
      break;
    default:
      GPR_ASSERT(op->dir == GRPC_CALL_DOWN);
      grpc_call_next_op(elem, op);
      break;
  }
}

static void channel_op(grpc_channel_element *elem, grpc_channel_op *op) {
  channel_data *chand = elem->channel_data;

  switch (op->type) {
    case GRPC_ACCEPT_CALL:
      /* create a call */
      grpc_call_create(chand->channel,
                       op->data.accept_call.transport_server_data);
      break;
    case GRPC_TRANSPORT_CLOSED:
      /* if the transport is closed for a server channel, we destroy the
         channel */
      gpr_mu_lock(&chand->server->mu);
      server_ref(chand->server);
      destroy_channel(chand);
      gpr_mu_unlock(&chand->server->mu);
      server_unref(chand->server);
      break;
    default:
      GPR_ASSERT(op->dir == GRPC_CALL_DOWN);
      grpc_channel_next_op(elem, op);
      break;
  }
}

static void finish_shutdown_channel(void *cd, grpc_em_cb_status status) {
  channel_data *chand = cd;
  grpc_channel_op op;
  op.type = GRPC_CHANNEL_SHUTDOWN;
  op.dir = GRPC_CALL_DOWN;
  channel_op(grpc_channel_stack_element(
                 grpc_channel_get_channel_stack(chand->channel), 0),
             &op);
  grpc_channel_internal_unref(chand->channel);
}

static void shutdown_channel(channel_data *chand) {
  grpc_channel_internal_ref(chand->channel);
  grpc_em_add_callback(chand->server->em, finish_shutdown_channel, chand);
}

static void init_call_elem(grpc_call_element *elem,
                           const void *server_transport_data) {
  call_data *calld = elem->call_data;
  channel_data *chand = elem->channel_data;
  memset(calld, 0, sizeof(call_data));
  calld->deadline = gpr_inf_future;
  calld->call = grpc_call_from_top_element(elem);

  gpr_mu_lock(&chand->server->mu);
  call_list_join(chand->server, calld, ALL_CALLS);
  gpr_mu_unlock(&chand->server->mu);

  server_ref(chand->server);
}

static void destroy_call_elem(grpc_call_element *elem) {
  channel_data *chand = elem->channel_data;
  int i;

  gpr_mu_lock(&chand->server->mu);
  for (i = 0; i < CALL_LIST_COUNT; i++) {
    call_list_remove(chand->server, elem->call_data, i);
  }
  gpr_mu_unlock(&chand->server->mu);

  server_unref(chand->server);
}

static void init_channel_elem(grpc_channel_element *elem,
                              const grpc_channel_args *args,
                              grpc_mdctx *metadata_context, int is_first,
                              int is_last) {
  channel_data *chand = elem->channel_data;
  GPR_ASSERT(is_first);
  GPR_ASSERT(!is_last);
  chand->server = NULL;
  chand->channel = NULL;
  chand->next = chand->prev = chand;
}

static void destroy_channel_elem(grpc_channel_element *elem) {
  channel_data *chand = elem->channel_data;
  if (chand->server) {
    gpr_mu_lock(&chand->server->mu);
    chand->next->prev = chand->prev;
    chand->prev->next = chand->next;
    chand->next = chand->prev = chand;
    gpr_mu_unlock(&chand->server->mu);
    server_unref(chand->server);
  }
}

static const grpc_channel_filter server_surface_filter = {
    call_op,              channel_op,

    sizeof(call_data),    init_call_elem,    destroy_call_elem,

    sizeof(channel_data), init_channel_elem, destroy_channel_elem,

    "server",
};

static void early_terminate_requested_calls(grpc_completion_queue *cq,
                                            void **tags, size_t ntags) {
  size_t i;

  for (i = 0; i < ntags; i++) {
    grpc_cq_end_new_rpc(cq, tags[i], NULL, do_nothing, NULL, NULL, NULL,
                        gpr_inf_past, 0, NULL);
  }
}

grpc_server *grpc_server_create_from_filters(grpc_completion_queue *cq,
                                             grpc_channel_filter **filters,
                                             size_t filter_count,
                                             const grpc_channel_args *args) {
  size_t i;
  int census_enabled = grpc_channel_args_is_census_enabled(args);

  grpc_server *server = gpr_malloc(sizeof(grpc_server));
  memset(server, 0, sizeof(grpc_server));

  gpr_mu_init(&server->mu);

  server->cq = cq;
  server->em = grpc_surface_em();
  /* decremented by grpc_server_destroy */
  gpr_ref_init(&server->internal_refcount, 1);
  server->root_channel_data.next = server->root_channel_data.prev =
      &server->root_channel_data;

