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import type { Evt } from "./Evt.ts";import type { StatefulEvt, UnpackEvt, NonPostableEvtLike, StatefulReadonlyEvtLike } from "./types/index.ts";import type { PromiseOrNot } from "https://deno.land/x/tsafe@v1.4.1/lab/PromiseOrNot.ts";import { importProxy } from "./importProxy.ts";


/**  * NOTE: Workaround until v2.0 where .pipe() will support async operators  * Usage example: https://stackblitz.com/edit/evt-async-op?file=index.ts  *  * When the argument is a StatefulEvt: * If, wile asyncOp was running, the state of the source evt * have changed then the result will be discarded. *  * If the asyncOp complete synchronously (meaning it does not return * a promise) then the result is synchronously transformed. (As with .pipe() ) *  * More usage example in src/test/test95.ts */export function asyncPipe<E extends NonPostableEvtLike<any>, U>(    evt: E,    asyncOp: (data: UnpackEvt<E>) => PromiseOrNot<[U] | null>):     E extends StatefulReadonlyEvtLike<any> ? StatefulEvt<U | undefined> : Evt<U> {
    const out = "state" in evt ?        importProxy.Evt.create<UnpackEvt<E> | undefined>(undefined) :        importProxy.Evt.create<UnpackEvt<E>>();
    let currentCallCount = 0;
    evt.attach(async (data: UnpackEvt<E>) => {
        currentCallCount++;
        const thisCallCount = currentCallCount;
        const prOpResult = asyncOp(data);
        let opResult: [U] | null;
        if (            prOpResult !== null &&            "then" in prOpResult        ) {
            opResult = await prOpResult;
            if (                "state" in evt &&                thisCallCount !== currentCallCount            ) {                return;            }
        } else {
            opResult = prOpResult;
        }
        if (!opResult) {
            return;        }
        out.post(opResult[0] as any);
    });
    return out as any;
}