//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2022
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#include "td/telegram/SequenceDispatcher.h"

#include "td/telegram/Global.h"
#include "td/telegram/net/NetQueryDispatcher.h"
#include "td/telegram/Td.h"

#include "td/actor/PromiseFuture.h"

#include "td/utils/algorithm.h"
#include "td/utils/ChainScheduler.h"
#include "td/utils/format.h"
#include "td/utils/logging.h"
#include "td/utils/misc.h"
#include "td/utils/Promise.h"
#include "td/utils/SliceBuilder.h"
#include "td/utils/Status.h"
#include "td/utils/StringBuilder.h"

#include <limits>

namespace td {

/*** Sequence Dispatcher ***/
// Sends queries with invokeAfter.
//
// Each query has three states Start/Wait/Finish
//
// finish_i points to the first not Finish query.
// next_i points to the next query to be sent.
//
// Each query has generation of InvokeAfter chain.
//
// When query is send, its generation is set to current chain generation.
//
// When query is failed and its generation is equals to current generation we must start new chain:
// increment the generation and set next_i to finish_i.
//
// last_sent_i points to the last sent query in current chain.
//
void SequenceDispatcher::send_with_callback(NetQueryPtr query, ActorShared<NetQueryCallback> callback) {
  cancel_timeout();
  query->debug("Waiting at SequenceDispatcher");
  auto query_weak_ref = query.get_weak();
  data_.push_back(Data{State::Start, std::move(query_weak_ref), std::move(query), std::move(callback), 0, 0, 0});
  loop();
}

void SequenceDispatcher::check_timeout(Data &data) {
  if (data.state_ != State::Start) {
    return;
  }
  data.query_->total_timeout_ += data.total_timeout_;
  data.total_timeout_ = 0;
  if (data.query_->total_timeout_ > data.query_->total_timeout_limit_) {
    LOG(WARNING) << "Fail " << data.query_ << " to " << data.query_->source_ << " because total_timeout "
                 << data.query_->total_timeout_ << " is greater than total_timeout_limit "
                 << data.query_->total_timeout_limit_;
    data.query_->set_error(Status::Error(429, PSLICE() << "Too Many Requests: retry after " << data.last_timeout_));
    data.state_ = State::Dummy;
    try_resend_query(data, std::move(data.query_));
  }
}

void SequenceDispatcher::try_resend_query(Data &data, NetQueryPtr query) {
  size_t pos = &data - &data_[0];
  CHECK(pos < data_.size());
  CHECK(data.state_ == State::Dummy);
  data.state_ = State::Wait;
  wait_cnt_++;
  auto token = pos + id_offset_;
  // TODO: if query is ok, use NetQueryCallback::on_result
  if (data.callback_.empty()) {
    do_finish(data);
    send_closure_later(G()->td(), &Td::on_result, std::move(query));
    loop();
    return;
  }
  auto promise = PromiseCreator::lambda([&, self = actor_shared(this, token)](NetQueryPtr query) mutable {
    if (!query.empty()) {
      send_closure(std::move(self), &SequenceDispatcher::on_resend_ok, std::move(query));
    } else {
      send_closure(std::move(self), &SequenceDispatcher::on_resend_error);
    }
  });
  send_closure(data.callback_, &NetQueryCallback::on_result_resendable, std::move(query), std::move(promise));
}

SequenceDispatcher::Data &SequenceDispatcher::data_from_token() {
  auto token = narrow_cast<size_t>(get_link_token());
  auto pos = token - id_offset_;
  CHECK(pos < data_.size());
  auto &data = data_[pos];
  CHECK(data.state_ == State::Wait);
  CHECK(wait_cnt_ > 0);
  wait_cnt_--;
  data.state_ = State::Dummy;
  return data;
}

void SequenceDispatcher::on_resend_ok(NetQueryPtr query) {
  auto &data = data_from_token();
  data.query_ = std::move(query);
  do_resend(data);
  loop();
}

void SequenceDispatcher::on_resend_error() {
  auto &data = data_from_token();
  do_finish(data);
  loop();
}

