// =======================================================================
// Notes Application - Main Orchestrator & Router (Native ES Module)
// Zero Bundlers, Zero npm, Native browser ES6 modules
// =======================================================================

import { api } from './modules/api.js';
import { initTheme, openModal, closeModal, showToast } from './modules/ui.js';
import { initDictionary, loadInitialData } from './modules/dictionary.js';
import { initSrs, startSrsTrainingSession, openStatsDashboard } from './modules/srs.js';
import { initReader, loadBookshelf, openBook } from './modules/reader.js';
import { initCefr, loadCefrOverview, startCefrQuiz } from './modules/cefr.js';
import { initGrammar, loadGrammarUnits, openGrammarUnit } from './modules/grammar.js';

let currentUser = null;
let isRouting = false;

// -----------------------------------------------------------------------
// Mobile Navigation Active Tab
// -----------------------------------------------------------------------
export function updateMobileActiveTab(tabName) {
    document.querySelectorAll('.mobile-tab-bar .tab-item').forEach(btn => {
        btn.classList.remove('active');
    });
    if (!tabName) return;
    const target = document.getElementById(`tab-nav-${tabName}`);
    if (target) target.classList.add('active');
}

// -----------------------------------------------------------------------
// Immediate Pre-flight Routing (Zero-flicker view restoration on F5)
// -----------------------------------------------------------------------
export function applyInitialViewPreflight() {
    let hash = window.location.hash || '';
    if (!hash || hash === '#') {
        try {
            const lastView = localStorage.getItem('notes_active_view');
            const lastBookId = localStorage.getItem('notes_active_book_id');
            if (lastView === 'reader-view') {
                hash = lastBookId ? `#reader/book/${lastBookId}` : '#reader';
            } else if (lastView === 'srs-view') {
                hash = '#srs';
            } else if (lastView === 'cefr-view') {
                hash = '#cefr';
            } else if (lastView === 'grammar-view') {
                hash = '#grammar';
            }
        } catch (e) {}
    }

    const dictionaryView = document.getElementById('dictionary-view');
    const srsView = document.getElementById('srs-view');
    const readerView = document.getElementById('reader-view');
    const cefrView = document.getElementById('cefr-view');
    const grammarView = document.getElementById('grammar-view');
    const bookshelfContainer = document.getElementById('bookshelf-container');
    const readerInterface = document.getElementById('reader-interface');
    const readerBookTitle = document.getElementById('reader-book-title');

    if (hash.startsWith('#reader') || hash === '#bookshelf') {
        if (dictionaryView) dictionaryView.classList.add('hidden');
        if (srsView) srsView.classList.add('hidden');
        if (cefrView) cefrView.classList.add('hidden');
        if (grammarView) grammarView.classList.add('hidden');
        if (readerView) readerView.classList.remove('hidden');
        updateMobileActiveTab('reader');
        if (hash.includes('/book/')) {
            if (bookshelfContainer) bookshelfContainer.classList.add('hidden');
            if (readerInterface) readerInterface.classList.remove('hidden');
            if (readerBookTitle) readerBookTitle.textContent = 'Загрузка книги...';
        }
    } else if (hash.startsWith('#srs')) {
        if (dictionaryView) dictionaryView.classList.add('hidden');
        if (readerView) readerView.classList.add('hidden');
        if (cefrView) cefrView.classList.add('hidden');
        if (grammarView) grammarView.classList.add('hidden');
        if (srsView) srsView.classList.remove('hidden');
        updateMobileActiveTab('srs');
    } else if (hash.startsWith('#cefr')) {
        if (dictionaryView) dictionaryView.classList.add('hidden');
        if (readerView) readerView.classList.add('hidden');
        if (srsView) srsView.classList.add('hidden');
        if (grammarView) grammarView.classList.add('hidden');
        if (cefrView) cefrView.classList.remove('hidden');
        updateMobileActiveTab('');
    } else if (hash.startsWith('#grammar')) {
        if (dictionaryView) dictionaryView.classList.add('hidden');
        if (readerView) readerView.classList.add('hidden');
        if (srsView) srsView.classList.add('hidden');
        if (cefrView) cefrView.classList.add('hidden');
        if (grammarView) grammarView.classList.remove('hidden');
        updateMobileActiveTab('');
    }
}

