const API_URL = '/api';
let allDrugs = [];
let currentDrug = null;
let showLowStockOnly = false;
let searchTerm = '';
let expandedDrugs = new Set();
let currentUser = null;
let accessToken = null;

// Toast notification system
function showToast(message, type = 'info', duration = 3000) {
    const container = document.getElementById('toastContainer');
    if (!container) return;
    
    const toast = document.createElement('div');
    toast.className = `toast ${type}`;
    
    const icons = {
        success: '✓',
        error: '✕',
        warning: '⚠',
        info: 'ℹ'
    };
    
    toast.innerHTML = `
        <span class="toast-icon">${icons[type] || icons.info}</span>
        <span class="toast-message">${message}</span>
    `;
    
    container.appendChild(toast);
    
    // Auto remove after duration
    setTimeout(() => {
        toast.classList.add('fade-out');
        setTimeout(() => {
            container.removeChild(toast);
        }, 300);
    }, duration);
}

// Initialize on page load
document.addEventListener('DOMContentLoaded', () => {
    checkAuth();
});

// Check if user is already logged in
function checkAuth() {
    const token = localStorage.getItem('accessToken');
    const user = localStorage.getItem('currentUser');
    
    if (token && user) {
        accessToken = token;
        currentUser = JSON.parse(user);
        showMainApp();
    } else {
        showLoginPage();
    }
}

// Show login page
function showLoginPage() {
    document.getElementById('loginPage').style.display = 'flex';
    document.getElementById('mainApp').style.display = 'none';
    
    const loginForm = document.getElementById('loginForm');
    if (loginForm) loginForm.addEventListener('submit', handleLogin);
}

// Show main app
function showMainApp() {
    document.getElementById('loginPage').style.display = 'none';
    document.getElementById('mainApp').style.display = 'block';
    
    const userDisplay = document.getElementById('currentUser');
    if (userDisplay) {
        userDisplay.textContent = `👤 ${currentUser.username}`;
    }
    
    const adminBtn = document.getElementById('adminBtn');
    if (adminBtn) {
        adminBtn.style.display = currentUser.is_admin ? 'block' : 'none';
    }
    
    setupEventListeners();
    loadDrugs();
}

// Handle login
async function handleLogin(e) {
    e.preventDefault();
    const username = document.getElementById('loginUsername').value;
    const password = document.getElementById('loginPassword').value;
    
    try {
        const response = await fetch(`${API_URL}/auth/login`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ username, password })
        });
        
        if (!response.ok) {
            throw new Error('Invalid credentials');
        }
        
        const data = await response.json();
        accessToken = data.access_token;
        currentUser = data.user;
        
        localStorage.setItem('accessToken', accessToken);
        localStorage.setItem('currentUser', JSON.stringify(currentUser));
        
        document.getElementById('loginForm').reset();
        const errorDiv = document.getElementById('loginError');
        if (errorDiv) errorDiv.style.display = 'none';
        showMainApp();
    } catch (error) {
        const errorDiv = document.getElementById('loginError');
        if (errorDiv) {
            errorDiv.textContent = error.message;
            errorDiv.style.display = 'block';
        }
    }
}

// Handle register
// Logout
function handleLogout() {
    localStorage.removeItem('accessToken');
    localStorage.removeItem('currentUser');
    accessToken = null;
    currentUser = null;
    const loginForm = document.getElementById('loginForm');
    if (loginForm) loginForm.reset();
    const registerForm = document.getElementById('registerForm');
    if (registerForm) {
        registerForm.style.display = 'none';
    }
    const form = document.getElementById('loginForm');
    if (form) form.style.display = 'block';
    showLoginPage();
}

// API helper with authentication
async function apiCall(endpoint, options = {}) {
    const headers = {
        'Content-Type': 'application/json',
        ...options.headers
    };
    
    if (accessToken) {
        headers['Authorization'] = `Bearer ${accessToken}`;
    }
    
    const response = await fetch(`${API_URL}${endpoint}`, {
        ...options,
        headers
    });
    
    if (response.status === 401) {
        handleLogout();
        throw new Error('Authentication expired');
    }
    