void SequenceDispatcher::do_resend(Data &data) {
  CHECK(data.state_ == State::Dummy);
  data.state_ = State::Start;
  if (data.generation_ == generation_) {
    next_i_ = finish_i_;
    generation_++;
    last_sent_i_ = std::numeric_limits<size_t>::max();
  }
  check_timeout(data);
}

void SequenceDispatcher::do_finish(Data &data) {
  CHECK(data.state_ == State::Dummy);
  data.state_ = State::Finish;
  if (!parent_.empty()) {
    send_closure(parent_, &Parent::on_result);
  }
}

void SequenceDispatcher::on_result(NetQueryPtr query) {
  auto &data = data_from_token();
  size_t pos = &data - &data_[0];
  CHECK(pos < data_.size());

  if (query->last_timeout_ != 0) {
    for (auto i = pos + 1; i < data_.size(); i++) {
      data_[i].total_timeout_ += query->last_timeout_;
      data_[i].last_timeout_ = query->last_timeout_;
      check_timeout(data_[i]);
    }
    query->last_timeout_ = 0;
  }

  if (query->is_error() && (query->error().code() == NetQuery::ResendInvokeAfter ||
                            (query->error().code() == 400 && (query->error().message() == "MSG_WAIT_FAILED" ||
                                                              query->error().message() == "MSG_WAIT_TIMEOUT")))) {
    VLOG(net_query) << "Resend " << query;
    query->resend();
    query->debug("Waiting at SequenceDispatcher");
    data.query_ = std::move(query);
    do_resend(data);
  } else {
    try_resend_query(data, std::move(query));
  }
  loop();
}

void SequenceDispatcher::loop() {
  for (; finish_i_ < data_.size() && data_[finish_i_].state_ == State::Finish; finish_i_++) {
  }
  if (next_i_ < finish_i_) {
    next_i_ = finish_i_;
  }
  for (; next_i_ < data_.size() && data_[next_i_].state_ != State::Wait && wait_cnt_ < MAX_SIMULTANEOUS_WAIT;
       next_i_++) {
    if (data_[next_i_].state_ == State::Finish) {
      continue;
    }
    NetQueryRef invoke_after;
    if (last_sent_i_ != std::numeric_limits<size_t>::max() && data_[last_sent_i_].state_ == State::Wait) {
      invoke_after = data_[last_sent_i_].net_query_ref_;
    }
    if (!invoke_after.empty()) {
      data_[next_i_].query_->set_invoke_after({invoke_after});
    } else {
      data_[next_i_].query_->set_invoke_after({});
    }
    data_[next_i_].query_->last_timeout_ = 0;

    VLOG(net_query) << "Send " << data_[next_i_].query_;

    data_[next_i_].query_->debug("send to Td::send_with_callback");
    G()->net_query_dispatcher().dispatch_with_callback(std::move(data_[next_i_].query_),
                                                       actor_shared(this, next_i_ + id_offset_));
    data_[next_i_].state_ = State::Wait;
    wait_cnt_++;
    data_[next_i_].generation_ = generation_;
    last_sent_i_ = next_i_;
  }

  try_shrink();

  if (finish_i_ == data_.size() && !parent_.empty()) {
    set_timeout_in(5);
  }
}

void SequenceDispatcher::try_shrink() {
  if (finish_i_ * 2 > data_.size() && data_.size() > 5) {
    CHECK(finish_i_ <= next_i_);
    data_.erase(data_.begin(), data_.begin() + finish_i_);
    next_i_ -= finish_i_;
    if (last_sent_i_ != std::numeric_limits<size_t>::max()) {
      if (last_sent_i_ >= finish_i_) {
        last_sent_i_ -= finish_i_;
      } else {
        last_sent_i_ = std::numeric_limits<size_t>::max();
      }
    }
    id_offset_ += finish_i_;
    finish_i_ = 0;
  }
}

void SequenceDispatcher::timeout_expired() {
  if (finish_i_ != data_.size()) {
    return;
  }
  CHECK(!parent_.empty());
  set_timeout_in(1);
  LOG(DEBUG) << "SequenceDispatcher ready to close";
  send_closure(parent_, &Parent::ready_to_close);
}

