const supabaseClient = supabase.createClient(window.SUPABASE_URL, window.SUPABASE_ANON_KEY);

// ─── App state ───────────────────────────────────────────────────────────────
let totalPoints = 0;
let tasks = [];
let chapters = [];
let chapterDescriptions = {};
let activeChapter = null;
let activeClassData = null;

// ─── Auth ────────────────────────────────────────────────────────────────────

function showAuthTab(tab) {
    document.getElementById('loginForm').style.display = tab === 'login' ? 'block' : 'none';
    document.getElementById('registerForm').style.display = tab === 'register' ? 'block' : 'none';
    document.getElementById('tabLogin').classList.toggle('active', tab === 'login');
    document.getElementById('tabRegister').classList.toggle('active', tab === 'register');
}

async function login() {
    const email = document.getElementById('loginEmail').value.trim();
    const password = document.getElementById('loginPassword').value;
    const errorEl = document.getElementById('loginError');
    errorEl.textContent = '';
    const { error } = await supabaseClient.auth.signInWithPassword({ email, password });
    if (error) errorEl.textContent = error.message;
}

async function register() {
    const name = document.getElementById('registerName').value.trim();
    const email = document.getElementById('registerEmail').value.trim();
    const password = document.getElementById('registerPassword').value;
    const errorEl = document.getElementById('registerError');
    errorEl.textContent = '';

    const { data: { session }, error } = await supabaseClient.auth.signUp({
        email,
        password,
        options: { data: { display_name: name || email.split('@')[0] } },
    });

    if (error) {
        errorEl.textContent = error.message;
    } else if (!session) {
        errorEl.style.color = '#27ae60';
        errorEl.textContent = 'Konto erstellt! Bitte E-Mail bestätigen, dann anmelden.';
    }
}

async function logout() {
    await supabaseClient.auth.signOut();
}

async function getToken() {
    const { data } = await supabaseClient.auth.getSession();
    return data.session?.access_token;
}

// ─── Authenticated fetch wrapper ─────────────────────────────────────────────

async function apiFetch(url, options = {}) {
    const token = await getToken();
    const res = await fetch(url, {
        ...options,
        headers: {
            'Content-Type': 'application/json',
            Authorization: `Bearer ${token}`,
            ...options.headers,
        },
    });
    if (res.status === 401) {
        await supabaseClient.auth.signOut();
        return null;
    }
    return res;
}

// ─── Theme ───────────────────────────────────────────────────────────────────

function applyTheme(themeName) {
    let link = document.getElementById('class-theme');
    if (!link) {
        link = document.createElement('link');
        link.id = 'class-theme';
        link.rel = 'stylesheet';
        document.head.appendChild(link);
    }
    link.href = `/themes/${encodeURIComponent(themeName)}.css`;
}


// ─── Screen management ───────────────────────────────────────────────────────

function showScreen(screen) {
    document.getElementById('authOverlay').style.display = 'none';
    document.getElementById('classPickerOverlay').style.display = 'none';
    document.getElementById('classCompletionOverlay').style.display = 'none';
    document.getElementById('appWrapper').style.display = 'none';

    if (screen === 'auth') {
        document.getElementById('authOverlay').style.display = 'flex';
    } else if (screen === 'class-picker') {
        document.getElementById('classPickerOverlay').style.display = 'flex';
    } else if (screen === 'class-completion') {
        document.getElementById('classCompletionOverlay').style.display = 'flex';
    } else if (screen === 'app') {
        document.getElementById('appWrapper').style.display = 'flex';
    }
}

