scripting environment values

[LazyStability]

I am trying to write a script playing sounds when a notification pops up. I want to customize its behaviour based on the notification und have found these environment variables in this file.

public async bool run_script (NotifyParams param, out string msg) {
    string[] spawn_env = {};
    spawn_env += "SWAYNC_APP_NAME=%s".printf (param.app_name);
    spawn_env += "SWAYNC_SUMMARY=%s".printf (param.summary);
    spawn_env += "SWAYNC_BODY=%s".printf (param.body);
    spawn_env += "SWAYNC_URGENCY=%s".printf (param.urgency.to_string ());
    spawn_env += "SWAYNC_CATEGORY=%s".printf (param.category);
    spawn_env += "SWAYNC_ID=%s".printf (param.applied_id.to_string ());
    spawn_env += "SWAYNC_REPLACES_ID=%s".printf (param.replaces_id.to_string ());
    spawn_env += "SWAYNC_TIME=%s".printf (param.time.to_string ());
    spawn_env += "SWAYNC_DESKTOP_ENTRY=%s".printf (param.desktop_entry ?? "");
    foreach (string hint in param.hints.get_keys ()) {
        if (hint.contains ("image") || hint.contains ("icon")) {
            continue;
        }
        spawn_env += "SWAYNC_HINT_%s=%s".printf (
            hint.up ().replace ("-", "_"),
            param.hints[hint].print (false));
    }

Environment Variables being set

My question is how do I access the hint variables?
I tried with the sound file hint like this $SWAYNC_HINT_SOUND_FILE but that variable seems to be empty.

HAS_NOTIFICATION_SOUND=("Discord" "Thunderbird" "vesktop")
case "$SWAYNC_URGENCY" in
    Critical)
        SOUNDFILE="error.oga"
        ;;
     Normal|Low)

        [[ $(swaync-client --get-dnd) == "true" ]] && exit 0
        if [ -n "$SWAYNC_HINT_SOUND_FILE" ]; then
            echo "$TEST"
            SOUNDFILE="$SWAYNC_HINT_SOUND_FILE"
            SOUNDFILE="dialog-error.oga"
        elif [[ " ${HAS_NOTIFICATION_SOUND[*]} " =~ [[:space:]]${SWAYNC_APP_NAME}[[:space:]] ]] ; then
            exit 0
        else
            SOUNDFILE="message.oga"
        fi
        ;;
esac
mpv --really-quiet "$SOUNDFILE" 

My script so far

[LazyStability]

Noticed that this discussion is still open, the following script worked for me and plays sounds corresponding to the urgency of the notification, any hints or the application sending the notification.

#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail

HAS_NOTIFICATION_SOUND=("Discord" "Thunderbird" "vesktop")

SOUNDFILE="/run/current-system/sw/share/sounds/freedesktop/stereo/suspend-error.oga" 

[[ "$SWAYNC_URGENCY" != "Critical" ]] && {
    # Got any sound files?
    if [[ -z "${SWAYNC_HINT_SOUND_FILE-}" ]] || [[ ! -f "${SWAYNC_HINT_SOUND_FILE//\'}" ]]; then
      SOUNDFILE="/run/current-system/sw/share/sounds/freedesktop/stereo/message.oga"
    else
      SOUNDFILE="${SWAYNC_HINT_SOUND_FILE//\'}"
    fi

    # Are we busy?
    [[ $(swaync-client --get-dnd) == "true" ]] && exit 0

    # Has the program its own sound effect?
    # Do this https://unix.stackexchange.com/questions/251013/bash-regex-capture-group
    SWAYNC_APP_NAME=${SWAYNC_APP_NAME:-"No name"}
    [[ " ${HAS_NOTIFICATION_SOUND[*]} " =~ [[:space:]]''${SWAYNC_APP_NAME}[[:space:]] ]] && {
        echo "there"
        exit 0
    }
}
mpv --really-quiet "$SOUNDFILE"

Script