Update Blob files downloading implementation to cover more websites

Author: Tyschenko

android/src/main/java/com/reactnativecommunity/webview/RNCWebView.java

@@ -46,6 +46,7 @@
 import com.facebook.react.views.scroll.ScrollEventType;
 import com.reactnativecommunity.webview.events.TopCustomMenuSelectionEvent;
 import com.reactnativecommunity.webview.events.TopMessageEvent;
+import com.reactnativecommunity.webview.extension.file.BlobFileDownloader;
 
 import org.json.JSONException;
 import org.json.JSONObject;
@@ -338,6 +339,10 @@ public void callInjectedJavaScript() {
         }
     }
 
+    public void injectBlobFileDownloaderScript() {
+        evaluateJavascriptWithFallback(BlobFileDownloader.Companion.getBlobFileInterceptor());
+    }
+
     public void callInjectedJavaScriptBeforeContentLoaded() {
         if (getSettings().getJavaScriptEnabled() &&
                 injectedJSBeforeContentLoaded != null &&

android/src/main/java/com/reactnativecommunity/webview/RNCWebViewClient.java

@@ -74,6 +74,8 @@ public void onPageFinished(WebView webView, String url) {
 
             reactWebView.callInjectedJavaScript();
 
+            reactWebView.injectBlobFileDownloaderScript();
+
             emitFinishEvent(webView, url);
         }
     }

android/src/main/java/com/reactnativecommunity/webview/RNCWebViewManagerImpl.kt

@@ -124,7 +124,7 @@ class RNCWebViewManagerImpl(private val newArch: Boolean = false) {
 			      	  return@DownloadListener
 			      }
 			      if (url.startsWith("blob:")) {
-			      	  webView.evaluateJavascriptWithFallback(BlobFileDownloader.getBase64StringFromBlobUrl(url))
+                      // Handled in RNCWebView.injectBlobFileDownloaderScript()
 			      	  return@DownloadListener
 			      }
             webView.setIgnoreErrFailedForThisURL(url)

android/src/main/java/com/reactnativecommunity/webview/extension/file/Base64FileDownloader.kt

@@ -80,7 +80,7 @@ internal object Base64FileDownloader {
 
 
 	private fun getMimeTypeAndFileExtension(header: String): Pair<String, String> {
-		val mimeType = Regex("data:(.*?);base64").find(header)?.groupValues?.get(1) ?: "application/octet-stream"
+		val mimeType = Regex("data:([^;]+)").find(header)?.groupValues?.get(1) ?: "application/octet-stream"
 		val extension = MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType) ?: "bin"
 		return mimeType to extension
 	}

android/src/main/java/com/reactnativecommunity/webview/extension/file/BlobFileDownloader.kt

@@ -28,24 +28,21 @@ internal class BlobFileDownloader(
 	companion object {
 		const val JS_INTERFACE_TAG: String = "BlobFileDownloader"
 
-		fun getBase64StringFromBlobUrl(blobUrl: String): String {
-			return """
-                javascript: var xhr = new XMLHttpRequest();
-                xhr.open('GET', '$blobUrl', true);
-                xhr.responseType = 'blob';
-                xhr.onload = function(e) {
-                    if (this.status == 200) {
-                        var blobFile = this.response;
-                        var reader = new FileReader();
-                        reader.readAsDataURL(blobFile);
-                        reader.onloadend = function() {
-                            var base64 = reader.result;
-                            ${JS_INTERFACE_TAG}.getBase64FromBlobData(base64);
-                        }
-                    }
-                };
-                xhr.send();
-            """.trimIndent()
-		}
+    fun getBlobFileInterceptor(): String =
+      """
+        (function() {
+          const originalCreateObjectURL = URL.createObjectURL;
+          URL.createObjectURL = function(blob) {
+            const url = originalCreateObjectURL.call(URL, blob);
+            const reader = new FileReader();
+            reader.readAsDataURL(blob);
+            reader.onloadend = function() {
+              const base64 = reader.result;
+              ${JS_INTERFACE_TAG}.getBase64FromBlobData(base64);
+            };
+            return url;
+          };
+        })();
+    """.trimIndent()
 	}
 }