// clang $(pkg-config --cflags taglib) $(pkg-config --libs taglib) -shared -o taglib-module.so taglib-module.cxx
#include <emacs-module.h>
#include <cstring>

#include <fileref.h>
#include <tstring.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 = (char *) 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);
}

static emacs_value Ftaglib_test(emacs_env *env, ptrdiff_t nargs, emacs_value args[], void *data) noexcept {
    emacs_value Qnil = env->intern(env, "nil");
    emacs_value ret = Qnil;
    char *path = copy_lisp_string(env, args[0]);
    TagLib::File *file = TagLib::FileRef::create(path);
    free(path);

    if (file && file->isValid()) {
        TagLib::String title = file->tag()->title();
        if (title != TagLib::String::null) {
            char *title_str = strdup(title.to8Bit(true).c_str());
            ret = env->make_string(env, title_str, strlen(title_str));
            free(title_str);
        }
    }

    delete file;
    return ret;
}

int emacs_module_init(struct emacs_runtime *ert) {
    emacs_env *env = ert->get_environment(ert);
    bind_function(env, "taglib-test", env->make_function(env, 1, 1, Ftaglib_test, NULL, NULL));
    provide(env, "taglib-module");
    return 0;
}