// Simulated vendor configuration data
const vendorConfig = [
    {"Vendor_Carrier": "Lenovo", "Method": "Pallet", "CUSTPONBR": "Customer PO", "SKU": "Product ID", "SHIPQTY": "Product Quantity", "PACKAGEID": "Pallet ID"},
    {"Vendor_Carrier": "HP", "Method": "Pallet", "CUSTPONBR": "PO", "SKU": "VPN", "SHIPQTY": "UNITS", "PACKAGEID": "PACKAHE"},
    {"Vendor_Carrier": "Microsoft", "Method": "VPN", "CUSTPONBR": "PONum", "SKU": "PARTID", "SHIPQTY": "SHPQTY", "PACKAGEID": "PARTID"}
];

// DOM Elements
const vendorSelect = document.getElementById('vendor-select');
const fileInput = document.getElementById('file-input');
const dropZone = document.getElementById('drop-zone');
const fileInfo = document.getElementById('file-info');
const fileName = document.getElementById('file-name');
const processBtn = document.getElementById('process-btn');
const resultsContainer = document.getElementById('results-container');
const errorContainer = document.getElementById('error-container');
const errorMessage = document.getElementById('error-message');
const jobInfo = document.getElementById('job-info');
const timestampEl = document.getElementById('timestamp');
const headerRowEl = document.getElementById('header-row');
const columnIndicesEl = document.getElementById('column-indices');
const resultsTableBody = document.querySelector('#results-table tbody');
const downloadBtn = document.getElementById('download-btn');

let currentFile = null;
let transformedData = [];

// Initialize vendor dropdown
function initVendorDropdown() {
    vendorConfig.forEach(vendor => {
        const option = document.createElement('option');
        option.value = vendor.Vendor_Carrier;
        option.textContent = vendor.Vendor_Carrier;
        vendorSelect.appendChild(option);
    });
}

// Handle file selection
function handleFileSelection(file) {
    if (!file) return;
    
    const validTypes = ['application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', 
                       'application/vnd.ms-excel', 
                       'text/csv', 
                       'text/plain'];
    
    if (!validTypes.includes(file.type)) {
        showError('Invalid file type. Please upload an Excel or CSV file.');
        return;
    }
    
    currentFile = file;
    fileName.textContent = file.name;
    fileInfo.classList.remove('hidden');
    processBtn.disabled = false;
}

// Drag and drop handlers
['dragenter', 'dragover', 'dragleave', 'drop'].forEach(eventName => {
    dropZone.addEventListener(eventName, preventDefaults, false);
});

function preventDefaults(e) {
    e.preventDefault();
    e.stopPropagation();
}

['dragenter', 'dragover'].forEach(eventName => {
    dropZone.addEventListener(eventName, highlight, false);
});

['dragleave', 'drop'].forEach(eventName => {
    dropZone.addEventListener(eventName, unhighlight, false);
});

function highlight() {
    dropZone.classList.add('dragover');
}

function unhighlight() {
    dropZone.classList.remove('dragover');
}

dropZone.addEventListener('drop', handleDrop, false);

function handleDrop(e) {
    const dt = e.dataTransfer;
    const file = dt.files[0];
    handleFileSelection(file);
}

// Click on drop zone triggers file input
dropZone.addEventListener('click', () => {
    fileInput.click();
});

fileInput.addEventListener('change', (e) => {
    handleFileSelection(e.target.files[0]);
});

// Process file button handler
processBtn.addEventListener('click', processFile);

// Download CSV handler
downloadBtn.addEventListener('click', downloadCSV);

// Initialize the app
initVendorDropdown();

// Main processing function
async function processFile() {
    if (!currentFile || !vendorSelect.value) {
        showError('Please select a vendor and upload a file.');
        return;
    }
    
    // Show loading state
    processBtn.disabled = true;
    processBtn.innerHTML = '<i data-feather="loader" class="mr-2 animate-spin"></i>Processing...';
    feather.replace();
    
    try {
        // In a real app, this would be an API call to the backend
        // For this demo, we'll simulate the processing
        await new Promise(resolve => setTimeout(resolve, 1500));
        
        // Get selected vendor config
        const vendor = vendorConfig.find(v => v.Vendor_Carrier === vendorSelect.value);
        if (!vendor) throw new Error('Vendor configuration not found');
        
        // Simulate data transformation
        const result = simulateDataTransformation(vendor);
        
        // Display results
        displayResults(result.data, result.jobInfo);
    } catch (error) {
        showError(error.message);
    } finally {
        processBtn.disabled = false;
        processBtn.innerHTML = '<i data-feather="play" class="mr-2"></i>Process File';
        feather.replace();
    }
}

