Implement onLoading(Start|Finish|Error) and injectedJavaScript props

Summary:
@public

This diff includes four very straightforward changes:
1. Whenever the WebView starts loading, the `onLoadingStart` hook should be executed. The event passed into this hook should be decorated with the `navigationType`.
1. Whenever the WebView errors out while loading, the `onLoadingError` hook should be executed.
1. Whenever the WebView finishes loading (without any errors), the `onLoadingFinish` hook should be executed.
1. The serialized JavaScript passed into the `injectedJavaScript` prop should be executed when the WebView finishes loading. After execution finishes, the `onLoadingFinish` prop should be called with the serialized completion value of this JavaScript.

Reviewed By: shergin

Differential Revision: D6293532

fbshipit-source-id: 21407c766f73413046823ae605afc21e85cf9db6

Author: RSNara

React/Views/RCTWKWebView.h

@@ -18,5 +18,6 @@
 
 @property (nonatomic, weak) id<RCTWKWebViewDelegate> delegate;
 @property (nonatomic, copy) NSDictionary *source;
+@property (nonatomic, copy) NSString *injectedJavaScript;
 
 @end

React/Views/RCTWKWebView.m

@@ -6,12 +6,15 @@
 
 #import "RCTAutoInsetsProtocol.h"
 
-@interface RCTWKWebView () <WKUIDelegate>
+@interface RCTWKWebView () <WKUIDelegate, WKNavigationDelegate>
+@property (nonatomic, copy) RCTDirectEventBlock onLoadingStart;
+@property (nonatomic, copy) RCTDirectEventBlock onLoadingFinish;
+@property (nonatomic, copy) RCTDirectEventBlock onLoadingError;
+@property (nonatomic, copy) WKWebView *webView;
 @end
 
 @implementation RCTWKWebView
 {
-  WKWebView *_webView;
 }
 
 - (void)dealloc
@@ -25,6 +28,7 @@ - (instancetype)initWithFrame:(CGRect)frame
     super.backgroundColor = [UIColor clearColor];
     _webView = [[WKWebView alloc] initWithFrame:self.bounds];
     _webView.UIDelegate = self;
+    _webView.navigationDelegate = self;
     [self addSubview:_webView];
   }
   return self;
@@ -69,4 +73,119 @@ - (void)layoutSubviews
   _webView.frame = self.bounds;
 }
 
+- (NSMutableDictionary<NSString *, id> *)baseEvent
+{
+  NSDictionary *event = @{
+    @"url": _webView.URL.absoluteString ?: @"",
+    @"title": _webView.title,
+    @"loading" : @(_webView.loading),
+    @"canGoBack": @(_webView.canGoBack),
+    @"canGoForward" : @(_webView.canGoForward)
+  };
+  return [[NSMutableDictionary alloc] initWithDictionary: event];
+}
+
+#pragma mark - WKNavigationDelegate methods
+
+/**
+ * Decides whether to allow or cancel a navigation.
+ * @see https://fburl.com/42r9fxob
+ */
+- (void)                  webView:(WKWebView *)webView
+  decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction
+                  decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler
+{
+  static NSDictionary<NSNumber *, NSString *> *navigationTypes;
+  static dispatch_once_t onceToken;
+
+  dispatch_once(&onceToken, ^{
+    navigationTypes = @{
+      @(WKNavigationTypeLinkActivated): @"click",
+      @(WKNavigationTypeFormSubmitted): @"formsubmit",
+      @(WKNavigationTypeBackForward): @"backforward",
+      @(WKNavigationTypeReload): @"reload",
+      @(WKNavigationTypeFormResubmitted): @"formresubmit",
+      @(WKNavigationTypeOther): @"other",
+    };
+  });
+
+  WKNavigationType navigationType = navigationAction.navigationType;
+  NSURLRequest *request = navigationAction.request;
+
+  if (_onLoadingStart) {
+    // We have this check to filter out iframe requests and whatnot
+    BOOL isTopFrame = [request.URL isEqual:request.mainDocumentURL];
+    if (isTopFrame) {
+      NSMutableDictionary<NSString *, id> *event = [self baseEvent];
+      [event addEntriesFromDictionary: @{
+        @"url": (request.URL).absoluteString,
+        @"navigationType": navigationTypes[@(navigationType)]
+      }];
+      _onLoadingStart(event);
+    }
+  }
+
+  // Allow all navigation by default
+  decisionHandler(WKNavigationResponsePolicyAllow);
+}
+
+/**
+ * Called when an error occurs while the web view is loading content.
+ * @see https://fburl.com/km6vqenw
+ */
+- (void)               webView:(WKWebView *)webView
+  didFailProvisionalNavigation:(WKNavigation *)navigation
+                     withError:(NSError *)error
+{
+  if (_onLoadingError) {
+    if ([error.domain isEqualToString:NSURLErrorDomain] && error.code == NSURLErrorCancelled) {
+      // NSURLErrorCancelled is reported when a page has a redirect OR if you load
+      // a new URL in the WebView before the previous one came back. We can just
+      // ignore these since they aren't real errors.
+      // http://stackoverflow.com/questions/1024748/how-do-i-fix-nsurlerrordomain-error-999-in-iphone-3-0-os
+      return;
+    }
+
+    NSMutableDictionary<NSString *, id> *event = [self baseEvent];
+    [event addEntriesFromDictionary:@{
+      @"didFailProvisionalNavigation": @YES,
+      @"domain": error.domain,
+      @"code": @(error.code),
+      @"description": error.localizedDescription,
+    }];
+    _onLoadingError(event);
+  }
+}
+
+- (void)evaluateJS:(NSString *)js
+          thenCall: (void (^)(NSString*)) callback
+{
+  [self.webView evaluateJavaScript: js completionHandler: ^(id result, NSError *error) {
+    if (error == nil) {
+      callback([NSString stringWithFormat:@"%@", result]);
+    }
+  }];
+}
+
+
+/**
+ * Called when the navigation is complete.
+ * @see https://fburl.com/rtys6jlb
+ */
+- (void)      webView:(WKWebView *)webView
+  didFinishNavigation:(WKNavigation *)navigation
+{
+  if (_injectedJavaScript) {
+    [self evaluateJS: _injectedJavaScript thenCall: ^(NSString *jsEvaluationValue) {
+      NSMutableDictionary *event = [self baseEvent];
+      event[@"jsEvaluationValue"] = jsEvaluationValue;
+      if (self.onLoadingFinish) {
+        self.onLoadingFinish(event);
+      }
+    }];
+  } else if (_onLoadingFinish) {
+    _onLoadingFinish([self baseEvent]);
+  }
+}
+
 @end

React/Views/RCTWKWebViewManager.m

@@ -14,5 +14,9 @@ - (UIView *)view
 }
 
 RCT_EXPORT_VIEW_PROPERTY(source, NSDictionary)
+RCT_EXPORT_VIEW_PROPERTY(onLoadingStart, RCTDirectEventBlock)
+RCT_EXPORT_VIEW_PROPERTY(onLoadingFinish, RCTDirectEventBlock)
+RCT_EXPORT_VIEW_PROPERTY(onLoadingError, RCTDirectEventBlock)
+RCT_EXPORT_VIEW_PROPERTY(injectedJavaScript, NSString)
 
 @end