global class EmailToApex implements Messaging.InboundEmailHandler {
    public static String getFieldValue(String plainTextBody, String pLabel) {
        Integer startPos = plainTextBody.indexOf(pLabel);
        Integer endPos = plainTextBody.indexOf('\n');
        return plainTextBody.substring(startPos+pLabel.length(), endPos);
    }

    global Messaging.InboundEmailResult handleInboundEmail(Messaging.inboundEmail email, Messaging.InboundEnvelope envelope) {
        Messaging.InboundEmailResult result = new Messaging.InboundEmailResult();
        String contactName =email.subject;
        Double mileageInt = Double.valueOf(getFieldValue(email.plainTextBody, 'Mileage:'));
        List<Contact> contactResult = new List<Contact>();
        contactName = '%'+contactName+'%';
        
        Mileage__c[] newMileage = new Mileage__c[0];
        try {
            for (Contact c :
                [Select Id, Name, Email From Contact Where Name like :contactName Limit 1]) {
                    newMileage.add(new Mileage__c(miles__c = mileageInt, Contact__c = c.Id));
            }
            insert newMileage;
        } catch (System.Exception e) {
            System.debug('Error: ' + e);
        }
        
        result.success = true; // If false, an email can be sent back with a message.
        return result;
    }
}