/*
 *
 * 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 <string.h>

#include <string>

#include "absl/strings/str_cat.h"

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

#include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
#include "src/core/lib/iomgr/resolve_address.h"
#include "src/core/lib/iomgr/resolve_address_impl.h"
#include "src/core/lib/iomgr/sockaddr.h"
#include "src/core/lib/iomgr/socket_utils.h"
#include "src/core/lib/resolver/server_address.h"
#include "test/core/end2end/cq_verifier.h"
#include "test/core/util/port.h"
#include "test/core/util/test_config.h"

static void* tag(intptr_t t) { return reinterpret_cast<void*>(t); }

static gpr_mu g_mu;
static int g_resolve_port = -1;

static grpc_ares_request* (*iomgr_dns_lookup_ares)(
    const char* dns_server, const char* addr, const char* default_port,
    grpc_pollset_set* interested_parties, grpc_closure* on_done,
    std::unique_ptr<grpc_core::ServerAddressList>* addresses,
    std::unique_ptr<grpc_core::ServerAddressList>* balancer_addresses,
    char** service_config_json, int query_timeout_ms);

static void (*iomgr_cancel_ares_request)(grpc_ares_request* request);

static void set_resolve_port(int port) {
  gpr_mu_lock(&g_mu);
  g_resolve_port = port;
  gpr_mu_unlock(&g_mu);
}

namespace {

grpc_core::DNSResolver* g_default_dns_resolver;

class TestDNSResolver : public grpc_core::DNSResolver {
 public:
  class TestDNSRequest : public grpc_core::DNSResolver::Request {
   public:
    explicit TestDNSRequest(
        std::function<void(absl::StatusOr<std::vector<grpc_resolved_address>>)>
            on_done)
        : on_done_(std::move(on_done)) {}

    void Start() override {
      gpr_mu_lock(&g_mu);
      if (g_resolve_port < 0) {
        gpr_mu_unlock(&g_mu);
        new grpc_core::DNSCallbackExecCtxScheduler(
            std::move(on_done_), absl::UnknownError("Forced Failure"));
      } else {
        std::vector<grpc_resolved_address> addrs;
        grpc_resolved_address addr;
        grpc_sockaddr_in* sa = reinterpret_cast<grpc_sockaddr_in*>(&addr);
        sa->sin_family = GRPC_AF_INET;
        sa->sin_addr.s_addr = 0x100007f;
        sa->sin_port = grpc_htons(static_cast<uint16_t>(g_resolve_port));
        addr.len = static_cast<socklen_t>(sizeof(*sa));
        addrs.push_back(addr);
        gpr_mu_unlock(&g_mu);
        new grpc_core::DNSCallbackExecCtxScheduler(std::move(on_done_),
                                                   std::move(addrs));
      }
    }

    void Orphan() override { Unref(); }

   private:
    std::function<void(absl::StatusOr<std::vector<grpc_resolved_address>>)>
        on_done_;
  };

  grpc_core::OrphanablePtr<grpc_core::DNSResolver::Request> ResolveName(
      absl::string_view name, absl::string_view default_port,
      grpc_pollset_set* interested_parties,
      std::function<void(absl::StatusOr<std::vector<grpc_resolved_address>>)>
          on_done) override {
    if (name != "test") {
      return g_default_dns_resolver->ResolveName(
          name, default_port, interested_parties, std::move(on_done));
    }
    return grpc_core::MakeOrphanable<TestDNSRequest>(std::move(on_done));
  }

  absl::StatusOr<std::vector<grpc_resolved_address>> ResolveNameBlocking(
      absl::string_view name, absl::string_view default_port) override {
    return g_default_dns_resolver->ResolveNameBlocking(name, default_port);
  }
};

