// Copyright (c) 2015-2021 The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

/**

 * Functionality for communicating with Tor.

 */

#ifndef BITCOIN_TORCONTROL_H

#define BITCOIN_TORCONTROL_H

#include <netaddress.h>

#include <util/fs.h>

#include <event2/util.h>

#include <cstdint>

#include <deque>

#include <functional>

#include <string>

#include <vector>

constexpr int DEFAULT_TOR_CONTROL_PORT = 9051;

extern const std::string DEFAULT_TOR_CONTROL;

static const bool DEFAULT_LISTEN_ONION = true;

void StartTorControl(CService onion_service_target);

void InterruptTorControl();

void StopTorControl();

CService DefaultOnionServiceTarget(uint16_t port);

/** Reply from Tor, can be single or multi-line */

class TorControlReply

{

public:

    TorControlReply() { Clear(); }

    int code;

    std::vector<std::string> lines;

    void Clear()

    {

        code = 0;

        lines.clear();

    }

};

/** Low-level handling for Tor control connection.

 * Speaks the SMTP-like protocol as defined in torspec/control-spec.txt

 */

class TorControlConnection

{

public:

    typedef std::function<void(TorControlConnection&)> ConnectionCB;

    typedef std::function<void(TorControlConnection &,const TorControlReply &)> ReplyHandlerCB;

    /** Create a new TorControlConnection.

     */

    explicit TorControlConnection(struct event_base *base);

    ~TorControlConnection();

    /**

     * Connect to a Tor control port.

     * tor_control_center is address of the form host:port.

     * connected is the handler that is called when connection is successfully established.

     * disconnected is a handler that is called when the connection is broken.

     * Return true on success.

     */

    bool Connect(const std::string& tor_control_center, const ConnectionCB& connected, const ConnectionCB& disconnected);

    /**

     * Disconnect from Tor control port.

     */

    void Disconnect();

    /** Send a command, register a handler for the reply.

     * A trailing CRLF is automatically added.

     * Return true on success.

     */

    bool Command(const std::string &cmd, const ReplyHandlerCB& reply_handler);

private:

    /** Callback when ready for use */

    std::function<void(TorControlConnection&)> connected;

    /** Callback when connection lost */

    std::function<void(TorControlConnection&)> disconnected;

    /** Libevent event base */

    struct event_base *base;

    /** Connection to control socket */

    struct bufferevent* b_conn{nullptr};

    /** Message being received */

    TorControlReply message;

    /** Response handlers */

    std::deque<ReplyHandlerCB> reply_handlers;

    /** Libevent handlers: internal */

    static void readcb(struct bufferevent *bev, void *ctx);

    static void eventcb(struct bufferevent *bev, short what, void *ctx);

};

/****** Bitcoin specific TorController implementation ********/

/** Controller that connects to Tor control socket, authenticate, then create

 * and maintain an ephemeral onion service.

 */

class TorController

{

public:

    TorController(struct event_base* base, const std::string& tor_control_center, const CService& target);

    TorController() : conn{nullptr} {

        // Used for testing only.

    }

    ~TorController();

    /** Get name of file to store private key in */

    fs::path GetPrivateKeyFile();

    /** Reconnect, after getting disconnected */

    void Reconnect();

private:

    struct event_base* base;

    const std::string m_tor_control_center;

    TorControlConnection conn;

    std::string private_key;

    std::string service_id;

    bool reconnect;

    struct event *reconnect_ev = nullptr;

    float reconnect_timeout;

    CService service;

    const CService m_target;

    /** Cookie for SAFECOOKIE auth */

    std::vector<uint8_t> cookie;

    /** ClientNonce for SAFECOOKIE auth */

    std::vector<uint8_t> clientNonce;

public:

    /** Callback for GETINFO net/listeners/socks result */

    void get_socks_cb(TorControlConnection& conn, const TorControlReply& reply);

    /** Callback for ADD_ONION result */

    void add_onion_cb(TorControlConnection& conn, const TorControlReply& reply);

    /** Callback for AUTHENTICATE result */

    void auth_cb(TorControlConnection& conn, const TorControlReply& reply);

    /** Callback for AUTHCHALLENGE result */

    void authchallenge_cb(TorControlConnection& conn, const TorControlReply& reply);

    /** Callback for PROTOCOLINFO result */

    void protocolinfo_cb(TorControlConnection& conn, const TorControlReply& reply);

    /** Callback after successful connection */

    void connected_cb(TorControlConnection& conn);

    /** Callback after connection lost or failed connection attempt */

    void disconnected_cb(TorControlConnection& conn);

    /** Callback for reconnect timer */

    static void reconnect_cb(evutil_socket_t fd, short what, void *arg);

};

#endif // BITCOIN_TORCONTROL_H