// Simulate data transformation (in a real app, this would be server-side)
function simulateDataTransformation(vendorConfig) {
    // Build mapping dictionary
    const mapping = {};
    const requiredHeaders = [];
    
    ['CUSTPONBR', 'SKU', 'SHIPQTY', 'PACKAGEID'].forEach(internal => {
        const external = vendorConfig[internal];
        if (external && external.trim() !== '') {
            mapping[external] = internal;
            requiredHeaders.push(external);
        }
    });
    
    // Simulate finding header row (in a real app, this would parse the file)
    const headerRowIndex = Math.floor(Math.random() * 3); // Random row 0-2
    
    // Validate headers (simulated)
    const missingHeaders = [];
    const foundHeaders = Object.keys(mapping);
    requiredHeaders.forEach(header => {
        if (!foundHeaders.includes(header)) {
            missingHeaders.push(header);
        }
    });
    
    if (missingHeaders.length > 0) {
        throw new Error(`Missing required headers: ${missingHeaders.join(', ')}`);
    }
    
    // Simulate transformed data
    const data = [];
    const rowCount = 5 + Math.floor(Math.random() * 10);
    
    for (let i = 0; i < rowCount; i++) {
        data.push({
            CUSTPONBR: `PO-${Math.floor(Math.random() * 10000)}`,
            SKU: `SKU-${Math.floor(Math.random() * 1000)}`,
            SHIPQTY: Math.floor(Math.random() * 100),
            PACKAGEID: `PKG-${Math.floor(Math.random() * 100)}`
        });
    }
    
    // Generate job info
    const now = new Date();
    const jobInfo = {
        timestamp: now.toISOString().replace('T', ' ').substring(0, 19),
        headerRow: headerRowIndex,
        columnIndices: generateColumnIndices(Object.keys(mapping).length)
    };
    
    return { data, jobInfo };
}

// Generate fake column indices (A, B, C, etc.)
function generateColumnIndices(count) {
    const indices = [];
    for (let i = 0; i < count; i++) {
        indices.push(String.fromCharCode(65 + i)); // ASCII 'A' is 65
    }
    return indices.join(', ');
}

// Display results in the table
function displayResults(data, jobInfoData) {
    // Clear previous results
    resultsTableBody.innerHTML = '';
    
    // Populate table with data
    transformedData = data;
    data.forEach(row => {
        const tr = document.createElement('tr');
        tr.innerHTML = `
            <td class="px-6 py-4 whitespace-nowrap text-sm text-gray-900">${row.CUSTPONBR}</td>
            <td class="px-6 py-4 whitespace-nowrap text-sm text-gray-900">${row.SKU}</td>
            <td class="px-6 py-4 whitespace-nowrap text-sm text-gray-900">${row.SHIPQTY}</td>
            <td class="px-6 py-4 whitespace-nowrap text-sm text-gray-900">${row.PACKAGEID}</td>
        `;
        resultsTableBody.appendChild(tr);
    });
    
    // Update job info
    timestampEl.textContent = jobInfoData.timestamp;
    headerRowEl.textContent = jobInfoData.headerRow;
    columnIndicesEl.textContent = jobInfoData.columnIndices;
    
    // Show results and job info
    resultsContainer.classList.remove('hidden');
    jobInfo.classList.remove('hidden');
    
    // Hide error if visible
    errorContainer.classList.add('hidden');
    
    // Scroll to results
    resultsContainer.scrollIntoView({ behavior: 'smooth' });
}

// Show error message
function showError(message) {
    errorMessage.innerHTML = `<p>${message}</p>`;
    errorContainer.classList.remove('hidden');
    resultsContainer.classList.add('hidden');
    jobInfo.classList.add('hidden');
    
    // Scroll to error
    errorContainer.scrollIntoView({ behavior: 'smooth' });
}

// Download CSV
function downloadCSV() {
    if (transformedData.length === 0) return;
    
    // Create CSV content
    let csvContent = "CUSTPONBR,SKU,SHIPQTY,PACKAGEID\n";
    transformedData.forEach(row => {
        csvContent += `${row.CUSTPONBR},${row.SKU},${row.SHIPQTY},${row.PACKAGEID}\n`;
    });
    
    // Create download link
    const blob = new Blob([csvContent], { type: 'text/csv;charset=utf-8;' });
    const url = URL.createObjectURL(blob);
    const link = document.createElement('a');
    link.setAttribute('href', url);
    link.setAttribute('download', `transformed_data_${new Date().toISOString().slice(0, 10)}.csv`);
    link.style.visibility = 'hidden';
    document.body.appendChild(link);
    link.click();
    document.body.removeChild(link);
}