/*
 * 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/>.
 *
 */

#include <mts/MTS_System.h>
#include <fstream>
#include <sstream>
#include <cassert>
#include <spawn.h>
#include <sys/wait.h>
#include <unistd.h>

#ifdef WIN32
#include <windows.h>

//WIN32: FILETIME structure has a 64-bit value representing the number of 100-nanosecond intervals since January 1, 1601.

static int64_t getEpochTimeMicros() {
    const SYSTEMTIME EPOCH = {1970, 1, 4, 1, 0, 0, 0, 0};
    FILETIME ft;
    BOOL ok = SystemTimeToFileTime(&EPOCH, &ft);
    assert(ok);
    int64_t epochTimeMicros = ((static_cast<uint64_t>(ft.dwHighDateTime) << 32) | ft.dwLowDateTime) / 10;
    return epochTimeMicros;
}

static int64_t getSystemTimeMicros() {
    SYSTEMTIME st;
    GetSystemTime(&st);
    FILETIME ft;
    BOOL ok = SystemTimeToFileTime(&st, &ft);
    assert(ok);
    int64_t systemTimeMicros = ((static_cast<uint64_t>(ft.dwHighDateTime) << 32) | ft.dwLowDateTime) / 10;
    return systemTimeMicros;
}

static int64_t getClockFrequency() {
    LARGE_INTEGER freq;
    BOOL ok = QueryPerformanceFrequency(&freq);
    assert(ok);
    return freq.QuadPart;
}

static int64_t getClockValue() {
    LARGE_INTEGER value;
    BOOL ok = QueryPerformanceCounter(&value);
    assert(ok);
    return value.QuadPart;
}

#else
#include <time.h>
#endif

using namespace MTS;

uint64_t System::timeMicros() {
    int64_t micros = 0;
#ifdef WIN32
    static const int64_t EPOCH_TIME_MICROS = getEpochTimeMicros();
    micros = getSystemTimeMicros() - EPOCH_TIME_MICROS;
#else
    timespec ts;
    int result = clock_gettime(CLOCK_REALTIME, &ts);
    if (result == 0) {
        micros = (static_cast<int64_t>(ts.tv_sec) * 1000000)
        + (ts.tv_nsec / 1000);
    }
#endif
    return micros;
}

uint64_t System::precisionTimeMicros() {
    int64_t micros = 0;
#ifdef WIN32
    static const double TO_MICROS = 1000000.0 / getClockFrequency();
    int64_t value = getClockValue();
    micros = static_cast<int64_t>(value * TO_MICROS);
#else
    micros = timeMicros();
#endif
    return micros;
}

uint64_t System::monoTimeMicros() {
    uint64_t micros = 0;
#ifdef WIN32
    micros = static_cast<uint64_t>(GetTickCount64()) * 1000;
#else
    timespec ts;
    int result = clock_gettime(CLOCK_MONOTONIC, &ts);
    if (result == 0) {
        micros = (static_cast<uint64_t>(ts.tv_sec) * 1000000)
            + (ts.tv_nsec / 1000);
    }
#endif
    return micros;
}

bool System::isBigEndian() {
    static union {
            uint32_t i;
            char c[4];
    } endian = { 0x01020304 };

    return endian.c[0] == 1;
}

void System::swapBytes(uint8_t* const pBuffer, const uint32_t iSize) {
    if (iSize > 1 && pBuffer != 0) {
        uint8_t cByte = 0;
        uint32_t i;
        uint32_t j;
        for (i = 0, j = iSize - 1; i < j; i++, j--) {
            cByte = pBuffer[i];
            pBuffer[i] = pBuffer[j];
            pBuffer[j] = cByte;
        }
    }
}

int32_t System::cmd(const std::string& cmd, std::string& result) {
    std::string output;
    FILE * stream;
    const int max_buffer = 256;
    char buffer[max_buffer];
    int32_t code = -1;

    stream = popen(cmd.c_str(), "r");
    if (stream) {
        while (!feof(stream))
            if (fgets(buffer, max_buffer, stream) != NULL)
                output.append(buffer);
        code = pclose(stream);
    }

    result = output;

    return code;
}

int32_t System::readFile(const std::string& path, std::string& result) {
    std::ifstream infile(path.c_str());
    std::stringstream ss;

    if (!infile.is_open()) {
        return -1;
    }

    ss << infile.rdbuf();

    infile.close();

    result = ss.str();

    return 0;
}

int32_t System::execute(const std::string& cmd, const std::vector<std::string>& argv, std::string& result) {
    // Ported directly from System::cmd
    std::string output;
    const int max_buffer = 256;
    char buffer[max_buffer];
    int32_t code = -1;
    ChildHandle child;

    if (executeBackground(cmd, argv, PipeType::READ, child)) {
        while (!feof(child.stream)) {
            if (fgets(buffer, max_buffer, child.stream) != NULL) {
                output.append(buffer);
            }
        }
        code = closeBackground(child);
    }

    result = output;

    return code;
}

int32_t System::executeEnv(const std::string& cmd, const std::vector<std::string>& argv, std::string& result) {
    // Ported directly from System::cmd
    std::string output;
    const int max_buffer = 256;
    char buffer[max_buffer];
    int32_t code = -1;
    ChildHandle child;

