/*

Copyright (c) 2014-2021, Arvid Norberg
Copyright (c) 2015, Thomas Yuan
Copyright (c) 2016, 2020, Alden Torres
Copyright (c) 2016, Steven Siloti
Copyright (c) 2019, Amir Abrams
Copyright (c) 2020, FranciscoPombal
All rights reserved.

You may use, distribute and modify this code under the terms of the BSD license,
see LICENSE file.
*/


#include "libtorrent/session.hpp"
#include "libtorrent/alert_types.hpp"
#include "libtorrent/bencode.hpp" // for bencode()
#include "libtorrent/kademlia/item.hpp" // for sign_mutable_item
#include "libtorrent/kademlia/ed25519.hpp"
#include "libtorrent/span.hpp"
#include "libtorrent/session_params.hpp"

#include <functional>
#include <cstdio> // for snprintf
#include <cinttypes> // for PRId64 et.al.
#include <cstdlib>
#include <fstream>

using namespace lt;
using namespace lt::dht;
using namespace std::placeholders;

#ifdef TORRENT_DISABLE_DHT

int main(int argc, char* argv[])
{
	std::fprintf(stderr, "not built with DHT support\n");
	return 1;
}

#else

namespace {

bool log_pkts = false;
bool log_dht = false;

std::string to_hex(lt::span<char const> key)
{
	std::string out;
	for (auto const b : key)
	{
		char buf[3]{};
		std::snprintf(buf, sizeof(buf), "%02x", static_cast<unsigned char>(b));
		out += static_cast<char const*>(buf);
	}
	return out;
}

int hex_to_int(char in)
{
	if (in >= '0' && in <= '9') return int(in) - '0';
	if (in >= 'A' && in <= 'F') return int(in) - 'A' + 10;
	if (in >= 'a' && in <= 'f') return int(in) - 'a' + 10;
	return -1;
}

bool from_hex(span<char const> in, span<char> out)
{
	if (in.size() != out.size() * 2) return false;
	auto o = out.begin();
	for (auto i = in.begin(); i != in.end(); ++i, ++o)
	{
		int const t1 = hex_to_int(*i);
		if (t1 == -1) return false;
		++i;
		if (i == in.end()) return false;
		int const t2 = hex_to_int(*i);
		if (t2 == -1) return false;
		*o = static_cast<char>((t1 << 4) | (t2 & 0xf));
	}
	return true;
}

[[noreturn]] void usage()
{
	std::fprintf(stderr,
		"USAGE:\ndht [options] <command> <arg>\n\nCOMMANDS:\n"
		"get <hash>                - retrieves and prints out the immutable\n"
		"                            item stored under hash.\n"
		"put <string>              - puts the specified string as an immutable\n"
		"                            item onto the DHT. The resulting target hash\n"
		"gen-key <key-file>        - generate ed25519 keypair and save it in\n"
		"                            the specified file\n"
		"dump-key <key-file>       - dump ed25519 keypair from the specified key\n"
		"                            file.\n"
		"mput <key-file> <string> [salt]\n"
		"                          - puts the specified string as a mutable\n"
		"                            object under the public key in key-file,\n"
		"                            and optionally specified salt\n"
		"mget <public-key> [salt]  - get a mutable object under the specified\n"
		"                            public key, and salt (optional)\n"
		"\n"
		"OPTIONS:\n"
		"--log-packets               print DHT messages as they are sent and received\n"
		"--log-dht                   print DHT log messages\n"
		);
	exit(1);
}

alert* wait_for_alert(lt::session& s, int alert_type)
{
	alert* ret = nullptr;
	while (!ret)
	{
		s.wait_for_alert(seconds(5));

