source: frontend/node_modules/globby/stream-utils.js

'use strict';
const {Transform} = require('stream');

class ObjectTransform extends Transform {
        constructor() {
                super({
                        objectMode: true
                });
        }
}

class FilterStream extends ObjectTransform {
        constructor(filter) {
                super();
                this._filter = filter;
        }

        _transform(data, encoding, callback) {
                if (this._filter(data)) {
                        this.push(data);
                }

                callback();
        }
}

class UniqueStream extends ObjectTransform {
        constructor() {
                super();
                this._pushed = new Set();
        }

        _transform(data, encoding, callback) {
                if (!this._pushed.has(data)) {
                        this.push(data);
                        this._pushed.add(data);
                }

                callback();
        }
}

module.exports = {
        FilterStream,
        UniqueStream
};