}  // namespace

static grpc_ares_request* my_dns_lookup_ares(
    const char* dns_server, const char* addr, const char* default_port,
    grpc_pollset_set* interested_parties, grpc_closure* on_done,
    std::unique_ptr<grpc_core::ServerAddressList>* addresses,
    std::unique_ptr<grpc_core::ServerAddressList>* balancer_addresses,
    char** service_config_json, int query_timeout_ms) {
  if (0 != strcmp(addr, "test")) {
    return iomgr_dns_lookup_ares(
        dns_server, addr, default_port, interested_parties, on_done, addresses,
        balancer_addresses, service_config_json, query_timeout_ms);
  }

  grpc_error_handle error = GRPC_ERROR_NONE;
  gpr_mu_lock(&g_mu);
  if (g_resolve_port < 0) {
    gpr_mu_unlock(&g_mu);
    error = GRPC_ERROR_CREATE_FROM_STATIC_STRING("Forced Failure");
  } else {
    *addresses = absl::make_unique<grpc_core::ServerAddressList>();
    grpc_sockaddr_in sa;
    memset(&sa, 0, sizeof(sa));
    sa.sin_family = GRPC_AF_INET;
    sa.sin_addr.s_addr = 0x100007f;
    sa.sin_port = grpc_htons(static_cast<uint16_t>(g_resolve_port));
    (*addresses)->emplace_back(&sa, sizeof(sa), nullptr);
    gpr_mu_unlock(&g_mu);
  }
  grpc_core::ExecCtx::Run(DEBUG_LOCATION, on_done, error);
  return nullptr;
}

static void my_cancel_ares_request(grpc_ares_request* request) {
  if (request != nullptr) {
    iomgr_cancel_ares_request(request);
  }
}

int main(int argc, char** argv) {
  grpc_completion_queue* cq;
  cq_verifier* cqv;
  grpc_op ops[6];
  grpc_op* op;

  grpc::testing::TestEnvironment env(argc, argv);

  gpr_mu_init(&g_mu);
  grpc_init();
  g_default_dns_resolver = grpc_core::GetDNSResolver();
  auto* resolver = new TestDNSResolver();
  grpc_core::SetDNSResolver(resolver);
  iomgr_dns_lookup_ares = grpc_dns_lookup_ares;
  iomgr_cancel_ares_request = grpc_cancel_ares_request;
  grpc_dns_lookup_ares = my_dns_lookup_ares;
  grpc_cancel_ares_request = my_cancel_ares_request;

  int was_cancelled1;
  int was_cancelled2;

  grpc_metadata_array trailing_metadata_recv1;
  grpc_metadata_array request_metadata1;
  grpc_call_details request_details1;
  grpc_status_code status1;
  grpc_slice details1;
  grpc_metadata_array_init(&trailing_metadata_recv1);
  grpc_metadata_array_init(&request_metadata1);
  grpc_call_details_init(&request_details1);

  grpc_metadata_array trailing_metadata_recv2;
  grpc_metadata_array request_metadata2;
  grpc_call_details request_details2;
  grpc_status_code status2;
  grpc_slice details2;
  grpc_metadata_array_init(&trailing_metadata_recv2);
  grpc_metadata_array_init(&request_metadata2);
  grpc_call_details_init(&request_details2);

  cq = grpc_completion_queue_create_for_next(nullptr);
  cqv = cq_verifier_create(cq);

  /* reserve two ports */
  int port1 = grpc_pick_unused_port_or_die();
  int port2 = grpc_pick_unused_port_or_die();

  std::string addr;

  grpc_channel_args client_args;
  grpc_arg arg_array[2];
  arg_array[0].type = GRPC_ARG_INTEGER;
  arg_array[0].key =
      const_cast<char*>("grpc.testing.fixed_reconnect_backoff_ms");
  arg_array[0].value.integer = 1000;
  /* When this test brings down server1 and then brings up server2,
   * the targetted server port number changes, and the client channel
   * needs to re-resolve to pick this up. This test requires that
   * happen within 10 seconds, but gRPC's DNS resolvers rate limit
   * resolution attempts to at most once every 30 seconds by default.
   * So we tweak it for this test. */
  arg_array[1].type = GRPC_ARG_INTEGER;
  arg_array[1].key =
      const_cast<char*>(GRPC_ARG_DNS_MIN_TIME_BETWEEN_RESOLUTIONS_MS);
  arg_array[1].value.integer = 1000;
  client_args.args = arg_array;
  client_args.num_args = 2;