    return response;
}

// Setup event listeners
function setupEventListeners() {
    const drugForm = document.getElementById('drugForm');
    const variantForm = document.getElementById('variantForm');
    const editVariantForm = document.getElementById('editVariantForm');
    const dispenseForm = document.getElementById('dispenseForm');
    const prescribeForm = document.getElementById('prescribeForm');
    const editForm = document.getElementById('editForm');
    const addModal = document.getElementById('addModal');
    const addVariantModal = document.getElementById('addVariantModal');
    const editVariantModal = document.getElementById('editVariantModal');
    const dispenseModal = document.getElementById('dispenseModal');
    const prescribeModal = document.getElementById('prescribeModal');
    const editModal = document.getElementById('editModal');
    const addDrugBtn = document.getElementById('addDrugBtn');
    const dispenseBtn = document.getElementById('dispenseBtn');
    const cancelAddBtn = document.getElementById('cancelAddBtn');
    const cancelVariantBtn = document.getElementById('cancelVariantBtn');
    const cancelEditVariantBtn = document.getElementById('cancelEditVariantBtn');
    const cancelDispenseBtn = document.getElementById('cancelDispenseBtn');
    const cancelPrescribeBtn = document.getElementById('cancelPrescribeBtn');
    const cancelEditBtn = document.getElementById('cancelEditBtn');
    const showAllBtn = document.getElementById('showAllBtn');
    const showLowStockBtn = document.getElementById('showLowStockBtn');
    const userMenuBtn = document.getElementById('userMenuBtn');
    const adminBtn = document.getElementById('adminBtn');
    const logoutBtn = document.getElementById('logoutBtn');
    const changePasswordBtn = document.getElementById('changePasswordBtn');

    // Modal close buttons
    const closeButtons = document.querySelectorAll('.close');

    if (drugForm) drugForm.addEventListener('submit', handleAddDrug);
    if (variantForm) variantForm.addEventListener('submit', handleAddVariant);
    if (editVariantForm) editVariantForm.addEventListener('submit', handleEditVariant);
    if (dispenseForm) dispenseForm.addEventListener('submit', handleDispenseDrug);
    if (prescribeForm) prescribeForm.addEventListener('submit', handlePrescribeDrug);
    if (editForm) editForm.addEventListener('submit', handleEditDrug);
    
    if (addDrugBtn) addDrugBtn.addEventListener('click', () => openModal(addModal));
    if (dispenseBtn) dispenseBtn.addEventListener('click', () => {
        updateDispenseDrugSelect();
        openModal(dispenseModal);
    });
    
    if (cancelAddBtn) cancelAddBtn.addEventListener('click', () => closeModal(addModal));
    if (cancelVariantBtn) cancelVariantBtn.addEventListener('click', () => closeModal(addVariantModal));
    if (cancelEditVariantBtn) cancelEditVariantBtn.addEventListener('click', () => closeModal(editVariantModal));
    if (cancelDispenseBtn) cancelDispenseBtn.addEventListener('click', () => closeModal(dispenseModal));
    if (cancelPrescribeBtn) cancelPrescribeBtn.addEventListener('click', () => closeModal(prescribeModal));
    if (cancelEditBtn) cancelEditBtn.addEventListener('click', closeEditModal);
    
    const closeHistoryBtn = document.getElementById('closeHistoryBtn');
    if (closeHistoryBtn) closeHistoryBtn.addEventListener('click', () => closeModal(document.getElementById('historyModal')));
    
    const closeUserManagementBtn = document.getElementById('closeUserManagementBtn');
    if (closeUserManagementBtn) closeUserManagementBtn.addEventListener('click', () => closeModal(document.getElementById('userManagementModal')));
    
    const changePasswordForm = document.getElementById('changePasswordForm');
    if (changePasswordForm) changePasswordForm.addEventListener('submit', handleChangePassword);
    
    const cancelChangePasswordBtn = document.getElementById('cancelChangePasswordBtn');
    if (cancelChangePasswordBtn) cancelChangePasswordBtn.addEventListener('click', () => closeModal(document.getElementById('changePasswordModal')));
    
    const adminChangePasswordForm = document.getElementById('adminChangePasswordForm');
    if (adminChangePasswordForm) adminChangePasswordForm.addEventListener('submit', handleAdminChangePassword);
    
    const cancelAdminChangePasswordBtn = document.getElementById('cancelAdminChangePasswordBtn');
    if (cancelAdminChangePasswordBtn) cancelAdminChangePasswordBtn.addEventListener('click', () => closeModal(document.getElementById('adminChangePasswordModal')));
    
    closeButtons.forEach(btn => btn.addEventListener('click', (e) => {
        const modal = e.target.closest('.modal');
        closeModal(modal);
    }));
    
    if (showAllBtn) showAllBtn.addEventListener('click', () => {
        showLowStockOnly = false;
        updateFilterButtons();
        renderDrugs();
    });
    if (showLowStockBtn) showLowStockBtn.addEventListener('click', () => {
        showLowStockOnly = true;
        updateFilterButtons();
        renderDrugs();
    });
    
    // User menu
    if (userMenuBtn) userMenuBtn.addEventListener('click', () => {
        const dropdown = document.getElementById('userDropdown');
        if (dropdown) dropdown.style.display = dropdown.style.display === 'none' ? 'block' : 'none';
    });
    
    if (changePasswordBtn) changePasswordBtn.addEventListener('click', openChangePasswordModal);
    if (adminBtn) adminBtn.addEventListener('click', openUserManagement);
    if (logoutBtn) logoutBtn.addEventListener('click', handleLogout);

