/*
 * Copyright (c) 2015 Cryptonomex, Inc., and contributors.
 *
 * The MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#include <graphene/app/api.hpp>
#include <graphene/app/api_access.hpp>
#include <graphene/app/application.hpp>
#include <graphene/app/plugin.hpp>

#include <graphene/chain/protocol/fee_schedule.hpp>
#include <graphene/chain/protocol/types.hpp>

#include <graphene/egenesis/egenesis.hpp>

#include <graphene/net/core_messages.hpp>
#include <graphene/net/exceptions.hpp>

#include <graphene/chain/worker_evaluator.hpp>
#include <graphene/utilities/key_conversion.hpp>

#include <fc/crypto/base64.hpp>
#include <fc/io/fstream.hpp>
#include <fc/network/resolve.hpp>
#include <fc/rpc/api_connection.hpp>
#include <fc/rpc/websocket_api.hpp>

#include <boost/algorithm/string.hpp>
#include <boost/filesystem/path.hpp>
#include <boost/range/algorithm/reverse.hpp>
#include <boost/signals2.hpp>

#include <atomic>
#include <iostream>

#include <fc/log/file_appender.hpp>
#include <fc/log/logger.hpp>
#include <fc/log/logger_config.hpp>

#include <boost/range/adaptor/reversed.hpp>

namespace graphene { namespace app {
using net::block_message;
using net::item_hash_t;
using net::item_id;
using net::message;
using net::trx_message;

using chain::block_header;
using chain::block_id_type;
using chain::signed_block;
using chain::signed_block_header;

using std::vector;

namespace bpo = boost::program_options;

namespace detail {

genesis_state_type create_example_genesis() {
   auto nathan_key = fc::ecc::private_key::regenerate(fc::sha256::hash(string("nathan")));
   dlog("Allocating all stake to ${key}", ("key", utilities::key_to_wif(nathan_key)));
   genesis_state_type initial_state;
   initial_state.initial_parameters.current_fees = std::make_shared<fee_schedule>(fee_schedule::get_default());
   initial_state.initial_active_witnesses = GRAPHENE_DEFAULT_MIN_WITNESS_COUNT;
   initial_state.initial_timestamp = time_point_sec(time_point::now().sec_since_epoch() /
                                                    initial_state.initial_parameters.block_interval *
                                                    initial_state.initial_parameters.block_interval);
   for (uint64_t i = 0; i < initial_state.initial_active_witnesses; ++i) {
      auto name = "init" + fc::to_string(i);
      initial_state.initial_accounts.emplace_back(name,
                                                  nathan_key.get_public_key(),
                                                  nathan_key.get_public_key(),
                                                  true);
      initial_state.initial_committee_candidates.push_back({name});
      initial_state.initial_witness_candidates.push_back({name, nathan_key.get_public_key()});
   }

   initial_state.initial_accounts.emplace_back("nathan", nathan_key.get_public_key());
   initial_state.initial_balances.push_back({nathan_key.get_public_key(),
                                             GRAPHENE_SYMBOL,
                                             GRAPHENE_MAX_SHARE_SUPPLY});
   initial_state.initial_chain_id = fc::sha256::hash("BOGUS");

   return initial_state;
}

class application_impl : public net::node_delegate {
public:
   fc::optional<fc::temp_file> _lock_file;
   bool _is_block_producer = false;
   bool _force_validate = false;
   std::atomic_bool _running{true};

   void reset_p2p_node(const fc::path &data_dir) {
      try {
         _p2p_network = std::make_shared<net::node>("PeerPlays Reference Implementation");

         _p2p_network->load_configuration(data_dir / "p2p");
         _p2p_network->set_node_delegate(this);

         vector<string> all_seeds;

         if (_options->count("seed-node")) {
            auto seeds = _options->at("seed-node").as<vector<string>>();
            all_seeds.insert(all_seeds.end(), seeds.begin(), seeds.end());
         }

         if (_options->count("seed-nodes")) {
            auto seeds_str = _options->at("seed-nodes").as<string>();
            auto seeds = fc::json::from_string(seeds_str).as<vector<string>>(2);
            all_seeds.insert(all_seeds.end(), seeds.begin(), seeds.end());
         }

         for (const string &endpoint_string : all_seeds) {
            try {
               std::vector<fc::ip::endpoint> endpoints = resolve_string_to_ip_endpoints(endpoint_string);
               for (const fc::ip::endpoint &endpoint : endpoints) {
                  ilog("Adding seed node ${endpoint}", ("endpoint", endpoint));
                  _p2p_network->add_node(endpoint);
               }
            } catch (const fc::exception &e) {
               wlog("caught exception ${e} while adding seed node ${endpoint}",
                    ("e", e.to_detail_string())("endpoint", endpoint_string));
            }
         }

         if (_options->count("p2p-endpoint"))
            _p2p_network->listen_on_endpoint(fc::ip::endpoint::from_string(_options->at("p2p-endpoint").as<string>()), true);
         else
            _p2p_network->listen_on_port(0, false);
         _p2p_network->listen_to_p2p_network();
         ilog("Configured p2p node to listen on ${ip}", ("ip", _p2p_network->get_actual_listening_endpoint()));