  /* create a channel that picks first amongst the servers */
  grpc_channel_credentials* creds = grpc_insecure_credentials_create();
  grpc_channel* chan = grpc_channel_create("test", creds, &client_args);
  grpc_channel_credentials_release(creds);
  /* and an initial call to them */
  grpc_slice host = grpc_slice_from_static_string("127.0.0.1");
  grpc_call* call1 =
      grpc_channel_create_call(chan, nullptr, GRPC_PROPAGATE_DEFAULTS, cq,
                               grpc_slice_from_static_string("/foo"), &host,
                               grpc_timeout_seconds_to_deadline(20), nullptr);
  /* send initial metadata to probe connectivity */
  memset(ops, 0, sizeof(ops));
  op = ops;
  op->op = GRPC_OP_SEND_INITIAL_METADATA;
  op->data.send_initial_metadata.count = 0;
  op->flags = GRPC_INITIAL_METADATA_WAIT_FOR_READY;
  op->reserved = nullptr;
  op++;
  GPR_ASSERT(GRPC_CALL_OK == grpc_call_start_batch(call1, ops,
                                                   (size_t)(op - ops),
                                                   tag(0x101), nullptr));
  /* and receive status to probe termination */
  memset(ops, 0, sizeof(ops));
  op = ops;
  op->op = GRPC_OP_RECV_STATUS_ON_CLIENT;
  op->data.recv_status_on_client.trailing_metadata = &trailing_metadata_recv1;
  op->data.recv_status_on_client.status = &status1;
  op->data.recv_status_on_client.status_details = &details1;
  op->flags = 0;
  op->reserved = nullptr;
  op++;
  GPR_ASSERT(GRPC_CALL_OK == grpc_call_start_batch(call1, ops,
                                                   (size_t)(op - ops),
                                                   tag(0x102), nullptr));

  /* bring a server up on the first port */
  grpc_server* server1 = grpc_server_create(nullptr, nullptr);
  addr = absl::StrCat("127.0.0.1:", port1);
  grpc_server_credentials* server_creds =
      grpc_insecure_server_credentials_create();
  grpc_server_add_http2_port(server1, addr.c_str(), server_creds);
  grpc_server_credentials_release(server_creds);
  grpc_server_register_completion_queue(server1, cq, nullptr);
  grpc_server_start(server1);

  /* request a call to the server */
  grpc_call* server_call1;
  GPR_ASSERT(GRPC_CALL_OK ==
             grpc_server_request_call(server1, &server_call1, &request_details1,
                                      &request_metadata1, cq, cq, tag(0x301)));

  set_resolve_port(port1);

  /* first call should now start */
  CQ_EXPECT_COMPLETION(cqv, tag(0x101), 1);
  CQ_EXPECT_COMPLETION(cqv, tag(0x301), 1);
  cq_verify(cqv);

  GPR_ASSERT(GRPC_CHANNEL_READY ==
             grpc_channel_check_connectivity_state(chan, 0));
  grpc_channel_watch_connectivity_state(chan, GRPC_CHANNEL_READY,
                                        gpr_inf_future(GPR_CLOCK_REALTIME), cq,
                                        tag(0x9999));

  /* listen for close on the server call to probe for finishing */
  memset(ops, 0, sizeof(ops));
  op = ops;
  op->op = GRPC_OP_RECV_CLOSE_ON_SERVER;
  op->data.recv_close_on_server.cancelled = &was_cancelled1;
  op->flags = 0;
  op++;
  GPR_ASSERT(GRPC_CALL_OK == grpc_call_start_batch(server_call1, ops,
                                                   (size_t)(op - ops),
                                                   tag(0x302), nullptr));

  /* shutdown first server:
   * we should see a connectivity change and then nothing */
  set_resolve_port(-1);
  grpc_server_shutdown_and_notify(server1, cq, tag(0xdead1));
  CQ_EXPECT_COMPLETION(cqv, tag(0x9999), 1);
  cq_verify(cqv);
  cq_verify_empty(cqv);

