/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Format.h>
#include <assert.h>
#include <errno.h>
#include <setjmp.h>
#include <signal.h>
#include <string.h>
#include <sys/select.h>
#include <syscall.h>
#include <unistd.h>

extern "C" {

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/kill.html
int kill(pid_t pid, int sig)
{
    int rc = syscall(SC_kill, pid, sig);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/killpg.html
int killpg(int pgrp, int sig)
{
    int rc = syscall(SC_killpg, pgrp, sig);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/raise.html
int raise(int sig)
{
    // FIXME: Support multi-threaded programs.
    return kill(getpid(), sig);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/signal.html
sighandler_t signal(int signum, sighandler_t handler)
{
    struct sigaction new_act;
    struct sigaction old_act;
    new_act.sa_handler = handler;
    new_act.sa_flags = 0;
    new_act.sa_mask = 0;
    int rc = sigaction(signum, &new_act, &old_act);
    if (rc < 0)
        return SIG_ERR;
    return old_act.sa_handler;
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigaction.html
int sigaction(int signum, const struct sigaction* act, struct sigaction* old_act)
{
    int rc = syscall(SC_sigaction, signum, act, old_act);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigemptyset.html
int sigemptyset(sigset_t* set)
{
    *set = 0;
    return 0;
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigfillset.html
int sigfillset(sigset_t* set)
{
    *set = 0xffffffff;
    return 0;
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigaddset.html
int sigaddset(sigset_t* set, int sig)
{
    if (sig < 1 || sig > 32) {
        errno = EINVAL;
        return -1;
    }
    *set |= 1 << (sig - 1);
    return 0;
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigaltstack.html
int sigaltstack(stack_t const* ss, stack_t* old_ss)
{
    int rc = syscall(SC_sigaltstack, ss, old_ss);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigdelset.html
int sigdelset(sigset_t* set, int sig)
{
    if (sig < 1 || sig > 32) {
        errno = EINVAL;
        return -1;
    }
    *set &= ~(1 << (sig - 1));
    return 0;
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigismember.html
int sigismember(sigset_t const* set, int sig)
{
    if (sig < 1 || sig > 32) {
        errno = EINVAL;
        return -1;
    }
    if (*set & (1 << (sig - 1)))
        return 1;
    return 0;
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigprocmask.html
int sigprocmask(int how, sigset_t const* set, sigset_t* old_set)
{
    int rc = syscall(SC_sigprocmask, how, set, old_set);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigpending.html
int sigpending(sigset_t* set)
{
    int rc = syscall(SC_sigpending, set);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

char const* sys_siglist[NSIG] = {
    "Invalid signal number",
    "Hangup",
    "Interrupt",
    "Quit",
    "Illegal instruction",
    "Trap",
    "Aborted",
    "Bus error",
    "Division by zero",
    "Killed",
    "User signal 1",
    "Segmentation violation",
    "User signal 2",
    "Broken pipe",
    "Alarm clock",
    "Terminated",
    "Stack fault",
    "Child exited",
    "Continued",
    "Stopped (signal)",
    "Stopped",
    "Stopped (tty input)",
    "Stopped (tty output)",
    "Urgent I/O condition)",
    "CPU limit exceeded",
    "File size limit exceeded",
    "Virtual timer expired",
    "Profiling timer expired",
    "Window changed",
    "I/O possible",
    "Power failure",
    "Bad system call",
};

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/siglongjmp.html
void siglongjmp(jmp_buf env, int val)
{
    if (env->did_save_signal_mask) {
        int rc = sigprocmask(SIG_SETMASK, &env->saved_signal_mask, nullptr);
        assert(rc == 0);
    }
    longjmp(env, val);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigsuspend.html
int sigsuspend(sigset_t const* set)
{
    return pselect(0, nullptr, nullptr, nullptr, nullptr, set);
}

// https://pubs.opengroup.org/onlinepubs/009604499/functions/sigwait.html
int sigwait(sigset_t const* set, int* sig)
{
    int rc = syscall(Syscall::SC_sigtimedwait, set, nullptr, nullptr);
    VERIFY(rc != 0);
    if (rc < 0)
        return -rc;
    *sig = rc;
    return 0;
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigwaitinfo.html
int sigwaitinfo(sigset_t const* set, siginfo_t* info)
{
    return sigtimedwait(set, info, nullptr);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigtimedwait.html
int sigtimedwait(sigset_t const* set, siginfo_t* info, struct timespec const* timeout)
{
    int rc = syscall(Syscall::SC_sigtimedwait, set, info, timeout);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

char const* sys_signame[] = {
    "INVAL",
    "HUP",
    "INT",
    "QUIT",
    "ILL",
    "TRAP",
    "ABRT",
    "BUS",
    "FPE",
    "KILL",
    "USR1",
    "SEGV",
    "USR2",
    "PIPE",
    "ALRM",
    "TERM",
    "STKFLT",
    "CHLD",
    "CONT",
    "STOP",
    "TSTP",
    "TTIN",
    "TTOU",
    "URG",
    "XCPU",
    "XFSZ",
    "VTALRM",
    "PROF",
    "WINCH",
    "IO",
    "INFO",
    "SYS",
};

static_assert(sizeof(sys_signame) == sizeof(char const*) * NSIG);

int getsignalbyname(char const* name)
{
    VERIFY(name);
    StringView name_sv(name);
    for (size_t i = 0; i < NSIG; ++i) {
        auto signal_name = StringView(sys_signame[i]);
        if (signal_name == name_sv || (name_sv.starts_with("SIG") && signal_name == name_sv.substring_view(3)))
            return i;
    }
    errno = EINVAL;
    return -1;
}

char const* getsignalname(int signal)
{
    if (signal < 0 || signal >= NSIG) {
        errno = EINVAL;
        return nullptr;
    }
    return sys_signame[signal];
}
}