script.js

document.addEventListener("DOMContentLoaded", function () {

    // --- Data Storage ---
    // This will hold the entire data structure from parameters.json
    let allData = {};

    // --- Element References ---
    const searchBranchContainer = document.getElementById("search-parameters-branch");
    const searchSemesterContainer = document.getElementById("search-parameters-semester");
    const searchSubjectContainer = document.getElementById("search-parameters-subject");

    // --- Helper Function to create dropdowns (to avoid repeating code) ---
    function createDropdown(container, id, defaultText, options) {
        // Clear the container first
        container.innerHTML = '';

        // Create the <select> element
        const select = document.createElement("select");
        select.id = id;
        select.className = "search-parameters-select";

        // Create the disabled default option
        const defaultOption = document.createElement("option");
        defaultOption.disabled = true;
        defaultOption.selected = true;
        defaultOption.innerHTML = defaultText;
        select.appendChild(defaultOption);

        // Create options from the provided array
        options.forEach(opt => {
            const option = document.createElement("option");
            option.value = opt;
            option.innerHTML = opt;
            select.appendChild(option);
        });

        // Add the new dropdown to the page
        container.appendChild(select);
        return select; // Return the created select element
    }

    // --- Functions to Update Dropdowns ---

    // Function to update the Semester dropdown based on the selected Branch
    function updateSemesters() {
        const selectedBranch = document.getElementById("selectBranch").value;
        let semesterNames = [];

        // Clear the subsequent dropdowns
        searchSemesterContainer.innerHTML = '';
        searchSubjectContainer.innerHTML = '';

        // Find the selected branch in our data and get its semesters
        const branchData = allData.branches.find(b => b.name === selectedBranch);
        if (branchData && branchData.semesters) {
            semesterNames = branchData.semesters.map(sem => sem.semester);
        }

        // Create the new semester dropdown
        const semesterSelect = createDropdown(searchSemesterContainer, "selectSemester", "Select Semester", semesterNames);
        
        // IMPORTANT: Add an event listener to the NEW semester dropdown
        semesterSelect.addEventListener("change", updateSubjects);
    }

    // Function to update the Subject dropdown based on the selected Semester
    function updateSubjects() {
        const selectedBranch = document.getElementById("selectBranch").value;
        const selectedSemester = document.getElementById("selectSemester").value;
        let subjectNames = [];
        
        // Clear the subject dropdown
        searchSubjectContainer.innerHTML = '';

        // Find the selected branch and semester to get the subjects
        const branchData = allData.branches.find(b => b.name === selectedBranch);
        if (branchData && branchData.semesters) {
            const semesterData = branchData.semesters.find(sem => sem.semester == selectedSemester);
            if (semesterData && semesterData.subjects) {
                // Extracts the name of the subject
                subjectNames = semesterData.subjects.map(sub => Object.values(sub)[0]);
            }
        }
        
        // Create the new subject dropdown
        createDropdown(searchSubjectContainer, "selectSubject", "Select Subject", subjectNames);
    }

    // --- Main Logic: Fetch data and initialize the first dropdown ---
    fetch("data/search_parameters/parameters.json")
        .then(res => res.json())
        .then(data => {
            allData = data; // Store all data globally within this script's scope
            const branchNames = allData.branches.map(b => b.name);
            const branchSelect = createDropdown(searchBranchContainer, "selectBranch", "Select Branch", branchNames);
            
            // Add the event listener to the main branch dropdown
            branchSelect.addEventListener("change", updateSemesters);
        })
        .catch(error => console.error("Error fetching parameters:", error));


    // --- Typewriter Effect ---
    // This is the single, corrected typewriter function
    const words = ["Branch", "Semester", "Subject", "Year"];
    let currentWordIndex = 0;
    let charIndex = 0;
    let isDeleting = false;

    function typeWriterEffect() {
        const currentWord = words[currentWordIndex];
        const typewriterElement = document.getElementById('typeWriterText');

        if (!typewriterElement) return; // Stop if the element doesn't exist

        if (isDeleting) {
            typewriterElement.textContent = currentWord.substring(0, charIndex - 1);
            charIndex--;
        } else {
            typewriterElement.textContent = currentWord.substring(0, charIndex + 1);
            charIndex++;
        }

        let typeSpeed = isDeleting ? 75 : 150; // Slower, more natural speeds

        if (!isDeleting && charIndex === currentWord.length) {
            typeSpeed = 2000; // Pause after typing a word
            isDeleting = true;
        } else if (isDeleting && charIndex === 0) {
            isDeleting = false;
            currentWordIndex = (currentWordIndex + 1) % words.length;
            typeSpeed = 500; // Pause before starting a new word
        }

        setTimeout(typeWriterEffect, typeSpeed);
    }
    
    // Start the typewriter
    typeWriterEffect();

