export const onCharactersMessageCreate = functions.firestore.document(`/${User.entity}/{userId}/${Message.entity}/{messageId}`).onCreate(async event => {
    const userId = event.params!.userId;
    const userRef = firestore.collection(User.entity).doc(userId);
    const tokenSnapshot = await userRef.collection(FcmToken.entity).get();
    const tokens = tokenSnapshot.docs.map(doc => { return doc.id; });
    const message = <Message> event.data.data();
    // TODO: Add sender user name
    // TODO: fix locale
    const title = (await new I18N('ja').notification())('newMessageTitle');
    const payload = notification.createPayload(
        title,
        message.text);
    const response = await admin.messaging().sendToDevice(tokens, payload);
    // 無効なtokenを削除
    // TODO: 動作確認
    // TODO: 別メソッドにする
    const results = response.results.map((response, i) => { return { response, token: tokens[i] }; });
    const errorCodes = [
        'messaging/invalid-registration-token',
        'messaging/registration-token-not-registered',
    ];
    for (const r of results) {
        const error = r.response.error;
        if (error == null) {
            continue;
        }
        console.error(error.code);
        if (errorCodes.indexOf(error.code) != null) {
            await userRef.collection(FcmToken.entity).doc(r.token).delete();
        }
    }
});