void SequenceDispatcher::hangup() {
  stop();
}

void SequenceDispatcher::tear_down() {
  for (auto &data : data_) {
    if (data.query_.empty()) {
      continue;
    }
    data.state_ = State::Dummy;
    data.query_->set_error(Global::request_aborted_error());
    do_finish(data);
  }
}

void SequenceDispatcher::close_silent() {
  for (auto &data : data_) {
    if (!data.query_.empty()) {
      data.query_->clear();
    }
  }
  stop();
}

void MultiSequenceDispatcherOld::send(NetQueryPtr query) {
  auto callback = query->move_callback();
  auto chain_ids = query->get_chain_ids();
  query->set_in_sequence_dispatcher(true);
  CHECK(all_of(chain_ids, [](auto chain_id) { return chain_id != 0; }));
  CHECK(!chain_ids.empty());
  auto sequence_id = chain_ids[0];

  auto it_ok = dispatchers_.emplace(sequence_id, Data{0, ActorOwn<SequenceDispatcher>()});
  auto &data = it_ok.first->second;
  if (it_ok.second) {
    LOG(DEBUG) << "Create SequenceDispatcher" << sequence_id;
    data.dispatcher_ = create_actor<SequenceDispatcher>("SequenceDispatcher", actor_shared(this, sequence_id));
  }
  data.cnt_++;
  query->debug(PSTRING() << "send to SequenceDispatcher " << tag("sequence_id", sequence_id));
  send_closure(data.dispatcher_, &SequenceDispatcher::send_with_callback, std::move(query), std::move(callback));
}

void MultiSequenceDispatcherOld::on_result() {
  auto it = dispatchers_.find(get_link_token());
  CHECK(it != dispatchers_.end());
  it->second.cnt_--;
}

void MultiSequenceDispatcherOld::ready_to_close() {
  auto it = dispatchers_.find(get_link_token());
  CHECK(it != dispatchers_.end());
  if (it->second.cnt_ == 0) {
    LOG(DEBUG) << "Close SequenceDispatcher " << get_link_token();
    dispatchers_.erase(it);
  }
}

class MultiSequenceDispatcherImpl final : public MultiSequenceDispatcher {
 public:
  void send(NetQueryPtr query) final {
    auto callback = query->move_callback();
    auto chain_ids = query->get_chain_ids();
    query->set_in_sequence_dispatcher(true);
    CHECK(all_of(chain_ids, [](auto chain_id) { return chain_id != 0; }));
    Node node;
    node.net_query = std::move(query);
    node.net_query->debug("Waiting at SequenceDispatcher");
    node.net_query_ref = node.net_query.get_weak();
    node.callback = std::move(callback);
    scheduler_.create_task(chain_ids, std::move(node));
    loop();
  }

 private:
  struct Node {
    NetQueryRef net_query_ref;
    NetQueryPtr net_query;
    int32 total_timeout{0};
    int32 last_timeout{0};
    ActorShared<NetQueryCallback> callback;
    friend StringBuilder &operator<<(StringBuilder &sb, const Node &node) {
      return sb << node.net_query;
    }
  };
  ChainScheduler<Node> scheduler_;

  using TaskId = ChainScheduler<Node>::TaskId;

  bool check_timeout(Node &node) {
    auto &net_query = node.net_query;
    if (net_query.empty() || net_query->is_ready()) {
      return false;
    }
    if (node.total_timeout > 0) {
      net_query->total_timeout_ += node.total_timeout;
      LOG(INFO) << "Set total_timeout to " << net_query->total_timeout_ << " for " << net_query->id();
      node.total_timeout = 0;

      if (net_query->total_timeout_ > net_query->total_timeout_limit_) {
        LOG(WARNING) << "Fail " << net_query << " to " << net_query->source_ << " because total_timeout "
                     << net_query->total_timeout_ << " is greater than total_timeout_limit "
                     << net_query->total_timeout_limit_;
        net_query->set_error(Status::Error(429, PSLICE() << "Too Many Requests: retry after " << node.last_timeout));
        return true;
      }
    }
    return false;
  }

  void on_result(NetQueryPtr query) final {
    auto task_id = TaskId(get_link_token());
    auto &node = *scheduler_.get_task_extra(task_id);

