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package se.fortnox.reactivewizard.util.rx;

import rx.Observable;
import rx.functions.Func0;

import static rx.Observable.just;

/**
 * Helper class used to chain sequential work in Rx, or omit foo variables. Turns code like this:
 * 
 * 
 * {@code
 * doStuff().flatMap(foo->empty());
 * }
 * 
 * Into this:
 * 
 * 
 * {@code
 * first(doStuff()).thenReturnEmpty();
 * }
 * 
 */
public class FirstThen {

    private Observable doFirst;

    private FirstThen(Observable doFirst) {
        this.doFirst = doFirst;
    }

    public static FirstThen first(Observable doFirst) {
        return new FirstThen(doFirst);
    }

    @SuppressWarnings("unchecked")
    private static  Observable ignoreElements(Observable toConsume) {
        return (Observable)toConsume.ignoreElements();
    }

    public  FirstThen then(Observable thenReturn) {
        return new FirstThen(ignoreElements(doFirst).concatWith(thenReturn));
    }

    public  FirstThen then(Func0> thenFn) {
        return new FirstThen(ignoreElements(doFirst).concatWith(Observable.defer(thenFn)));
    }

    public  Observable thenReturn(Func0> thenFn) {
        return thenReturn(Observable.defer(thenFn));
    }

    public  Observable thenReturn(T thenReturn) {
        return thenReturn(just(thenReturn));
    }

    public  Observable thenReturn(Observable thenReturn) {
        return FirstThen.ignoreElements(doFirst).concatWith(thenReturn);
    }

    /**
     * An empty observable, signalling success or error.
     */
    public  Observable thenReturnEmpty() {
        return thenReturn(Observable.empty());
    }

}