#include <bits/errno-return.h>
#include <bits/termios.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <luna/Heap.h>
#include <luna/NumberParsing.h>
#include <luna/Sort.h>
#include <luna/Utf8.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <unistd.h>

template <typename ArgT, typename ResultT> static inline ResultT __generic_div(ArgT a, ArgT b)
{
    ResultT result;
    result.quot = a / b;
    result.rem = a % b;

    if (a >= 0 && result.rem < 0)
    {
        result.quot++;
        result.rem -= b;
    }

    return result;
}

extern "C"
{
    int abs(int v)
    {
        return __builtin_abs(v);
    }

    long labs(long v)
    {
        return __builtin_labs(v);
    }

    long long llabs(long long v)
    {
        return __builtin_llabs(v);
    }

    div_t div(int num, int den)
    {
        return __generic_div<int, div_t>(num, den);
    }

    ldiv_t ldiv(long num, long den)
    {
        return __generic_div<long, ldiv_t>(num, den);
    }

    lldiv_t lldiv(long long num, long long den)
    {
        return __generic_div<long long, lldiv_t>(num, den);
    }

    int atoi(const char* s)
    {
        return (int)strtol(s, NULL, 10);
    }

    long atol(const char* s)
    {
        return strtol(s, NULL, 10);
    }

    // Assuming LP64, long long == long.
    long long atoll(const char* s)
    {
        return (long long)strtol(s, NULL, 10);
    }

    // These checks are only necessary on LLP64 platforms, where long won't match size_t/ssize_t. Probably redundant
    // then (since Luna follows the regular LP64 model), but oh well...
    long strtol(const char* str, char** endptr, int base)
    {
        isize rc = parse_signed_integer(str, const_cast<const char**>(endptr), base);

        if (rc > (isize)LONG_MAX) return LONG_MAX;
        if (rc < (isize)LONG_MIN) return LONG_MIN;

        return rc;
    }

    unsigned long strtoul(const char* str, char** endptr, int base)
    {
        usize rc = parse_unsigned_integer(str, const_cast<const char**>(endptr), base);

        if (rc > (usize)ULONG_MAX) return ULONG_MAX;

        return rc;
    }

    __noreturn void abort()
    {
        // First, try to unblock SIGABRT and then raise it.
        sigset_t set;
        sigemptyset(&set);
        sigaddset(&set, SIGABRT);
        sigprocmask(SIG_UNBLOCK, &set, nullptr);

        raise(SIGABRT);

        // Still here? The program must have catched it. Reset the disposition to default.
        struct sigaction act;
        act.sa_handler = SIG_DFL;
        sigemptyset(&act.sa_mask);
        act.sa_flags = 0;
        sigaction(SIGABRT, &act, nullptr);

        raise(SIGABRT);

        __builtin_trap();
    }

    __noreturn void _Exit(int status)
    {
        syscall(SYS_exit, status);
        __builtin_unreachable();
    }

    size_t mbstowcs(wchar_t* buf, const char* src, size_t max)
    {
        if (max == 0) return 0;
        size_t result = (size_t)-1;

        Utf8StringDecoder decoder(src);

        if (!buf)
        {
            decoder.code_points().try_set_value_or_error(result, errno);
            return result;
        }

        decoder.decode(buf, max).try_set_value_or_error(result, errno);
        return result;
    }

    size_t wcstombs(char* buf, const wchar_t* src, size_t max)
    {
        if (max == 0) return 0;
        size_t result = (size_t)-1;

        Utf8StringEncoder encoder(src);

        if (!buf)
        {
            encoder.byte_length().try_set_value_or_error(result, errno);
            return result;
        }

        encoder.encode(buf, max).try_set_value_or_error(result, errno);
        return result;
    }

    void* malloc(size_t size)
    {
        return TRY_OR_SET_ERRNO(malloc_impl(size), void*, nullptr);
    }

    void* calloc(size_t nmemb, size_t size)
    {
        return TRY_OR_SET_ERRNO(calloc_impl(nmemb, size), void*, nullptr);
    }

    void* realloc(void* ptr, size_t size)
    {
        return TRY_OR_SET_ERRNO(realloc_impl(ptr, size), void*, nullptr);
    }

    void free(void* ptr)
    {
        free_impl(ptr);
    }

    int system(const char* cmd)
    {
        if (!cmd)
        {
            struct stat st;
            if (stat("/bin/sh", &st) < 0) return 0;
            return S_ISREG(st.st_mode);
        }

        pid_t child = fork();
        if (child == 0)
        {
            execl("/bin/sh", "sh", "-c", cmd, NULL);
            _Exit(127);
        }

        if (child < 0) return -1;

        sigset_t set, oldset;
        sigemptyset(&set);
        sigaddset(&set, SIGCHLD);
        sigprocmask(SIG_BLOCK, &set, &oldset);

        auto old_int = signal(SIGINT, SIG_IGN);
        auto old_quit = signal(SIGQUIT, SIG_IGN);

        int status;
        waitpid(child, &status, 0);

        sigprocmask(SIG_SETMASK, &oldset, nullptr);
        signal(SIGINT, old_int);
        signal(SIGQUIT, old_quit);

        return status;
    }

    void qsort(void* base, size_t nmemb, size_t size, int (*compar)(const void*, const void*))
    {
        c_quicksort(base, nmemb, size, compar);
    }

    static unsigned next = 42;

    int rand()
    {
        next = next * 1103515245 + 12345;
        return (int)((unsigned)(next / 65536) % 32768);
    }

    void srand(unsigned int seed)
    {
        next = seed;
    }

    static void generate_random_character(char* ptr)
    {
        constexpr const char chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_";
        *ptr = chars[rand() % (sizeof(chars) - 1)];
    }

    static int check_template(char* _template, size_t* len)
    {
        *len = strlen(_template);
        if (*len < 6)
        {
            errno = EINVAL;
            return -1;
        }

        if (strncmp(_template + (*len - 6), "XXXXXX", 6))
        {
            errno = EINVAL;
            return -1;
        }

        return 0;
    }

    static void generate_random_name(char* _template, const size_t* len)
    {
        size_t index = *len - 6;
        while (index < *len) generate_random_character(&_template[index++]);
    }

    char* mkdtemp(char* _template)
    {
        size_t len;
        if (check_template(_template, &len) < 0) return nullptr;

        while (true)
        {
            generate_random_name(_template, &len);

            if (mkdir(_template, 0700) == 0) return _template;

            if (errno != EEXIST) return nullptr;
        }
    }

    int mkstemp(char* _template)
    {
        size_t len;
        if (check_template(_template, &len) < 0) return -1;

        while (true)
        {
            generate_random_name(_template, &len);

            int fd;

            if ((fd = open(_template, O_RDWR | O_CREAT | O_EXCL, 0600)) >= 0) return fd;

            if (errno != EEXIST) return -1;
        }
    }

    double atof(const char* str)
    {
        return strtod(str, nullptr);
    }

    int posix_openpt(int flags)
    {
        return open("/dev/ptmx", flags);
    }

    int grantpt(int)
    {
        return 0;
    }

    int unlockpt(int)
    {
        return 0;
    }

    char* ptsname(int fd)
    {
        static char buffer[4096];

        int index;
        if (ioctl(fd, TIOCGPTN, &index) < 0) return nullptr;

        snprintf(buffer, sizeof(buffer), "/dev/pts/%d", index);

        return buffer;
    }
}