/*
 * Copyright (C) 2016 Anton Khirnov <anton@khirnov.net>
 *
 * mixnotify is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * mixnotify 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with mixnotify.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <alsa/asoundlib.h>

#include <stdio.h>
#include <string.h>

typedef struct MixerPrivate {
    snd_mixer_elem_t *elem;
} MixerPrivate;

static int elem_callback(snd_mixer_elem_t *elem, unsigned int mask)
{
    MixerPrivate *s = snd_mixer_elem_get_callback_private(elem);
    long val, min, max;
    int ret;

    if (!(mask & SND_CTL_EVENT_MASK_VALUE))
        return 0;

    ret = snd_mixer_selem_get_playback_volume(elem, SND_MIXER_SCHN_UNKNOWN, &val);
    if (ret < 0) {
        fprintf(stderr, "Error getting element volume: %d (%s)\n");
        return ret;
    }

    ret = snd_mixer_selem_get_playback_volume_range(elem, &min, &max);
    if (ret < 0) {
        fprintf(stderr, "Error getting element volume range: %d (%s)\n",
                ret, snd_strerror(ret));
        return ret;
    }

    fprintf(stdout, "%ld %ld %ld\n", val, min, max);
    fflush(stdout);

    return 0;
}

int main(int argc, const char **argv)
{
    static const char  *ctl_name = "default";
    static const char *elem_name = "Master";

    MixerPrivate priv = { NULL };

    snd_mixer_t *mixer = NULL;
    snd_mixer_elem_t *elem;
    int ret;

    if (argc > 1)
        ctl_name = argv[1];
    if (argc > 2)
        elem_name = argv[2];

    fprintf(stderr, "Using CTL: %s\n", ctl_name);
    fprintf(stderr, "Using mixer element: %s\n", elem_name);

    ret = snd_mixer_open(&mixer, 0);
    if (ret < 0) {
        fprintf(stderr, "Error opening a new mixer: %d (%s)\n",
                ret, snd_strerror(ret));
        return -1;
    }

    ret = snd_mixer_attach(mixer, ctl_name);
    if (ret < 0) {
        fprintf(stderr, "Error attachng a HCTL '%s' to the mixer: %d (%s)\n",
                ctl_name, ret, snd_strerror(ret));
        ret = -1;
        goto fail;
    }

    ret = snd_mixer_selem_register(mixer, NULL, NULL);
    if (ret < 0) {
        fprintf(stderr, "Error registering simple element class: %d (%s)\n",
                ctl_name, ret, snd_strerror(ret));
        ret = -1;
        goto fail;
    }

    ret = snd_mixer_load(mixer);
    if (ret < 0) {
        fprintf(stderr, "Error loading mixer elements: %d (%s)\n",
                ret, snd_strerror(ret));
        ret = -1;
        goto fail;
    }

    for (elem = snd_mixer_first_elem(mixer); elem; elem = snd_mixer_elem_next(elem)) {
        snd_mixer_elem_type_t type = snd_mixer_elem_get_type(elem);

        if (type == SND_MIXER_ELEM_SIMPLE &&
            !strcmp(snd_mixer_selem_get_name(elem), elem_name))
            break;
    }
    if (!elem) {
        fprintf(stderr, "Mixer element '%s' not found\n", elem_name);
        ret = -1;
        goto fail;
    }

    snd_mixer_elem_set_callback_private(elem, &priv);
    snd_mixer_elem_set_callback(elem, elem_callback);

    while (!(ret = snd_mixer_wait(mixer, -1))) {
        ret = snd_mixer_handle_events(mixer);
        if (ret < 0) {
            fprintf(stderr, "Error handling events: %d (%s)\n",
                    ret, snd_strerror(ret));
            ret = -1;
            goto fail;
        }
    }
    if (ret < 0) {
        fprintf(stderr, "Error waiting for mixer events: %d (%s)\n",
                ret, snd_strerror(ret));
        ret = -1;
        goto fail;
    }

fail:
    snd_mixer_close(mixer);

    return ret;
}