document.addEventListener('DOMContentLoaded', () => {
    // --- Password Strength Checker for Registration ---
    const passwordInput = document.getElementById('password');
    const passwordStrengthDiv = document.getElementById('password-strength');
    const passwordCriteriaUl = passwordStrengthDiv ? passwordStrengthDiv.querySelector('ul') : null;


    if (passwordInput && passwordStrengthDiv && passwordCriteriaUl) {
        const criteria = [
            { regex: /.{8,}/, message: "At least 8 characters", id: "len" },
            { regex: /[A-Z]/, message: "An uppercase letter", id: "upper" },
            { regex: /[a-z]/, message: "A lowercase letter", id: "lower" },
            { regex: /[0-9]/, message: "A number", id: "num" },
            { regex: /[^A-Za-z0-9]/, message: "A special character", id: "special" }
        ];

        // Populate criteria list
        criteria.forEach(c => {
            const li = document.createElement('li');
            li.id = `crit-${c.id}`;
            li.textContent = `✗ ${c.message}`;
            li.classList.add('invalid');
            passwordCriteriaUl.appendChild(li);
        });
        
        passwordInput.addEventListener('input', () => {
            const password = passwordInput.value;
            let strengthScore = 0;

            criteria.forEach(c => {
                const li = document.getElementById(`crit-${c.id}`);
                if (c.regex.test(password)) {
                    li.textContent = `✓ ${c.message}`;
                    li.classList.remove('invalid');
                    li.classList.add('valid');
                    strengthScore++;
                } else {
                    li.textContent = `✗ ${c.message}`;
                    li.classList.remove('valid');
                    li.classList.add('invalid');
                }
            });

            const strengthBar = document.querySelector('.password-strength-meter div');
            if (strengthBar) {
                strengthBar.style.width = (strengthScore / criteria.length * 100) + '%';
                if (strengthScore < 2) strengthBar.style.backgroundColor = 'red';
                else if (strengthScore < 4) strengthBar.style.backgroundColor = 'orange';
                else strengthBar.style.backgroundColor = 'green';
            }
            
            if (password.length === 0) {
                 if (strengthBar) strengthBar.style.width = '0%';
            }
        });
         // Trigger initial check if there's a value (e.g. browser autofill)
        if(passwordInput.value) passwordInput.dispatchEvent(new Event('input'));
    }

    // --- Drag and Drop File Upload ---
    const dropZone = document.getElementById('drop-zone');
    const noteTitleInput = document.getElementById('title'); 
    const noteContentInput = document.getElementById('content'); 
    const markdownPreview = document.getElementById('markdown-preview'); 

    if (dropZone && noteTitleInput && noteContentInput) {
        dropZone.addEventListener('dragover', (event) => {
            event.preventDefault();
            dropZone.classList.add('drag-over');
        });
        dropZone.addEventListener('dragleave', () => {
            dropZone.classList.remove('drag-over');
        });
        dropZone.addEventListener('drop', (event) => {
            event.preventDefault();
            dropZone.classList.remove('drag-over');
            const files = event.dataTransfer.files;
            if (files.length > 0) {
                const file = files[0];
                if (file.type === 'text/plain' || file.type === 'text/markdown' || file.name.endsWith('.md') || file.name.endsWith('.txt')) {
                    const reader = new FileReader();
                    reader.onload = (e) => {
                        noteTitleInput.value = file.name.replace(/\.(md|txt)$/i, '');
                        noteContentInput.value = e.target.result;
                        if (window.updateMarkdownPreview) updateMarkdownPreview(); 
                    };
                    reader.readAsText(file);
                } else {
                    displayMessage('Please drop a .txt or .markdown file.', 'info');
                }
            }
        });
    }
    
    if (noteContentInput && markdownPreview && typeof showdown !== 'undefined') { 
        const converter = new showdown.Converter({sanitize: true}); 
        window.updateMarkdownPreview = function() {
            markdownPreview.innerHTML = converter.makeHtml(noteContentInput.value);
        }
        noteContentInput.addEventListener('input', window.updateMarkdownPreview);
        if(noteContentInput.value) window.updateMarkdownPreview(); 
    } else if (noteContentInput && markdownPreview) {
        noteContentInput.addEventListener('input', () => {
             markdownPreview.textContent = "Preview updates on save (or include Showdown.js library for live preview).";
        });
         if(noteContentInput.value) markdownPreview.textContent = "Preview updates on save (or include Showdown.js library for live preview).";
    }


    // --- Table Sorting ---
    document.querySelectorAll('.notes-table th[data-sort]').forEach(headerCell => {
        headerCell.addEventListener('click', () => {
            const sortBy = headerCell.dataset.sort;
            const currentUrl = new URL(window.location.href);
            const currentSortBy = currentUrl.searchParams.get('sort_by');
            const currentSortOrder = currentUrl.searchParams.get('sort_order') || 'asc'; // Default to asc if not set
            
            let newSortOrder = 'asc';
            if (sortBy === currentSortBy && currentSortOrder.toLowerCase() === 'asc') {
                newSortOrder = 'desc';
            }
            // If different column, or current is desc, start with asc for the new column
            
            currentUrl.searchParams.set('sort_by', sortBy);
            currentUrl.searchParams.set('sort_order', newSortOrder);
            window.location.href = currentUrl.toString();
        });
    });
}); // End DOMContentLoaded

function displayMessage(message, type = 'info') {
    const existingAlert = document.querySelector('#alert-container .alert');
    if (existingAlert) {
        existingAlert.remove();
    }

    const alertDiv = document.createElement('div');
    alertDiv.className = `alert alert-${type}`;
    alertDiv.innerHTML = message; // Use innerHTML if message contains HTML (e.g. list from server)
    
    let alertContainer = document.getElementById('alert-container');
    if (!alertContainer) {
        alertContainer = document.createElement('div');
        alertContainer.id = 'alert-container';
        alertContainer.style.position = 'fixed';
        alertContainer.style.top = '70px'; 
        alertContainer.style.left = '50%';
        alertContainer.style.transform = 'translateX(-50%)';
        alertContainer.style.zIndex = '1000';
        alertContainer.style.width = 'auto'; // Fit content
        alertContainer.style.minWidth = '300px';
        alertContainer.style.maxWidth = '90%';
        document.body.prepend(alertContainer);
    }
    alertContainer.appendChild(alertDiv);

    setTimeout(() => {
        alertDiv.style.opacity = '0';
        alertDiv.style.transition = 'opacity 0.5s ease-out';
        setTimeout(() => { 
            if (alertDiv.parentNode) alertDiv.remove();
        }, 500);
    }, 5000); 
}