import {Operator} from '../Operator';
import {Subscriber} from '../Subscriber';
import {tryCatch} from '../util/tryCatch';
import {errorObject} from '../util/errorObject';
import {bindCallback} from '../util/bindCallback';
/**
* Similar to the well-known `Array.prototype.filter` method, this operator filters values down to a set
* allowed by a `select` function
*
* @param {Function} select a function that is used to select the resulting values
* if it returns `true`, the value is emitted, if `false` the value is not passed to the resulting observable
* @param {any} [thisArg] an optional argument to determine the value of `this` in the `select` function
* @returns {Observable} an observable of values allowed by the select function
*/
export function filter<T>(select: (x: T, ix?: number) => boolean, thisArg?: any) {
return this.lift(new FilterOperator(select, thisArg));
}
class FilterOperator<T, R> implements Operator<T, R> {
select: (x: T, ix?: number) => boolean;
constructor(select: (x: T, ix?: number) => boolean, thisArg?: any) {
this.select = <(x: T, ix?: number) => boolean>bindCallback(select, thisArg, 2);
}
call(subscriber: Subscriber<T>): Subscriber<T> {
return new FilterSubscriber(subscriber, this.select);
}
}
class FilterSubscriber<T> extends Subscriber<T> {
count: number = 0;
select: (x: T, ix?: number) => boolean;
constructor(destination: Subscriber<T>, select: (x: T, ix?: number) => boolean) {
super(destination);
this.select = select;
}
_next(x) {
const result = tryCatch(this.select)(x, this.count++);
if (result === errorObject) {
this.destination.error(errorObject.e);
} else if (Boolean(result)) {
this.destination.next(x);
}
}
}
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