CB-7667 iOS8: Handle case where camera is not authorized (closes #49)

In iOS 7+, when the app does not have access to the camera, show a
prompt notifying the user so they're not puzzled by looking at a black
screen.

In iOS 8+, include a link on the dialog to open the Setting app to allow
the user to change their Camera privacy setting.

Signed-off-by: Shazron Abdullah <shazron@apache.org>

plugin.xml

@@ -146,6 +146,7 @@
          <framework src="AssetsLibrary.framework" />
          <framework src="MobileCoreServices.framework" />
          <framework src="CoreGraphics.framework" />
+         <framework src="AVFoundation.framework" />
          
          <config-file target="*-Info.plist" parent="NSLocationWhenInUseUsageDescription">
              <string></string>

src/ios/CDVCamera.m

@@ -24,6 +24,7 @@
 #import <ImageIO/CGImageProperties.h>
 #import <AssetsLibrary/ALAssetRepresentation.h>
 #import <AssetsLibrary/AssetsLibrary.h>
+#import <AVFoundation/AVFoundation.h>
 #import <ImageIO/CGImageSource.h>
 #import <ImageIO/CGImageProperties.h>
 #import <ImageIO/CGImageDestination.h>
@@ -141,7 +142,29 @@ static NSString* toBase64(NSData* data) {
             [weakSelf.commandDelegate sendPluginResult:result callbackId:command.callbackId];
             return;
         }
-        
+
+        // Validate the app has permission to access the camera
+        if (pictureOptions.sourceType == UIImagePickerControllerSourceTypeCamera && [AVCaptureDevice respondsToSelector:@selector(authorizationStatusForMediaType:)]) {
+            AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
+            if (authStatus == AVAuthorizationStatusDenied ||
+                authStatus == AVAuthorizationStatusRestricted) {
+                // If iOS 8+, offer a link to the Settings app
+                NSString* settingsButton = (&UIApplicationOpenSettingsURLString != NULL)
+                    ? NSLocalizedString(@"Settings", nil)
+                    : nil;
+
+                // Denied; show an alert
+                dispatch_async(dispatch_get_main_queue(), ^{
+                    [[[UIAlertView alloc] initWithTitle:[[NSBundle mainBundle]
+                                                         objectForInfoDictionaryKey:@"CFBundleDisplayName"]
+                                                message:NSLocalizedString(@"Access to the camera has been prohibited; please enable it in the Settings app to continue.", nil)
+                                               delegate:self
+                                      cancelButtonTitle:NSLocalizedString(@"OK", nil)
+                                      otherButtonTitles:settingsButton, nil] show];
+                });
+            }
+        }
+
         CDVCameraPicker* cameraPicker = [CDVCameraPicker createFromPictureOptions:pictureOptions];
         weakSelf.pickerController = cameraPicker;
         
@@ -174,6 +197,25 @@ static NSString* toBase64(NSData* data) {
     }];
 }
 
+// Delegate for camera permission UIAlertView
+- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
+{
+    // If Settings button (on iOS 8), open the settings app
+    if (buttonIndex == 1) {
+        [[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
+    }
+
+    // Dismiss the view
+    [[self.pickerController presentingViewController] dismissViewControllerAnimated:YES completion:nil];
+
+    CDVPluginResult* result = [CDVPluginResult resultWithStatus:CDVCommandStatus_ERROR messageAsString:@"has no access to camera"];   // error callback expects string ATM
+
+    [self.commandDelegate sendPluginResult:result callbackId:self.pickerController.callbackId];
+
+    self.hasPendingOperation = NO;
+    self.pickerController = nil;
+}
+
 - (void)repositionPopover:(CDVInvokedUrlCommand*)command
 {
     NSDictionary* options = [command argumentAtIndex:0 withDefault:nil];