/// <summary>
/// Here we have an application used to conduct market and sales research at our
/// local farmer's market. As part of our efforts to improve the services we provide
/// at the farmer's market, we need to aggregate sales and demographic data already collected
/// by our vendors.
/// Each class of vendor has different means of collecting its data, and we want to write
/// an extensible way to aggregate and report on this data without modifying each class to
/// write custom research reports. This would help us write more extensible code (Open/Closed principle)
/// and keep us from adding unwanted responsibility to the data processing classes
/// (Single Responsibility principle).
/// We can leverage the Visitor Pattern, where we make our data processing classes "visitable"
/// by anything that generates a Report. Then, we can create individual Visitor classes that
/// generate their own specific types of reports.
/// If a processor doesn't provide the data we need for a particular report, we can handle that
/// logic altogether differently, perhaps notifying the stakeholders that we can't access this data
/// for reporting purposes.
/// </summary>
private static void Main()
{
var logger = new ConsoleLogger();
var emailer = new Emailer(logger);
var farmDatabase = new Database(Configuration.ConnectionString, logger);
var floristDatabase = new Database(Configuration.ConnectionString, logger);
var bakeryDatabase = new Database(Configuration.ConnectionString, logger);
logger.LogInfo("🌾 Welcome to the Farmer's Market Research Application!");
logger.LogInfo("-------------------------------------------------------");
// Various existing components know how to produce the data we need
// But we don't want to modify them to add new responsibilities, like
// generating reports. We make these Visitable, so that a Visitor
// can use them as it needs.
var bakeryDataProcessor = new BakeryDataProcessor(emailer, bakeryDatabase);
var farmerDataProcessor = new FarmerDataProcessor(farmDatabase);
var floristDataProcessor = new FloristDataProcessor(emailer, floristDatabase);
var dataProcessors = new List <IVisitable <Report> > {
bakeryDataProcessor,
farmerDataProcessor,
floristDataProcessor
};
var reporter = new ReportRunner(logger);
logger.LogInfo("==== Generating Sales Reports ====");
reporter.RunReports(dataProcessors, new SaleDataVisitor(logger));
logger.LogInfo("==== Generating Market Reports ====");
reporter.RunReports(dataProcessors, new MarketResearchReportVisitor(logger));
}
public SalesReport Visit(FarmerDataProcessor processor)
{
Console.ForegroundColor = ConsoleColor.Magenta;
_logger.LogInfo("Visiting Farmer for Sales Report");
var sales = processor.GetDailyOrderAmounts();
Console.ResetColor();
return(new SalesReport(_logger, DateTime.UtcNow, sales.Sum()));
}
public MarketResearchReport Visit(FarmerDataProcessor order)
{
_logger.LogDebug("Market research is not yet available for Farm Data");
return(null);
}