    // Search functionality
    const drugSearch = document.getElementById('drugSearch');
    if (drugSearch) {
        let searchTimeout;
        drugSearch.addEventListener('input', (e) => {
            clearTimeout(searchTimeout);
            searchTimeout = setTimeout(() => {
                searchTerm = e.target.value.toLowerCase().trim();
                renderDrugs();
            }, 150);
        });
    }

    // Close modal when clicking outside
    window.addEventListener('click', (e) => {
        if (e.target.classList.contains('modal')) {
            closeModal(e.target);
        }
    });
}

// Load drugs from API
async function loadDrugs() {
    try {
        const response = await apiCall('/drugs');
        if (!response.ok) throw new Error('Failed to load drugs');
        allDrugs = await response.json();
        
        renderDrugs();
        updateDispenseDrugSelect();
    } catch (error) {
        console.error('Error loading drugs:', error);
        document.getElementById('drugsList').innerHTML = 
            '<p class="empty">Error loading drugs. Make sure the backend is running.</p>';
    }
}

// Modal utility functions
function openModal(modal) {
    // Find the highest z-index among currently visible modals
    const visibleModals = document.querySelectorAll('.modal.show');
    let maxZIndex = 1000;
    
    visibleModals.forEach(m => {
        const zIndex = parseInt(window.getComputedStyle(m).zIndex, 10) || 1000;
        if (zIndex > maxZIndex) {
            maxZIndex = zIndex;
        }
    });
    
    // Set the new modal's z-index higher than any existing modal
    modal.style.zIndex = (maxZIndex + 100).toString();
    modal.classList.add('show');
    document.body.style.overflow = 'hidden';
}

function closeModal(modal) {
    modal.classList.remove('show');
    modal.style.zIndex = '1000';
    document.body.style.overflow = 'auto';
}

function closeEditModal() {
    closeModal(document.getElementById('editModal'));
}
function updateDispenseDrugSelect() {
    const select = document.getElementById('dispenseDrugSelect');
    select.innerHTML = '<option value="">-- Select a drug variant --</option>';
    
    allDrugs.forEach(drug => {
        drug.variants.forEach(variant => {
            const option = document.createElement('option');
            option.value = variant.id;
            option.textContent = `${drug.name} ${variant.strength} (${variant.quantity} ${variant.unit})`;
            select.appendChild(option);
        });
    });
}

// Render drugs list
function renderDrugs() {
    const drugsList = document.getElementById('drugsList');
    let drugsToShow = allDrugs;

    // Apply search filter
    if (searchTerm) {
        drugsToShow = drugsToShow.filter(drug => 
            drug.name.toLowerCase().includes(searchTerm) ||
            (drug.description && drug.description.toLowerCase().includes(searchTerm)) ||
            drug.variants.some(variant => variant.strength.toLowerCase().includes(searchTerm))
        );
    }

    // Apply stock filter
    if (showLowStockOnly) {
        drugsToShow = drugsToShow.filter(drug => 
            drug.variants.some(variant => variant.quantity <= variant.low_stock_threshold)
        );
    }

    // Sort alphabetically by drug name
    drugsToShow = drugsToShow.sort((a, b) => 
        a.name.toLowerCase().localeCompare(b.name.toLowerCase())
    );

    if (drugsToShow.length === 0) {
        drugsList.innerHTML = '<p class="empty">No drugs found matching your criteria</p>';
        return;
    }

    drugsList.innerHTML = drugsToShow.map(drug => {
        const totalVariants = drug.variants.length;
        const lowStockVariants = drug.variants.filter(v => v.quantity <= v.low_stock_threshold).length;
        const totalQuantity = drug.variants.reduce((sum, v) => sum + v.quantity, 0);
        const isLowStock = lowStockVariants > 0;
        const isExpanded = expandedDrugs.has(drug.id);
        
