@electric-sql/d2ts/dist/operators/output.js

D2TS is a TypeScript implementation of Differential Dataflow.

import { MessageType, } from '../types.js';
import { DifferenceStreamWriter, UnaryOperator, } from '../graph.js';
import { StreamBuilder } from '../d2.js';
/**
 * Operator that outputs the messages in the stream
 */
export class OutputOperator extends UnaryOperator {
    #fn;
    constructor(id, inputA, output, fn, initialFrontier) {
        super(id, inputA, output, initialFrontier);
        this.#fn = fn;
    }
    run() {
        for (const message of this.inputMessages()) {
            this.#fn(message);
            if (message.type === MessageType.DATA) {
                const { version, collection } = message.data;
                this.output.sendData(version, collection);
            }
            else if (message.type === MessageType.FRONTIER) {
                const frontier = message.data;
                if (!this.inputFrontier().lessEqual(frontier)) {
                    throw new Error('Invalid frontier update');
                }
                this.setInputFrontier(frontier);
                if (!this.outputFrontier.lessEqual(this.inputFrontier())) {
                    throw new Error('Invalid frontier state');
                }
                if (this.outputFrontier.lessThan(this.inputFrontier())) {
                    this.outputFrontier = this.inputFrontier();
                    this.output.sendFrontier(this.outputFrontier);
                }
            }
        }
    }
}
/**
 * Outputs the messages in the stream
 * @param fn - The function to call with each message
 */
export function output(fn) {
    return (stream) => {
        const output = new StreamBuilder(stream.graph, new DifferenceStreamWriter());
        const operator = new OutputOperator(stream.graph.getNextOperatorId(), stream.connectReader(), output.writer, fn, stream.graph.frontier());
        stream.graph.addOperator(operator);
        stream.graph.addStream(output.connectReader());
        return output;
    };
}
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