(function () {
    function initTelegramFab() {
        const root = document.getElementById('telegramFabRoot');
        if (!root || root.dataset.initialized === 'true') {
            return;
        }

        root.dataset.initialized = 'true';

        const dataset = root.dataset;
        const offcanvasElement = document.getElementById('telegramPremiumOffcanvas');
        const loadingSection = document.getElementById('telegramFabLoading');
        const connectedSection = document.getElementById('telegramFabConnected');
        const disconnectedSection = document.getElementById('telegramFabDisconnected');
        const alertElement = document.getElementById('telegramFabAlert');
        const retryButton = root.querySelector('.telegram-fab-retry');
        const openButton = root.querySelector('.telegram-fab-open');
        const unlinkButton = root.querySelector('.telegram-fab-unlink');
        const usernameElement = root.querySelector('.telegram-fab-username');
        const widgetPlaceholder = document.getElementById('telegramLoginWidgetPlaceholder');
        const toastContainer = document.getElementById('telegramFabToasts');
        const fabButton = document.getElementById('telegramPremiumFab');

        if (!offcanvasElement || !loadingSection || !connectedSection || !disconnectedSection) {
            console.warn('[Telegram FAB] Missing required DOM nodes. Aborting initialization.');
            return;
        }

        const offcanvas = bootstrap.Offcanvas.getOrCreateInstance(offcanvasElement);
        let currentStatus = null;
        let currentDeepLink = null;
        let widgetMounted = false;

        const messages = {
            loading: dataset.statusLoading || 'Loading...',
            error: dataset.statusError || 'Something went wrong.',
            connectedTemplate: dataset.statusConnected || 'Connected as {0}',
            disconnected: dataset.statusDisconnected || '',
            linkSuccess: dataset.linkSuccess || 'Linked successfully.',
            unlinkSuccess: dataset.unlinkSuccess || 'Unlinked successfully.',
            linkError: dataset.linkError || 'Unable to link. Try again.',
            unlinkError: dataset.unlinkError || 'Unable to unlink. Try again.',
            retry: dataset.retryLabel || 'Try again',
            open: dataset.openLabel || 'Open',
            unlink: dataset.unlinkLabel || 'Unlink'
        };

        function toggleSections(state) {
            loadingSection.classList.toggle('d-none', state !== 'loading');
            connectedSection.classList.toggle('d-none', state !== 'connected');
            disconnectedSection.classList.toggle('d-none', state !== 'disconnected');
        }

        function showAlert(message) {
            if (!alertElement) {
                return;
            }

            alertElement.textContent = message;
            alertElement.classList.remove('d-none');
        }

        function hideAlert() {
            if (!alertElement) {
                return;
            }

            alertElement.classList.add('d-none');
            alertElement.textContent = '';
        }

        function showToast(message, type) {
            if (!toastContainer || !message) {
                return;
            }

            const palette = {
                success: 'text-bg-success',
                error: 'text-bg-danger',
                info: 'text-bg-info'
            };
            const toast = document.createElement('div');
            toast.className = `toast align-items-center ${palette[type] || palette.info} border-0`;
            toast.role = 'status';
            toast.setAttribute('aria-live', 'polite');
            toast.innerHTML = [
                '<div class="d-flex">',
                `<div class="toast-body">${message}</div>`,
                '<button type="button" class="btn-close btn-close-white me-2 m-auto" data-bs-dismiss="toast" aria-label="Close"></button>',
                '</div>'
            ].join('');

            toastContainer.appendChild(toast);

            const toastInstance = bootstrap.Toast.getOrCreateInstance(toast, {
                delay: 4000,
                autohide: true
            });

            toast.addEventListener('hidden.bs.toast', function () {
                toast.remove();
            });

            toastInstance.show();
        }

        function updateConnectedView(username, deepLink) {
            toggleSections('connected');
            hideAlert();

            if (usernameElement) {
                usernameElement.textContent = username || '';
            }

            currentDeepLink = deepLink || null;
        }

        function updateDisconnectedView() {
            toggleSections('disconnected');
            hideAlert();

            if (!widgetMounted) {
                mountLoginWidget();
            }
        }

        function applyErrorState(message) {
            toggleSections('disconnected');
            showAlert(message || messages.error);

            if (retryButton) {
                retryButton.classList.remove('d-none');
            }
        }

        async function fetchStatus() {
            toggleSections('loading');
            hideAlert();

            try {
                const response = await fetch('/telegram/status', {
                    method: 'GET',
                    credentials: 'same-origin',
                    headers: {
                        'Accept': 'application/json'
                    }
                });