// -----------------------------------------------------------------------
// View Transitions
// -----------------------------------------------------------------------
export function openDictionaryView(updateHash = true) {
    if (updateHash && window.location.hash !== '#dictionary') {
        window.location.hash = '#dictionary';
        return;
    }
    const dictionaryView = document.getElementById('dictionary-view');
    const srsView = document.getElementById('srs-view');
    const readerView = document.getElementById('reader-view');
    const cefrView = document.getElementById('cefr-view');
    const grammarView = document.getElementById('grammar-view');

    if (srsView) srsView.classList.add('hidden');
    if (readerView) readerView.classList.add('hidden');
    if (cefrView) cefrView.classList.add('hidden');
    if (grammarView) grammarView.classList.add('hidden');
    if (dictionaryView) dictionaryView.classList.remove('hidden');
    updateMobileActiveTab('dict');
    try { localStorage.setItem('notes_active_view', 'dictionary-view'); } catch (e) {}
    loadInitialData();
}

export function openSrsView(tagFilter = null, updateHash = true) {
    const targetHash = tagFilter ? `#srs/${encodeURIComponent(tagFilter)}` : '#srs';
    if (updateHash && window.location.hash !== targetHash) {
        window.location.hash = targetHash;
        return;
    }
    const dictionaryView = document.getElementById('dictionary-view');
    const srsView = document.getElementById('srs-view');
    const readerView = document.getElementById('reader-view');
    const cefrView = document.getElementById('cefr-view');
    const grammarView = document.getElementById('grammar-view');

    if (dictionaryView) dictionaryView.classList.add('hidden');
    if (readerView) readerView.classList.add('hidden');
    if (cefrView) cefrView.classList.add('hidden');
    if (grammarView) grammarView.classList.add('hidden');
    if (srsView) srsView.classList.remove('hidden');
    updateMobileActiveTab('srs');
    try { localStorage.setItem('notes_active_view', 'srs-view'); } catch (e) {}
    startSrsTrainingSession(false, tagFilter);
}

export function closeSrsView() {
    openDictionaryView(true);
}

export function openBookshelfView(updateHash = true) {
    if (updateHash && window.location.hash !== '#reader') {
        window.location.hash = '#reader';
        return;
    }
    const dictionaryView = document.getElementById('dictionary-view');
    const srsView = document.getElementById('srs-view');
    const readerView = document.getElementById('reader-view');
    const cefrView = document.getElementById('cefr-view');
    const grammarView = document.getElementById('grammar-view');
    const bookshelfContainer = document.getElementById('bookshelf-container');
    const readerInterface = document.getElementById('reader-interface');

    if (dictionaryView) dictionaryView.classList.add('hidden');
    if (srsView) srsView.classList.add('hidden');
    if (cefrView) cefrView.classList.add('hidden');
    if (grammarView) grammarView.classList.add('hidden');
    if (readerView) readerView.classList.remove('hidden');
    if (bookshelfContainer) bookshelfContainer.classList.remove('hidden');
    if (readerInterface) readerInterface.classList.add('hidden');
    updateMobileActiveTab('reader');
    try {
        localStorage.setItem('notes_active_view', 'reader-view');
        localStorage.removeItem('notes_active_book_id');
    } catch (e) {}
    loadBookshelf();
}

export function openReaderView(updateHash = true) {
    const lastBookId = localStorage.getItem('notes_active_book_id');
    if (lastBookId) {
        window.location.hash = `#reader/book/${lastBookId}`;
    } else {
        openBookshelfView(updateHash);
    }
}

export function openCefrView(level = null, mode = 'all', updateHash = true) {
    const targetHash = level
        ? (mode === 'mistakes' ? `#cefr/${encodeURIComponent(level)}/mistakes` : `#cefr/${encodeURIComponent(level)}`)
        : '#cefr';

    if (updateHash && window.location.hash !== targetHash) {
        window.location.hash = targetHash;
        return;
    }

    const dictionaryView = document.getElementById('dictionary-view');
    const srsView = document.getElementById('srs-view');
    const readerView = document.getElementById('reader-view');
    const cefrView = document.getElementById('cefr-view');
    const grammarView = document.getElementById('grammar-view');

