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

// Initialize
document.addEventListener('DOMContentLoaded', () => {
    const drugForm = document.getElementById('drugForm');
    const variantForm = document.getElementById('variantForm');
    const editVariantForm = document.getElementById('editVariantForm');
    const dispenseForm = document.getElementById('dispenseForm');
    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 editModal = document.getElementById('editModal');
    const addDrugBtn = document.getElementById('addDrugBtn');
    const cancelAddBtn = document.getElementById('cancelAddBtn');
    const cancelVariantBtn = document.getElementById('cancelVariantBtn');
    const cancelEditVariantBtn = document.getElementById('cancelEditVariantBtn');
    const cancelDispenseBtn = document.getElementById('cancelDispenseBtn');
    const cancelEditBtn = document.getElementById('cancelEditBtn');
    const showAllBtn = document.getElementById('showAllBtn');
    const showLowStockBtn = document.getElementById('showLowStockBtn');

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

    drugForm.addEventListener('submit', handleAddDrug);
    variantForm.addEventListener('submit', handleAddVariant);
    editVariantForm.addEventListener('submit', handleEditVariant);
    dispenseForm.addEventListener('submit', handleDispenseDrug);
    editForm.addEventListener('submit', handleEditDrug);
    
    addDrugBtn.addEventListener('click', () => openModal(addModal));
    
    cancelAddBtn.addEventListener('click', () => closeModal(addModal));
    cancelVariantBtn.addEventListener('click', () => closeModal(addVariantModal));
    cancelEditVariantBtn.addEventListener('click', () => closeModal(editVariantModal));
    cancelDispenseBtn.addEventListener('click', () => closeModal(dispenseModal));
    cancelEditBtn.addEventListener('click', closeEditModal);
    const closeHistoryBtn = document.getElementById('closeHistoryBtn');
    closeHistoryBtn.addEventListener('click', () => closeModal(document.getElementById('historyModal')));
    
    closeButtons.forEach(btn => btn.addEventListener('click', (e) => {
        const modal = e.target.closest('.modal');
        closeModal(modal);
    }));
    
    showAllBtn.addEventListener('click', () => {
        showLowStockOnly = false;
        updateFilterButtons();
        renderDrugs();
    });
    showLowStockBtn.addEventListener('click', () => {
        showLowStockOnly = true;
        updateFilterButtons();
        renderDrugs();
    });

    // 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);
        }
    });

    loadDrugs();
});

// Load drugs from API
async function loadDrugs() {
    try {
        const response = await fetch(`${API_URL}/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 on http://localhost:8000</p>';
    }
}

// Modal utility functions
function openModal(modal) {
    modal.classList.add('show');
    document.body.style.overflow = 'hidden';
}

function closeModal(modal) {
    modal.classList.remove('show');
    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)
        );
    }

    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'}">
                                    ${variantIsLowStock ? 'Low Stock' : 'OK'}
                                </span>
                            </div>
                        </div>
                        <div class="variant-actions">
                            <button class="btn btn-success btn-small" onclick="dispenseVariant(${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 fetch(`${API_URL}/drugs`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            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 fetch(`${API_URL}/drugs/${createdDrug.id}/variants`, {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                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();
        alert('Drug added successfully!');
    } catch (error) {
        console.error('Error adding drug:', error);
        alert('Failed to add drug. Check the console for details.');
    }
}

// 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) {
        alert('Please fill in all required fields (Drug Variant, Quantity > 0, Dispensed by)');
        return;
    }

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

    try {
        const response = await fetch(`${API_URL}/dispense`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            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();
        alert('Drug dispensed successfully!');
    } catch (error) {
        console.error('Error dispensing drug:', error);
        alert('Failed to dispense drug: ' + error.message);
    }
}

// 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 fetch(`${API_URL}/drugs/${drugId}/variants`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            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();
        alert('Variant added successfully!');
    } catch (error) {
        console.error('Error adding variant:', error);
        alert('Failed to add variant. Check the console for details.');
    }
}

// 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 fetch(`${API_URL}/variants/${variantId}`, {
            method: 'PUT',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify(variantData)
        });

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

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

// 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'));
}

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

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

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

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

// 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 fetch(`${API_URL}/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 fetch(`${API_URL}/drugs/${drugId}`, {
            method: 'PUT',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify(drugData)
        });

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

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

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

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

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

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

// 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;
}