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import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
import { map } from './map';
import { innerFrom } from '../observable/innerFrom';
import { operate } from '../util/lift';
import { mergeInternals } from './mergeInternals';
import { isFunction } from '../util/isFunction';
/* tslint:disable:max-line-length */
export function mergeMap<T, O extends ObservableInput<any>>(
project: (value: T, index: number) => O,
concurrent?: number
): OperatorFunction<T, ObservedValueOf<O>>;
/** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
export function mergeMap<T, O extends ObservableInput<any>>(
project: (value: T, index: number) => O,
resultSelector: undefined,
concurrent?: number
): OperatorFunction<T, ObservedValueOf<O>>;
/** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
export function mergeMap<T, R, O extends ObservableInput<any>>(
project: (value: T, index: number) => O,
resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R,
concurrent?: number
): OperatorFunction<T, R>;
/* tslint:enable:max-line-length */
/**
* Projects each source value to an Observable which is merged in the output
* Observable.
*
* <span class="informal">Maps each value to an Observable, then flattens all of
* these inner Observables using {@link mergeAll}.</span>
*
* 
*
* Returns an Observable that emits items based on applying a function that you
* supply to each item emitted by the source Observable, where that function
* returns an Observable, and then merging those resulting Observables and
* emitting the results of this merger.
*
* ## Example
*
* Map and flatten each letter to an Observable ticking every 1 second
*
* ```ts
* import { of, mergeMap, interval, map } from 'rxjs';
*
* const letters = of('a', 'b', 'c');
* const result = letters.pipe(
* mergeMap(x => interval(1000).pipe(map(i => x + i)))
* );
*
* result.subscribe(x => console.log(x));
*
* // Results in the following:
* // a0
* // b0
* // c0
* // a1
* // b1
* // c1
* // continues to list a, b, c every second with respective ascending integers
* ```
*
* @see {@link concatMap}
* @see {@link exhaustMap}
* @see {@link merge}
* @see {@link mergeAll}
* @see {@link mergeMapTo}
* @see {@link mergeScan}
* @see {@link switchMap}
*
* @param {function(value: T, ?index: number): ObservableInput} project A function
* that, when applied to an item emitted by the source Observable, returns an
* Observable.
* @param {number} [concurrent=Infinity] Maximum number of input
* Observables being subscribed to concurrently.
* @return A function that returns an Observable that emits the result of
* applying the projection function (and the optional deprecated
* `resultSelector`) to each item emitted by the source Observable and merging
* the results of the Observables obtained from this transformation.
*/
export function mergeMap<T, R, O extends ObservableInput<any>>(
project: (value: T, index: number) => O,
resultSelector?: ((outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R) | number,
concurrent: number = Infinity
): OperatorFunction<T, ObservedValueOf<O> | R> {
if (isFunction(resultSelector)) {
// DEPRECATED PATH
return mergeMap((a, i) => map((b: any, ii: number) => resultSelector(a, b, i, ii))(innerFrom(project(a, i))), concurrent);
} else if (typeof resultSelector === 'number') {
concurrent = resultSelector;
}
return operate((source, subscriber) => mergeInternals(source, subscriber, project, concurrent));
}