    if (dictionaryView) dictionaryView.classList.add('hidden');
    if (srsView) srsView.classList.add('hidden');
    if (readerView) readerView.classList.add('hidden');
    if (grammarView) grammarView.classList.add('hidden');
    if (cefrView) cefrView.classList.remove('hidden');

    updateMobileActiveTab('');
    try { localStorage.setItem('notes_active_view', 'cefr-view'); } catch (e) {}

    if (level) {
        startCefrQuiz(level, mode);
    } else {
        loadCefrOverview();
    }
}

export function openGrammarView(unitId = null, updateHash = true) {
    const targetHash = unitId ? `#grammar/unit/${unitId}` : '#grammar';

    if (updateHash && window.location.hash !== targetHash) {
        window.location.hash = targetHash;
        return;
    }

    const dictionaryView = document.getElementById('dictionary-view');
    const srsView = document.getElementById('srs-view');
    const readerView = document.getElementById('reader-view');
    const cefrView = document.getElementById('cefr-view');
    const grammarView = document.getElementById('grammar-view');

    if (dictionaryView) dictionaryView.classList.add('hidden');
    if (srsView) srsView.classList.add('hidden');
    if (readerView) readerView.classList.add('hidden');
    if (cefrView) cefrView.classList.add('hidden');
    if (grammarView) grammarView.classList.remove('hidden');

    updateMobileActiveTab('');
    try { localStorage.setItem('notes_active_view', 'grammar-view'); } catch (e) {}

    if (unitId) {
        openGrammarUnit(unitId);
    } else {
        loadGrammarUnits();
    }
}

// -----------------------------------------------------------------------
// Route Handler
// -----------------------------------------------------------------------
export async function handleRouting() {
    if (isRouting) return;
    isRouting = true;
    try {
        let hash = window.location.hash || '';
        if (!hash || hash === '#') {
            try {
                const lastView = localStorage.getItem('notes_active_view');
                const lastBookId = localStorage.getItem('notes_active_book_id');
                if (lastView === 'reader-view') {
                    hash = lastBookId ? `#reader/book/${lastBookId}` : '#reader';
                    window.location.hash = hash;
                    return;
                } else if (lastView === 'srs-view') {
                    hash = '#srs';
                    window.location.hash = hash;
                    return;
                } else if (lastView === 'cefr-view') {
                    hash = '#cefr';
                    window.location.hash = hash;
                    return;
                } else if (lastView === 'grammar-view') {
                    hash = '#grammar';
                    window.location.hash = hash;
                    return;
                } else {
                    hash = '#dictionary';
                }
            } catch (e) {
                hash = '#dictionary';
            }
        }

        const cleanHash = hash.replace(/^#\/?/, '');

        if (!cleanHash || cleanHash === 'dictionary') {
            openDictionaryView(false);
        } else if (cleanHash.startsWith('srs')) {
            const parts = cleanHash.split('/');
            const tag = parts.length > 1 ? decodeURIComponent(parts.slice(1).join('/')) : null;
            openSrsView(tag, false);
        } else if (cleanHash.startsWith('cefr')) {
            const parts = cleanHash.split('/');
            const level = parts[1] || null;
            const mode = parts[2] === 'mistakes' ? 'mistakes' : 'all';
            openCefrView(level, mode, false);
        } else if (cleanHash.startsWith('grammar')) {
            const parts = cleanHash.split('/');
            if (parts[1] === 'unit' && parts[2]) {
                const unitId = parseInt(parts[2], 10);
                openGrammarView(unitId, false);
            } else {
                openGrammarView(null, false);
            }
        } else if (cleanHash.startsWith('reader') || cleanHash === 'bookshelf') {
            const parts = cleanHash.split('/');
            if (parts[1] === 'book' && parts[2]) {
                const bookId = parseInt(parts[2], 10);
                const chIdx = (parts[3] === 'ch' && parts[4] !== undefined) ? parseInt(parts[4], 10) : null;
                await openBook(bookId, chIdx, false);
            } else {
                openBookshelfView(false);
            }
        } else {
            openDictionaryView(false);
        }
    } finally {
        isRouting = false;
    }
}