    
    // --- Mobile Menu Toggle Functionality ---
    const nav = document.getElementById('header-navigation');
    const hamburger = document.getElementById('hamburgerMenu');

    if(hamburger) {
        hamburger.addEventListener('click', () => {
             nav.classList.toggle('show');
             hamburger.classList.toggle('active');
        });
    }

    document.addEventListener('click', function(event) {
        if (nav && hamburger && !nav.contains(event.target) && !hamburger.contains(event.target)) {
            nav.classList.remove('show');
            hamburger.classList.remove('active');
        }
    });

    // --- Theme Toggle ---
    function toggleTheme() {
        const html = document.documentElement;
        const currentTheme = html.getAttribute('data-theme') || 'light';
        const newTheme = currentTheme === 'dark' ? 'light' : 'dark';
        html.setAttribute('data-theme', newTheme);
        localStorage.setItem('theme', newTheme);
    }

    const themeToggleButton = document.getElementById('themeToggle');
    if(themeToggleButton) {
        themeToggleButton.addEventListener('click', toggleTheme);
    }

    // Initialize theme on page load
    (function initTheme() {
        const savedTheme = localStorage.getItem('theme');
        const prefersDark = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches;
        document.documentElement.setAttribute('data-theme', savedTheme || (prefersDark ? 'dark' : 'light'));
    })();
    
  document.querySelectorAll(".upload-btn").forEach(btn => {
  btn.addEventListener("click", () => {
    window.location.href = "upload.html";
  });
});


// Update the DOMContentLoaded event listener to include theme initialization



const branchFilter = document.getElementById("branch-filter");
const semesterFilter = document.getElementById("semester-filter");
const subjectFilter = document.getElementById("subject-filter");
const notesContainer = document.getElementById("notes-container");

const subjectMap = {
  "CSE": ["Maths", "DBMS", "OS", "DSA"],
  "CSE AIML": ["AI", "ML", "Python"],
  "CSE IOT": ["IoT Fundamentals", "Sensors", "Microcontrollers"],
  "CSE DS": ["Data Science Basics", "Statistics", "Python for DS"]
};

let notesData = [];

fetch("data/notes.json")
  .then(res => res.json())
  .then(data => {
    notesData = data;
    updateSubjects("");
    displayNotes(notesData);
  });

function updateSubjects(branch) {
  subjectFilter.innerHTML = '<option value="">All Subjects</option>';
  const subjects = subjectMap[branch] || [].concat(...Object.values(subjectMap));
  [...new Set(subjects)].forEach(sub => {
    const opt = document.createElement("option");
    opt.value = sub;
    opt.textContent = sub;
    subjectFilter.appendChild(opt);
  });
}

function displayNotes(notes) {
  notesContainer.innerHTML = notes.length === 0 ? "<p>No notes found.</p>" : "";
  notes.forEach(note => {
    const card = document.createElement("div");
    card.className = "note-card";
    card.innerHTML = `
      <h3>${note.title}</h3>
      <p><strong>Branch:</strong> ${note.branch}</p>
      <p><strong>Semester:</strong> ${note.semester}</p>
      <p><strong>Subject:</strong> ${note.subject}</p>
      <a href="${note.link}" target="_blank" download>Download</a>
    `;
    notesContainer.appendChild(card);
  });
}

[branchFilter, semesterFilter, subjectFilter].forEach(filter => {
  filter.addEventListener("change", () => {
    const branchVal = branchFilter.value;
    if (filter === branchFilter) updateSubjects(branchVal);
    const filtered = notesData.filter(note =>
      (branchVal === "" || note.branch === branchVal) &&
      (semesterFilter.value === "" || note.semester === semesterFilter.value) &&
      (subjectFilter.value === "" || note.subject === subjectFilter.value)
    );
    displayNotes(filtered);
  });
});

});