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