// -----------------------------------------------------------------------
// Session & Auth
// -----------------------------------------------------------------------
export async function checkAuth() {
    try {
        const resp = await api.auth.me();
        if (resp.ok) {
            const data = await resp.json();
            currentUser = data.user;
            showApp();
            await handleRouting();
            loadInitialData();
        } else {
            showLogin();
        }
    } catch (e) {
        showLogin();
    }
}

export function showLogin() {
    const loginOverlay = document.getElementById('login-overlay');
    const appShell = document.getElementById('app-shell');
    const loginUsername = document.getElementById('login-username');

    if (loginOverlay) loginOverlay.classList.remove('hidden');
    if (appShell) appShell.classList.add('hidden');
    if (loginUsername) loginUsername.focus();
}

export function showApp() {
    const loginOverlay = document.getElementById('login-overlay');
    const appShell = document.getElementById('app-shell');
    const userDisplayName = document.getElementById('user-display-name');
    const mobileUserName = document.getElementById('mobile-user-name');

    if (loginOverlay) loginOverlay.classList.add('hidden');
    if (appShell) appShell.classList.remove('hidden');
    const name = currentUser ? currentUser.username : 'user';
    if (userDisplayName) userDisplayName.textContent = name;
    if (mobileUserName) mobileUserName.textContent = name;
}

// -----------------------------------------------------------------------
// Mobile Navigation & Drawer
// -----------------------------------------------------------------------
function initMobileNavigation() {
    const tabDict = document.getElementById('tab-nav-dict');
    const tabSrs = document.getElementById('tab-nav-srs');
    const tabReader = document.getElementById('tab-nav-reader');
    const tabStats = document.getElementById('tab-nav-stats');
    const tabMenu = document.getElementById('tab-nav-menu');

    const mobileMenuModal = document.getElementById('mobile-menu-modal');
    const mobileMenuToggleBtn = document.getElementById('mobile-menu-toggle-btn');
    const mobileMenuCloseBtn = document.getElementById('mobile-menu-close-btn');

    const mobileStatsBtn = document.getElementById('mobile-stats-btn');
    const mobileExportBtn = document.getElementById('mobile-export-btn');
    const mobilePwdBtn = document.getElementById('mobile-pwd-btn');
    const mobileThemeBtn = document.getElementById('mobile-theme-btn');
    const mobileLogoutBtn = document.getElementById('mobile-logout-btn');

    const exportModal = document.getElementById('export-modal');
    const changePasswordModal = document.getElementById('change-password-modal');
    const themeToggle = document.getElementById('theme-toggle');
    const logoutBtn = document.getElementById('logout-btn');

    if (tabDict) tabDict.addEventListener('click', () => { window.location.hash = '#dictionary'; });
    if (tabSrs) tabSrs.addEventListener('click', () => { window.location.hash = '#srs'; });
    if (tabReader) tabReader.addEventListener('click', () => { window.location.hash = '#reader'; });

    if (tabStats) {
        tabStats.addEventListener('click', () => {
            openStatsDashboard();
        });
    }

    function openMobileMenu() {
        if (mobileMenuModal) {
            const mobileUserName = document.getElementById('mobile-user-name');
            if (mobileUserName && currentUser) {
                mobileUserName.textContent = currentUser.username;
            }
            openModal(mobileMenuModal);
        }
    }

    function closeMobileMenu() {
        if (mobileMenuModal) {
            closeModal(mobileMenuModal);
        }
    }

    if (tabMenu) tabMenu.addEventListener('click', openMobileMenu);
    if (mobileMenuToggleBtn) mobileMenuToggleBtn.addEventListener('click', openMobileMenu);
    if (mobileMenuCloseBtn) mobileMenuCloseBtn.addEventListener('click', closeMobileMenu);

    if (mobileMenuModal) {
        mobileMenuModal.addEventListener('click', (e) => {
            if (e.target === mobileMenuModal) closeMobileMenu();
        });
    }

    const mobileGrammarBtn = document.getElementById('mobile-grammar-btn');
    if (mobileGrammarBtn) {
        mobileGrammarBtn.addEventListener('click', () => {
            closeMobileMenu();
            openGrammarView(null, true);
        });
    }

