// SPDX-License-Identifier: GPL-2.0-or-later
//
// loadkeys -- choose the keyboard layout.
//
//     loadkeys              print the active layout
//     loadkeys -l           list the layouts the kernel has
//     loadkeys pl           switch to Polish (programmers)
//     loadkeys -c           apply KEYMAP from /etc/vconsole.conf
//
// Named after the Linux tool because that is what anyone would type, but it is
// not the same program and takes no keymap files. Linux's loadkeys compiles a
// text keymap and uploads it a key at a time through KDSKBENT, which means the
// data lives in userspace and a machine whose /usr is not mounted has no
// layout at all. The layouts here are in the kernel and this only names one.
//
// The setting is machine-wide, not per-terminal: there is one keyboard, and
// switching to tty3 does not move anybody's fingers.

#include "types.h"
#include "user.h"
#include "fcntl.h"
#include "posix.h"

// No printf, memset or strcpy in lib/; this needs a little of each.
static void
puts_(const char *s)
{
    int n = 0;
    while (s[n]) n++;
    write(1, (void *)s, n);
}

static void
zero(void *p, int n)
{
    char *c = p;
    while (n-- > 0) *c++ = 0;
}

static void
copy_bounded(char *dst, const char *src, int cap)
{
    int i = 0;
    while (i < cap - 1 && src[i]) { dst[i] = src[i]; i++; }
    dst[i] = 0;
}

// /dev/console rather than fd 0: the caller may have redirected its input,
// and the layout being set belongs to the machine's keyboard, not to whichever
// terminal this process happens to be reading from.
static int
console(void)
{
    int fd = open("/dev/console", O_RDWR);
    if (fd < 0) {
        puts_("loadkeys: no console to ask\n");
        exit();
    }
    return fd;
}

#define VCONSOLE "/etc/vconsole.conf"

// Pull KEYMAP= out of /etc/vconsole.conf.
//
// Deliberately not a config parser. One key, whole file in one buffer, first
// match wins -- and a missing or unreadable file is not an error, because the
// kernel's default is already a working keyboard and refusing to boot over a
// preference would be absurd.
static int
keymap_from_file(char *out, int cap)
{
    char buf[512];
    int fd, n, i, j;

    fd = open(VCONSOLE, O_RDONLY);
    if (fd < 0)
        return -1;
    n = read(fd, buf, sizeof(buf) - 1);
    close(fd);
    if (n <= 0)
        return -1;
    buf[n] = 0;

    for (i = 0; i < n; i++) {
        if (buf[i] == '#') {                        // skip to end of comment
            while (i < n && buf[i] != '\n') i++;
            continue;
        }
        if (buf[i] != 'K')
            continue;
        const char *k = "KEYMAP=";
        for (j = 0; k[j] && buf[i + j] == k[j]; j++)
            ;
        if (k[j])
            continue;
        i += j;
        for (j = 0; j < cap - 1 && buf[i + j] &&
                    buf[i + j] != '\n' && buf[i + j] != ' '; j++)
            out[j] = buf[i + j];
        out[j] = 0;
        return j > 0 ? 0 : -1;
    }
    return -1;
}

int
main(int argc, char *argv[])
{
    struct kb_layout k;
    char want[16];
    int fd, i;

    if (argc > 2 || (argc == 2 && argv[1][0] == '-' &&
                     argv[1][1] != 'l' && argv[1][1] != 'c')) {
        puts_("usage: loadkeys [-l | -c | <layout>]\n"
              "  -l        list the available layouts\n"
              "  -c        apply KEYMAP from " VCONSOLE "\n"
              "  <layout>  switch to it; with no argument, print the active one\n");
        return 1;
    }

    fd = console();

    if (argc == 2 && argv[1][0] == '-' && argv[1][1] == 'c') {
        if (keymap_from_file(want, sizeof(want)) < 0) {
            close(fd);
            return 0;                   // no preference recorded; not a failure
        }
        zero(&k, sizeof(k));
        copy_bounded(k.name, want, sizeof(k.name));
        if (ioctl(fd, KB_SETLAYOUT, &k) < 0) {
            puts_("loadkeys: " VCONSOLE " asks for '");
            puts_(want);
            puts_("', which this kernel does not have\n");
            close(fd);
            return 1;
        }
        close(fd);
        return 0;
    }

    if (argc == 2 && argv[1][0] == '-') {           // -l
        for (i = 0; ; i++) {
            zero(&k, sizeof(k));
            k.index = i;
            if (ioctl(fd, KB_LISTLAYOUT, &k) < 0)
                break;                              // past the end
            puts_(k.name);
            puts_("\t");
            puts_(k.desc);
            puts_("\n");
        }
        close(fd);
        return 0;
    }

    if (argc == 2) {                                // set
        zero(&k, sizeof(k));
        copy_bounded(k.name, argv[1], sizeof(k.name));
        if (ioctl(fd, KB_SETLAYOUT, &k) < 0) {
            puts_("loadkeys: no layout called '");
            puts_(argv[1]);
            puts_("' -- try loadkeys -l\n");
            close(fd);
            return 1;
        }
        close(fd);
        return 0;
    }

    zero(&k, sizeof(k));                       // report
    if (ioctl(fd, KB_GETLAYOUT, &k) < 0) {
        puts_("loadkeys: the kernel has no layout to report\n");
        close(fd);
        return 1;
    }
    puts_(k.name);
    puts_("\t");
    puts_(k.desc);
    puts_("\n");
    close(fd);
    return 0;
}