grafserv/dist/mapIterator.js

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"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.mapIterator = mapIterator;
function mapIterator(iterable, cb, end, initial) {
    const iterator = iterable[Symbol.asyncIterator]();
    /**
     * -1 - starting
     * 0 - normal
     * 1 - ending
     * 2 - ended
     */
    let status = -1;
    const mappedIterator = {
        async [Symbol.asyncDispose]() {
            await this.return(undefined);
        },
        next() {
            if (status === -1) {
                status = 0;
                if (typeof initial === "function") {
                    return Promise.resolve({ value: initial(), done: false });
                }
            }
            if (status === 1) {
                status = 2;
            }
            // NO 'else' here!
            if (status === 2) {
                return Promise.resolve({ value: undefined, done: true });
            }
            const next = iterator.next();
            return next.then((v) => {
                if (v.done) {
                    if (v.value !== undefined) {
                        throw new Error("Invalid assumption; tell Benjie he did bad.");
                    }
                    if (end) {
                        status = 1;
                        return { value: end(), done: false };
                    }
                    else {
                        status = 2;
                        return { value: undefined, done: true };
                    }
                }
                else {
                    return { value: cb(v.value), done: false };
                }
            });
        },
        return(value) {
            status = 2;
            iterator.return?.(value);
            return Promise.resolve({ value: undefined, done: true });
        },
        throw(error) {
            status = 2;
            iterator.throw?.(error);
            return Promise.reject(error);
        },
        [Symbol.asyncIterator]() {
            return this;
        },
    };
    return mappedIterator;
}
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