/*
* Copyright (c) 2018 Calvin Rose
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/

#include <janet/janet.h>
#include <stdlib.h>
#include <time.h>
#include "util.h"

#ifdef JANET_WINDOWS
#include <Windows.h>
#include <direct.h>
#else
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#endif

/* For macos */
#ifdef __MACH__
#include <mach/clock.h>
#include <mach/mach.h>
#endif

static Janet os_which(int32_t argc, Janet *argv) {
    janet_fixarity(argc, 0);
    (void) argv;
    #ifdef JANET_WINDOWS
        return janet_ckeywordv("windows");
    #elif __APPLE__
        return janet_ckeywordv("macos");
    #elif defined(__EMSCRIPTEN__)
        return janet_ckeywordv("web");
    #else
        return janet_ckeywordv("posix");
    #endif
}

#ifdef JANET_WINDOWS
static Janet os_execute(int32_t argc, Janet *argv) {
    janet_arity(argc, 1, -1);
    JanetBuffer *buffer = janet_buffer(10);
    for (int32_t i = 0; i < argc; i++) {
        const uint8_t *argstring = janet_getstring(argv, i);
        janet_buffer_push_bytes(buffer, argstring, janet_string_length(argstring));
        if (i != argc - 1) {
            janet_buffer_push_u8(buffer, ' ');
        }
    }
    janet_buffer_push_u8(buffer, 0);

    /* Convert to wide chars */
    wchar_t *sys_str = malloc(buffer->count * sizeof(wchar_t));
    if (NULL == sys_str) {
        JANET_OUT_OF_MEMORY;
    }
    int nwritten = MultiByteToWideChar(
        CP_UTF8,
        MB_PRECOMPOSED,
        buffer->data,
        buffer->count,
        sys_str,
        buffer->count);
    if (nwritten == 0) {
        free(sys_str);
        janet_panic("could not create process");
    }

    STARTUPINFO si;
    PROCESS_INFORMATION pi;

    ZeroMemory(&si, sizeof(si));
    si.cb = sizeof(si);
    ZeroMemory(&pi, sizeof(pi));

    // Start the child process.
    if(!CreateProcess(NULL,
                (LPSTR) sys_str,
                NULL,
                NULL,
                FALSE,
                0,
                NULL,
                NULL,
                &si,
                &pi)) {
        free(sys_str);
        janet_panic("could not create process");
    }
    free(sys_str);

    // Wait until child process exits.
    WaitForSingleObject(pi.hProcess, INFINITE);

    // Close process and thread handles.
    WORD status;
    GetExitCodeProcess(pi.hProcess, (LPDWORD)&status);
    CloseHandle(pi.hProcess);
    CloseHandle(pi.hThread);
    return janet_wrap_integer(status);
}
#else
static Janet os_execute(int32_t argc, Janet *argv) {
    janet_arity(argc, 1, -1);
    const uint8_t **child_argv = malloc(sizeof(uint8_t *) * (argc + 1));
    if (NULL == child_argv) {
        JANET_OUT_OF_MEMORY;
    }
    for (int32_t i = 0; i < argc; i++) {
        child_argv[i] = janet_getstring(argv, i);
    }
    child_argv[argc] = NULL;

    /* Fork child process */
    pid_t pid = fork();
    if (pid < 0) {
        janet_panic("failed to execute");
    } else if (pid == 0) {
        if (-1 == execve((const char *)child_argv[0], (char **)child_argv, NULL)) {
            exit(1);
        }
    }
    int status;
    waitpid(pid, &status, 0);
    return janet_wrap_integer(status);
}
#endif

static Janet os_shell(int32_t argc, Janet *argv) {
    janet_arity(argc, 0, 1);
    const char *cmd = argc
        ? (const char *)janet_getstring(argv, 0)
        : NULL;
    int stat = system(cmd);
    return argc
        ? janet_wrap_integer(stat)
        : janet_wrap_boolean(stat);
}

static Janet os_getenv(int32_t argc, Janet *argv) {
    janet_fixarity(argc, 1);
    const uint8_t *k = janet_getstring(argv, 0);
    const char *cstr = (const char *) k;
    const char *res = getenv(cstr);
    return (res && cstr)
        ? janet_cstringv(res)
        : janet_wrap_nil();
}

static Janet os_setenv(int32_t argc, Janet *argv) {
#ifdef JANET_WINDOWS
#define SETENV(K,V) _putenv_s(K, V)
#define UNSETENV(K) _putenv_s(K, "")
#else
#define SETENV(K,V) setenv(K, V, 1)
#define UNSETENV(K) unsetenv(K)
#endif
    janet_arity(argc, 1, 2);
    const uint8_t *k = janet_getstring(argv, 0);
    const char *ks = (const char *) k;
    if (argc == 1 || janet_checktype(argv[1], JANET_NIL)) {
        UNSETENV(ks);
    } else {
        const uint8_t *v = janet_getstring(argv, 1);
        SETENV(ks, (const char *)v);
    }
    return janet_wrap_nil();
}

static Janet os_exit(int32_t argc, Janet *argv) {
    janet_arity(argc, 0, 1);
    if (argc == 0) {
        exit(EXIT_SUCCESS);
    } else if (janet_checkint(argv[0])) {
        exit(janet_unwrap_integer(argv[0]));
    } else {
        exit(EXIT_FAILURE);
    }
    return janet_wrap_nil();
}

static Janet os_time(int32_t argc, Janet *argv) {
    janet_fixarity(argc, 0);
    (void) argv;
    double dtime = (double)(time(NULL));
    return janet_wrap_number(dtime);
}

