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Tweaks/FLEX/GlobalStateExplorers/SystemLog/FLEXSystemLogViewController.m

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+//
+//  FLEXSystemLogViewController.m
+//  FLEX
+//
+//  Created by Ryan Olson on 1/19/15.
+//  Copyright (c) 2020 FLEX Team. All rights reserved.
+//
+
+#import "FLEXSystemLogViewController.h"
+#import "FLEXASLLogController.h"
+#import "FLEXOSLogController.h"
+#import "FLEXSystemLogCell.h"
+#import "FLEXMutableListSection.h"
+#import "FLEXUtility.h"
+#import "FLEXColor.h"
+#import "FLEXResources.h"
+#import "UIBarButtonItem+FLEX.h"
+#import "NSUserDefaults+FLEX.h"
+#import "flex_fishhook.h"
+#import <dlfcn.h>
+
+@interface FLEXSystemLogViewController ()
+
+@property (nonatomic, readonly) FLEXMutableListSection<FLEXSystemLogMessage *> *logMessages;
+@property (nonatomic, readonly) id<FLEXLogController> logController;
+
+@end
+
+static void (*MSHookFunction)(void *symbol, void *replace, void **result);
+
+static BOOL FLEXDidHookNSLog = NO;
+static BOOL FLEXNSLogHookWorks = NO;
+
+BOOL (*os_log_shim_enabled)(void *addr) = nil;
+BOOL (*orig_os_log_shim_enabled)(void *addr) = nil;
+static BOOL my_os_log_shim_enabled(void *addr) {
+    return NO;
+}
+
+@implementation FLEXSystemLogViewController
+
+#pragma mark - Initialization
+
++ (void)load {
+    // User must opt-into disabling os_log
+    if (!NSUserDefaults.standardUserDefaults.flex_disableOSLog) {
+        return;
+    }
+
+    // Thanks to @Ram4096 on GitHub for telling me that
+    // os_log is conditionally enabled by the SDK version
+    void *addr = __builtin_return_address(0);
+    void *libsystem_trace = dlopen("/usr/lib/system/libsystem_trace.dylib", RTLD_LAZY);
+    os_log_shim_enabled = dlsym(libsystem_trace, "os_log_shim_enabled");
+    if (!os_log_shim_enabled) {
+        return;
+    }
+
+    FLEXDidHookNSLog = flex_rebind_symbols((struct rebinding[1]) {{
+        "os_log_shim_enabled",
+        (void *)my_os_log_shim_enabled,
+        (void **)&orig_os_log_shim_enabled
+    }}, 1) == 0;
+
+    if (FLEXDidHookNSLog && orig_os_log_shim_enabled != nil) {
+        // Check if our rebinding worked
+        FLEXNSLogHookWorks = my_os_log_shim_enabled(addr) == NO;
+    }
+
+    // So, just because we rebind the lazily loaded symbol for
+    // this function doesn't mean it's even going to be used.
+    // While it seems to be sufficient for the simulator, for
+    // whatever reason it is not sufficient on-device. We need
+    // to actually hook the function with something like Substrate.