// ─── Class picker ────────────────────────────────────────────────────────────

async function showClassPicker() {
    showScreen('class-picker');
    const listEl = document.getElementById('classList');
    listEl.innerHTML = '<p style="opacity:0.6">Laden...</p>';

    const res = await apiFetch('/api/classes');
    if (!res) return;
    const { classes } = await res.json();

    listEl.innerHTML = '';

    if (classes.length === 0) {
        listEl.innerHTML = '<p style="opacity:0.6">Keine Klassen verfügbar.</p>';
        return;
    }

    classes.forEach(cls => {
        const card = document.createElement('div');
        card.className = 'class-card';
        const c = cls.colors || {};
        if (c.bg)     card.style.background   = c.bg;
        if (c.accent) card.style.borderColor  = c.accent;
        card.innerHTML = `
            <div class="class-card-icon">${cls.icon || '📚'}</div>
            <div class="class-card-info">
                <div class="class-card-name" style="${c.text ? `color:${c.text}` : ''}">${cls.name}</div>
                <div class="class-card-desc" style="${c.muted ? `color:${c.muted}` : ''}">${cls.description || ''}</div>
            </div>
        `;
        card.onclick = () => selectClass(cls.id);
        listEl.appendChild(card);
    });
}

async function selectClass(classId) {
    const res = await apiFetch('/api/set-class', {
        method: 'POST',
        body: JSON.stringify({ classId }),
    });
    if (!res || !res.ok) return;

    const data = await res.json();
    activeClassData = data.class;
    applyTheme(activeClassData.theme);

    const h1 = document.querySelector('header h1');
    if (h1) h1.textContent = activeClassData.name;

    activeChapter = null;
    showScreen('app');
    await loadAndRenderApp();
}

async function completeAndPickClass() {
    await apiFetch('/api/complete-class', { method: 'POST' });
    activeClassData = null;
    activeChapter = null;
    tasks = [];
    await showClassPicker();
}

// ─── App init ────────────────────────────────────────────────────────────────

async function initApp(user) {
    const displayName = user.user_metadata?.display_name || user.email;
    document.getElementById('userDisplayName').textContent = displayName;

    const meRes = await apiFetch('/api/me');
    if (!meRes) return;
    const meta = await meRes.json();

    if (!meta.activeClass) {
        await showClassPicker();
        return;
    }

    const classesRes = await apiFetch('/api/classes');
    if (classesRes) {
        const { classes } = await classesRes.json();
        activeClassData = classes.find(c => c.id === meta.activeClass) || null;
        if (activeClassData) {
            applyTheme(activeClassData.theme);
            const h1 = document.querySelector('header h1');
            if (h1) h1.textContent = activeClassData.name;
        }
    }

    showScreen('app');
    await loadAndRenderApp();
}

async function loadAndRenderApp() {
    await loadTasks();
    extractChapters();
    calculateTotalPoints();
    renderSidebar();
    renderTasks();
    updateProgress();
    checkClassCompletion();
}

supabaseClient.auth.onAuthStateChange((_event, session) => {
    if (session?.user) {
        initApp(session.user);
    } else {
        showScreen('auth');
    }
});

// ─── Tasks ───────────────────────────────────────────────────────────────────

async function loadTasks() {
    const res = await apiFetch('/api/tasks');
    if (!res) return;
    const data = await res.json();
    tasks = data.tasks || [];
}

function extractChapters() {
    const chapterSet = new Set();
    chapterDescriptions = {};

    tasks.forEach(task => {
        if (task.chapter) {
            chapterSet.add(task.chapter);
            if (task.chapterDescription && !chapterDescriptions[task.chapter]) {
                chapterDescriptions[task.chapter] = task.chapterDescription;
            }
        }
    });
    chapters = Array.from(chapterSet).sort();

    if (chapters.length > 0 && !activeChapter) {
        activeChapter = chapters[0];
    } else if (chapters.length === 0) {
        activeChapter = null;
    }
}

function calculateTotalPoints() {
    totalPoints = tasks
        .filter(task => task.isCorrect === true)
        .reduce((sum, task) => sum + (task.points || 0), 0);
    updatePointsDisplay();
}