    if (executeBackgroundEnv(cmd, argv, PipeType::READ, child)) {
        while (!feof(child.stream)) {
            if (fgets(buffer, max_buffer, child.stream) != NULL) {
                output.append(buffer);
            }
        }
        code = closeBackground(child);
    }

    result = output;

    return code;
}

bool System::executeBackground(const std::string& cmd, const std::vector<std::string>& argv, System::PipeType type, System::ChildHandle& child) {
    std::vector<char*> arguments = castArgVector(cmd, argv);
    return executeBackground(cmd, arguments.data(), false, type, child);
}

bool System::executeBackgroundEnv(const std::string& cmd, const std::vector<std::string>& argv, System::PipeType type, System::ChildHandle& child) {
    std::vector<char*> arguments = castArgVector(cmd, argv);
    return executeBackground(cmd, arguments.data(), true, type, child);
}

int System::closeBackground(System::ChildHandle& child) {
    int pstat;
    pid_t pid;

    fclose(child.stream);

    do {
        pid = waitpid(child.pid, &pstat, 0);
    } while (pid == -1 && errno == EINTR);

    return pstat;
}

extern char **environ;

bool System::executeBackground(const std::string& cmd, char* const argv[], bool env, System::PipeType type, ChildHandle& child) {
    pid_t childPid;
    FILE* stream = NULL;
    posix_spawn_file_actions_t actions;
    int childTargetFd;
    const char* parentMode = nullptr;
    bool bActionsInitialized = false;
    bool bSuccess = false;

    do {

        Pipe pipe;
        if (initPipe(pipe, type) != 0) {
            // failed to create pipe
            break;
        }

        if (type == PipeType::READ) {
            childTargetFd = STDOUT_FILENO;
            parentMode = "r";
        } else if (type == PipeType::WRITE) {
            childTargetFd = STDIN_FILENO;
            parentMode = "w";
        } else {
            break;  // unreachable, unknown mode
        }

        // Define how child process should handle pipes
        if (posix_spawn_file_actions_init(&actions) != 0) {
            // failed to initialize file actions
            break;
        }

        bActionsInitialized = true;

        if (posix_spawn_file_actions_addclose(&actions, pipe.parent.get()) != 0) {
            // failed to add action to close parent pipe fd
            break;
        }

        if (posix_spawn_file_actions_adddup2(&actions, pipe.child.get(), childTargetFd) != 0) {
            // failed to add an action to use child pipe fd for output
            break;
        }

        if (posix_spawn_file_actions_addclose(&actions, pipe.child.get()) != 0) {
            // failed to add an action to close dupped child pipe fd
            break;
        }

        if (posix_spawnp(&childPid, cmd.c_str(), &actions, NULL, argv, env ? environ : NULL) != 0) {
            // failed to spawn the process
            break;
        }

        // Close child-specific file descriptor
        pipe.child.reset();

        // Convert parent fd to FILE pointer
        stream = fdopen(pipe.parent.release(), parentMode);

        // Save data about child
        child.pid = childPid;
        child.stream = stream;

        bSuccess = true;

    } while (false);

    if (bActionsInitialized) {
        posix_spawn_file_actions_destroy(&actions);
    }

    return bSuccess;
}

char* System::castArgument(const std::string& arg) {
    // Casting const away is required only to be compatible with some C-style system functions.
    // Arguments are not actually modified in such functions.
    return const_cast<char*>(arg.c_str());
}

std::vector<char*> System::castArgVector(const std::string& cmd, const std::vector<std::string>& argv) {
    std::vector<char*> result;

    // Append application name as argument zero
    result.push_back(castArgument(cmd));

    // Append all other arguments
    for (const std::string& arg : argv) {
        result.push_back(castArgument(arg));
    }

    // Terminate with NULL
    result.push_back(NULL);
    return result;
}

int System::initPipe(System::Pipe& pipe, System::PipeType type) {
    const int READ_END_IDX = 0;
    const int WRITE_END_IDX = 1;

    int holder[2];
    int parentIndex;
    int childIndex;
    int ret = -1;

    do {

        if (type == PipeType::READ) {
            parentIndex = READ_END_IDX;
            childIndex = WRITE_END_IDX;
        } else if (type == PipeType::WRITE) {
            parentIndex = WRITE_END_IDX;
            childIndex = READ_END_IDX;
        } else {
            // unreachable, unknown mode
            break; // error
        }

        ret = ::pipe(holder);
        if (ret != 0) {
            break;
        }

        pipe.parent.reset(holder[parentIndex]);
        pipe.child.reset(holder[childIndex]);

    } while (false);

    return ret;
}

System::FdWrapper::FdWrapper(int fd)
    : m_fd(fd)
{}

System::FdWrapper::~FdWrapper() {
    reset();
}

int System::FdWrapper::get() const {
    return m_fd;
}

int System::FdWrapper::release() {
    int fd = m_fd;
    m_fd = FD_NOT_READY;
    return fd;
}

void System::FdWrapper::reset(int fd) {
    if (FD_NOT_READY != m_fd) {
        ::close(m_fd);
    }
    m_fd = fd;
}