+
+    // Check if we have substrate, and if so use that instead
+    void *handle = dlopen("/usr/lib/libsubstrate.dylib", RTLD_LAZY);
+    if (handle) {
+        MSHookFunction = dlsym(handle, "MSHookFunction");
+
+        if (MSHookFunction) {
+            // Set the hook and check if it worked
+            void *unused;
+            MSHookFunction(os_log_shim_enabled, my_os_log_shim_enabled, &unused);
+            FLEXNSLogHookWorks = os_log_shim_enabled(addr) == NO;
+        }
+    }
+}
+
+- (id)init {
+    return [super initWithStyle:UITableViewStylePlain];
+}
+
+
+#pragma mark - Overrides
+
+- (void)viewDidLoad {
+    [super viewDidLoad];
+
+    self.showsSearchBar = YES;
+    self.pinSearchBar = YES;
+
+    weakify(self)
+    id logHandler = ^(NSArray<FLEXSystemLogMessage *> *newMessages) { strongify(self)
+        [self handleUpdateWithNewMessages:newMessages];
+    };
+
+    if (FLEXOSLogAvailable() && !FLEXNSLogHookWorks) {
+        _logController = [FLEXOSLogController withUpdateHandler:logHandler];
+    } else {
+        _logController = [FLEXASLLogController withUpdateHandler:logHandler];
+    }
+
+    self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
+    self.title = @"Waiting for Logs...";
+
+    // Toolbar buttons //
+
+    UIBarButtonItem *scrollDown = [UIBarButtonItem
+        flex_itemWithImage:FLEXResources.scrollToBottomIcon
+        target:self
+        action:@selector(scrollToLastRow)
+    ];
+    UIBarButtonItem *settings = [UIBarButtonItem
+        flex_itemWithImage:FLEXResources.gearIcon
+        target:self
+        action:@selector(showLogSettings)
+    ];
+
+    [self addToolbarItems:@[scrollDown, settings]];
+}
+
+- (void)viewWillAppear:(BOOL)animated {
+    [super viewWillAppear:animated];
+
+    [self.logController startMonitoring];
+}
+
+- (NSArray<FLEXTableViewSection *> *)makeSections { weakify(self)
+    _logMessages = [FLEXMutableListSection list:@[]
+        cellConfiguration:^(FLEXSystemLogCell *cell, FLEXSystemLogMessage *message, NSInteger row) {
+            strongify(self)
+        
+            cell.logMessage = message;
+            cell.highlightedText = self.filterText;
+
+            if (row % 2 == 0) {
+                cell.backgroundColor = FLEXColor.primaryBackgroundColor;
+            } else {
+                cell.backgroundColor = FLEXColor.secondaryBackgroundColor;
+            }
+        } filterMatcher:^BOOL(NSString *filterText, FLEXSystemLogMessage *message) {
+            NSString *displayedText = [FLEXSystemLogCell displayedTextForLogMessage:message];
+            return [displayedText localizedCaseInsensitiveContainsString:filterText];
+        }
+    ];
+
+    self.logMessages.cellRegistrationMapping = @{
+        kFLEXSystemLogCellIdentifier : [FLEXSystemLogCell class]
+    };
+
+    return @[self.logMessages];
+}
+
+- (NSArray<FLEXTableViewSection *> *)nonemptySections {
+    return @[self.logMessages];
+}
+
+
+#pragma mark - Private
+
+- (void)handleUpdateWithNewMessages:(NSArray<FLEXSystemLogMessage *> *)newMessages {
+    self.title = [self.class globalsEntryTitle:FLEXGlobalsRowSystemLog];
+
+    [self.logMessages mutate:^(NSMutableArray *list) {
+        [list addObjectsFromArray:newMessages];
+    }];
+    
+    // Re-filter messages to filter against new messages
+    if (self.filterText.length) {
+        [self updateSearchResults:self.filterText];
+    }
+
+    // "Follow" the log as new messages stream in if we were previously near the bottom.