        const variantsHtml = isExpanded ? `
            ${drug.variants.map(variant => {
                const variantIsLowStock = variant.quantity <= variant.low_stock_threshold;
                return `
                    <div class="variant-item ${variantIsLowStock ? 'low-stock' : ''}">
                        <div class="variant-info">
                            <div class="variant-details">
                                <div class="variant-name">${escapeHtml(drug.name)} ${escapeHtml(variant.strength)}</div>
                                <div class="variant-quantity">${variant.quantity} ${escapeHtml(variant.unit)}</div>
                            </div>
                            <div class="variant-status">
                                <span class="variant-badge ${variantIsLowStock ? 'badge-low' : 'badge-normal'}">
                                    ${variantIsLowStock ? 'Low Stock' : 'OK'}
                                </span>
                            </div>
                        </div>
                        <div class="variant-actions">
                            <button class="btn btn-primary btn-small" onclick="prescribeVariant(${variant.id}, '${drug.name.replace(/'/g, "\\'")}', '${variant.strength.replace(/'/g, "\\'")}', '${variant.unit.replace(/'/g, "\\'")}')">🏷️ Prescribe & Print</button>
                            <button class="btn btn-success btn-small" onclick="dispenseVariant(${variant.id})">💊 Dispense</button>
                            <button class="btn btn-warning btn-small" onclick="openEditVariantModal(${variant.id})">Edit</button>
                            <button class="btn btn-danger btn-small" onclick="deleteVariant(${variant.id})">Delete</button>
                        </div>
                    </div>
                `;
            }).join('')}` : '';
        
        return `
            <div class="drug-item ${isLowStock ? 'low-stock' : ''} ${isExpanded ? 'expanded' : ''}" onclick="toggleDrugExpansion(${drug.id})">
                <div class="drug-info">
                    <div class="drug-name">${escapeHtml(drug.name)}</div>
                    <div class="drug-description">${drug.description ? escapeHtml(drug.description) : 'No description'}</div>
                    <div class="drug-quantity">${totalVariants} variant${totalVariants !== 1 ? 's' : ''} (${totalQuantity} total units)</div>
                    <div class="drug-status">
                        <span class="drug-badge ${isLowStock ? 'badge-low' : 'badge-normal'}">
                            ${isLowStock ? `${lowStockVariants} low` : 'All OK'}
                        </span>
                    </div>
                </div>
                <div class="drug-actions">
                    <button class="btn btn-primary btn-small" onclick="event.stopPropagation(); openAddVariantModal(${drug.id})">➕ Add</button>
                    <button class="btn btn-info btn-small" onclick="event.stopPropagation(); showDrugHistory(${drug.id})">📋 History</button>
                    <button class="btn btn-warning btn-small" onclick="event.stopPropagation(); openEditModal(${drug.id})">Edit Drug</button>
                    <button class="btn btn-danger btn-small" onclick="event.stopPropagation(); deleteDrug(${drug.id})">Delete</button>
                    <span class="expand-icon">${isExpanded ? '▼' : '▶'}</span>
                </div>
            </div>
            <div class="drug-variants ${isExpanded ? 'expanded' : ''}" id="variants-${drug.id}">
                ${variantsHtml}
            </div>
        `;
    }).join('');
}

// Handle add drug form
async function handleAddDrug(e) {
    e.preventDefault();

    const drugData = {
        name: document.getElementById('drugName').value,
        description: document.getElementById('drugDescription').value
    };

    try {
        // Create the drug first
        const drugResponse = await apiCall('/drugs', {
            method: 'POST',
            body: JSON.stringify(drugData)
        });

        if (!drugResponse.ok) throw new Error('Failed to add drug');
        const createdDrug = await drugResponse.json();

        // Check if initial variant data was provided
        const variantStrength = document.getElementById('initialVariantStrength').value.trim();
        if (variantStrength) {
            const variantData = {
                strength: variantStrength,
                quantity: parseFloat(document.getElementById('initialVariantQuantity').value) || 0,
                unit: document.getElementById('initialVariantUnit').value || 'units',
                low_stock_threshold: parseFloat(document.getElementById('initialVariantThreshold').value) || 10
            };

            const variantResponse = await apiCall(`/drugs/${createdDrug.id}/variants`, {
                method: 'POST',
                body: JSON.stringify(variantData)
            });

            if (!variantResponse.ok) throw new Error('Failed to add variant');
        }

        document.getElementById('drugForm').reset();
        document.getElementById('initialVariantUnit').value = 'units';
        document.getElementById('initialVariantThreshold').value = '10';
        closeModal(document.getElementById('addModal'));
        await loadDrugs();
        showToast('Drug added successfully!', 'success');
    } catch (error) {
        console.error('Error adding drug:', error);
        showToast('Failed to add drug. Check the console for details.', 'error');
    }
}

