script.js

const items = document.querySelectorAll('.nav-item');
const sections = document.querySelectorAll('.chapter, .hero');
const sidebarToggle = document.getElementById('sidebarToggle');
const sidebar = document.getElementById('sidebarNav');
const clockTime = document.getElementById('clockTime');
const clockDate = document.getElementById('clockDate');
const calendarMonth = document.getElementById('calendarMonth');
const calendarGrid = document.getElementById('calendarGrid');
const quoteText = document.getElementById('quoteText');
const quoteAuthor = document.getElementById('quoteAuthor');

const SIDEBAR_STATE_KEY = 'cp-sidebar-collapsed';

const setSidebarState = (isCollapsed) => {
  document.body.classList.toggle('sidebar-collapsed', isCollapsed);
  if (sidebarToggle) {
    sidebarToggle.setAttribute('aria-expanded', String(!isCollapsed));
    sidebarToggle.setAttribute('aria-label', isCollapsed ? 'Expand sidebar' : 'Collapse sidebar');
  }
};

const savedSidebarState = localStorage.getItem(SIDEBAR_STATE_KEY);
if (savedSidebarState !== null) {
  setSidebarState(savedSidebarState === 'true');
}

if (sidebarToggle && sidebar) {
  sidebarToggle.addEventListener('click', () => {
    const isCollapsed = !document.body.classList.contains('sidebar-collapsed');
    setSidebarState(isCollapsed);
    localStorage.setItem(SIDEBAR_STATE_KEY, String(isCollapsed));
  });
}

window.addEventListener('scroll', () => {
  let current = '';
  sections.forEach((section) => {
    if (window.scrollY >= section.offsetTop - 100) {
      current = section.id;
    }
  });

  items.forEach((item) => {
    item.classList.toggle('active', item.getAttribute('href') === `#${current}`);
  });
});

const updateClock = () => {
  if (!clockTime || !clockDate) {
    return;
  }

  const now = new Date();
  clockTime.textContent = now.toLocaleTimeString('en-US', {
    hour12: false,
    hour: '2-digit',
    minute: '2-digit',
    second: '2-digit'
  });

  clockDate.textContent = now.toLocaleDateString('en-US', {
    weekday: 'long',
    month: 'long',
    day: 'numeric',
    year: 'numeric'
  });
};

const renderCalendar = () => {
  if (!calendarMonth || !calendarGrid) {
    return;
  }

  const today = new Date();
  const year = today.getFullYear();
  const month = today.getMonth();
  const monthStart = new Date(year, month, 1);
  const daysInMonth = new Date(year, month + 1, 0).getDate();
  const startOffset = (monthStart.getDay() + 6) % 7;

  calendarMonth.textContent = today.toLocaleDateString('en-US', {
    month: 'long',
    year: 'numeric'
  });

  calendarGrid.innerHTML = '';

  for (let i = 0; i < startOffset; i += 1) {
    const emptyCell = document.createElement('span');
    emptyCell.className = 'calendar-cell empty';
    calendarGrid.appendChild(emptyCell);
  }

  for (let day = 1; day <= daysInMonth; day += 1) {
    const dayCell = document.createElement('span');
    dayCell.className = 'calendar-cell';
    dayCell.textContent = String(day);

    if (day === today.getDate()) {
      dayCell.classList.add('today');
    }

    calendarGrid.appendChild(dayCell);
  }
};

const quotes = [
  { text: 'Discipline beats motivation when the contest starts.', author: 'CP Wisdom' },
  { text: 'First make it correct, then make it fast.', author: 'Programming Principle' },
  { text: 'Every wrong answer teaches the next accepted solution.', author: 'Contest Mindset' },
  { text: 'Patterns appear only after enough solved problems.', author: 'Daily Practice Rule' },
  { text: 'Think in constraints, code in clarity.', author: 'Problem Solving Rule' }
];

let quoteIndex = 0;

const updateQuote = () => {
  if (!quoteText || !quoteAuthor) {
    return;
  }

  const currentQuote = quotes[quoteIndex % quotes.length];
  quoteText.textContent = `"${currentQuote.text}"`;
  quoteAuthor.textContent = `- ${currentQuote.author}`;
  quoteIndex += 1;
};

updateClock();
renderCalendar();
updateQuote();

setInterval(updateClock, 1000);
setInterval(updateQuote, 10000);