// ==UserScript==
// @name         50ohm.de Quiz-Modus
// @namespace    https://50ohm.de/
// @version      0.3.0
// @description  Blendet Erklärungen aus und zeigt nur die Prüfungsfragen.
// @author       DN9KGB
// @match        https://50ohm.de/*.html
// @match        https://www.50ohm.de/*.html
// @grant        none
// @run-at       document-idle
// ==/UserScript==

(function () {
    'use strict';

    const BTN_ID = 'quiz-mode-toggle';
    const NOTICE_ID = 'quiz-mode-notice';
    const STYLE_ID = 'quiz-mode-style';
    const STORAGE_KEY = 'quiz-mode-enabled';
    const QUIZ_CLASS = 'quiz-mode-active';
    const HAS_Q_CLASS = 'quiz-has-questions';

    function injectStyles() {
        if (document.getElementById(STYLE_ID)) return;
        const s = document.createElement('style');
        s.id = STYLE_ID;
        s.textContent = `
            #${BTN_ID} {
                position: fixed; top: 12px; right: 12px; z-index: 99999;
                padding: 8px 14px;
                font: 600 14px/1 system-ui, -apple-system, sans-serif;
                color: #fff; background: #c00;
                border: none; border-radius: 6px;
                box-shadow: 0 2px 8px rgba(0,0,0,.25);
                cursor: pointer; user-select: none;
            }
            #${BTN_ID}:hover { filter: brightness(1.1); }
            #${BTN_ID}.active { background: #0a7a2a; }

            #${NOTICE_ID} {
                position: fixed; top: 54px; right: 12px; z-index: 99999;
                max-width: 260px; padding: 8px 12px;
                font: 500 13px/1.35 system-ui, -apple-system, sans-serif;
                color: #333; background: #fff3cd;
                border: 1px solid #ffe69c; border-radius: 6px;
                box-shadow: 0 2px 8px rgba(0,0,0,.15);
            }

            body.${QUIZ_CLASS}.${HAS_Q_CLASS} .course > * {
                display: none !important;
            }
            body.${QUIZ_CLASS}.${HAS_Q_CLASS} .course > h1,
            body.${QUIZ_CLASS}.${HAS_Q_CLASS} .course > nav,
            body.${QUIZ_CLASS}.${HAS_Q_CLASS} .course > .question,
            body.${QUIZ_CLASS}.${HAS_Q_CLASS} .course > [data-quiz-tail],
            body.${QUIZ_CLASS}.${HAS_Q_CLASS} .course > [data-quiz-tail] ~ * {
                display: revert !important;
            }
        `;
        document.head.appendChild(s);
    }

    function pageHasQuestions() {
        return document.querySelector('.course .question') !== null;
    }

    function tagSectionTail() {
        const course = document.querySelector('.course');
        if (!course) return false;
        course.querySelectorAll('[data-quiz-tail]').forEach(el => {
            el.removeAttribute('data-quiz-tail');
        });
        for (const child of course.children) {
            if (child.tagName !== 'DIV') continue;
            const text = (child.textContent || '').toLowerCase();
            if (text.includes('weiter zum nächsten abschnitt')) {
                child.setAttribute('data-quiz-tail', '');
                return true;
            }
        }
        return false;
    }

    function showNotice(text) {
        let n = document.getElementById(NOTICE_ID);
        if (!n) {
            n = document.createElement('div');
            n.id = NOTICE_ID;
            document.body.appendChild(n);
        }
        n.textContent = text;
    }

    function hideNotice() {
        const n = document.getElementById(NOTICE_ID);
        if (n) n.remove();
    }

    function createButton() {
        if (document.getElementById(BTN_ID)) return;
        const btn = document.createElement('button');
        btn.id = BTN_ID;
        btn.type = 'button';
        btn.addEventListener('click', () => {
            const next = !document.body.classList.contains(QUIZ_CLASS);
            setQuizMode(next);
            try { localStorage.setItem(STORAGE_KEY, next ? '1' : '0'); }
            catch (_) { /* ignore */ }
        });
        document.body.appendChild(btn);
        updateButton(btn, document.body.classList.contains(QUIZ_CLASS));
    }

    function updateButton(btn, on) {
        btn.textContent = on ? 'Quiz-Modus: an' : 'Quiz-Modus: aus';
        btn.classList.toggle('active', on);
    }

    function setQuizMode(on) {
        const hasQ = pageHasQuestions();
        document.body.classList.toggle(HAS_Q_CLASS, hasQ);
        if (on && hasQ) tagSectionTail();
        document.body.classList.toggle(QUIZ_CLASS, on);
        const btn = document.getElementById(BTN_ID);
        if (btn) updateButton(btn, on);
        if (on && !hasQ) showNotice('Keine Fragen auf dieser Seite gefunden.');
        else hideNotice();
    }

    function init() {
        injectStyles();
        createButton();
        let initial = false;
        try { initial = localStorage.getItem(STORAGE_KEY) === '1'; }
        catch (_) { /* ignore */ }
        if (initial) setQuizMode(true);
    }

    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', init);
    } else {
        init();
    }
})();