    if (query->last_timeout_ != 0) {
      vector<TaskId> to_check_timeout;

      auto tl_constructor = query->tl_constructor();
      scheduler_.for_each_dependent(task_id, [&](TaskId child_task_id) {
        auto &child_node = *scheduler_.get_task_extra(child_task_id);
        if (child_node.net_query_ref->tl_constructor() == tl_constructor && child_task_id != task_id) {
          child_node.total_timeout += query->last_timeout_;
          child_node.last_timeout = query->last_timeout_;
          to_check_timeout.push_back(child_task_id);
        }
      });
      query->last_timeout_ = 0;

      for (auto dependent_task_id : to_check_timeout) {
        auto &child_node = *scheduler_.get_task_extra(dependent_task_id);
        if (check_timeout(child_node)) {
          scheduler_.pause_task(dependent_task_id);
          try_resend(dependent_task_id);
        }
      }
    }

    if (query->is_error() && (query->error().code() == NetQuery::ResendInvokeAfter ||
                              (query->error().code() == 400 && (query->error().message() == "MSG_WAIT_FAILED" ||
                                                                query->error().message() == "MSG_WAIT_TIMEOUT")))) {
      VLOG(net_query) << "Resend " << query;
      query->resend();
      do_resend(task_id, node, std::move(query));
      loop();
      return;
    }
    node.net_query = std::move(query);
    try_resend(task_id);
  }

  void try_resend(TaskId task_id) {
    auto &node = *scheduler_.get_task_extra(task_id);
    if (node.callback.empty()) {
      auto query = std::move(node.net_query);
      scheduler_.finish_task(task_id);
      send_closure_later(G()->td(), &Td::on_result, std::move(query));
      loop();
      return;
    }
    auto promise = promise_send_closure(actor_shared(this, task_id), &MultiSequenceDispatcherImpl::on_resend);
    send_closure(node.callback, &NetQueryCallback::on_result_resendable, std::move(node.net_query), std::move(promise));
  }

  void on_resend(Result<NetQueryPtr> r_query) {
    auto task_id = TaskId(get_link_token());
    auto &node = *scheduler_.get_task_extra(task_id);
    if (r_query.is_error()) {
      scheduler_.finish_task(task_id);
    } else {
      do_resend(task_id, node, r_query.move_as_ok());
    }
    loop();
  }

  void do_resend(TaskId task_id, Node &node, NetQueryPtr &&query) {
    node.net_query = std::move(query);
    node.net_query->debug("Waiting at SequenceDispatcher");
    node.net_query_ref = node.net_query.get_weak();
    if (check_timeout(node)) {
      scheduler_.pause_task(task_id);
      try_resend(task_id);
    } else {
      scheduler_.reset_task(task_id);
    }
  }

  void loop() final {
    flush_pending_queries();
  }

  void tear_down() final {
    // Leaves scheduler_ in an invalid state, but we are closing anyway
    scheduler_.for_each([](Node &node) {
      if (node.net_query.empty()) {
        return;
      }
      node.net_query->set_error(Global::request_aborted_error());
    });
  }

  void flush_pending_queries() {
    while (true) {
      auto o_task = scheduler_.start_next_task();
      if (!o_task) {
        break;
      }
      auto task = o_task.unwrap();
      auto &node = *scheduler_.get_task_extra(task.task_id);
      CHECK(!node.net_query.empty());

      auto query = std::move(node.net_query);
      vector<NetQueryRef> parents;
      for (auto parent_id : task.parents) {
        auto &parent_node = *scheduler_.get_task_extra(parent_id);
        parents.push_back(parent_node.net_query_ref);
        CHECK(!parent_node.net_query_ref.empty());
      }

      query->set_invoke_after(std::move(parents));
      query->last_timeout_ = 0;
      query->debug("dispatch_with_callback");
      G()->net_query_dispatcher().dispatch_with_callback(std::move(query), actor_shared(this, task.task_id));
    }
  }
};

ActorOwn<MultiSequenceDispatcher> MultiSequenceDispatcher::create(Slice name) {
  return ActorOwn<MultiSequenceDispatcher>(create_actor<MultiSequenceDispatcherImpl>(name));
}

}  // namespace td