  /* Server filter stack is:

     server_surface_filter - for making surface API calls
     grpc_server_census_filter (optional) - for stats collection and tracing
     {passed in filter stack}
     grpc_connected_channel_filter - for interfacing with transports */
  server->channel_filter_count = filter_count + 1 + census_enabled;
  server->channel_filters =
      gpr_malloc(server->channel_filter_count * sizeof(grpc_channel_filter *));
  server->channel_filters[0] = &server_surface_filter;
  if (census_enabled) {
    server->channel_filters[1] = &grpc_server_census_filter;
  }
  for (i = 0; i < filter_count; i++) {
    server->channel_filters[i + 1 + census_enabled] = filters[i];
  }

  server->channel_args = grpc_channel_args_copy(args);

  return server;
}

void grpc_server_start(grpc_server *server) {
  listener *l;

  for (l = server->listeners; l; l = l->next) {
    l->start(server, l->arg);
  }
}

grpc_transport_setup_result grpc_server_setup_transport(
    grpc_server *s, grpc_transport *transport,
    grpc_channel_filter const **extra_filters, size_t num_extra_filters,
    grpc_mdctx *mdctx) {
  size_t num_filters = s->channel_filter_count + num_extra_filters + 1;
  grpc_channel_filter const **filters =
      gpr_malloc(sizeof(grpc_channel_filter *) * num_filters);
  size_t i;
  grpc_channel *channel;
  channel_data *chand;

  for (i = 0; i < s->channel_filter_count; i++) {
    filters[i] = s->channel_filters[i];
  }
  for (; i < s->channel_filter_count + num_extra_filters; i++) {
    filters[i] = extra_filters[i - s->channel_filter_count];
  }
  filters[i] = &grpc_connected_channel_filter;

  channel = grpc_channel_create_from_filters(filters, num_filters,
                                             s->channel_args, mdctx, 0);
  chand = (channel_data *)grpc_channel_stack_element(
              grpc_channel_get_channel_stack(channel), 0)->channel_data;
  chand->server = s;
  server_ref(s);
  chand->channel = channel;

  gpr_mu_lock(&s->mu);
  chand->next = &s->root_channel_data;
  chand->prev = chand->next->prev;
  chand->next->prev = chand->prev->next = chand;
  gpr_mu_unlock(&s->mu);

  gpr_free(filters);

  return grpc_connected_channel_bind_transport(
      grpc_channel_get_channel_stack(channel), transport);
}

void grpc_server_shutdown(grpc_server *server) {
  /* TODO(ctiller): send goaway, etc */
  listener *l;
  void **tags;
  size_t ntags;

  /* lock, and gather up some stuff to do */
  gpr_mu_lock(&server->mu);
  if (server->shutdown) {
    gpr_mu_unlock(&server->mu);
    return;
  }

  tags = server->tags;
  ntags = server->ntags;
  server->tags = NULL;
  server->ntags = 0;

  server->shutdown = 1;
  gpr_mu_unlock(&server->mu);

  /* terminate all the requested calls */
  early_terminate_requested_calls(server->cq, tags, ntags);
  gpr_free(tags);

  /* Shutdown listeners */
  for (l = server->listeners; l; l = l->next) {
    l->destroy(server, l->arg);
  }
  while (server->listeners) {
    l = server->listeners;
    server->listeners = l->next;
    gpr_free(l);
  }
}

void grpc_server_destroy(grpc_server *server) {
  channel_data *c;
  gpr_mu_lock(&server->mu);
  for (c = server->root_channel_data.next; c != &server->root_channel_data;
       c = c->next) {
    shutdown_channel(c);
  }
  gpr_mu_unlock(&server->mu);

  server_unref(server);
}

void grpc_server_add_listener(grpc_server *server, void *arg,
                              void (*start)(grpc_server *server, void *arg),
                              void (*destroy)(grpc_server *server, void *arg)) {
  listener *l = gpr_malloc(sizeof(listener));
  l->arg = arg;
  l->start = start;
  l->destroy = destroy;
  l->next = server->listeners;
  server->listeners = l;
}

grpc_call_error grpc_server_request_call(grpc_server *server, void *tag_new) {
  call_data *calld;

  grpc_cq_begin_op(server->cq, NULL, GRPC_SERVER_RPC_NEW);

  gpr_mu_lock(&server->mu);

  if (server->shutdown) {
    gpr_mu_unlock(&server->mu);
    early_terminate_requested_calls(server->cq, &tag_new, 1);
    return GRPC_CALL_OK;
  }

  calld = call_list_remove_head(server, PENDING_START);
  if (calld) {
    GPR_ASSERT(calld->state == PENDING);
    calld->state = ACTIVATED;
    queue_new_rpc(server, calld, tag_new);
  } else {
    if (server->tag_cap == server->ntags) {
      server->tag_cap = GPR_MAX(3 * server->tag_cap / 2, server->tag_cap + 1);
      server->tags =
          gpr_realloc(server->tags, sizeof(void *) * server->tag_cap);
    }
    server->tags[server->ntags++] = tag_new;
  }
  gpr_mu_unlock(&server->mu);

  return GRPC_CALL_OK;
}

const grpc_channel_args *grpc_server_get_channel_args(grpc_server *server) {
  return server->channel_args;
}