function isChapterCompleted(chapter) {
    const chapterTasks = tasks.filter(task => task.chapter === chapter);
    return chapterTasks.length > 0 && chapterTasks.every(task => task.isCorrect === true);
}

function checkClassCompletion() {
    if (tasks.length > 0 && tasks.every(t => t.isCorrect === true)) {
        const maxPoints = tasks.reduce((sum, task) => sum + (task.points || 0), 0);
        document.getElementById('completionPoints').textContent = maxPoints;
        showScreen('class-completion');
    }
}

async function resetClassProgress(btn) {
    if (!btn.dataset.confirmed) {
        btn.dataset.confirmed = '1';
        btn.textContent = 'Wirklich löschen? Nochmal klicken.';
        btn.style.background = '#7f3030';
        btn.style.color = '#fff';
        setTimeout(() => {
            delete btn.dataset.confirmed;
            btn.textContent = 'Fortschritt zurücksetzen';
            btn.style.background = '';
            btn.style.color = '';
        }, 3000);
        return;
    }

    const res = await apiFetch('/api/reset-class-progress', { method: 'POST' });
    if (!res || !res.ok) return;

    activeChapter = null;
    await loadTasks();
    extractChapters();
    calculateTotalPoints();
    showScreen('app');
    renderSidebar();
    renderTasks();
    updateProgress();
}

function renderSidebar() {
    const sidebar = document.getElementById('sidebar');
    sidebar.innerHTML = '';

    if (chapters.length === 0) {
        sidebar.style.display = 'none';
        return;
    }
    sidebar.style.display = 'block';

    const header = document.createElement('div');
    header.className = 'sidebar-header';
    header.innerHTML = '<h2>Lektionen</h2>';
    sidebar.appendChild(header);

    chapters.forEach(chapter => {
        const isCompleted = isChapterCompleted(chapter);
        const item = document.createElement('div');
        item.className = `sidebar-item ${activeChapter === chapter ? 'active' : ''} ${isCompleted ? 'completed' : ''}`;
        item.onclick = () => switchChapter(chapter);
        item.innerHTML = `<div class="sidebar-item-title">${isCompleted ? '✓ ' : ''}${chapter}</div>`;
        sidebar.appendChild(item);
    });

}

function switchChapter(chapter) {
    activeChapter = chapter;
    renderSidebar();
    renderTasks();
}

function renderTasks() {
    const container = document.getElementById('taskContainer');
    const descriptionEl = document.getElementById('chapterDescription');
    container.innerHTML = '';

    if (activeChapter && chapterDescriptions[activeChapter]) {
        descriptionEl.textContent = chapterDescriptions[activeChapter];
        descriptionEl.style.display = 'block';
    } else {
        descriptionEl.style.display = 'none';
    }

    const visibleTasks = (activeChapter ? tasks.filter(t => t.chapter === activeChapter) : tasks)
        .filter(task => task.isCorrect !== true);

    visibleTasks.forEach(task => {
        const hasAnswer = task.userAnswer !== undefined;
        const card = document.createElement('div');
        card.className = 'task-card';
        card.id = `task-${task.id}`;
        card.innerHTML = `
            <div class="task-header">
                <div class="task-title">Aufgabe</div>
                <div class="task-points">${task.points} Punkte</div>
            </div>
            <div class="task-question">${task.question}</div>
            <div class="task-input-group">
                <input type="number" class="task-input" id="input-${task.id}"
                    placeholder="?" value="${hasAnswer ? task.userAnswer : ''}">
                <button class="task-button" onclick="checkAnswer('${task.id}')">Prüfen</button>
            </div>
            <div class="task-status ${hasAnswer && !task.isCorrect ? 'error' : ''}" id="status-${task.id}">
                ${hasAnswer && !task.isCorrect ? '✗ Falsche Antwort. Bitte erneut versuchen.' : ''}
            </div>
        `;
        container.appendChild(card);
    });
}