  /* and a new call: should go through to server2 when we start it */
  grpc_call* call2 =
      grpc_channel_create_call(chan, nullptr, GRPC_PROPAGATE_DEFAULTS, cq,
                               grpc_slice_from_static_string("/foo"), &host,
                               grpc_timeout_seconds_to_deadline(20), nullptr);
  /* send initial metadata to probe connectivity */
  memset(ops, 0, sizeof(ops));
  op = ops;
  op->op = GRPC_OP_SEND_INITIAL_METADATA;
  op->data.send_initial_metadata.count = 0;
  op->flags = GRPC_INITIAL_METADATA_WAIT_FOR_READY;
  op->reserved = nullptr;
  op++;
  GPR_ASSERT(GRPC_CALL_OK == grpc_call_start_batch(call2, ops,
                                                   (size_t)(op - ops),
                                                   tag(0x201), nullptr));
  /* and receive status to probe termination */
  memset(ops, 0, sizeof(ops));
  op = ops;
  op->op = GRPC_OP_RECV_STATUS_ON_CLIENT;
  op->data.recv_status_on_client.trailing_metadata = &trailing_metadata_recv2;
  op->data.recv_status_on_client.status = &status2;
  op->data.recv_status_on_client.status_details = &details2;
  op->flags = 0;
  op->reserved = nullptr;
  op++;
  GPR_ASSERT(GRPC_CALL_OK == grpc_call_start_batch(call2, ops,
                                                   (size_t)(op - ops),
                                                   tag(0x202), nullptr));

  /* and bring up second server */
  set_resolve_port(port2);
  grpc_server* server2 = grpc_server_create(nullptr, nullptr);
  addr = absl::StrCat("127.0.0.1:", port2);
  grpc_server_credentials* another_server_creds =
      grpc_insecure_server_credentials_create();
  grpc_server_add_http2_port(server2, addr.c_str(), another_server_creds);
  grpc_server_credentials_release(another_server_creds);
  grpc_server_register_completion_queue(server2, cq, nullptr);
  grpc_server_start(server2);

  /* request a call to the server */
  grpc_call* server_call2;
  GPR_ASSERT(GRPC_CALL_OK ==
             grpc_server_request_call(server2, &server_call2, &request_details2,
                                      &request_metadata2, cq, cq, tag(0x401)));

  /* second call should now start */
  CQ_EXPECT_COMPLETION(cqv, tag(0x201), 1);
  CQ_EXPECT_COMPLETION(cqv, tag(0x401), 1);
  cq_verify(cqv);

  /* listen for close on the server call to probe for finishing */
  memset(ops, 0, sizeof(ops));
  op = ops;
  op->op = GRPC_OP_RECV_CLOSE_ON_SERVER;
  op->data.recv_close_on_server.cancelled = &was_cancelled2;
  op->flags = 0;
  op++;
  GPR_ASSERT(GRPC_CALL_OK == grpc_call_start_batch(server_call2, ops,
                                                   (size_t)(op - ops),
                                                   tag(0x402), nullptr));

  /* shutdown second server: we should see nothing */
  grpc_server_shutdown_and_notify(server2, cq, tag(0xdead2));
  cq_verify_empty(cqv);

  grpc_call_cancel(call1, nullptr);
  grpc_call_cancel(call2, nullptr);

  /* now everything else should finish */
  CQ_EXPECT_COMPLETION(cqv, tag(0x102), 1);
  CQ_EXPECT_COMPLETION(cqv, tag(0x202), 1);
  CQ_EXPECT_COMPLETION(cqv, tag(0x302), 1);
  CQ_EXPECT_COMPLETION(cqv, tag(0x402), 1);
  CQ_EXPECT_COMPLETION(cqv, tag(0xdead1), 1);
  CQ_EXPECT_COMPLETION(cqv, tag(0xdead2), 1);
  cq_verify(cqv);

  grpc_call_unref(call1);
  grpc_call_unref(call2);
  grpc_call_unref(server_call1);
  grpc_call_unref(server_call2);
  grpc_server_destroy(server1);
  grpc_server_destroy(server2);
  grpc_channel_destroy(chan);

  grpc_metadata_array_destroy(&trailing_metadata_recv1);
  grpc_metadata_array_destroy(&request_metadata1);
  grpc_call_details_destroy(&request_details1);
  grpc_slice_unref(details1);
  grpc_metadata_array_destroy(&trailing_metadata_recv2);
  grpc_metadata_array_destroy(&request_metadata2);
  grpc_call_details_destroy(&request_details2);
  grpc_slice_unref(details2);

  cq_verifier_destroy(cqv);
  grpc_completion_queue_destroy(cq);

  grpc_core::SetDNSResolver(g_default_dns_resolver);
  delete resolver;
  grpc_shutdown();
  gpr_mu_destroy(&g_mu);

  return 0;
}