/* Watch for properties starting with droid.parameter. and translate them directly to
 * HAL set_parameters() calls. */
static pa_hook_result_t sink_proplist_changed_hook_cb(pa_core *c, pa_sink *sink, struct userdata *u) {
    bool changed = false;
    const char *pkey;
    const char *key;
    const char *value;
    char *tmp;
    void *state = NULL;
    droid_parameter_mapping *parameter = NULL;

    pa_assert(sink);
    pa_assert(u);

    if (u->sink != sink)
        return PA_HOOK_OK;

    while ((key = pa_proplist_iterate(sink->proplist, &state))) {
        if (!pa_startswith(key, PROP_DROID_PARAMETER_PREFIX))
            continue;

        pkey = key + strlen(PROP_DROID_PARAMETER_PREFIX);
        if (pkey[0] == '\0')
            continue;

        changed = false;

        if (!(parameter = pa_hashmap_get(u->parameters, pkey))) {
            parameter = pa_xnew0(droid_parameter_mapping, 1);
            parameter->key = pa_xstrdup(pkey);
            parameter->value = pa_xstrdup(pa_proplist_gets(sink->proplist, key));
            pa_hashmap_put(u->parameters, parameter->key, parameter);
            changed = true;
        } else {
            value = pa_proplist_gets(sink->proplist, key);
            if (!pa_streq(parameter->value, value)) {
                pa_xfree(parameter->value);
                parameter->value = pa_xstrdup(value);
                changed = true;
            }
        }

        if (changed) {
            pa_assert(parameter);
            tmp = pa_sprintf_malloc("%s=%s;", parameter->key, parameter->value);
            pa_log_debug("sink proplist changed: set_parameters(): %s", tmp);
            pa_droid_hw_module_lock(u->hw_module);
            u->stream_out->common.set_parameters(&u->stream_out->common, tmp);
            pa_droid_hw_module_unlock(u->hw_module);
            pa_xfree(tmp);
        }
    }    

    return PA_HOOK_OK;
}