    const mobileCefrBtn = document.getElementById('mobile-cefr-btn');
    if (mobileCefrBtn) {
        mobileCefrBtn.addEventListener('click', () => {
            closeMobileMenu();
            openCefrView(null, 'all', true);
        });
    }

    if (mobileStatsBtn) {
        mobileStatsBtn.addEventListener('click', () => {
            closeMobileMenu();
            openStatsDashboard();
        });
    }

    if (mobileExportBtn && exportModal) {
        mobileExportBtn.addEventListener('click', () => {
            closeMobileMenu();
            openModal(exportModal);
        });
    }

    if (mobilePwdBtn && changePasswordModal) {
        mobilePwdBtn.addEventListener('click', () => {
            closeMobileMenu();
            openModal(changePasswordModal);
        });
    }

    if (mobileThemeBtn && themeToggle) {
        mobileThemeBtn.addEventListener('click', () => {
            themeToggle.click();
        });
    }

    if (mobileLogoutBtn && logoutBtn) {
        mobileLogoutBtn.addEventListener('click', () => {
            closeMobileMenu();
            logoutBtn.click();
        });
    }
}

// -----------------------------------------------------------------------
// Password Change Modal
// -----------------------------------------------------------------------
function initChangePasswordModal() {
    const changePasswordModal = document.getElementById('change-password-modal');
    const closeChangePwdBtn = document.getElementById('close-change-pwd-btn');
    const changePwdCancelBtn = document.getElementById('change-pwd-cancel-btn');
    const changePwdOpenBtn = document.getElementById('change-pwd-open-btn');
    const changePasswordForm = document.getElementById('change-password-form');
    const currentPasswordInput = document.getElementById('current-password-input');
    const newPasswordInput = document.getElementById('new-password-input');
    const confirmPasswordInput = document.getElementById('confirm-password-input');
    const changePwdError = document.getElementById('change-pwd-error');
    const changePwdSuccess = document.getElementById('change-pwd-success');

    if (changePwdOpenBtn && changePasswordModal) {
        changePwdOpenBtn.addEventListener('click', () => {
            if (changePwdError) changePwdError.classList.add('hidden');
            if (changePwdSuccess) changePwdSuccess.classList.add('hidden');
            if (currentPasswordInput) currentPasswordInput.value = '';
            if (newPasswordInput) newPasswordInput.value = '';
            if (confirmPasswordInput) confirmPasswordInput.value = '';
            openModal(changePasswordModal);
            if (currentPasswordInput) currentPasswordInput.focus();
        });
    }

    if (closeChangePwdBtn && changePasswordModal) {
        closeChangePwdBtn.addEventListener('click', () => closeModal(changePasswordModal));
    }
    if (changePwdCancelBtn && changePasswordModal) {
        changePwdCancelBtn.addEventListener('click', () => closeModal(changePasswordModal));
    }

    if (changePasswordForm) {
        changePasswordForm.addEventListener('submit', async (e) => {
            e.preventDefault();
            if (changePwdError) changePwdError.classList.add('hidden');
            if (changePwdSuccess) changePwdSuccess.classList.add('hidden');

            const currentPwd = currentPasswordInput ? currentPasswordInput.value : '';
            const newPwd = newPasswordInput ? newPasswordInput.value : '';
            const confirmPwd = confirmPasswordInput ? confirmPasswordInput.value : '';

            if (newPwd !== confirmPwd) {
                if (changePwdError) {
                    changePwdError.textContent = 'Новые пароли не совпадают';
                    changePwdError.classList.remove('hidden');
                }
                return;
            }

            try {
                const resp = await api.auth.changePassword(currentPwd, newPwd);
                const data = await resp.json();
                if (resp.ok) {
                    if (changePwdSuccess) {
                        changePwdSuccess.textContent = 'Пароль успешно обновлен!';
                        changePwdSuccess.classList.remove('hidden');
                    }
                    setTimeout(() => {
                        if (changePasswordModal) closeModal(changePasswordModal);
                    }, 1200);
                } else {
                    if (changePwdError) {
                        changePwdError.textContent = data.detail || 'Ошибка смены пароля';
                        changePwdError.classList.remove('hidden');
                    }
                }
            } catch (err) {
                if (changePwdError) {
                    changePwdError.textContent = 'Ошибка сетевого соединения';
                    changePwdError.classList.remove('hidden');
                }
            }
        });
    }
}