		std::vector<alert*> alerts;
		s.pop_alerts(&alerts);
		for (auto const a : alerts)
		{
			if (!log_pkts && !log_dht)
			{
				static int spinner = 0;
				static const char anim[] = {'-', '\\', '|', '/'};
				std::printf("\r%c", anim[spinner]);
				std::fflush(stdout);
				spinner = (spinner + 1) & 3;
			}
			if (a->type() == dht_pkt_alert::alert_type && log_pkts)
				std::printf("%s\n", a->message().c_str());
			else if (a->type() == dht_log_alert::alert_type && log_dht)
				std::printf("%s\n", a->message().c_str());
			else if (a->type() == dht_error_alert::alert_type)
				std::printf("%s\n", a->message().c_str());
			if (a->type() != alert_type) continue;
			ret = a;
		}
	}
	std::printf("\r");
	return ret;
}

void put_string(entry& e, std::array<char, 64>& sig
	, std::int64_t& seq
	, std::string const& salt
	, std::array<char, 32> const& pk
	, std::array<char, 64> const& sk
	, char const* str)
{
	using lt::dht::sign_mutable_item;

	e = std::string(str);
	std::vector<char> buf;
	bencode(std::back_inserter(buf), e);
	dht::signature sign;
	++seq;
	sign = sign_mutable_item(buf, salt, dht::sequence_number(seq)
		, dht::public_key(pk.data())
		, dht::secret_key(sk.data()));
	sig = sign.bytes;
}

void bootstrap(lt::session& s)
{
	std::printf("bootstrapping\n");
	wait_for_alert(s, dht_bootstrap_alert::alert_type);
	std::printf("bootstrap done.\n");
}

int dump_key(char const* filename)
{
	std::array<char, 32> seed;

	std::fstream f(filename, std::ios_base::in | std::ios_base::binary);
	f.read(seed.data(), seed.size());
	if (f.fail())
	{
		std::fprintf(stderr, "invalid key file.\n");
		return 1;
	}

	auto const [pk, sk] = ed25519_create_keypair(seed);

	std::printf("public key: %s\nprivate key: %s\n"
		, to_hex(pk.bytes).c_str()
		, to_hex(sk.bytes).c_str());

	return 0;
}

int generate_key(char const* filename)
{
	std::array<char, 32> seed = ed25519_create_seed();

	std::fstream f(filename, std::ios_base::out | std::ios_base::binary);
	f.write(seed.data(), seed.size());
	if (f.fail())
	{
		std::fprintf(stderr, "failed to write key file.\n");
		return 1;
	}

	return 0;
}

lt::session_params load_dht_state()
{
	std::fstream f(".dht", std::ios_base::in | std::ios_base::binary);
	f.unsetf(std::ios_base::skipws);
	std::printf("load dht state from .dht\n");
	std::vector<char> const state(std::istream_iterator<char>{f}
		, std::istream_iterator<char>{});

	if (f.bad() || state.empty())
	{
		std::fprintf(stderr, "failed to read .dht\n");
		return {};
	}
	return read_session_params(state);
}

} // anonymous namespace

int main(int argc, char* argv[])
{
	// skip pointer to self
	++argv;
	--argc;

	if (argc < 1) usage();

	while (argc > 1)
	{
		lt::string_view const option(argv[0]);
		if (option.substr(0, 2) != "--"_sv)
			break;

		if (option == "--log-packets"_sv)
			log_pkts = true;
		else if (option == "--log-dht"_sv)
			log_dht = true;

		++argv;
		--argc;
	}

	if (argv[0] == "dump-key"_sv)
	{
		++argv;
		--argc;
		if (argc < 1) usage();

		return dump_key(argv[0]);
	}

	if (argv[0] == "gen-key"_sv)
	{
		++argv;
		--argc;
		if (argc < 1) usage();

		return generate_key(argv[0]);
	}

	session_params sp = load_dht_state();
	sp.settings.set_bool(settings_pack::enable_dht, true);
	sp.settings.set_int(settings_pack::alert_mask, 0x7fffffff);
	lt::session s(sp);