// Handle dispense drug form
async function handleDispenseDrug(e) {
    e.preventDefault();

    const variantId = parseInt(document.getElementById('dispenseDrugSelect').value);
    const quantity = parseFloat(document.getElementById('dispenseQuantity').value);
    const animalName = document.getElementById('dispenseAnimal').value;
    const userName = document.getElementById('dispenseUser').value;
    const notes = document.getElementById('dispenseNotes').value;

    if (!variantId || isNaN(quantity) || quantity <= 0 || !userName) {
        showToast('Please fill in all required fields (Drug Variant, Quantity > 0, Dispensed by)', 'warning');
        return;
    }

    const dispensingData = {
        drug_variant_id: variantId,
        quantity: quantity,
        animal_name: animalName || null,
        user_name: userName,
        notes: notes || null
    };

    try {
        const response = await apiCall('/dispense', {
            method: 'POST',
            body: JSON.stringify(dispensingData)
        });

        if (!response.ok) {
            const error = await response.json();
            throw new Error(error.detail || 'Failed to dispense drug');
        }

        document.getElementById('dispenseForm').reset();
        closeModal(document.getElementById('dispenseModal'));
        await loadDrugs();
        showToast('Drug dispensed successfully!', 'success');
    } catch (error) {
        console.error('Error dispensing drug:', error);
        showToast('Failed to dispense drug: ' + error.message, 'error');
    }
}

// Open edit modal
function openEditModal(drugId) {
    const drug = allDrugs.find(d => d.id === drugId);
    if (!drug) return;

    document.getElementById('editDrugId').value = drug.id;
    document.getElementById('editDrugName').value = drug.name;
    document.getElementById('editDrugDescription').value = drug.description || '';

    document.getElementById('editModal').classList.add('show');
}

// Close edit modal
function closeEditModal() {
    document.getElementById('editModal').classList.remove('show');
    document.getElementById('editForm').reset();
}

// Show variants for a drug
function toggleDrugExpansion(drugId) {
    if (expandedDrugs.has(drugId)) {
        expandedDrugs.delete(drugId);
    } else {
        expandedDrugs.add(drugId);
    }
    renderDrugs();
}

// Open add variant modal
function openAddVariantModal(drugId) {
    const drug = allDrugs.find(d => d.id === drugId);
    if (!drug) return;
    
    currentDrug = drug;
    document.getElementById('variantDrugId').value = drug.id;
    document.getElementById('addVariantModal').classList.add('show');
}

// Handle add variant form
async function handleAddVariant(e) {
    e.preventDefault();

    const drugId = parseInt(document.getElementById('variantDrugId').value);
    const variantData = {
        strength: document.getElementById('variantStrength').value,
        quantity: parseFloat(document.getElementById('variantQuantity').value),
        unit: document.getElementById('variantUnit').value,
        low_stock_threshold: parseFloat(document.getElementById('variantThreshold').value)
    };

    try {
        const response = await apiCall(`/drugs/${drugId}/variants`, {
            method: 'POST',
            body: JSON.stringify(variantData)
        });

        if (!response.ok) throw new Error('Failed to add variant');

        document.getElementById('variantForm').reset();
        closeModal(document.getElementById('addVariantModal'));
        await loadDrugs();
        renderDrugs();
        showToast('Variant added successfully!', 'success');
    } catch (error) {
        console.error('Error adding variant:', error);
        showToast('Failed to add variant. Check the console for details.', 'error');
    }
}

// Open edit variant modal
function openEditVariantModal(variantId) {
    // Find the variant from all drugs
    let variant = null;
    for (const drug of allDrugs) {
        variant = drug.variants.find(v => v.id === variantId);
        if (variant) break;
    }
    
    if (!variant) return;

    document.getElementById('editVariantId').value = variant.id;
    document.getElementById('editVariantStrength').value = variant.strength;
    document.getElementById('editVariantQuantity').value = variant.quantity;
    document.getElementById('editVariantUnit').value = variant.unit;
    document.getElementById('editVariantThreshold').value = variant.low_stock_threshold;

    document.getElementById('editVariantModal').classList.add('show');
}

// Handle edit variant form
async function handleEditVariant(e) {
    e.preventDefault();

    const variantId = parseInt(document.getElementById('editVariantId').value);
    const variantData = {
        strength: document.getElementById('editVariantStrength').value,
        quantity: parseFloat(document.getElementById('editVariantQuantity').value),
        unit: document.getElementById('editVariantUnit').value,
        low_stock_threshold: parseFloat(document.getElementById('editVariantThreshold').value)
    };

    try {
        const response = await apiCall(`/variants/${variantId}`, {
            method: 'PUT',
            body: JSON.stringify(variantData)
        });

        if (!response.ok) throw new Error('Failed to update variant');

        closeModal(document.getElementById('editVariantModal'));
        await loadDrugs();
        renderDrugs();
        showToast('Variant updated successfully!', 'success');
    } catch (error) {
        console.error('Error updating variant:', error);
        showToast('Failed to update variant. Check the console for details.', 'error');
    }
}

// Dispense from variant
function dispenseVariant(variantId) {
    // Update the dropdown display with all variants
    updateDispenseDrugSelect();
    
    // Pre-select the variant in the dispense modal
    const drugSelect = document.getElementById('dispenseDrugSelect');
    drugSelect.value = variantId;
    
    // Open dispense modal
    openModal(document.getElementById('dispenseModal'));
}