async function checkAnswer(taskId) {
    const task = tasks.find(t => t.id === taskId);
    if (!task || task.isCorrect === true) return;

    const input = document.getElementById(`input-${taskId}`);
    const status = document.getElementById(`status-${taskId}`);
    const userAnswer = parseInt(input.value);

    if (isNaN(userAnswer)) {
        status.textContent = 'Ungültige Eingabe. Bitte eine Zahl eingeben.';
        status.className = 'task-status error';
        return;
    }

    const res = await apiFetch('/api/check-answer', {
        method: 'POST',
        body: JSON.stringify({ taskId, answer: userAnswer }),
    });
    if (!res) return;

    const data = await res.json();

    await loadTasks();
    extractChapters();
    calculateTotalPoints();

    if (data.correct) {
        status.textContent = '✓ Richtig!';
        status.className = 'task-status success';
        showMessage(`✓ ${data.points} Punkte erhalten`, 'success');

        const taskCard = document.getElementById(`task-${taskId}`);
        if (taskCard) {
            createConfetti(taskCard);
            taskCard.classList.add('confetti-animation');
            setTimeout(() => {
                renderSidebar();
                renderTasks();
                updateProgress();
                checkClassCompletion();
            }, 1500);
        }
    } else {
        status.textContent = '✗ Falsche Antwort. Bitte erneut versuchen.';
        status.className = 'task-status error';
        input.focus();
        renderSidebar();
        renderTasks();
        updateProgress();
    }
}

// ─── UI helpers ──────────────────────────────────────────────────────────────

function updatePointsDisplay() {
    document.getElementById('totalPoints').textContent = totalPoints;
}

function updateProgress() {
    const maxPoints = tasks.reduce((sum, task) => sum + (task.points || 0), 0);
    const percentage = maxPoints > 0 ? Math.min((totalPoints / maxPoints) * 100, 100) : 0;
    document.getElementById('progressBar').style.width = `${percentage}%`;
    document.getElementById('progressText').textContent = `${totalPoints} / ${maxPoints}`;
}

function createConfetti(element) {
    const colors = ['#3498db', '#2980b9', '#34495e', '#2c3e50', '#1a252f', '#27ae60', '#16a085', '#7f8c8d'];
    const rect = element.getBoundingClientRect();

    for (let i = 0; i < 50; i++) {
        const confetti = document.createElement('div');
        confetti.className = 'confetti';
        const randomX = (Math.random() - 0.5) * 2;
        confetti.style.left = (rect.left + rect.width / 2 + (Math.random() - 0.5) * rect.width) + 'px';
        confetti.style.top = (rect.top - 10) + 'px';
        confetti.style.background = colors[Math.floor(Math.random() * colors.length)];
        confetti.style.width = (Math.random() * 8 + 6) + 'px';
        confetti.style.height = (Math.random() * 8 + 6) + 'px';
        confetti.style.animationDuration = (Math.random() * 0.8 + 0.7) + 's';
        confetti.style.animationDelay = Math.random() * 0.3 + 's';
        confetti.style.borderRadius = Math.random() > 0.5 ? '50%' : '0%';
        confetti.style.setProperty('--random-x', randomX);
        confetti.style.position = 'fixed';
        document.body.appendChild(confetti);
        setTimeout(() => confetti.remove(), 2000);
    }
}

function showMessage(text, type) {
    const message = document.getElementById('message');
    message.textContent = text;
    message.className = `message ${type} show`;
    setTimeout(() => message.classList.remove('show'), 3000);
}

// ─── Enter key support ───────────────────────────────────────────────────────

document.addEventListener('keypress', e => {
    if (e.key === 'Enter') {
        const input = document.activeElement;
        if (input?.classList.contains('task-input')) {
            checkAnswer(input.id.replace('input-', ''));
        }
        if (input?.id === 'loginPassword') login();
        if (input?.id === 'registerPassword') register();
    }
});