planning

node_modules/react-redux/es/utils/Subscription.js

@@ -0,0 +1,126 @@
+import { getBatch } from './batch'; // encapsulates the subscription logic for connecting a component to the redux store, as
+// well as nesting subscriptions of descendant components, so that we can ensure the
+// ancestor components re-render before descendants
+
+function createListenerCollection() {
+  var batch = getBatch();
+  var first = null;
+  var last = null;
+  return {
+    clear: function clear() {
+      first = null;
+      last = null;
+    },
+    notify: function notify() {
+      batch(function () {
+        var listener = first;
+
+        while (listener) {
+          listener.callback();
+          listener = listener.next;
+        }
+      });
+    },
+    get: function get() {
+      var listeners = [];
+      var listener = first;
+
+      while (listener) {
+        listeners.push(listener);
+        listener = listener.next;
+      }
+
+      return listeners;
+    },
+    subscribe: function subscribe(callback) {
+      var isSubscribed = true;
+      var listener = last = {
+        callback: callback,
+        next: null,
+        prev: last
+      };
+
+      if (listener.prev) {
+        listener.prev.next = listener;
+      } else {
+        first = listener;
+      }
+
+      return function unsubscribe() {
+        if (!isSubscribed || first === null) return;
+        isSubscribed = false;
+
+        if (listener.next) {
+          listener.next.prev = listener.prev;
+        } else {
+          last = listener.prev;
+        }
+
+        if (listener.prev) {
+          listener.prev.next = listener.next;
+        } else {
+          first = listener.next;
+        }
+      };
+    }
+  };
+}
+
+var nullListeners = {
+  notify: function notify() {},
+  get: function get() {
+    return [];
+  }
+};
+export function createSubscription(store, parentSub) {
+  var unsubscribe;
+  var listeners = nullListeners;
+
+  function addNestedSub(listener) {
+    trySubscribe();
+    return listeners.subscribe(listener);
+  }
+
+  function notifyNestedSubs() {
+    listeners.notify();
+  }
+
+  function handleChangeWrapper() {
+    if (subscription.onStateChange) {
+      subscription.onStateChange();
+    }
+  }
+
+  function isSubscribed() {
+    return Boolean(unsubscribe);
+  }
+
+  function trySubscribe() {
+    if (!unsubscribe) {
+      unsubscribe = parentSub ? parentSub.addNestedSub(handleChangeWrapper) : store.subscribe(handleChangeWrapper);
+      listeners = createListenerCollection();
+    }
+  }
+
+  function tryUnsubscribe() {
+    if (unsubscribe) {
+      unsubscribe();
+      unsubscribe = undefined;
+      listeners.clear();
+      listeners = nullListeners;
+    }
+  }
+
+  var subscription = {
+    addNestedSub: addNestedSub,
+    notifyNestedSubs: notifyNestedSubs,
+    handleChangeWrapper: handleChangeWrapper,
+    isSubscribed: isSubscribed,
+    trySubscribe: trySubscribe,
+    tryUnsubscribe: tryUnsubscribe,
+    getListeners: function getListeners() {
+      return listeners;
+    }
+  };
+  return subscription;
+}