fix(deprecation warnings): Fix deprecation warnings (#301)

* fix(deprecations): Add `+ (UIWindow *)getKeyWindow;` wrapper to AMPUtils

* fix(deprecations): Add diagnostic ignored around `statusBarFrame` usage

* fix(deprecations): Add availability-checked unarchive method to Amplitude

* fix(deprecations): Add availability checking to archive method in Amplitude

* fix(deprecations): Wrap usage of `CC_MD5` into `diagnostic ignored`

As mentioned by @haoliu-amp in
#250 (comment),
> This crypto algorithm is used for our checksum field, actually you don't need to worry about the security concern for that.
> However, we will see if we wanna switch it to SHA256.
Based on this, we can silence the compile warning here until a fix is implemented.

* fix(deprecations): Add tvOS to availability checks

* style: Add missing newlines, replace dot syntax by bracket syntax

Sources/Amplitude/AMPEventExplorer.m

@@ -59,7 +59,7 @@ - (void)showBubbleView {
 
         dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.1 * NSEC_PER_SEC));
         dispatch_after(popTime, dispatch_get_main_queue(), ^(void) {
-            [[[AMPUtils getSharedApplication] keyWindow] addSubview:self.bubbleView];
+            [[AMPUtils getKeyWindow] addSubview:self.bubbleView];
         });
 
         [self.bubbleView addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(showInfoView)]];
@@ -70,7 +70,7 @@ - (void)showBubbleView {
 - (void)showInfoView {
     dispatch_async(dispatch_get_main_queue(), ^(void){
         if (self.bubbleView != nil) {
-            UIViewController *rootViewController = [[[AMPUtils getSharedApplication] keyWindow] rootViewController];
+            UIViewController *rootViewController = [[AMPUtils getKeyWindow] rootViewController];
 
             NSBundle *bundle = [NSBundle bundleForClass:[AMPInfoViewController class]];
             AMPInfoViewController *infoVC = [[AMPInfoViewController alloc] initWithNibName:@"AMPInfoViewController" bundle:bundle];

Sources/Amplitude/AMPUtils.h

@@ -41,6 +41,7 @@
 #if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 + (NSInteger)barBottomOffset;
 + (CGFloat)statusBarHeight;
++ (UIWindow *)getKeyWindow;
 #endif
 
 @end

Sources/Amplitude/AMPUtils.m

@@ -172,12 +172,38 @@ + (NSInteger)barBottomOffset {
 + (CGFloat)statusBarHeight {
     CGSize statusBarSize;
     if (@available(iOS 13.0, *)) {
-        statusBarSize = [[[[AMPUtils getSharedApplication].keyWindow windowScene] statusBarManager] statusBarFrame].size;
+        statusBarSize = [[[[AMPUtils getKeyWindow] windowScene] statusBarManager] statusBarFrame].size;
     } else {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+        // Even with the availability check above, Xcode would still emit a deprecation warning here.
+        // Since there's no way that it could be reached on iOS's >= 13.0
+        // (where `[UIApplication statusBarFrame]` was deprecated), we simply ignore the warning.
         statusBarSize = [[AMPUtils getSharedApplication] statusBarFrame].size;
+#pragma clang diagnostic pop
     }
     return MIN(statusBarSize.width, statusBarSize.height);
 }
+
++ (UIWindow *)getKeyWindow {
+    if (@available(iOS 13.0, *)) {
+        for (UIWindow *window in [[AMPUtils getSharedApplication] windows]) {
+            if ([window isKeyWindow]) {
+                return window;
+            }
+        }
+        return nil;
+    } else {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+        // Even with the availability check above, Xcode would still emit a deprecation warning here.
+        // Since there's no way that it could be reached on iOS's >= 13.0
+        // (where `[UIApplication keyWindow]` was deprecated), we simply ignore the warning.
+        return [[AMPUtils getSharedApplication] keyWindow];
+#pragma clang diagnostic pop
+    }
+}
+
 #endif
 