// Prescribe variant and print label
function prescribeVariant(variantId, drugName, variantStrength, unit) {
    // Set hidden fields
    document.getElementById('prescribeVariantId').value = variantId;
    document.getElementById('prescribeDrugName').value = drugName;
    document.getElementById('prescribeVariantStrength').value = variantStrength;
    document.getElementById('prescribeUnit').value = unit || 'units';
    
    // Pre-fill user name if available
    if (currentUser) {
        document.getElementById('prescribeUser').value = currentUser.username;
    }
    
    // Set default expiry date to 1 month from now
    const defaultExpiry = new Date();
    defaultExpiry.setMonth(defaultExpiry.getMonth() + 1);
    document.getElementById('prescribeExpiry').value = defaultExpiry.toISOString().split('T')[0];
    
    // Open prescribe modal
    openModal(document.getElementById('prescribeModal'));
}

// Handle prescribe drug form submission
async function handlePrescribeDrug(e) {
    e.preventDefault();

    const variantId = parseInt(document.getElementById('prescribeVariantId').value);
    const drugName = document.getElementById('prescribeDrugName').value;
    const variantStrength = document.getElementById('prescribeVariantStrength').value;
    const unit = document.getElementById('prescribeUnit').value;
    const quantity = parseFloat(document.getElementById('prescribeQuantity').value);
    const animalName = document.getElementById('prescribeAnimal').value;
    const dosage = document.getElementById('prescribeDosage').value;
    const expiryDate = document.getElementById('prescribeExpiry').value;
    const userName = document.getElementById('prescribeUser').value;
    const notes = document.getElementById('prescribeNotes').value;

    if (!variantId || isNaN(quantity) || quantity <= 0 || !animalName || !dosage || !expiryDate || !userName) {
        showToast('Please fill in all required fields', 'warning');
        return;
    }

    // Convert expiry date to DD/MM/YYYY format
    const expiryParts = expiryDate.split('-');
    const formattedExpiry = `${expiryParts[2]}/${expiryParts[1]}/${expiryParts[0]}`;

    try {
        // First, print the label
        const labelData = {
            variables: {
                practice_name: "Many Tears Animal Rescue",
                animal_name: animalName,
                drug_name: `${drugName} ${variantStrength}`,
                dosage: dosage,
                quantity: `${quantity} ${unit}`,
                expiry_date: formattedExpiry
            }
        };

        const labelResponse = await apiCall('/labels/print', {
            method: 'POST',
            body: JSON.stringify(labelData)
        });

        if (!labelResponse.ok) {
            const error = await labelResponse.json();
            throw new Error(error.detail || 'Label printing request failed');
        }

        const labelResult = await labelResponse.json();
        console.log('Label print result:', labelResult);
        
        if (!labelResult.success) {
            // Label printing failed - don't dispense the drug
            const isError = labelResult.message && (
                labelResult.message.includes('not found') || 
                labelResult.message.includes('error') ||
                labelResult.message.includes('failed')
            );
            const toastType = isError ? 'error' : 'warning';
            showToast('Cannot dispense: ' + labelResult.message, toastType, 5000);
            return;
        }

        // Label printed successfully, now dispense the drug
        const dispensingData = {
            drug_variant_id: variantId,
            quantity: quantity,
            animal_name: animalName,
            user_name: userName,
            notes: notes || null
        };

        const dispenseResponse = await apiCall('/dispense', {
            method: 'POST',
            body: JSON.stringify(dispensingData)
        });

        if (!dispenseResponse.ok) {
            const error = await dispenseResponse.json();
            throw new Error(error.detail || 'Failed to dispense drug');
        }

        // Both operations succeeded
        showToast('Drug prescribed and label printed successfully!', 'success');

        document.getElementById('prescribeForm').reset();
        closeModal(document.getElementById('prescribeModal'));
        await loadDrugs();
    } catch (error) {
        console.error('Error prescribing drug:', error);
        showToast('Failed to prescribe drug: ' + error.message, 'error');
    }
}

// Delete variant
async function deleteVariant(variantId) {
    if (!confirm('Are you sure you want to delete this variant?')) return;

    try {
        const response = await apiCall(`/variants/${variantId}`, {
            method: 'DELETE'
        });

        if (!response.ok) throw new Error('Failed to delete variant');

        await loadDrugs();
        renderDrugs();
        showToast('Variant deleted successfully!', 'success');
    } catch (error) {
        console.error('Error deleting variant:', error);
        showToast('Failed to delete variant. Check the console for details.', 'error');
    }
}