/* Clock shims */
#ifdef JANET_WINDOWS
static int gettime(struct timespec *spec) {
    int64_t wintime = 0LL;
    GetSystemTimeAsFileTime((FILETIME*)&wintime);
    /* Windows epoch is January 1, 1601 apparently*/
    wintime -= 116444736000000000LL;
    spec->tv_sec  = wintime / 10000000LL;
    /* Resolution is 100 nanoseconds. */
    spec->tv_nsec = wintime % 10000000LL * 100;
    return 0;
}
#elif defined(__MACH__)
static int gettime(struct timespec *spec) {
    clock_serv_t cclock;
    mach_timespec_t mts;
    host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock);
    clock_get_time(cclock, &mts);
    mach_port_deallocate(mach_task_self(), cclock);
    spec->tv_sec = mts.tv_sec;
    spec->tv_nsec = mts.tv_nsec;
    return 0;
}
#else
#define gettime(TV) clock_gettime(CLOCK_MONOTONIC, (TV))
#endif

static Janet os_clock(int32_t argc, Janet *argv) {
    janet_fixarity(argc, 0);
    (void) argv;
    struct timespec tv;
    if (gettime(&tv)) janet_panic("could not get time");
    double dtime = tv.tv_sec + (tv.tv_nsec / 1E9);
    return janet_wrap_number(dtime);
}

static Janet os_sleep(int32_t argc, Janet *argv) {
    janet_fixarity(argc, 1);
    double delay = janet_getnumber(argv, 0);
    if (delay < 0) janet_panic("invalid argument to sleep");
#ifdef JANET_WINDOWS
    Sleep((DWORD) (delay * 1000));
#else
    struct timespec ts;
    ts.tv_sec = (time_t) delay;
    ts.tv_nsec = (delay <= UINT32_MAX)
        ? (long)((delay - ((uint32_t)delay)) * 1000000000)
        : 0;
    nanosleep(&ts, NULL);
#endif
    return janet_wrap_nil();
}

static Janet os_cwd(int32_t argc, Janet *argv) {
    janet_fixarity(argc, 0);
    (void) argv;
    char buf[FILENAME_MAX];
    char *ptr;
#ifdef JANET_WINDOWS
    ptr = _getcwd(buf, FILENAME_MAX);
#else
    ptr = getcwd(buf, FILENAME_MAX);
#endif
    if (NULL == ptr) janet_panic("could not get current directory");
    return janet_cstringv(ptr);
}

static const JanetReg cfuns[] = {
    {
        "os/which", os_which,
        JDOC("(os/which)\n\n"
                "Check the current operating system. Returns one of:\n\n"
                "\t:windows - Microsoft Windows\n"
                "\t:macos - Apple macos\n"
                "\t:posix - A POSIX compatible system (default)")
    },
    {
        "os/execute", os_execute,
        JDOC("(os/execute program & args)\n\n"
                "Execute a program on the system and pass it string arguments. Returns "
                "the exit status of the program.")
    },
    {
        "os/shell", os_shell,
        JDOC("(os/shell str)\n\n"
                "Pass a command string str directly to the system shell.")
    },
    {
        "os/exit", os_exit,
        JDOC("(os/exit x)\n\n"
                "Exit from janet with an exit code equal to x. If x is not an integer, "
                "the exit with status equal the hash of x.")
    },
    {
        "os/getenv", os_getenv,
        JDOC("(os/getenv variable)\n\n"
                "Get the string value of an environment variable.")
    },
    {
        "os/setenv", os_setenv,
        JDOC("(os/setenv variable value)\n\n"
            "Set an environment variable.")
    },
    {
        "os/time", os_time,
        JDOC("(os/time)\n\n"
            "Get the current time expressed as the number of seconds since "
            "January 1, 1970, the Unix epoch. Returns a real number.")
    },
    {
        "os/clock", os_clock,
        JDOC("(os/clock)\n\n"
            "Return the number of seconds since some fixed point in time. The clock "
            "is guaranteed to be non decreased in real time.")
    },
    {
        "os/sleep", os_sleep,
        JDOC("(os/sleep nsec)\n\n"
            "Suspend the program for nsec seconds. 'nsec' can be a real number. Returns "
            "nil.")
    },
    {
        "os/cwd", os_cwd,
        JDOC("(os/cwd)\n\n"
            "Returns the current working directory.")
    },
    {NULL, NULL, NULL}
};

/* Module entry point */
void janet_lib_os(JanetTable *env) {
    janet_cfuns(env, NULL, cfuns);
}