         _p2p_network->connect_to_p2p_network();
         _p2p_network->sync_from(net::item_id(net::core_message_type_enum::block_message_type,
                                              _chain_db->head_block_id()),
                                 std::vector<uint32_t>());
      }
      FC_CAPTURE_AND_RETHROW()
   }

   std::vector<fc::ip::endpoint> resolve_string_to_ip_endpoints(const std::string &endpoint_string) {
      try {
         string::size_type colon_pos = endpoint_string.find(':');
         if (colon_pos == std::string::npos)
            FC_THROW("Missing required port number in endpoint string \"${endpoint_string}\"",
                     ("endpoint_string", endpoint_string));
         std::string port_string = endpoint_string.substr(colon_pos + 1);
         try {
            uint16_t port = boost::lexical_cast<uint16_t>(port_string);

            std::string hostname = endpoint_string.substr(0, colon_pos);
            std::vector<fc::ip::endpoint> endpoints = fc::resolve(hostname, port);
            if (endpoints.empty())
               FC_THROW_EXCEPTION(fc::unknown_host_exception, "The host name can not be resolved: ${hostname}", ("hostname", hostname));
            return endpoints;
         } catch (const boost::bad_lexical_cast &) {
            FC_THROW("Bad port: ${port}", ("port", port_string));
         }
      }
      FC_CAPTURE_AND_RETHROW((endpoint_string))
   }

   void new_connection(const fc::http::websocket_connection_ptr &c) {
      auto wsc = std::make_shared<fc::rpc::websocket_api_connection>(c, GRAPHENE_MAX_NESTED_OBJECTS);
      auto login = std::make_shared<graphene::app::login_api>(std::ref(*_self));
      login->enable_api("database_api");

      wsc->register_api(login->database());
      wsc->register_api(fc::api<graphene::app::login_api>(login));

      wsc->register_api(fc::api<graphene::app::login_api>(login));

      c->set_session_data(wsc);

      std::string username = "*";
      std::string password = "*";

      // Try to extract login information from "Authorization" header if present
      std::string auth = c->get_request_header("Authorization");
      if (boost::starts_with(auth, "Basic ")) {

         FC_ASSERT(auth.size() > 6);
         auto user_pass = fc::base64_decode(auth.substr(6));

         std::vector<std::string> parts;
         boost::split(parts, user_pass, boost::is_any_of(":"));

         FC_ASSERT(parts.size() == 2);

         username = parts[0];
         password = parts[1];
      }

      login->login(username, password);
   }

   void reset_websocket_server() {
      try {
         if (!_options->count("rpc-endpoint"))
            return;

         _websocket_server = std::make_shared<fc::http::websocket_server>();
         _websocket_server->on_connection(std::bind(&application_impl::new_connection, this, std::placeholders::_1));

         ilog("Configured websocket rpc to listen on ${ip}", ("ip", _options->at("rpc-endpoint").as<string>()));
         _websocket_server->listen(fc::ip::endpoint::from_string(_options->at("rpc-endpoint").as<string>()));
         _websocket_server->start_accept();
      }
      FC_CAPTURE_AND_RETHROW()
   }

   void reset_websocket_tls_server() {
      try {
         if (!_options->count("rpc-tls-endpoint"))
            return;
         if (!_options->count("server-pem")) {
            wlog("Please specify a server-pem to use rpc-tls-endpoint");
            return;
         }

         string password = _options->count("server-pem-password") ? _options->at("server-pem-password").as<string>() : "";
         _websocket_tls_server = std::make_shared<fc::http::websocket_tls_server>(_options->at("server-pem").as<string>(), password);
         _websocket_tls_server->on_connection(std::bind(&application_impl::new_connection, this, std::placeholders::_1));

         ilog("Configured websocket TLS rpc to listen on ${ip}", ("ip", _options->at("rpc-tls-endpoint").as<string>()));
         _websocket_tls_server->listen(fc::ip::endpoint::from_string(_options->at("rpc-tls-endpoint").as<string>()));
         _websocket_tls_server->start_accept();
      }
      FC_CAPTURE_AND_RETHROW()
   }

   explicit application_impl(application *self) :
         _self(self),
         _chain_db(std::make_shared<chain::database>()) {
   }

   ~application_impl() {
   }

   void set_dbg_init_key(genesis_state_type &genesis, const std::string &init_key) {
      flat_set<std::string> initial_witness_names;
      public_key_type init_pubkey(init_key);
      for (uint64_t i = 0; i < genesis.initial_active_witnesses; i++)
         genesis.initial_witness_candidates[i].block_signing_key = init_pubkey;
   }

   void startup() {
      try {
         fc::create_directories(_data_dir / "blockchain");