+    UITableView *tv = self.tableView;
+    BOOL wasNearBottom = tv.contentOffset.y >= tv.contentSize.height - tv.frame.size.height - 100.0;
+    [self reloadData];
+    if (wasNearBottom) {
+        [self scrollToLastRow];
+    }
+}
+
+- (void)scrollToLastRow {
+    NSInteger numberOfRows = [self.tableView numberOfRowsInSection:0];
+    if (numberOfRows > 0) {
+        NSIndexPath *last = [NSIndexPath indexPathForRow:numberOfRows - 1 inSection:0];
+        [self.tableView scrollToRowAtIndexPath:last atScrollPosition:UITableViewScrollPositionBottom animated:YES];
+    }
+}
+
+- (void)showLogSettings {
+    NSUserDefaults *defaults = NSUserDefaults.standardUserDefaults;
+    BOOL disableOSLog = defaults.flex_disableOSLog;
+    BOOL persistent = defaults.flex_cacheOSLogMessages;
+
+    NSString *aslToggle = disableOSLog ? @"Enable os_log (default)" : @"Disable os_log";
+    NSString *persistence = persistent ? @"Disable persistent logging" : @"Enable persistent logging";
+
+    NSString *title = @"System Log Settings";
+    NSString *body = @"In iOS 10 and up, ASL has been replaced by os_log. "
+    "The os_log API is much more limited. Below, you can opt-into the old behavior "
+    "if you want cleaner, more reliable logs within FLEX, but this will break "
+    "anything that expects os_log to be working, such as Console.app. "
+    "This setting requires the app to restart to take effect. \n\n"
+
+    "To get as close to the old behavior as possible with os_log enabled, logs must "
+    "be collected manually at launch and stored. This setting has no effect "
+    "on iOS 9 and below, or if os_log is disabled. "
+    "You should only enable persistent logging when you need it.";
+
+    FLEXOSLogController *logController = (FLEXOSLogController *)self.logController;
+
+    [FLEXAlert makeAlert:^(FLEXAlert *make) {
+        make.title(title).message(body);
+        make.button(aslToggle).destructiveStyle().handler(^(NSArray<NSString *> *strings) {
+            [defaults flex_toggleBoolForKey:kFLEXDefaultsDisableOSLogForceASLKey];
+        });
+
+        make.button(persistence).handler(^(NSArray<NSString *> *strings) {
+            [defaults flex_toggleBoolForKey:kFLEXDefaultsiOSPersistentOSLogKey];
+            logController.persistent = !persistent;
+            [logController.messages addObjectsFromArray:self.logMessages.list];
+        });
+        make.button(@"Dismiss").cancelStyle();
+    } showFrom:self];
+}
+
+
+#pragma mark - FLEXGlobalsEntry
+
++ (NSString *)globalsEntryTitle:(FLEXGlobalsRow)row {
+    return @"⚠️  System Log";
+}
+
++ (UIViewController *)globalsEntryViewController:(FLEXGlobalsRow)row {
+    return [self new];
+}
+
+
+#pragma mark - Table view data source
+
+- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
+    FLEXSystemLogMessage *logMessage = self.logMessages.filteredList[indexPath.row];
+    return [FLEXSystemLogCell preferredHeightForLogMessage:logMessage inWidth:self.tableView.bounds.size.width];
+}
+
+
+#pragma mark - Copy on long press
+
+- (BOOL)tableView:(UITableView *)tableView shouldShowMenuForRowAtIndexPath:(NSIndexPath *)indexPath {
+    return YES;
+}
+
+- (BOOL)tableView:(UITableView *)tableView canPerformAction:(SEL)action forRowAtIndexPath:(NSIndexPath *)indexPath withSender:(id)sender {
+    return action == @selector(copy:);
+}
+
+- (void)tableView:(UITableView *)tableView performAction:(SEL)action forRowAtIndexPath:(NSIndexPath *)indexPath withSender:(id)sender {
+    if (action == @selector(copy:)) {
+        // We usually only want to copy the log message itself, not any metadata associated with it.
+        UIPasteboard.generalPasteboard.string = self.logMessages.filteredList[indexPath.row].messageText ?: @"";
+    }
+}
+
+- (UIContextMenuConfiguration *)tableView:(UITableView *)tableView
+contextMenuConfigurationForRowAtIndexPath:(NSIndexPath *)indexPath
+                                    point:(CGPoint)point __IOS_AVAILABLE(13.0) {
+    weakify(self)
+    return [UIContextMenuConfiguration configurationWithIdentifier:nil previewProvider:nil
+        actionProvider:^UIMenu *(NSArray<UIMenuElement *> *suggestedActions) {
+            UIAction *copy = [UIAction actionWithTitle:@"Copy"
+                                                 image:nil
+                                            identifier:@"Copy"
+                                               handler:^(UIAction *action) { strongify(self)
+                // We usually only want to copy the log message itself, not any metadata associated with it.
+                UIPasteboard.generalPasteboard.string = self.logMessages.filteredList[indexPath.row].messageText ?: @"";
+            }];
+            return [UIMenu menuWithTitle:@"" image:nil identifier:nil options:UIMenuOptionsDisplayInline children:@[copy]];
+        }
+    ];
+}
+
+@end