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/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */
package stream;

import stream.data.Customer;
import stream.data.Product;
import stream.data.Order;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.function.Predicate;
import static java.util.stream.Collectors.*;

/**
 * This class demos conditional filter usage for collection interface. Which
 * includes
 * 1. Simple filter on collection
 * 2. Combination of predicates filter on collection
 * 3. Grouping collection, also attach filter at the same time
 * @author tyan
 */
public class Conditional extends DemoHelper {
    /**
     * Filter products that are out of stock. This is demo for simple filter for
     * one predicate. <p>
     *
     * @return     name list of product that is out of stock
     */
    public static List<String> outOfStock() {
        return products.stream().
                //filter out of stock product
                filter(p -> p.getUnitsInStock() == 0).
                //map product to name
                map(Product::getProductName).
                //get product name list
                collect(toList());
    }

    /*
     * Filter products that are in stock. This demo shows case that uses a given
     * predicate concatenate another predicate.
     *
     * @predicate  a predicate that filter on products
     * @return     product lists which fits predicate and in-sotck both
     */
    public static List<String> inStockWithPreicate(Predicate<Product> predicate) {
        //Oher way to do this is filter(isInStock).filter(predicate)
        return products.stream().
                //filter product with predicate and in-stcok
                filter(predicate.and(p -> p.getUnitsInStock() > 0))
                //map product to name
                .map(Product::getProductName).
                //get product name lis
                collect(toList());
    }
    /*
     * Filter customers in state and their orders, this is a demo for filter
     * predicate join with other data source
     *
     * @region     region be used to look for customer
     * @return     map from customer to its order list in given state
     */

    public static Map<Customer, List<Order>> customerMapOrdersFromRegion(
            String region) {
        return customers.stream()
                //filter customer in given region
                .filter(c -> region.equals(c.getRegion()))
                //convert customers into a map, which key is customer, value is
                //customer's list of orders
                .collect(
                        //Accumulate customers into a Map, key is customer and value
                        //is cusromer's orders
                        toMap(Function.identity(), Customer::getOrders));
    }
}