         auto initial_state = [this] {
            ilog("Initializing database...");
            if (_options->count("genesis-json")) {
               std::string genesis_str;
               fc::read_file_contents(_options->at("genesis-json").as<boost::filesystem::path>(), genesis_str);
               genesis_state_type genesis = fc::json::from_string(genesis_str).as<genesis_state_type>(20);
               bool modified_genesis = false;
               if (_options->count("genesis-timestamp")) {
                  genesis.initial_timestamp = fc::time_point_sec(fc::time_point::now()) + genesis.initial_parameters.block_interval + _options->at("genesis-timestamp").as<uint32_t>();
                  genesis.initial_timestamp -= genesis.initial_timestamp.sec_since_epoch() % genesis.initial_parameters.block_interval;
                  modified_genesis = true;
                  std::cerr << "Used genesis timestamp:  " << genesis.initial_timestamp.to_iso_string() << " (PLEASE RECORD THIS)\n";
               }
               if (_options->count("dbg-init-key")) {
                  std::string init_key = _options->at("dbg-init-key").as<string>();
                  FC_ASSERT(genesis.initial_witness_candidates.size() >= genesis.initial_active_witnesses);
                  set_dbg_init_key(genesis, init_key);
                  modified_genesis = true;
                  std::cerr << "Set init witness key to " << init_key << "\n";
               }
               if (modified_genesis) {
                  std::cerr << "WARNING:  GENESIS WAS MODIFIED, YOUR CHAIN ID MAY BE DIFFERENT\n";
                  genesis_str += "BOGUS";
                  genesis.initial_chain_id = fc::sha256::hash(genesis_str);
               } else
                  genesis.initial_chain_id = fc::sha256::hash(genesis_str);
               return genesis;
            } else {
               std::string egenesis_json;
               graphene::egenesis::compute_egenesis_json(egenesis_json);
               FC_ASSERT(egenesis_json != "");
               FC_ASSERT(graphene::egenesis::get_egenesis_json_hash() == fc::sha256::hash(egenesis_json));
               auto genesis = fc::json::from_string(egenesis_json).as<genesis_state_type>(20);
               genesis.initial_chain_id = fc::sha256::hash(egenesis_json);
               return genesis;
            }
         };

         if (_options->count("resync-blockchain"))
            _chain_db->wipe(_data_dir / "blockchain", true);

         flat_map<uint32_t, block_id_type> loaded_checkpoints;
         if (_options->count("checkpoint")) {
            auto cps = _options->at("checkpoint").as<vector<string>>();
            loaded_checkpoints.reserve(cps.size());
            for (auto cp : cps) {
               auto item = fc::json::from_string(cp).as<std::pair<uint32_t, block_id_type>>(2);
               loaded_checkpoints[item.first] = item.second;
            }
         }
         _chain_db->add_checkpoints(loaded_checkpoints);

         if (_options->count("enable-standby-votes-tracking")) {
            _chain_db->enable_standby_votes_tracking(_options->at("enable-standby-votes-tracking").as<bool>());
         }

         std::string replay_reason = "reason not provided";

         if (_options->count("replay-blockchain"))
            _chain_db->wipe(_data_dir / "blockchain", false);

         try {
            _chain_db->open(_data_dir / "blockchain", initial_state, GRAPHENE_CURRENT_DB_VERSION);
         } catch (const fc::exception &e) {
            elog("Caught exception ${e} in open(), you might want to force a replay", ("e", e.to_detail_string()));
            throw;
         }

         if (_options->count("force-validate")) {
            ilog("All transaction signatures will be validated");
            _force_validate = true;
         }

         if (_options->count("api-access")) {

            if (fc::exists(_options->at("api-access").as<boost::filesystem::path>())) {
               _apiaccess = fc::json::from_file(_options->at("api-access").as<boost::filesystem::path>()).as<api_access>(20);
               ilog("Using api access file from ${path}",
                    ("path", _options->at("api-access").as<boost::filesystem::path>().string()));
            } else {
               elog("Failed to load file from ${path}",
                    ("path", _options->at("api-access").as<boost::filesystem::path>().string()));
               std::exit(EXIT_FAILURE);
            }
         } else {
            // TODO:  Remove this generous default access policy
            // when the UI logs in properly
            _apiaccess = api_access();
            api_access_info wild_access;
            wild_access.password_hash_b64 = "*";
            wild_access.password_salt_b64 = "*";
            wild_access.allowed_apis.push_back("database_api");
            wild_access.allowed_apis.push_back("network_broadcast_api");
            wild_access.allowed_apis.push_back("history_api");
            wild_access.allowed_apis.push_back("bookie_api");
            wild_access.allowed_apis.push_back("affiliate_stats_api");
            wild_access.allowed_apis.push_back("sidechain_api");
            _apiaccess.permission_map["*"] = wild_access;
         }

         reset_p2p_node(_data_dir);
         reset_websocket_server();
         reset_websocket_tls_server();
      }
      FC_LOG_AND_RETHROW()
   }

   optional<api_access_info> get_api_access_info(const string &username) const {
      optional<api_access_info> result;
      auto it = _apiaccess.permission_map.find(username);
      if (it == _apiaccess.permission_map.end()) {
         it = _apiaccess.permission_map.find("*");
         if (it == _apiaccess.permission_map.end())
            return result;
      }
      return it->second;
   }

   void set_api_access_info(const string &username, api_access_info &&permissions) {
      _apiaccess.permission_map.insert(std::make_pair(username, std::move(permissions)));
   }

   /**
       * If delegate has the item, the network has no need to fetch it.
       */
   virtual bool has_item(const net::item_id &id) override {
      try {
         if (id.item_type == graphene::net::block_message_type)
            return _chain_db->is_known_block(id.item_hash);
         else
            return _chain_db->is_known_transaction(id.item_hash);
      }
      FC_CAPTURE_AND_RETHROW((id))
   }

