const jwt = require('jsonwebtoken');

// Generate secure token for transactions
function generateToken(data, expiresIn = '1h') {
    try {
        const secret = process.env.JWT_SECRET || 'your-fallback-secret-key';
        return jwt.sign(data, secret, { expiresIn });
    } catch (error) {
        console.error('Token generation error:', error);
        return null;
    }
}

// Verify transaction token
function verifyToken(token) {
    try {
        const secret = process.env.JWT_SECRET || 'your-fallback-secret-key';
        return jwt.verify(token, secret);
    } catch (error) {
        console.error('Token verification error:', error);
        return null;
    }
}

// Format currency amount
function formatCurrency(amount, currency = 'USD') {
    try {
        return new Intl.NumberFormat('en-US', {
            style: 'currency',
            currency: currency,
            minimumFractionDigits: 2,
            maximumFractionDigits: 2
        }).format(parseFloat(amount));
    } catch (error) {
        return `${currency} ${parseFloat(amount).toFixed(2)}`;
    }
}

// Validate email format
function isValidEmail(email) {
    const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
    return emailRegex.test(email);
}

// Sanitize order data for logging
function sanitizeOrderData(orderData) {
    const sanitized = { ...orderData };

    // Remove sensitive data
    delete sanitized.billing?.email;
    delete sanitized.billing?.phone;
    delete sanitized.customer_id;

    return {
        id: sanitized.id,
        status: sanitized.status,
        total: sanitized.total,
        currency: sanitized.currency,
        payment_method: sanitized.payment_method,
        date_created: sanitized.date_created
    };
}

// Generate reference ID
function generateReferenceId(prefix = 'REF') {
    const timestamp = Date.now();
    const random = Math.random().toString(36).substring(2, 8).toUpperCase();
    return `${prefix}-${timestamp}-${random}`;
}

// Validate PayPal amount format
function validateAmount(amount) {
    if (!amount) return false;

    const numAmount = parseFloat(amount);
    if (isNaN(numAmount)) return false;
    if (numAmount <= 0) return false;
    if (numAmount > 10000) return false; // Max amount check

    // Check decimal places (max 2)
    const decimalPlaces = (amount.toString().split('.')[1] || '').length;
    if (decimalPlaces > 2) return false;

    return true;
}

// Parse query parameters safely
function parseQueryParams(req) {
    const {
        wc_order_id,
        total,
        currency,
        customer_email,
        return_url,
        cancel_url
    } = req.query;

    return {
        wc_order_id: wc_order_id ? parseInt(wc_order_id) : null,
        total: total ? parseFloat(total) : null,
        currency: currency || 'USD',
        customer_email: customer_email || null,
        return_url: return_url || `${process.env.FRONTEND_URL}/success`,
        cancel_url: cancel_url || `${process.env.FRONTEND_URL}/cancel`
    };
}

// Log API request/response
function logApiCall(type, endpoint, data, response) {
    console.log(`${type.toUpperCase()} API Call:`, {
        endpoint,
        timestamp: new Date().toISOString(),
        data: sanitizeLogData(data),
        response: sanitizeLogData(response),
        success: response?.success || false
    });
}

// Sanitize data for logging (remove sensitive info)
function sanitizeLogData(data) {
    if (!data || typeof data !== 'object') return data;

    const sanitized = { ...data };
    const sensitiveFields = [
        'password', 'secret', 'token', 'key', 'auth',
        'email', 'phone', 'address', 'credit_card'
    ];

    sensitiveFields.forEach(field => {
        if (sanitized[field]) {
            sanitized[field] = '[REDACTED]';
        }
    });

    return sanitized;
}

// Error response helper
function createErrorResponse(message, details = null, statusCode = 500) {
    const response = {
        success: false,
        error: message,
        timestamp: new Date().toISOString()
    };

    if (details && process.env.NODE_ENV !== 'production') {
        response.details = details;
    }

    return { response, statusCode };
}

// Success response helper
function createSuccessResponse(data, message = null) {
    return {
        success: true,
        data: data,
        message: message,
        timestamp: new Date().toISOString()
    };
}

// Retry mechanism for API calls
async function retryOperation(operation, maxRetries = 3, delayMs = 1000) {
    let lastError;

    for (let attempt = 1; attempt <= maxRetries; attempt++) {
        try {
            return await operation();
        } catch (error) {
            lastError = error;
            console.warn(`Operation failed (attempt ${attempt}/${maxRetries}):`, error.message);

            if (attempt < maxRetries) {
                await new Promise(resolve => setTimeout(resolve, delayMs * attempt));
            }
        }
    }

    throw lastError;
}

module.exports = {
    generateToken,
    verifyToken,
    formatCurrency,
    isValidEmail,
    sanitizeOrderData,
    generateReferenceId,
    validateAmount,
    parseQueryParams,
    logApiCall,
    sanitizeLogData,
    createErrorResponse,
    createSuccessResponse,
    retryOperation
};