Implement the "download as" functionality properly in the iOS app

We need to catch the downloadas message already in
-[DocumentViewController
userContentController:didReceiveScriptMessage:] and use an
UIDocumentPickerViewController to let the user choose where to
download (or export) the document. The iOS-specific code in
ChildSession::downloadAs() can go away.

Change-Id: I626b9986ec6156f7e83bda02b04e65f7819f8017
Reviewed-on: https://gerrit.libreoffice.org/c/online/+/92112
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Tor Lillqvist <tml@collabora.com>

ios/Mobile/DocumentViewController.mm

@@ -28,8 +28,9 @@
 
 static DocumentViewController* theSingleton = nil;
 
-@interface DocumentViewController() <WKNavigationDelegate, WKUIDelegate, WKScriptMessageHandler, UIScrollViewDelegate> {
+@interface DocumentViewController() <WKNavigationDelegate, WKUIDelegate, WKScriptMessageHandler, UIScrollViewDelegate, UIDocumentPickerDelegate> {
     int closeNotificationPipeForForwardingThread[2];
+    NSURL *downloadAsTmpURL;
 }
 
 @end
@@ -449,6 +450,46 @@ static IMP standardImpOfInputAccessoryView = nil;
                 [application openURL:url options:@{} completionHandler:nil];
                 return;
             }
+        } else if ([message.body hasPrefix:@"downloadas "]) {
+            NSArray<NSString*> *messageBodyItems = [message.body componentsSeparatedByString:@" "];
+            NSString *format = nil;
+            if ([messageBodyItems count] >= 2) {
+                for (int i = 1; i < [messageBodyItems count]; i++) {
+                    if ([messageBodyItems[i] hasPrefix:@"format="])
+                        format = [messageBodyItems[i] substringFromIndex:[@"format=" length]];
+                }
+
+                if (format == nil)
+                    return;     // Warn?
+
+                // First save it in the requested format to a temporary location. First remove any
+                // leftover identically named temporary file.
+
+                NSString *tmpFileName = [[[self.document->copyFileURL lastPathComponent] stringByDeletingPathExtension] stringByAppendingString:[@"." stringByAppendingString:format]];
+                downloadAsTmpURL = [[NSFileManager.defaultManager temporaryDirectory] URLByAppendingPathComponent:tmpFileName];
+
+                std::remove([[downloadAsTmpURL path] UTF8String]);
+
+                lok_document->saveAs([[downloadAsTmpURL absoluteString] UTF8String], [format UTF8String], nullptr);
+
+                // Then verify that it indeed was saved, and then use an
+                // UIDocumentPickerViewController to ask the user where to store the exported
+                // document.
+
+                struct stat statBuf;
+                if (stat([[downloadAsTmpURL path] UTF8String], &statBuf) == -1) {
+                    LOG_ERR("Could apparently not save to '" <<  [[downloadAsTmpURL path] UTF8String] << "'");
+                } else {
+                    UIDocumentPickerViewController *picker =
+                        [[UIDocumentPickerViewController alloc] initWithURL:downloadAsTmpURL
+                                                                     inMode:UIDocumentPickerModeExportToService];
+                    picker.delegate = self;
+                    [self presentViewController:picker
+                                       animated:YES
+                                     completion:nil];
+                }
+                return;
+            }
         }
 
         const char *buf = [message.body UTF8String];
@@ -461,6 +502,14 @@ static IMP standardImpOfInputAccessoryView = nil;
     }
 }
 
+- (void)documentPicker:(UIDocumentPickerViewController *)controller didPickDocumentsAtURLs:(NSArray<NSURL *> *)urls {
+    std::remove([[downloadAsTmpURL path] UTF8String]);
+}
+
+- (void)documentPickerWasCancelled:(UIDocumentPickerViewController *)controller {
+    std::remove([[downloadAsTmpURL path] UTF8String]);
+}
+
 - (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(UIView *)view {
     scrollView.pinchGestureRecognizer.enabled = NO;
 }

kit/ChildSession.cpp

@@ -921,56 +921,8 @@ bool ChildSession::downloadAs(const char* /*buffer*/, int /*length*/, const Stri
     }
 
 #ifdef IOS
-    NSURL *docURL = [NSURL URLWithString:[NSString stringWithUTF8String:getDocURL().c_str()]];
+    NSLog(@"We should never come here, aborting");
-
+    std::abort();
-#if 0
-    // Experimentation
-
-    // Check if we can figure out the name of the file provider service the document is on. (No, the
-    // services dictionary passed to the completion handler is always empty, except for On My iPad
-    // and iCloud Drive.)
-    [NSFileManager.defaultManager
-     getFileProviderServicesForItemAtURL:docURL
-                       completionHandler:^(NSDictionary<NSFileProviderServiceName,NSFileProviderService *> *services,
-                                           NSError *error) {
-            if (services == nil) {
-                std::cerr << "Could not get file provider services for " << [[docURL absoluteString] UTF8String] << "\n";
-            } else if ([services count] == 0) {
-                std::cerr << "No file provider services returned for " << [[docURL absoluteString] UTF8String] << "\n";
-            } else {
-                std::cerr << "File provider services for " << [[docURL absoluteString] UTF8String] << ":\n";
-                for (auto key in [services allKeys]) {
-                    std::cerr << "  " << [(NSString*)key UTF8String] << "\n";
-                }
-            }
-        }];
-
-    // Check if we can figure out the "ubiquitous item container" name, which apparently means the file provider extension name.
-    // Alas, this seems to work only for documents on iCloud Drive.
-    NSError *error;
-    auto resources = [docURL promisedItemResourceValuesForKeys:@[NSURLUbiquitousItemContainerDisplayNameKey] error:&error];
-    if (resources == nil) {
-        std::cerr << "Could not get ubiquitous container names for " << [[docURL absoluteString] UTF8String] << "\n";
-    } else if ([resources count] == 0) {
-        std::cerr << "No ubiquitous container names for " << [[docURL absoluteString] UTF8String] << "\n";
-    } else {
-        std::cerr << "Ubiquitous container names for " << [[docURL absoluteString] UTF8String] << ":\n";
-        for (auto name in [resources allValues]) {
-            std::cerr << "  " << [(NSString*)name UTF8String] << "\n";
-        }
-    }
-#endif
-
-    NSArray<NSString *> *pathComponents = [docURL pathComponents];
-    NSString *baseName = [[pathComponents lastObject] stringByDeletingPathExtension];
-    NSURL *documentDirectory = [NSFileManager.defaultManager URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask][0];
-    NSString *dotFormat = [@"." stringByAppendingString:[NSString stringWithUTF8String:format.c_str()]];
-    NSURL *exportedURL = [documentDirectory URLByAppendingPathComponent:[baseName stringByAppendingString:dotFormat]];
-    LOG_TRC("Exporting as " << [[exportedURL absoluteString] UTF8String]);
-
-    getLOKitDocument()->saveAs([[exportedURL absoluteString] UTF8String],
-                               format.empty() ? nullptr : format.c_str(),
-                               filterOptions.empty() ? nullptr : filterOptions.c_str());
 #else
     // Prevent user inputting anything funny here.
     // A "name" should always be a name, not a path