   /**
       * @brief allows the application to validate an item prior to broadcasting to peers.
       *
       * @param sync_mode true if the message was fetched through the sync process, false during normal operation
       * @returns true if this message caused the blockchain to switch forks, false if it did not
       *
       * @throws exception if error validating the item, otherwise the item is safe to broadcast on.
       */
   virtual bool handle_block(const graphene::net::block_message &blk_msg, bool sync_mode,
                             std::vector<fc::uint160_t> &contained_transaction_message_ids) override {

      // check point for the threads which may be cancled on application shutdown
      if (!_running.load()) {
         return true;
      }

      try {
         auto latency = fc::time_point::now() - blk_msg.block.timestamp;
         FC_ASSERT((latency.count() / 1000) > -5000, "Rejecting block with timestamp in the future");
         if (!sync_mode || blk_msg.block.block_num() % 10000 == 0) {
            const auto &witness = blk_msg.block.witness(*_chain_db);
            const auto &witness_account = witness.witness_account(*_chain_db);
            auto last_irr = _chain_db->get_dynamic_global_properties().last_irreversible_block_num;
            ilog("Got block: #${n} time: ${t} latency: ${l} ms from: ${w}  irreversible: ${i} (-${d})",
                 ("t", blk_msg.block.timestamp)("n", blk_msg.block.block_num())("l", (latency.count() / 1000))("w", witness_account.name)("i", last_irr)("d", blk_msg.block.block_num() - last_irr));
         }
         FC_ASSERT((latency.count() / 1000) > -5000, "Rejecting block with timestamp in the future");

         try {
            // TODO: in the case where this block is valid but on a fork that's too old for us to switch to,
            // you can help the network code out by throwing a block_older_than_undo_history exception.
            // when the net code sees that, it will stop trying to push blocks from that chain, but
            // leave that peer connected so that they can get sync blocks from us
            bool result = _chain_db->push_block(blk_msg.block, (_is_block_producer | _force_validate) ? database::skip_nothing : database::skip_transaction_signatures);

            // the block was accepted, so we now know all of the transactions contained in the block
            if (!sync_mode) {
               // if we're not in sync mode, there's a chance we will be seeing some transactions
               // included in blocks before we see the free-floating transaction itself.  If that
               // happens, there's no reason to fetch the transactions, so  construct a list of the
               // transaction message ids we no longer need.
               // during sync, it is unlikely that we'll see any old
               for (const processed_transaction &transaction : blk_msg.block.transactions) {
                  graphene::net::trx_message transaction_message(transaction);
                  contained_transaction_message_ids.push_back(graphene::net::message(transaction_message).id());
               }
            }

            return result;
         } catch (const graphene::chain::unlinkable_block_exception &e) {
            // translate to a graphene::net exception
            elog("Error when pushing block:\n${e}", ("e", e.to_detail_string()));
            FC_THROW_EXCEPTION(graphene::net::unlinkable_block_exception, "Error when pushing block:\n${e}", ("e", e.to_detail_string()));
         } catch (const fc::exception &e) {
            elog("Error when pushing block:\n${e}", ("e", e.to_detail_string()));
            throw;
         }

         if (!_is_finished_syncing && !sync_mode) {
            _is_finished_syncing = true;
            _self->syncing_finished();
         }
      }
      FC_CAPTURE_AND_RETHROW((blk_msg)(sync_mode))
   }

   virtual void handle_transaction(const graphene::net::trx_message &transaction_message) override {
      try {
         static fc::time_point last_call;
         static int trx_count = 0;
         ++trx_count;
         auto now = fc::time_point::now();
         if (now - last_call > fc::seconds(1)) {
            ilog("Got ${c} transactions from network", ("c", trx_count));
            last_call = now;
            trx_count = 0;
         }

         _chain_db->push_transaction(transaction_message.trx);
      }
      FC_CAPTURE_AND_RETHROW((transaction_message))
   }

   virtual void handle_message(const message &message_to_process) override {
      // not a transaction, not a block
      FC_THROW("Invalid Message Type");
   }

   bool is_included_block(const block_id_type &block_id) {
      uint32_t block_num = block_header::num_from_id(block_id);
      block_id_type block_id_in_preferred_chain = _chain_db->get_block_id_for_num(block_num);
      return block_id == block_id_in_preferred_chain;
   }

   /**
       * Assuming all data elements are ordered in some way, this method should
       * return up to limit ids that occur *after* the last ID in synopsis that
       * we recognize.
       *
       * On return, remaining_item_count will be set to the number of items
       * in our blockchain after the last item returned in the result,
       * or 0 if the result contains the last item in the blockchain
       */
   virtual std::vector<item_hash_t> get_block_ids(const std::vector<item_hash_t> &blockchain_synopsis,
                                                  uint32_t &remaining_item_count,
                                                  uint32_t limit) override {
      try {
         vector<block_id_type> result;
         remaining_item_count = 0;
         if (_chain_db->head_block_num() == 0)
            return result;

         result.reserve(limit);
         block_id_type last_known_block_id;

         if (blockchain_synopsis.empty() ||
             (blockchain_synopsis.size() == 1 && blockchain_synopsis[0] == block_id_type())) {
            // peer has sent us an empty synopsis meaning they have no blocks.
            // A bug in old versions would cause them to send a synopsis containing block 000000000
            // when they had an empty blockchain, so pretend they sent the right thing here.

