wrap block tracker in events proxy

1 files changed, 31 insertions, 0 deletions

diff --git a/app/scripts/lib/events-proxy.js b/app/scripts/lib/events-proxy.js
new file mode 100644
index 000000000..d1199a278
--- /dev/null
+++ b/app/scripts/lib/events-proxy.js
@@ -0,0 +1,31 @@
+module.exports = function createEventEmitterProxy(eventEmitter, listeners) {
+  let target = eventEmitter
+  const eventHandlers = listeners || {}
+  const proxy = new Proxy({}, {
+    get: (obj, name) => {
+      // intercept listeners
+      if (name === 'on') return addListener
+      if (name === 'setTarget') return setTarget
+      if (name === 'proxyEventHandlers') return eventHandlers
+      return target[name]
+    },
+    set: (obj, name, value) => {
+      target[name] = value
+      return true
+    },
+  })
+  function setTarget (eventEmitter) {
+    target = eventEmitter
+    // migrate listeners
+    Object.keys(eventHandlers).forEach((name) => {
+      eventHandlers[name].forEach((handler) => target.on(name, handler))
+    })
+  }
+  function addListener (name, handler) {
+    if (!eventHandlers[name]) eventHandlers[name] = []
+    eventHandlers[name].push(handler)
+    target.on(name, handler)
+  }
+  if (listeners) proxy.setTarget(eventEmitter)
+  return proxy
+}
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