koa-mongo-router/lib/utils/promise-transform-stream.js

KOA REST API Router for MongoDB

Object.defineProperty(exports, "__esModule", { value: true });
exports.PromiseTransformStream = void 0;
const stream_1 = require("stream");
const defaultTransformOptions = {
    writableObjectMode: true,
    readableObjectMode: true,
    objectMode: true,
    autoDestroy: false,
};
class PromiseTransformStream extends stream_1.Transform {
    constructor(transform, concurrency = 100, options = defaultTransformOptions) {
        super(options);
        this.transform = transform;
        this.concurrency = concurrency;
        this.results = [];
        this.pushIndex = 0;
        this.activeCount = 0;
    }
    _transform(chunk, encoding, callback) {
        const index = this.results.length;
        this.results.push(null);
        this.activeCount++;
        if (this.activeCount === this.concurrency) {
            this.resumeCallback = callback;
        }
        else {
            callback();
        }
        void this.transform(chunk).then((item) => {
            this.activeCount--;
            this.results[index] = item;
            while (this.results[this.pushIndex] != null && this.pushIndex < this.results.length) {
                this.push(this.results[this.pushIndex]);
                this.results[this.pushIndex] = undefined;
                this.pushIndex++;
            }
            if (this.resumeCallback != undefined) {
                const tempResumeCallback = this.resumeCallback;
                this.resumeCallback = undefined;
                tempResumeCallback();
            }
            if (this.endCallback != undefined && this.activeCount === 0) {
                this.endCallback();
            }
        });
    }
    end(chunk, encoding, cb) {
        if (this.results.length === 0) {
            super.end(chunk, encoding, cb);
        }
        else {
            this.endCallback = () => {
                super.end(chunk, encoding, cb);
            };
        }
    }
}
exports.PromiseTransformStream = PromiseTransformStream;