 @end

Sources/Amplitude/Amplitude.m

@@ -1534,7 +1534,15 @@ - (BOOL)isArgument:(id) argument validType:(Class) class methodName:(NSString*)m
 - (NSString*)md5HexDigest:(NSString*)input {
     const char* str = [input UTF8String];
     unsigned char result[CC_MD5_DIGEST_LENGTH];
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+    // As mentioned by @haoliu-amp in // https://github.com/amplitude/Amplitude-iOS/issues/250#issuecomment-655224554,
+    // > This crypto algorithm is used for our checksum field, actually you don't need to worry about the security concern for that.
+    // > However, we will see if we wanna switch it to SHA256.
+    // Based on this, we can silence the compile warning here until a fix is implemented.
     CC_MD5(str, (CC_LONG) strlen(str), result);
+#pragma clang diagnostic pop
 
     NSMutableString *ret = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH*2];
     for(int i = 0; i<CC_MD5_DIGEST_LENGTH; i++) {
@@ -1647,7 +1655,7 @@ - (id)unarchive:(NSString*)path {
             NSData *inputData = [fileManager contentsAtPath:path];
             NSError *error = nil;
             if (inputData != nil) {
-                id data = [NSKeyedUnarchiver unarchiveTopLevelObjectWithData:inputData error:&error];
+                id data = [self unarchive:inputData error:&error];
                 if (error == nil) {
                     if (data != nil) {
                         return data;
@@ -1677,8 +1685,50 @@ - (id)unarchive:(NSString*)path {
     return nil;
 }
 
+- (id)unarchive:(NSData *)data error:(NSError **)error {
+    if (@available(iOS 12, tvOS 11.0, *)) {
+        return [NSKeyedUnarchiver unarchivedObjectOfClass:[NSDictionary class] fromData:data error:error];
+    } else {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+        // Even with the availability check above, Xcode would still emit a deprecation warning here.
+        // Since there's no way that it could be reached on iOS's >= 12.0 or tvOS's >= 11.0
+        // (where `[NSKeyedUnarchiver unarchiveTopLevelObjectWithData:error:]` was deprecated),
+        // we simply ignore the warning.
+        return [NSKeyedUnarchiver unarchiveTopLevelObjectWithData:data error:error];
+#pragma clang diagnostic pop
+    }
+}
+
 - (BOOL)archive:(id) obj toFile:(NSString*)path {
-    return [NSKeyedArchiver archiveRootObject:obj toFile:path];
+    if (@available(tvOS 11.0, iOS 12, *)) {
+        NSError *archiveError = nil;
+        NSData *data = [NSKeyedArchiver archivedDataWithRootObject:obj requiringSecureCoding:NO error:&archiveError];
+        if (archiveError != nil) {
+            AMPLITUDE_ERROR(@"ERROR: Unable to archive object %@: %@", obj, archiveError);
+            return NO;
+        }
+        if (data == nil) {
+            AMPLITUDE_ERROR(@"ERROR: Archived data is nil for obj: %@", obj);
+            return NO;
+        }
+        NSError *writeError = nil;
+        BOOL writeSuccessful = [data writeToFile:path options:NSDataWritingAtomic error:&writeError];
+        if (writeError != nil || !writeSuccessful) {
+            AMPLITUDE_ERROR(@"ERROR: Unable to write data to file for object %@: %@", obj, archiveError);
+            return NO;
+        }
+        return YES;
+    } else {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+        // Even with the availability check above, Xcode would still emit a deprecation warning here.
+        // Since there's no way that this path could be reached on iOS's >= 12.0 or tvOS's >= 11.0
+        // (where `[NSKeyedArchiver archiveRootObject:toFile:]` was deprecated),
+        // we simply ignore the warning.
+        return [NSKeyedArchiver archiveRootObject:obj toFile:path];
+#pragma clang diagnostic pop
+    }
 }
 
 - (BOOL)moveFileIfNotExists:(NSString*)from to:(NSString*)to {