@thi.ng/rstream/metastream.js

Reactive streams & subscription primitives for constructing dataflow graphs / pipelines

import { assert } from "@thi.ng/errors/assert";
import { State } from "./api.js";
import { __optsWithID } from "./idgen.js";
import { Subscription } from "./subscription.js";
const metaStream = (factory, opts) => new MetaStream(factory, opts);
class MetaStream extends Subscription {
  factory;
  stream;
  sub;
  emitLast;
  doneRequested;
  constructor(factory, opts = {}) {
    super(void 0, __optsWithID("metastram", opts));
    this.factory = factory;
    this.emitLast = opts.emitLast === true;
    this.doneRequested = false;
  }
  next(x) {
    if (this.state < State.DONE) {
      if (this.stream) {
        this.stream.unsubscribe(this.sub);
      }
      let stream = this.factory(x);
      if (stream) {
        this.stream = stream;
        this.sub = this.stream.subscribe({
          next: (x2) => {
            stream === this.stream && super.dispatch(x2);
            this.doneRequested && this.done();
          },
          done: () => {
            this.stream.unsubscribe(this.sub);
            if (stream === this.stream) {
              this.stream = void 0;
              this.sub = void 0;
            }
          },
          error: (e) => super.error(e),
          __owner: this
        });
      }
    }
  }
  done() {
    if (this.emitLast && !this.doneRequested) {
      this.doneRequested = true;
    } else {
      if (this.stream) {
        this.detach(true);
      }
      this.closeIn !== "never" && super.done();
    }
  }
  unsubscribe(sub) {
    if (this.stream && (!sub || this.subs.length === 1)) {
      this.detach(!sub);
    }
    return super.unsubscribe(sub);
  }
  detach(force) {
    if (force || this.closeOut !== "never") {
      assert(!!this.stream, "input stream already removed");
      this.stream.unsubscribe(this.sub);
      delete this.stream;
      delete this.sub;
    }
  }
}
export {
  MetaStream,
  metaStream
};