/*
 * This file is part of PowerDNS or dnsdist.
 * Copyright -- PowerDNS.COM B.V. and its contributors
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * In addition, for the avoidance of any doubt, permission is granted to
 * link this program with OpenSSL and to (re)distribute the binaries
 * produced as the result of such linking.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#pragma once

#include <string>
#include <ctime>
#include <iostream>
#include <optional>
#include <sstream>
#include <variant>
#include <syslog.h>

#include "namespaces.hh"
#include "dnsname.hh"
#include "iputils.hh"

//! The Logger class can be used to log messages in various ways.
class Logger
{
public:
  Logger(string, int facility = LOG_DAEMON); //!< pass the identification you wish to appear in the log

  //! The urgency of a log message
  enum Urgency
  {
    All = 32767,
    Alert = LOG_ALERT,
    Critical = LOG_CRIT,
    Error = LOG_ERR,
    Warning = LOG_WARNING,
    Notice = LOG_NOTICE,
    Info = LOG_INFO,
    Debug = LOG_DEBUG,
    None = -1
  };

  /** Log a message.
      \param msg Message you wish to log
      \param u Urgency of the message you wish to log
  */
  void log(const string& msg, Urgency u = Notice) noexcept;

  void setFacility(int f)
  {
    d_facility = f;
    open();
  } //!< Choose logging facility
  void setFlag(int f)
  {
    flags |= f;
    open();
  } //!< set a syslog flag
  void setName(const string&);

  //! set lower limit of urgency needed for console display. Messages of this urgency, and higher, will be displayed
  void toConsole(Urgency);
  void setLoglevel(Urgency);

  void disableSyslog(bool d)
  {
    d_disableSyslog = d;
  }

  void setTimestamps(bool t)
  {
    d_timestamps = t;
  }

  void setPrefixed(bool p)
  {
    d_prefixed = p;
  }

  //! Log to a file.
  void toFile(const string& filename);

  void resetFlags()
  {
    flags = 0;
    open();
  } //!< zero the flags
  /** Use this to stream to your log, like this:
      \code
      g_log<<"This is an informational message"<<endl; // logged at default loglevel (Info)
      g_log<<Logger::Warning<<"Out of diskspace"<<endl; // Logged as a warning
      g_log<<"This is an informational message"<<endl; // logged AGAIN at default loglevel (Info)
      \endcode
  */
  Logger& operator<<(const char* s);
  Logger& operator<<(const string& s); //!< log a string
  Logger& operator<<(const DNSName&);
  Logger& operator<<(const ComboAddress&); //!< log an address
  Logger& operator<<(Urgency); //!< set the urgency, << style

  Logger& operator<<(const QType& qtype)
  {
    *this << qtype.toString();
    return *this;
  }

  Logger& operator<<(const QClass& qclass)
  {
    *this << qclass.toString();
    return *this;
  }

  // Using const & since otherwise SyncRes:: values induce (illegal) copies
  template <typename T>
  Logger& operator<<(const T& i)
  {
    ostringstream tmp;
    tmp << i;
    *this << tmp.str();
    return *this;
  }

  Logger& operator<<(std::ostream& (&)(std::ostream&)); //!< this is to recognise the endl, and to commit the log

private:
  struct PerThread
  {
    PerThread() :
      d_urgency(Info)
    {}
    string d_output;
    Urgency d_urgency;
  };
  PerThread& getPerThread();
  void open();

  static thread_local PerThread t_perThread;
  string name;
  int flags;
  int d_facility;
  Urgency d_loglevel;
  Urgency consoleUrgency;
  bool opened;
  bool d_disableSyslog;
  bool d_timestamps{true};
  bool d_prefixed{false}; // this used to prefix the loglevel, but now causes formatting like structured logging
};

Logger& getLogger();

#define g_log getLogger()

#ifdef VERBOSELOG
#define DLOG(x) x
#else
#define DLOG(x) ((void)0)
#endif

// The types below are used by rec, which can log to g_log (general logging) or a string stream
// (trace-regexp). We pass an OptLog object to the code that should not know anything about this
// That code should then log using VLOG

struct LogVariant
{
  string prefix;
  timeval start;
  // variant cannot hold references directly, use a wrapper
  std::variant<std::reference_wrapper<Logger>, std::reference_wrapper<ostringstream>> v;
};

using OptLog = std::optional<LogVariant>;

void addTraceTS(const timeval& start, ostringstream& str);

// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define VLOG(log, x)                                                                                     \
  if (log) {                                                                                             \
    if (std::holds_alternative<std::reference_wrapper<Logger>>((log)->v)) {                              \
      /* NOLINTNEXTLINE(bugprone-macro-parentheses) */                                                   \
      std::get<std::reference_wrapper<Logger>>((log)->v).get() << Logger::Warning << (log)->prefix << x; \
    }                                                                                                    \
    else if (std::holds_alternative<std::reference_wrapper<ostringstream>>((log)->v)) {                  \
      addTraceTS((log)->start, std::get<std::reference_wrapper<ostringstream>>((log)->v).get());         \
      /* NOLINTNEXTLINE(bugprone-macro-parentheses) */                                                   \
      std::get<std::reference_wrapper<ostringstream>>((log)->v).get() << (log)->prefix << x;             \
    }                                                                                                    \
  }

// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define VLOG_NO_PREFIX(log, x)                                                                   \
  if (log) {                                                                                     \
    if (std::holds_alternative<std::reference_wrapper<Logger>>((log)->v)) {                      \
      /* NOLINTNEXTLINE(bugprone-macro-parentheses) */                                           \
      std::get<std::reference_wrapper<Logger>>((log)->v).get() << Logger::Warning << x;          \
    }                                                                                            \
    else if (std::holds_alternative<std::reference_wrapper<ostringstream>>((log)->v)) {          \
      addTraceTS((log)->start, std::get<std::reference_wrapper<ostringstream>>((log)->v).get()); \
      /* NOLINTNEXTLINE(bugprone-macro-parentheses) */                                           \
      std::get<std::reference_wrapper<ostringstream>>((log)->v).get() << x;                      \
    }                                                                                            \
  }
