import {Observable} from '../Observable';
import {Operator} from '../Operator';
import {Subscriber} from '../Subscriber';
import {Observer} from '../Observer';
import {tryCatch} from '../util/tryCatch';
import {errorObject} from '../util/errorObject';
import {bindCallback} from '../util/bindCallback';
import {EmptyError} from '../util/EmptyError';
export function single<T>(predicate?: (value: T,
index: number,
source: Observable<T>) => boolean,
thisArg?: any): Observable<T> {
return this.lift(new SingleOperator(predicate, thisArg, this));
}
class SingleOperator<T, R> implements Operator<T, R> {
constructor(private predicate?: (value: T, index: number, source: Observable<T>) => boolean,
private thisArg?: any,
private source?: Observable<T>) {
}
call(subscriber: Subscriber<T>): Subscriber<T> {
return new SingleSubscriber(subscriber, this.predicate, this.thisArg, this.source);
}
}
class SingleSubscriber<T> extends Subscriber<T> {
private predicate: Function;
private seenValue: boolean = false;
private singleValue: T;
private index: number = 0;
constructor(destination: Observer<T>,
predicate?: (value: T, index: number, source: Observable<T>) => boolean,
private thisArg?: any,
private source?: Observable<T>) {
super(destination);
if (typeof predicate === 'function') {
this.predicate = bindCallback(predicate, thisArg, 3);
}
}
private applySingleValue(value): void {
if (this.seenValue) {
this.destination.error('Sequence contains more than one element');
} else {
this.seenValue = true;
this.singleValue = value;
}
}
_next(value: T): void {
const predicate = this.predicate;
const currentIndex = this.index++;
if (predicate) {
let result = tryCatch(predicate)(value, currentIndex, this.source);
if (result === errorObject) {
this.destination.error(result.e);
} else if (result) {
this.applySingleValue(value);
}
} else {
this.applySingleValue(value);
}
}
_complete(): void {
const destination = this.destination;
if (this.index > 0) {
destination.next(this.seenValue ? this.singleValue : undefined);
destination.complete();
} else {
destination.error(new EmptyError);
}
}
}
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