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/*
 * Copyright (C) 2015 by Multi-Tech Systems
 *
 * This file is part of libmts.
 *
 * libmts is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * libmts 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with libmts.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

/*! \file   MTS_System.h
 \brief  System Utilities
 \date   15JUN11
 \author Sean Godinez

 System utilities for time, endian, etc.
 */
#ifndef MTS_SYSTEM_H
#define MTS_SYSTEM_H

#include <mts/MTS_NonConstructable.h>
#include <mts/MTS_Stdint.h>
#include <string>
#include <vector>

namespace MTS {

    class System: private NonConstructable {

        public:

            //! Type of the pipe to be opened in executeBackground
            enum class PipeType {
                READ, WRITE
            };

            //! Utility structure with information about the child process
            struct ChildHandle {
                pid_t pid;
                FILE* stream;
            };

            //UTC (Coordinated Universal Time) : This is the standard international time or the Greenwich Mean Time.
            //EPOCH : number of seconds elapsed since 00:00:00 on January 1, 1970, Coordinated Universal Time.

            static uint64_t timeMicros();
            static uint64_t precisionTimeMicros();

            //MONOTONIC : number of seconds elapsed since some unspecified starting point. When time is changed by user, timer are unaffected.

            static uint64_t monoTimeMicros();

            static bool isBigEndian();
            static void swapBytes(uint8_t* const pBuffer, const uint32_t iSize);

            static int32_t cmd(const std::string& cmd, std::string& result);
            static int32_t readFile(const std::string& path, std::string& result);

            //! Execute application with specified arguments.
            /*!
             * A safer alternative to System::cmd that allows to execute applications with controlled
             * list of arguments bypasing the system shell.
             *
             * \param  cmd    name of the application to be executed
             * \param  argv   vector of arguments (excluding argument zero)
             * \param  result stdout output from the application is stored here
             * \return result code as for std::system and UNIX pclose
             */
            static int32_t execute(const std::string& cmd, const std::vector<std::string>& argv, std::string& result);

            //! Spawn a process and open pipe with the specified type (READ or WRITE)
            /*!
            * A safer alternative to POSIX popen that allows to execute applications with controlled
            * list of arguments bypasing the system shell. If succeded, information about the spawned
            * process is written to the \p child structure.
            *
            * \param  cmd   name of the application to be executed
            * \param  argv  vector of arguments (excluding argument zero)
            * \param  type  open pipe for read from child or write to child
            * \param  child on success is populated with child process information, on failure is not defined
            * \return true  on success, false on failure
            */
            static bool executeBackground(const std::string& cmd, const std::vector<std::string>& argv, PipeType type, ChildHandle& child);

            //! Close the pipe and wait for a child to finish execution
            /*!
            * \param  child  structure with child process information as populated by executeBackground
            * \return result code as for std::system and UNIX pclose
            */
            static int closeBackground(ChildHandle& child);

        private:

            //! Spawn a process and open pipe with the specified type (READ or WRITE)
            static bool executeBackground(const std::string& cmd, char* const argv[], PipeType type, ChildHandle& child);

            //! Utility method. Cast argument to a C pointer required by some C-style functions.
            static inline char* castArgument(const std::string& arg);

            //! Utility method. Convert argument vector to a format required by execve and posix_spawn.
            static std::vector<char*> castArgVector(const std::string& cmd, const std::vector<std::string>& argv);

            //! Lightweight C++ wrapper with auto-close for file descriptors
            class FdWrapper {

                public:
                    static const int FD_NOT_READY = -1;

                    explicit FdWrapper(int fd = FD_NOT_READY);
                    ~FdWrapper();

                    inline int get() const;
                    int release();
                    void reset(int fd = FD_NOT_READY);

                private:
                    int m_fd;

            };

            //! Utility structure, used by popen wrapper
            struct Pipe {
                FdWrapper parent;
                FdWrapper child;
            };

            //! Initialize UNIX pipe
            static int initPipe(Pipe& pipe, PipeType type);

    };
}

#endif