QuoteGenerator.java

package io.spring.demo.quotes;

import java.math.BigDecimal;
import java.math.MathContext;
import java.time.Duration;
import java.time.Instant;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.function.BiFunction;

import reactor.core.publisher.Flux;
import reactor.core.publisher.SynchronousSink;

import org.springframework.stereotype.Component;

@Component
public class QuoteGenerator {

	private MathContext mathContext = new MathContext(2);

	private Random random = new Random();

	private List<Quote> prices = new ArrayList();

	public QuoteGenerator() {
		this.prices.add(new Quote("CTXS", 82.26));
		this.prices.add(new Quote("DELL", 63.74));
		this.prices.add(new Quote("GOOG", 847.24));
		this.prices.add(new Quote("MSFT", 65.11));
		this.prices.add(new Quote("ORCL", 45.71));
		this.prices.add(new Quote("RHT", 84.29));
		this.prices.add(new Quote("VMW", 92.21));
	}


	public Flux<Quote> fetchQuoteStream(Duration period) {

		return Flux.generate(() -> 0,
				(BiFunction<Integer, SynchronousSink<Quote>, Integer>) (index, sink) -> {
					Quote updatedQuote = updateQuote(prices.get(index));
					sink.next(updatedQuote);
					return ++index % prices.size();
				})
				.zipWith(Flux.interval(period)).map(t -> t.getT1())
				.map(quote -> {quote.setInstant(Instant.now()); return quote;})
				.share()
				.log();
	}

	private Quote updateQuote(Quote quote) {
		BigDecimal priceChange = quote.getPrice()
				.multiply(new BigDecimal(0.05 * this.random.nextDouble()), this.mathContext);
		return new Quote(quote.getTicker(), quote.getPrice().add(priceChange));
	}
}