callbag-remember/dist/callbag-remember.esm.js

👜 Callbag operator which shares input stream between subscribers and emits last emitted value upon subscription.

var noop = function noop() {};

var UNIQUE = {};
function remember(source) {
  var sinks = [];
  var inited = false;
  var endValue = UNIQUE;
  var sourceTalkback;
  var value;
  return function (start, sink) {
    if (start !== 0) return;

    if (endValue !== UNIQUE) {
      sink(0, noop);

      if (inited) {
        sink(1, value);
      }

      sink(2, endValue);
      return;
    }

    sinks.push(sink);

    var talkback = function talkback(type, data) {
      if (type === 2) {
        var index = sinks.indexOf(sink);

        if (index !== -1) {
          sinks.splice(index, 1);
        }

        return;
      }

      if (endValue !== UNIQUE) {
        return;
      }

      sourceTalkback(type, data);
    };

    if (sinks.length === 1) {
      source(0, function (type, data) {
        if (type === 0) {
          sourceTalkback = data;
          sink(0, talkback);
          return;
        }

        if (type === 1) {
          inited = true;
          value = data;
        }

        var sinksCopy = sinks.slice(0);

        if (type === 2) {
          endValue = data;
          sinks = null;
        }

        sinksCopy.forEach(function (sink) {
          sink(type, data);
        });
      });
      return;
    }

    sink(0, talkback);

    if (inited && endValue === UNIQUE) {
      sink(1, value);
    }
  };
}

export default remember;