// clang $(pkg-config --cflags SDL2_mixer) $(pkg-config --libs SDL2_mixer) -shared -o sdl2-mixer-module.so sdl2-mixer-module.c
#include <emacs-module.h>

#include "SDL_mixer.h"

int plugin_is_GPL_compatible;

static char* copy_lisp_string(emacs_env *env, emacs_value arg) {
    ptrdiff_t len;
    char *buf;

    if (!env->copy_string_contents(env, arg, NULL, &len)) {
        return NULL;
    }

    buf = malloc(len);
    if (!buf) {
        return NULL;
    }

    if (!env->copy_string_contents(env, arg, buf, &len)) {
        return NULL;
    }

    return buf;
}

static void bind_function(emacs_env *env, const char *name, emacs_value Sfun) {
    emacs_value Qfset = env->intern(env, "fset");
    emacs_value Qsym = env->intern(env, name);
    emacs_value args[] = { Qsym, Sfun };
    env->funcall(env, Qfset, 2, args);
}

static void provide(emacs_env *env, const char *feature) {
    emacs_value Qfeat = env->intern(env, feature);
    emacs_value Qprovide = env->intern (env, "provide");
    emacs_value args[] = { Qfeat };
    env->funcall(env, Qprovide, 1, args);
}

#include <stdio.h>
static emacs_value Fsdl2_mixer_enable_bg_music(emacs_env *env, ptrdiff_t nargs, emacs_value args[], void *data) {
    char *path = copy_lisp_string(env, args[0]);
    Mix_OpenAudio(44100, MIX_DEFAULT_FORMAT, 2, 4096);
    Mix_AllocateChannels(2);
    Mix_Music *music = Mix_LoadMUS(path);
    Mix_PlayMusic(music, -1);
    return NULL;
}

int emacs_module_init(struct emacs_runtime *ert) {
    emacs_env *env = ert->get_environment(ert);
    bind_function(env, "sdl2-mixer-enable-bg-music", env->make_function(env, 1, 1, Fsdl2_mixer_enable_bg_music, NULL, NULL));
    provide(env, "sdl2-mixer-module");
    return 0;
}