Split up AnimatedImplementation.js

Summary:
AnimatedImplementation.js is getting pretty hard to navigate and reason about so I split it up into different modules. Also took the opportunity to run prettier on that code and do some minor const/let refactorings. This doesn't change any logic, mostly just moves code around and add proper imports / exports.

This opens the door for further cleanup and flow type improvements but want to keep this already big PR as small as possible.

Discussion points:
- Should I use haste for this? Animated is pretty much a standalone module, it still uses a few haste imports but for new modules I used commonjs imports to avoid polluting the haste global namespace too much. The new modules are all internal to Animated and should not be imported externally.
- We're using `requestAnimationFrame` from fbjs instead of the one available globally in RN and browsers is there a reason for that?
- Should we even support web in this implementation? There is a standalone repo that exist for Animated web. Is this implementation of Animated web used internally at facebook?
- Probably still related to web, we used some weird Set polyfill is that still needed?

Notes:
There is a small regression for docs where the type of some classes that are exported like AnimatedValue show up as CallExpression instead if Class.

<img width="655" alt="screen shot 2017-08-14 at 3 19 18 am" src="https://user-images.githubusercontent.com/2677334/29261820-8f243036-809f-11e7-8bf0-0fe9f93939ca.png">

**Test plan**
Tested that all Animated related examples still work in RNTester on iOS and Android.
Tested that the doc is still working
Ran unit tests
Closes #15485

Differential Revision: D5679886

Pulled By: sahrens

fbshipit-source-id: d3e9b6987ab5ff2cd20108c3b9d860c7536be8a0

Libraries/Animated/src/AnimatedEvent.js

@@ -0,0 +1,195 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
+ * @format
+ */
+'use strict';
+
+const AnimatedValue = require('./nodes/AnimatedValue');
+const NativeAnimatedHelper = require('./NativeAnimatedHelper');
+const ReactNative = require('ReactNative');
+
+const invariant = require('fbjs/lib/invariant');
+const {shouldUseNativeDriver} = require('./NativeAnimatedHelper');
+
+export type Mapping = {[key: string]: Mapping} | AnimatedValue;
+export type EventConfig = {
+  listener?: ?Function,
+  useNativeDriver?: boolean,
+};
+
+function attachNativeEvent(
+  viewRef: any,
+  eventName: string,
+  argMapping: Array<?Mapping>,
+) {
+  // Find animated values in `argMapping` and create an array representing their
+  // key path inside the `nativeEvent` object. Ex.: ['contentOffset', 'x'].
+  const eventMappings = [];
+
+  const traverse = (value, path) => {
+    if (value instanceof AnimatedValue) {
+      value.__makeNative();
+
+      eventMappings.push({
+        nativeEventPath: path,
+        animatedValueTag: value.__getNativeTag(),
+      });
+    } else if (typeof value === 'object') {
+      for (const key in value) {
+        traverse(value[key], path.concat(key));
+      }
+    }
+  };
+
+  invariant(
+    argMapping[0] && argMapping[0].nativeEvent,
+    'Native driven events only support animated values contained inside `nativeEvent`.',
+  );
+
+  // Assume that the event containing `nativeEvent` is always the first argument.
+  traverse(argMapping[0].nativeEvent, []);
+
+  const viewTag = ReactNative.findNodeHandle(viewRef);
+
+  eventMappings.forEach(mapping => {
+    NativeAnimatedHelper.API.addAnimatedEventToView(
+      viewTag,
+      eventName,
+      mapping,
+    );
+  });
+
+  return {
+    detach() {
+      eventMappings.forEach(mapping => {
+        NativeAnimatedHelper.API.removeAnimatedEventFromView(
+          viewTag,
+          eventName,
+          mapping.animatedValueTag,
+        );
+      });
+    },
+  };
+}
+
+class AnimatedEvent {
+  _argMapping: Array<?Mapping>;
+  _listeners: Array<Function> = [];
+  _callListeners: Function;
+  _attachedEvent: ?{
+    detach: () => void,
+  };
+  __isNative: boolean;
+
+  constructor(argMapping: Array<?Mapping>, config?: EventConfig = {}) {
+    this._argMapping = argMapping;
+    if (config.listener) {
+      this.__addListener(config.listener);
+    }
+    this._callListeners = this._callListeners.bind(this);
+    this._attachedEvent = null;
+    this.__isNative = shouldUseNativeDriver(config);
+
+    if (__DEV__) {
+      this._validateMapping();
+    }
+  }
+
+  __addListener(callback: Function): void {
+    this._listeners.push(callback);
+  }
+
+  __removeListener(callback: Function): void {
+    this._listeners = this._listeners.filter(listener => listener !== callback);
+  }
+
+  __attach(viewRef: any, eventName: string) {
+    invariant(
+      this.__isNative,
+      'Only native driven events need to be attached.',
+    );
+
+    this._attachedEvent = attachNativeEvent(
+      viewRef,
+      eventName,
+      this._argMapping,
+    );
+  }
+
+  __detach(viewTag: any, eventName: string) {
+    invariant(
+      this.__isNative,
+      'Only native driven events need to be detached.',
+    );
+
+    this._attachedEvent && this._attachedEvent.detach();
+  }
+
+  __getHandler() {
+    if (this.__isNative) {
+      return this._callListeners;
+    }
+
+    return (...args: any) => {
+      const traverse = (recMapping, recEvt, key) => {
+        if (typeof recEvt === 'number' && recMapping instanceof AnimatedValue) {
+          recMapping.setValue(recEvt);
+        } else if (typeof recMapping === 'object') {
+          for (const mappingKey in recMapping) {
+            /* $FlowFixMe(>=0.53.0 site=react_native_fb) This comment
+             * suppresses an error found when Flow v0.53 was deployed. To see
+             * the error delete this comment and run Flow. */
+            traverse(recMapping[mappingKey], recEvt[mappingKey], mappingKey);
+          }
+        }
+      };
+
+      if (!this.__isNative) {
+        this._argMapping.forEach((mapping, idx) => {
+          traverse(mapping, args[idx], 'arg' + idx);
+        });
+      }
+      this._callListeners(...args);
+    };
+  }
+
+  _callListeners(...args) {
+    this._listeners.forEach(listener => listener(...args));
+  }
+
+  _validateMapping() {
+    const traverse = (recMapping, recEvt, key) => {
+      if (typeof recEvt === 'number') {
+        invariant(
+          recMapping instanceof AnimatedValue,
+          'Bad mapping of type ' +
+            typeof recMapping +
+            ' for key ' +
+            key +
+            ', event value must map to AnimatedValue',
+        );
+        return;
+      }
+      invariant(
+        typeof recMapping === 'object',
+        'Bad mapping of type ' + typeof recMapping + ' for key ' + key,
+      );
+      invariant(
+        typeof recEvt === 'object',
+        'Bad event of type ' + typeof recEvt + ' for key ' + key,
+      );
+      for (const mappingKey in recMapping) {
+        traverse(recMapping[mappingKey], recEvt[mappingKey], mappingKey);
+      }
+    };
+  }
+}
+
+module.exports = {AnimatedEvent, attachNativeEvent};