	if (argv[0] == "get"_sv)
	{
		++argv;
		--argc;

		if (argc < 1) usage();

		if (strlen(argv[0]) != 40)
		{
			std::fprintf(stderr, "the hash is expected to be 40 hex characters\n");
			usage();
		}
		sha1_hash target;
		if (!from_hex({argv[0], 40}, target))
		{
			std::fprintf(stderr, "invalid hex encoding of target hash\n");
			return 1;
		}

		bootstrap(s);
		s.dht_get_item(target);

		std::printf("GET %s\n", to_hex(target).c_str());

		alert* a = wait_for_alert(s, dht_immutable_item_alert::alert_type);

		dht_immutable_item_alert* item = alert_cast<dht_immutable_item_alert>(a);

		std::string str = item->item.to_string();
		std::printf("%s\n", str.c_str());
	}
	else if (argv[0] == "put"_sv)
	{
		++argv;
		--argc;
		if (argc < 1) usage();

		entry data;
		data = std::string(argv[0]);

		bootstrap(s);
		sha1_hash const target = s.dht_put_item(data);

		std::printf("PUT %s\n", to_hex(target).c_str());

		alert* a = wait_for_alert(s, dht_put_alert::alert_type);
		dht_put_alert* pa = alert_cast<dht_put_alert>(a);
		std::printf("%s\n", pa->message().c_str());
	}
	else if (argv[0] == "mput"_sv)
	{
		++argv;
		--argc;
		if (argc < 1) usage();

		std::array<char, 32> seed;

		std::fstream f(argv[0], std::ios_base::in | std::ios_base::binary);
		f.read(seed.data(), seed.size());

		++argv;
		--argc;
		if (argc < 1) usage();

		auto const [pk, sk] = ed25519_create_keypair(seed);
		std::string salt;

		if (argc > 1) salt = argv[1];

		bootstrap(s);
		s.dht_put_item(pk.bytes, std::bind(&put_string, _1, _2, _3, _4
			, pk.bytes, sk.bytes, argv[0]), salt);

		std::printf("MPUT public key: %s [salt: %s]\n", to_hex(pk.bytes).c_str()
			, salt.c_str());

		alert* a = wait_for_alert(s, dht_put_alert::alert_type);
		dht_put_alert* pa = alert_cast<dht_put_alert>(a);
		std::printf("%s\n", pa->message().c_str());
	}
	else if (argv[0] == "mget"_sv)
	{
		++argv;
		--argc;
		if (argc < 1) usage();

		auto const len = static_cast<std::ptrdiff_t>(strlen(argv[0]));
		if (len != 64)
		{
			std::fprintf(stderr, "public key is expected to be 64 hex digits\n");
			return 1;
		}
		std::array<char, 32> public_key;
		if (!from_hex({argv[0], len}, public_key))
		{
			std::fprintf(stderr, "invalid hex encoding of public key\n");
			return 1;
		}

		std::string salt;
		if (argc > 1) salt = argv[1];

		bootstrap(s);
		s.dht_get_item(public_key, salt);
		std::printf("MGET %s [salt: %s]\n", argv[0], salt.c_str());

		bool authoritative = false;

		while (!authoritative)
		{
			alert* a = wait_for_alert(s, dht_mutable_item_alert::alert_type);

			dht_mutable_item_alert* item = alert_cast<dht_mutable_item_alert>(a);

			authoritative = item->authoritative;
			std::string str = item->item.to_string();
			std::printf("%s: %s\n", authoritative ? "auth" : "non-auth", str.c_str());
		}
	}
	else
	{
		usage();
	}

	std::vector<char> state = write_session_params_buf(s.session_state(session::save_dht_state));
	std::fstream f(".dht", std::ios_base::out | std::ios_base::binary | std::ios_base::trunc);
	f.write(state.data(), static_cast<std::streamsize>(state.size()));

	return 0;
}

#endif