            // do nothing, leave last_known_block_id set to zero
         } else {
            bool found_a_block_in_synopsis = false;
            for (const item_hash_t &block_id_in_synopsis : boost::adaptors::reverse(blockchain_synopsis))
               if (block_id_in_synopsis == block_id_type() ||
                   (_chain_db->is_known_block(block_id_in_synopsis) && is_included_block(block_id_in_synopsis))) {
                  last_known_block_id = block_id_in_synopsis;
                  found_a_block_in_synopsis = true;
                  break;
               }
            if (!found_a_block_in_synopsis)
               FC_THROW_EXCEPTION(graphene::net::peer_is_on_an_unreachable_fork, "Unable to provide a list of blocks starting at any of the blocks in peer's synopsis");
         }
         for (uint32_t num = block_header::num_from_id(last_known_block_id);
              num <= _chain_db->head_block_num() && result.size() < limit;
              ++num)
            if (num > 0)
               result.push_back(_chain_db->get_block_id_for_num(num));

         if (!result.empty() && block_header::num_from_id(result.back()) < _chain_db->head_block_num())
            remaining_item_count = _chain_db->head_block_num() - block_header::num_from_id(result.back());

         return result;
      }
      FC_CAPTURE_AND_RETHROW((blockchain_synopsis)(remaining_item_count)(limit))
   }

   /**
       * Given the hash of the requested data, fetch the body.
       */
   virtual message get_item(const item_id &id) override {
      try {
         // ilog("Request for item ${id}", ("id", id));
         if (id.item_type == graphene::net::block_message_type) {
            auto opt_block = _chain_db->fetch_block_by_id(id.item_hash);
            if (!opt_block)
               elog("Couldn't find block ${id} -- corresponding ID in our chain is ${id2}",
                    ("id", id.item_hash)("id2", _chain_db->get_block_id_for_num(block_header::num_from_id(id.item_hash))));
            FC_ASSERT(opt_block.valid());
            // ilog("Serving up block #${num}", ("num", opt_block->block_num()));
            return block_message(std::move(*opt_block));
         }
         return trx_message(_chain_db->get_recent_transaction(id.item_hash));
      }
      FC_CAPTURE_AND_RETHROW((id))
   }

   virtual chain_id_type get_chain_id() const override {
      return _chain_db->get_chain_id();
   }

   /**
       * Returns a synopsis of the blockchain used for syncing.  This consists of a list of
       * block hashes at intervals exponentially increasing towards the genesis block.
       * When syncing to a peer, the peer uses this data to determine if we're on the same
       * fork as they are, and if not, what blocks they need to send us to get us on their
       * fork.
       *
       * In the over-simplified case, this is a straighforward synopsis of our current
       * preferred blockchain; when we first connect up to a peer, this is what we will be sending.
       * It looks like this:
       *   If the blockchain is empty, it will return the empty list.
       *   If the blockchain has one block, it will return a list containing just that block.
       *   If it contains more than one block:
       *     the first element in the list will be the hash of the highest numbered block that
       *         we cannot undo
       *     the second element will be the hash of an item at the half way point in the undoable
       *         segment of the blockchain
       *     the third will be ~3/4 of the way through the undoable segment of the block chain
       *     the fourth will be at ~7/8...
       *       &c.
       *     the last item in the list will be the hash of the most recent block on our preferred chain
       * so if the blockchain had 26 blocks labeled a - z, the synopsis would be:
       *    a n u x z
       * the idea being that by sending a small (<30) number of block ids, we can summarize a huge
       * blockchain.  The block ids are more dense near the end of the chain where because we are
       * more likely to be almost in sync when we first connect, and forks are likely to be short.
       * If the peer we're syncing with in our example is on a fork that started at block 'v',
       * then they will reply to our synopsis with a list of all blocks starting from block 'u',
       * the last block they know that we had in common.
       *
       * In the real code, there are several complications.
       *
       * First, as an optimization, we don't usually send a synopsis of the entire blockchain, we
       * send a synopsis of only the segment of the blockchain that we have undo data for.  If their
       * fork doesn't build off of something in our undo history, we would be unable to switch, so there's
       * no reason to fetch the blocks.
       *
       * Second, when a peer replies to our initial synopsis and gives us a list of the blocks they think
       * we are missing, they only send a chunk of a few thousand blocks at once.  After we get those
       * block ids, we need to request more blocks by sending another synopsis (we can't just say "send me
       * the next 2000 ids" because they may have switched forks themselves and they don't track what
       * they've sent us).  For faster performance, we want to get a fairly long list of block ids first,
       * then start downloading the blocks.
       * The peer doesn't handle these follow-up block id requests any different from the initial request;
       * it treats the synopsis we send as our blockchain and bases its response entirely off that.  So to
       * get the response we want (the next chunk of block ids following the last one they sent us, or,
       * failing that, the shortest fork off of the last list of block ids they sent), we need to construct
       * a synopsis as if our blockchain was made up of:
       *    1. the blocks in our block chain up to the fork point (if there is a fork) or the head block (if no fork)
       *    2. the blocks we've already pushed from their fork (if there's a fork)
       *    3. the block ids they've previously sent us
       * Segment 3 is handled in the p2p code, it just tells us the number of blocks it has (in
       * number_of_blocks_after_reference_point) so we can leave space in the synopsis for them.
       * We're responsible for constructing the synopsis of Segments 1 and 2 from our active blockchain and
       * fork database.  The reference_point parameter is the last block from that peer that has been
       * successfully pushed to the blockchain, so that tells us whether the peer is on a fork or on
       * the main chain.
       */
   virtual std::vector<item_hash_t> get_blockchain_synopsis(const item_hash_t &reference_point,
                                                            uint32_t number_of_blocks_after_reference_point) override {
      try {
         std::vector<item_hash_t> synopsis;
         synopsis.reserve(30);
         uint32_t high_block_num;
         uint32_t non_fork_high_block_num;
         uint32_t low_block_num = _chain_db->last_non_undoable_block_num();
         std::vector<block_id_type> fork_history;