// Show dispensing history for a drug
async function showDrugHistory(drugId) {
    const drug = allDrugs.find(d => d.id === drugId);
    if (!drug) return;

    const historyModal = document.getElementById('historyModal');
    const historyContent = document.getElementById('historyContent');
    document.getElementById('historyDrugName').textContent = drug.name;
    
    historyContent.innerHTML = '<p class="loading">Loading history...</p>';
    openModal(historyModal);
    
    try {
        const response = await apiCall(`/dispense/history`);
        if (!response.ok) throw new Error('Failed to fetch history');
        
        const allHistory = await response.json();
        
        // Filter history for this drug's variants
        const variantIds = drug.variants.map(v => v.id);
        const drugHistory = allHistory.filter(item => variantIds.includes(item.drug_variant_id));
        
        if (drugHistory.length === 0) {
            historyContent.innerHTML = '<p class="empty">No dispensing history for this drug.</p>';
            return;
        }
        
        // Sort by dispensed_at descending (most recent first)
        drugHistory.sort((a, b) => new Date(b.dispensed_at) - new Date(a.dispensed_at));
        
        const historyHtml = drugHistory.map(item => {
            const variant = drug.variants.find(v => v.id === item.drug_variant_id);
            const date = new Date(item.dispensed_at).toLocaleDateString();
            const time = new Date(item.dispensed_at).toLocaleTimeString();
            
            return `
                <div class="history-item">
                    <div class="history-header">
                        <div class="history-variant">${drug.name} ${variant.strength}</div>
                        <div class="history-datetime">${date} ${time}</div>
                    </div>
                    <div class="history-details">
                        <div class="history-row">
                            <span class="history-label">Quantity:</span>
                            <span class="history-value">${item.quantity} ${variant.unit}</span>
                        </div>
                        <div class="history-row">
                            <span class="history-label">Animal:</span>
                            <span class="history-value">${escapeHtml(item.animal_name)}</span>
                        </div>
                        <div class="history-row">
                            <span class="history-label">User:</span>
                            <span class="history-value">${escapeHtml(item.user_name)}</span>
                        </div>
                        ${item.notes ? `
                        <div class="history-row">
                            <span class="history-label">Notes:</span>
                            <span class="history-value">${escapeHtml(item.notes)}</span>
                        </div>
                        ` : ''}
                    </div>
                </div>
            `;
        }).join('');
        
        historyContent.innerHTML = historyHtml;
    } catch (error) {
        console.error('Error fetching history:', error);
        historyContent.innerHTML = '<p class="error">Failed to load history. Check the console for details.</p>';
    }
}

// Handle edit drug form
async function handleEditDrug(e) {
    e.preventDefault();

    const drugId = parseInt(document.getElementById('editDrugId').value);
    const drugData = {
        name: document.getElementById('editDrugName').value,
        description: document.getElementById('editDrugDescription').value
    };

    try {
        const response = await apiCall(`/drugs/${drugId}`, {
            method: 'PUT',
            body: JSON.stringify(drugData)
        });

        if (!response.ok) throw new Error('Failed to update drug');

        closeEditModal();
        await loadDrugs();
        showToast('Drug updated successfully!', 'success');
    } catch (error) {
        console.error('Error updating drug:', error);
        showToast('Failed to update drug. Check the console for details.', 'error');
    }
}

// Delete drug
async function deleteDrug(drugId) {
    if (!confirm('Are you sure you want to delete this drug?')) return;

    try {
        const response = await apiCall(`/drugs/${drugId}`, {
            method: 'DELETE'
        });

        if (!response.ok) throw new Error('Failed to delete drug');

        await loadDrugs();
        showToast('Drug deleted successfully!', 'success');
    } catch (error) {
        console.error('Error deleting drug:', error);
        showToast('Failed to delete drug. Check the console for details.', 'error');
    }
}

// Password Management
function openChangePasswordModal() {
    const modal = document.getElementById('changePasswordModal');
    document.getElementById('changePasswordForm').reset();
    
    // Close dropdown
    const dropdown = document.getElementById('userDropdown');
    if (dropdown) dropdown.style.display = 'none';
    
    openModal(modal);
}

async function handleChangePassword(e) {
    e.preventDefault();
    
    const currentPassword = document.getElementById('currentPassword').value;
    const newPassword = document.getElementById('newPassword').value;
    const confirmPassword = document.getElementById('confirmNewPassword').value;
    
    if (newPassword !== confirmPassword) {
        showToast('New passwords do not match!', 'warning');
        return;
    }
    
    if (newPassword.length < 1) {
        showToast('New password cannot be empty!', 'warning');
        return;
    }
    
    try {
        const response = await apiCall('/auth/change-password', {
            method: 'POST',
            body: JSON.stringify({
                current_password: currentPassword,
                new_password: newPassword
            })
        });

        if (!response.ok) {
            const error = await response.json();
            throw new Error(error.detail || 'Failed to change password');
        }