                if (response.status === 401 || response.status === 403) {
                    if (fabButton) {
                        fabButton.setAttribute('hidden', 'hidden');
                        fabButton.setAttribute('tabindex', '-1');
                    }
                    root.setAttribute('aria-hidden', 'true');
                    root.style.display = 'none';
                    return;
                }

                if (!response.ok) {
                    throw new Error('status_request_failed');
                }

                currentStatus = await response.json();

                if (currentStatus && currentStatus.connected) {
                    updateConnectedView(currentStatus.username || '', currentStatus.deepLink || null);
                } else {
                    updateDisconnectedView();
                }
            } catch (error) {
                console.warn('[Telegram FAB] Status request failed:', error);
                applyErrorState(messages.error);
            }
        }

        function mountLoginWidget() {
            const botUsernameRaw = (dataset.botUsername || '').trim();

            if (!botUsernameRaw) {
                console.warn('[Telegram FAB] Telegram bot username missing. Configure Telegram:LoginWidgetBotUsername.');
                applyErrorState(messages.error);
                return;
            }

            const botUsername = botUsernameRaw.startsWith('@')
                ? botUsernameRaw.slice(1)
                : botUsernameRaw;

            if (!widgetPlaceholder) {
                return;
            }

            widgetPlaceholder.innerHTML = '';

            const widgetScript = document.createElement('script');
            widgetScript.src = 'https://telegram.org/js/telegram-widget.js?22';
            widgetScript.async = true;
            widgetScript.dataset.telegramLogin = botUsername;
            widgetScript.dataset.size = 'large';
            widgetScript.dataset.userpic = 'false';
            widgetScript.dataset.requestAccess = dataset.requestAccess || 'write';

            const lang = (dataset.telegramLang || 'en').replace('-', '_');
            widgetScript.dataset.lang = lang;

            widgetScript.dataset.onauth = 'telegramFabOnAuth';

            widgetPlaceholder.appendChild(widgetScript);
            widgetMounted = true;
        }

        async function linkTelegram(payload) {
            toggleSections('loading');
            hideAlert();

            try {
                const response = await fetch('/telegram/link', {
                    method: 'POST',
                    credentials: 'same-origin',
                    headers: {
                        'Content-Type': 'application/json',
                        'Accept': 'application/json'
                    },
                    body: JSON.stringify(payload)
                });

                if (!response.ok) {
                    throw new Error('link_failed');
                }

                showToast(messages.linkSuccess, 'success');
                await fetchStatus();
            } catch (error) {
                console.error('[Telegram FAB] Link failed:', error);
                showToast(messages.linkError, 'error');
                applyErrorState(messages.linkError);
            }
        }

        async function unlinkTelegram() {
            toggleSections('loading');
            hideAlert();

            try {
                const response = await fetch('/telegram/unlink', {
                    method: 'POST',
                    credentials: 'same-origin',
                    headers: {
                        'Accept': 'application/json'
                    }
                });

                if (!response.ok) {
                    throw new Error('unlink_failed');
                }

                showToast(messages.unlinkSuccess, 'success');
                widgetMounted = false;
                await fetchStatus();
            } catch (error) {
                console.error('[Telegram FAB] Unlink failed:', error);
                showToast(messages.unlinkError, 'error');
                toggleSections('connected');
                showAlert(messages.unlinkError);
            }
        }

        offcanvasElement.addEventListener('show.bs.offcanvas', function () {
            fetchStatus();
        });

        if (retryButton) {
            retryButton.addEventListener('click', function () {
                hideAlert();
                fetchStatus();
            });
        }

        if (openButton) {
            openButton.addEventListener('click', function () {
                if (currentDeepLink) {
                    window.open(currentDeepLink, '_blank', 'noopener');
                } else {
                    fetchStatus();
                }
            });
        }

        if (unlinkButton) {
            unlinkButton.addEventListener('click', function () {
                unlinkTelegram();
            });
        }

        window.telegramFabOnAuth = function (user) {
            if (!user) {
                showToast(messages.linkError, 'error');
                return;
            }

            const payload = {
                id: user.id,
                hash: user.hash,
                first_name: user.first_name,
                last_name: user.last_name,
                username: user.username,
                photo_url: user.photo_url,
                auth_date: user.auth_date,
                bot_id: dataset.botId || null
            };

            linkTelegram(payload);
        };

        if (fabButton) {
            fabButton.addEventListener('keydown', function (event) {
                if (event.key === 'Enter' || event.key === ' ') {
                    event.preventDefault();
                    offcanvas.show();
                }
            });
        }
    }

    document.addEventListener('DOMContentLoaded', initTelegramFab);
    window.initTelegramFab = initTelegramFab;
})();