         if (reference_point != item_hash_t()) {
            // the node is asking for a summary of the block chain up to a specified
            // block, which may or may not be on a fork
            // for now, assume it's not on a fork
            if (is_included_block(reference_point)) {
               // reference_point is a block we know about and is on the main chain
               uint32_t reference_point_block_num = block_header::num_from_id(reference_point);
               assert(reference_point_block_num > 0);
               high_block_num = reference_point_block_num;
               non_fork_high_block_num = high_block_num;

               if (reference_point_block_num < low_block_num) {
                  // we're on the same fork (at least as far as reference_point) but we've passed
                  // reference point and could no longer undo that far if we diverged after that
                  // block.  This should probably only happen due to a race condition where
                  // the network thread calls this function, and then immediately pushes a bunch of blocks,
                  // then the main thread finally processes this function.
                  // with the current framework, there's not much we can do to tell the network
                  // thread what our current head block is, so we'll just pretend that
                  // our head is actually the reference point.
                  // this *may* enable us to fetch blocks that we're unable to push, but that should
                  // be a rare case (and correctly handled)
                  low_block_num = reference_point_block_num;
               }
            } else {
               // block is a block we know about, but it is on a fork
               try {
                  fork_history = _chain_db->get_block_ids_on_fork(reference_point);
                  // returns a vector where the last element is the common ancestor with the preferred chain,
                  // and the first element is the reference point you passed in
                  assert(fork_history.size() >= 2);

                  if (fork_history.front() != reference_point) {
                     edump((fork_history)(reference_point));
                     assert(fork_history.front() == reference_point);
                  }
                  block_id_type last_non_fork_block = fork_history.back();
                  fork_history.pop_back(); // remove the common ancestor
                  boost::reverse(fork_history);

                  if (last_non_fork_block == block_id_type()) // if the fork goes all the way back to genesis (does graphene's fork db allow this?)
                     non_fork_high_block_num = 0;
                  else
                     non_fork_high_block_num = block_header::num_from_id(last_non_fork_block);

                  high_block_num = non_fork_high_block_num + fork_history.size();
                  assert(high_block_num == block_header::num_from_id(fork_history.back()));
               } catch (const fc::exception &e) {
                  // unable to get fork history for some reason.  maybe not linked?
                  // we can't return a synopsis of its chain
                  elog("Unable to construct a blockchain synopsis for reference hash ${hash}: ${exception}", ("hash", reference_point)("exception", e));
                  throw;
               }
               if (non_fork_high_block_num < low_block_num) {
                  wlog("Unable to generate a usable synopsis because the peer we're generating it for forked too long ago "
                       "(our chains diverge after block #${non_fork_high_block_num} but only undoable to block #${low_block_num})",
                       ("low_block_num", low_block_num)("non_fork_high_block_num", non_fork_high_block_num));
                  FC_THROW_EXCEPTION(graphene::net::block_older_than_undo_history, "Peer is are on a fork I'm unable to switch to");
               }
            }
         } else {
            // no reference point specified, summarize the whole block chain
            high_block_num = _chain_db->head_block_num();
            non_fork_high_block_num = high_block_num;
            if (high_block_num == 0)
               return synopsis; // we have no blocks
         }

         if (low_block_num == 0)
            low_block_num = 1;

         // at this point:
         // low_block_num is the block before the first block we can undo,
         // non_fork_high_block_num is the block before the fork (if the peer is on a fork, or otherwise it is the same as high_block_num)
         // high_block_num is the block number of the reference block, or the end of the chain if no reference provided

         // true_high_block_num is the ending block number after the network code appends any item ids it
         // knows about that we don't
         uint32_t true_high_block_num = high_block_num + number_of_blocks_after_reference_point;
         do {
            // for each block in the synopsis, figure out where to pull the block id from.
            // if it's <= non_fork_high_block_num, we grab it from the main blockchain;
            // if it's not, we pull it from the fork history
            if (low_block_num <= non_fork_high_block_num)
               synopsis.push_back(_chain_db->get_block_id_for_num(low_block_num));
            else
               synopsis.push_back(fork_history[low_block_num - non_fork_high_block_num - 1]);
            low_block_num += (true_high_block_num - low_block_num + 2) / 2;
         } while (low_block_num <= high_block_num);

         //idump((synopsis));
         return synopsis;
      }
      FC_CAPTURE_AND_RETHROW()
   }