        showToast('Password changed successfully!', 'success');
        closeModal(document.getElementById('changePasswordModal'));
    } catch (error) {
        console.error('Error changing password:', error);
        showToast('Failed to change password: ' + error.message, 'error');
    }
}

async function openAdminChangePasswordModal(userId, username) {
    const modal = document.getElementById('adminChangePasswordModal');
    document.getElementById('adminChangePasswordForm').reset();
    document.getElementById('adminChangePasswordUserId').value = userId;
    document.getElementById('adminChangePasswordUsername').value = username;
    openModal(modal);
}

async function handleAdminChangePassword(e) {
    e.preventDefault();
    
    const userId = document.getElementById('adminChangePasswordUserId').value;
    const newPassword = document.getElementById('adminChangePasswordNewPassword').value;
    const confirmPassword = document.getElementById('adminChangePasswordConfirm').value;
    
    if (newPassword !== confirmPassword) {
        showToast('Passwords do not match!', 'warning');
        return;
    }
    
    if (newPassword.length < 1) {
        showToast('Password cannot be empty!', 'warning');
        return;
    }
    
    try {
        const response = await apiCall(`/users/${userId}/change-password`, {
            method: 'POST',
            body: JSON.stringify({
                new_password: newPassword
            })
        });

        if (!response.ok) {
            const error = await response.json();
            throw new Error(error.detail || 'Failed to change password');
        }

        showToast('Password changed successfully!', 'success');
        closeModal(document.getElementById('adminChangePasswordModal'));
        openUserManagement();
    } catch (error) {
        console.error('Error changing password:', error);
        showToast('Failed to change password: ' + error.message, 'error');
    }
}

// Update filter button states
function updateFilterButtons() {
    document.getElementById('showAllBtn').classList.toggle('active', !showLowStockOnly);
    document.getElementById('showLowStockBtn').classList.toggle('active', showLowStockOnly);
}

// Escape HTML to prevent XSS
function escapeHtml(text) {
    const div = document.createElement('div');
    div.textContent = text;
    return div.innerHTML;
}

// User Management
async function openUserManagement() {
    const modal = document.getElementById('userManagementModal');
    document.getElementById('newUsername').value = '';
    document.getElementById('newUserPassword').value = '';
    
    const usersList = document.getElementById('usersList');
    usersList.innerHTML = '<h3>Users</h3><p class="loading">Loading users...</p>';
    
    try {
        const response = await apiCall('/users');
        if (!response.ok) throw new Error('Failed to load users');

        const users = await response.json();
        
        const usersHtml = `
            <h3>Users</h3>
            <div class="users-table">
                ${users.map(user => `
                    <div class="user-item">
                        <span>${user.username}</span>
                        <span class="admin-badge">${user.is_admin ? '👑 Admin' : 'User'}</span>
                        <button class="btn btn-secondary btn-small" onclick="openAdminChangePasswordModal(${user.id}, '${escapeHtml(user.username)}')">🔑 Password</button>
                        ${user.id !== currentUser.id ? `
                            <button class="btn btn-danger btn-small" onclick="deleteUser(${user.id})">Delete</button>
                        ` : ''}
                    </div>
                `).join('')}
            </div>
        `;
        
        usersList.innerHTML = usersHtml;
    } catch (error) {
        console.error('Error loading users:', error);
        usersList.innerHTML = '<h3>Users</h3><p class="empty">Error loading users</p>';
    }
    
    const createUserForm = document.getElementById('createUserForm');
    if (createUserForm) {
        createUserForm.onsubmit = createUser;
    }
    
    openModal(modal);
}

// Create user
async function createUser(e) {
    e.preventDefault();
    
    const username = document.getElementById('newUsername').value;
    const password = document.getElementById('newUserPassword').value;
    
    try {
        const response = await apiCall('/users', {
            method: 'POST',
            body: JSON.stringify({ username, password })
        });

        if (!response.ok) {
            const error = await response.json();
            throw new Error(error.detail || 'Failed to create user');
        }

        document.getElementById('newUsername').value = '';
        document.getElementById('newUserPassword').value = '';
        showToast('User created successfully!', 'success');
        openUserManagement();
    } catch (error) {
        console.error('Error creating user:', error);
        showToast('Failed to create user: ' + error.message, 'error');
    }
}

// Delete user
async function deleteUser(userId) {
    if (!confirm('Are you sure you want to delete this user?')) return;

    try {
        const response = await apiCall(`/users/${userId}`, { method: 'DELETE' });

        if (!response.ok) throw new Error('Failed to delete user');

        showToast('User deleted successfully!', 'success');
        openUserManagement();
    } catch (error) {
        console.error('Error deleting user:', error);
        showToast('Failed to delete user: ' + error.message, 'error');
    }
}