export const START_PARAM_SEPARATOR = '!';
const REF_STORAGE_KEY = 'ref_id';

type StartPayload = {
    contentId: string | null;
    referralId: string | null;
};

const safeSessionStorage = (): Storage | null => {
    if (typeof window === 'undefined') {
        return null;
    }
    try {
        return window.sessionStorage;
    } catch (error) {
        return null;
    }
};

export const resolveStartPayload = (): StartPayload => {
    if (typeof window === 'undefined') {
        return { contentId: null, referralId: null };
    }

    const searchParams = new URLSearchParams(window.location.search);
    const telegramApp = (window as any)?.Telegram?.WebApp;
    const rawStartParam = telegramApp?.initDataUnsafe?.start_param ?? null;

    let contentId: string | null = null;
    let referralId: string | null = null;

    const parsePayload = (payload: string | null) => {
        if (!payload) {
            return;
        }
        const [contentPart, refPart] = payload.split(START_PARAM_SEPARATOR, 2);
        if (contentPart) {
            contentId = contentPart;
        }
        if (refPart) {
            referralId = refPart;
        }
    };

    parsePayload(rawStartParam);

    if (!contentId) {
        const queryContent =
            searchParams.get('content') ||
            searchParams.get('cid') ||
            searchParams.get('start_param');
        if (queryContent) {
            contentId = queryContent;
        }
    }

    if (!referralId) {
        const queryRef = searchParams.get('ref') || searchParams.get('ref_id');
        if (queryRef) {
            referralId = queryRef;
        }
    }

    const storage = safeSessionStorage();
    if (storage) {
        if (referralId) {
            storage.setItem(REF_STORAGE_KEY, referralId);
        } else {
            const stored = storage.getItem(REF_STORAGE_KEY);
            if (stored) {
                referralId = stored;
            }
        }
    }

    return { contentId, referralId };
};

export const appendReferral = <T extends Record<string, unknown>>(payload: T): T => {
    const { referralId } = resolveStartPayload();
    if (referralId && !payload.ref_id) {
        return { ...payload, ref_id: referralId } as T;
    }
    return payload;
};