   /**
       * Call this after the call to handle_message succeeds.
       *
       * @param item_type the type of the item we're synchronizing, will be the same as item passed to the sync_from() call
       * @param item_count the number of items known to the node that haven't been sent to handle_item() yet.
       *                   After `item_count` more calls to handle_item(), the node will be in sync
       */
   virtual void sync_status(uint32_t item_type, uint32_t item_count) override {
      // any status reports to GUI go here
   }

   /**
       * Call any time the number of connected peers changes.
       */
   virtual void connection_count_changed(uint32_t c) override {
      // any status reports to GUI go here
   }

   virtual uint32_t get_block_number(const item_hash_t &block_id) override {
      try {
         return block_header::num_from_id(block_id);
      }
      FC_CAPTURE_AND_RETHROW((block_id))
   }

   virtual fc::time_point_sec get_last_known_hardfork_time() override {
      return _chain_db->_hardfork_times[_chain_db->_hardfork_times.size() - 1];
   }

   /**
       * Returns the time a block was produced (if block_id = 0, returns genesis time).
       * If we don't know about the block, returns time_point_sec::min()
       */
   virtual fc::time_point_sec get_block_time(const item_hash_t &block_id) override {
      try {
         auto opt_block = _chain_db->fetch_block_by_id(block_id);
         if (opt_block.valid())
            return opt_block->timestamp;
         return fc::time_point_sec::min();
      }
      FC_CAPTURE_AND_RETHROW((block_id))
   }

   virtual item_hash_t get_head_block_id() const override {
      return _chain_db->head_block_id();
   }

   virtual uint32_t estimate_last_known_fork_from_git_revision_timestamp(uint32_t unix_timestamp) const override {
      return 0; // there are no forks in graphene
   }

   virtual void error_encountered(const std::string &message, const fc::oexception &error) override {
      // notify GUI or something cool
   }

   uint8_t get_current_block_interval_in_seconds() const override {
      return _chain_db->get_global_properties().parameters.block_interval;
   }

   application *_self;

   fc::path _data_dir;
   const bpo::variables_map *_options = nullptr;
   api_access _apiaccess;

   std::shared_ptr<graphene::chain::database> _chain_db;
   std::shared_ptr<graphene::net::node> _p2p_network;
   std::shared_ptr<fc::http::websocket_server> _websocket_server;
   std::shared_ptr<fc::http::websocket_tls_server> _websocket_tls_server;

   std::map<string, std::shared_ptr<abstract_plugin>> _active_plugins;
   std::map<string, std::shared_ptr<abstract_plugin>> _available_plugins;

   bool _is_finished_syncing = false;
};

} // namespace detail

application::application() :
      my(new detail::application_impl(this)) {
}

application::~application() {
   if (my->_p2p_network) {
      my->_p2p_network->close();
      my->_p2p_network.reset();
   }
   if (my->_chain_db) {
      my->_chain_db->close();
   }
}

void application::set_program_options(boost::program_options::options_description &cli,
                                      boost::program_options::options_description &cfg) const {

   std::vector<string> seed_nodes = {
#ifdef BUILD_PEERPLAYS_TESTNET
#else
         "51.222.110.110:9777",
         "95.216.90.243:9777",
         "ca.peerplays.info:9777",
         "de.peerplays.xyz:9777",
         "pl.peerplays.org:9777",
         "seed.i9networks.net.br:9777",
         "witness.serverpit.com:9777"
#endif
   };
   std::string seed_nodes_str = fc::json::to_string(seed_nodes);

   cfg.add_options()("p2p-endpoint", bpo::value<string>()->default_value("0.0.0.0:9777"), "Endpoint for P2P node to listen on");
   cfg.add_options()("seed-node,s", bpo::value<vector<string>>()->composing(), "P2P nodes to connect to on startup (may specify multiple times)");
   cfg.add_options()("seed-nodes", bpo::value<string>()->composing()->default_value(seed_nodes_str), "JSON array of P2P nodes to connect to on startup");
   cfg.add_options()("checkpoint,c", bpo::value<vector<string>>()->composing(), "Pairs of [BLOCK_NUM,BLOCK_ID] that should be enforced as checkpoints.");
   cfg.add_options()("rpc-endpoint", bpo::value<string>()->default_value("127.0.0.1:8090"), "Endpoint for websocket RPC to listen on");
   cfg.add_options()("rpc-tls-endpoint", bpo::value<string>()->implicit_value("127.0.0.1:8089"), "Endpoint for TLS websocket RPC to listen on");
   cfg.add_options()("server-pem,p", bpo::value<string>()->implicit_value("server.pem"), "The TLS certificate file for this server");
   cfg.add_options()("server-pem-password,P", bpo::value<string>()->implicit_value(""), "Password for this certificate");
   cfg.add_options()("genesis-json", bpo::value<boost::filesystem::path>(), "File to read Genesis State from");
   cfg.add_options()("dbg-init-key", bpo::value<string>(), "Block signing key to use for init witnesses, overrides genesis file");
   cfg.add_options()("api-access", bpo::value<boost::filesystem::path>(), "JSON file specifying API permissions");
   cfg.add_options()("enable-standby-votes-tracking", bpo::value<bool>()->implicit_value(true),
                     "Whether to enable tracking of votes of standby witnesses and committee members. "
                     "Set it to true to provide accurate data to API clients, set to false for slightly better performance.");
   cfg.add_options()("plugins", bpo::value<string>()->default_value("account_history accounts_list affiliate_stats bookie market_history witness"),
                     "Space-separated list of plugins to activate");

