ix/asyncsink.mjs

The Interactive Extensions for JavaScript

const ARRAY_VALUE = 'value';
const ARRAY_ERROR = 'error';
export class AsyncSink {
    constructor() {
        this._ended = false;
        this._values = [];
        this._resolvers = [];
    }
    [Symbol.asyncIterator]() {
        return this;
    }
    write(value) {
        this._push({ type: ARRAY_VALUE, value });
    }
    error(error) {
        this._push({ type: ARRAY_ERROR, error });
    }
    _push(item) {
        if (this._ended) {
            throw new Error('AsyncSink already ended');
        }
        if (this._resolvers.length > 0) {
            const { resolve, reject } = this._resolvers.shift();
            if (item.type === ARRAY_ERROR) {
                reject(item.error);
            }
            else {
                resolve({ done: false, value: item.value });
            }
        }
        else {
            this._values.push(item);
        }
    }
    next() {
        if (this._values.length > 0) {
            const { type, value, error } = this._values.shift();
            if (type === ARRAY_ERROR) {
                return Promise.reject(error);
            }
            else {
                return Promise.resolve({ done: false, value });
            }
        }
        if (this._ended) {
            return Promise.resolve({ done: true });
        }
        return new Promise((resolve, reject) => {
            this._resolvers.push({ resolve, reject });
        });
    }
    end() {
        while (this._resolvers.length > 0) {
            this._resolvers.shift().resolve({ done: true });
        }
        this._ended = true;
    }
}

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