// -----------------------------------------------------------------------
// Initialization & Entry Point
// -----------------------------------------------------------------------
document.addEventListener('DOMContentLoaded', () => {
    // 1. PWA Service Worker Registration
    if ('serviceWorker' in navigator) {
        navigator.serviceWorker.register('/sw.js', { scope: '/' })
            .then(reg => console.log('Notes PWA ServiceWorker active:', reg.scope))
            .catch(err => console.log('Notes ServiceWorker failed:', err));
    }

    // 2. Pre-flight routing check to avoid DOM flicker on reload
    applyInitialViewPreflight();

    // 3. UI theme initialization
    initTheme();

    // 4. Initialize Feature Modules
    initDictionary();
    initSrs();
    initReader();
    initCefr();
    initGrammar();

    // 5. Global Navigation & Header Actions
    const navBrandHome = document.getElementById('nav-brand-home');
    const navReaderBtn = document.getElementById('nav-reader-btn');
    const navCefrBtn = document.getElementById('nav-cefr-btn');
    const navGrammarBtn = document.getElementById('nav-grammar-btn');
    const srsTrainerBtn = document.getElementById('srs-trainer-btn');
    const srsJumpCefrBtn = document.getElementById('srs-jump-cefr-btn');
    const loginForm = document.getElementById('login-form');
    const loginUsername = document.getElementById('login-username');
    const loginPassword = document.getElementById('login-password');
    const loginError = document.getElementById('login-error');
    const logoutBtn = document.getElementById('logout-btn');

    if (navBrandHome) {
        navBrandHome.addEventListener('click', () => { window.location.hash = '#dictionary'; });
    }
    if (navReaderBtn) {
        navReaderBtn.addEventListener('click', () => { window.location.hash = '#reader'; });
    }
    if (navCefrBtn) {
        navCefrBtn.addEventListener('click', () => { window.location.hash = '#cefr'; });
    }
    if (navGrammarBtn) {
        navGrammarBtn.addEventListener('click', () => { window.location.hash = '#grammar'; });
    }
    if (srsTrainerBtn) {
        srsTrainerBtn.addEventListener('click', () => { window.location.hash = '#srs'; });
    }
    if (srsJumpCefrBtn) {
        srsJumpCefrBtn.addEventListener('click', () => { window.location.hash = '#cefr'; });
    }

    // 6. Mobile Tab Bar & Drawer
    initMobileNavigation();

    // 7. Change Password Modal
    initChangePasswordModal();

    // 8. Hash Change Listener
    window.addEventListener('hashchange', handleRouting);

    // 9. Auth Actions
    if (loginForm) {
        loginForm.addEventListener('submit', async (e) => {
            e.preventDefault();
            if (loginError) loginError.classList.add('hidden');
            try {
                const resp = await api.auth.login(
                    loginUsername ? loginUsername.value.trim() : '',
                    loginPassword ? loginPassword.value : ''
                );
                const data = await resp.json();
                if (resp.ok && data.status === 'ok') {
                    if (data.token) {
                        localStorage.setItem('notes_token', data.token);
                    }
                    currentUser = data.user;
                    showApp();
                    await handleRouting();
                    loadInitialData();
                } else {
                    if (loginError) {
                        loginError.textContent = data.detail || 'Неверный логин или пароль';
                        loginError.classList.remove('hidden');
                    }
                }
            } catch (err) {
                if (loginError) {
                    loginError.textContent = 'Ошибка сетевого соединения';
                    loginError.classList.remove('hidden');
                }
            }
        });
    }

    if (logoutBtn) {
        logoutBtn.addEventListener('click', async () => {
            localStorage.removeItem('notes_token');
            localStorage.removeItem('notes_active_book_id');
            try { await api.auth.logout(); } catch (e) {}
            currentUser = null;
            window.location.hash = '';
            window.location.reload();
        });
    }

    // 10. Check Session Auth & Kickoff
    checkAuth();
});