   cli.add(cfg);
   cli.add_options()("create-genesis-json", bpo::value<boost::filesystem::path>(),
                     "Path to create a Genesis State at. If a well-formed JSON file exists at the path, it will be parsed and any "
                     "missing fields in a Genesis State will be added, and any unknown fields will be removed. If no file or an "
                     "invalid file is found, it will be replaced with an example Genesis State.");
   cli.add_options()("replay-blockchain", "Rebuild object graph by replaying all blocks");
   cli.add_options()("resync-blockchain", "Delete all blocks and re-sync with network from scratch");
   cli.add_options()("force-validate", "Force validation of all transactions");
   cli.add_options()("genesis-timestamp", bpo::value<uint32_t>(), "Replace timestamp from genesis.json with current time plus this many seconds (experts only!)");
   cli.add(_cli_options);
   cfg.add(_cfg_options);
}

void application::initialize(const fc::path &data_dir, const boost::program_options::variables_map &options) {
   my->_data_dir = data_dir;
   my->_options = &options;

   if (options.count("create-genesis-json")) {
      fc::path genesis_out = options.at("create-genesis-json").as<boost::filesystem::path>();
      genesis_state_type genesis_state = detail::create_example_genesis();
      if (fc::exists(genesis_out)) {
         try {
            genesis_state = fc::json::from_file(genesis_out).as<genesis_state_type>(20);
         } catch (const fc::exception &e) {
            std::cerr << "Unable to parse existing genesis file:\n"
                      << e.to_string()
                      << "\nWould you like to replace it? [y/N] ";
            char response = std::cin.get();
            if (toupper(response) != 'Y')
               return;
         }

         std::cerr << "Updating genesis state in file " << genesis_out.generic_string() << "\n";
      } else {
         std::cerr << "Creating example genesis state in file " << genesis_out.generic_string() << "\n";
      }
      fc::json::save_to_file(genesis_state, genesis_out);

      std::exit(EXIT_SUCCESS);
   }

   std::set<string> wanted;
   if (options.count("plugins")) {
      boost::split(wanted, options.at("plugins").as<std::string>(), [](char c) {
         return c == ' ';
      });
   } else {
      wanted.insert("account_history");
      wanted.insert("market_history");
      wanted.insert("accounts_list");
      wanted.insert("affiliate_stats");
   }
   if (!wanted.count("delayed_node") && !wanted.count("witness")) // explicitly requested delayed_node functionality suppresses witness functions
      wanted.insert("witness");
   wanted.insert("bookie");

   int es_ah_conflict_counter = 0;
   for (auto &it : wanted) {
      if (it == "account_history")
         ++es_ah_conflict_counter;
      if (it == "elasticsearch")
         ++es_ah_conflict_counter;

      if (es_ah_conflict_counter > 1) {
         elog("Can't start program with elasticsearch and account_history plugin at the same time");
         std::exit(EXIT_FAILURE);
      }
      if (!it.empty())
         enable_plugin(it);
   }
}

void application::startup() {
   try {
      my->startup();
   } catch (const fc::exception &e) {
      elog("${e}", ("e", e.to_detail_string()));
      throw;
   } catch (...) {
      elog("unexpected exception");
      throw;
   }
}

std::shared_ptr<abstract_plugin> application::get_plugin(const string &name) const {
   return is_plugin_enabled(name) ? my->_active_plugins[name] : nullptr;
}

bool application::is_plugin_enabled(const string &name) const {
   return !(my->_active_plugins.find(name) == my->_active_plugins.end());
}

net::node_ptr application::p2p_node() {
   return my->_p2p_network;
}

std::shared_ptr<chain::database> application::chain_database() const {
   return my->_chain_db;
}

void application::set_block_production(bool producing_blocks) {
   my->_is_block_producer = producing_blocks;
}

optional<api_access_info> application::get_api_access_info(const string &username) const {
   return my->get_api_access_info(username);
}

void application::set_api_access_info(const string &username, api_access_info &&permissions) {
   my->set_api_access_info(username, std::move(permissions));
}

bool application::is_finished_syncing() const {
   return my->_is_finished_syncing;
}

void graphene::app::application::enable_plugin(const string &name) {
   FC_ASSERT(my->_available_plugins[name], "Unknown plugin '" + name + "'");
   my->_active_plugins[name] = my->_available_plugins[name];
   my->_active_plugins[name]->plugin_set_app(this);
}

void graphene::app::application::add_available_plugin(std::shared_ptr<graphene::app::abstract_plugin> p) {
   my->_available_plugins[p->plugin_name()] = p;
}

void application::shutdown_plugins() {
   for (auto &entry : my->_active_plugins)
      entry.second->plugin_shutdown();
   return;
}
void application::shutdown() {
   my->_running.store(false);
   if (my->_p2p_network)
      my->_p2p_network->close();
   if (my->_chain_db)
      my->_chain_db->close();
}

void application::initialize_plugins(const boost::program_options::variables_map &options) {
   for (auto &entry : my->_active_plugins)
      entry.second->plugin_initialize(options);
   return;
}

void application::startup_plugins() {
   for (auto &entry : my->_active_plugins)
      entry.second->plugin_startup();
   return;
}

}} // namespace graphene::app