FLEX/Classes/GlobalStateExplorers/SystemLog/FLEXSystemLogTableViewController.m

//
//  FLEXSystemLogTableViewController.m
//  UICatalog
//
//  Created by Ryan Olson on 1/19/15.
//  Copyright (c) 2015 f. All rights reserved.
//

#import "FLEXSystemLogTableViewController.h"
#import "FLEXUtility.h"
#import "FLEXSystemLogMessage.h"
#import "FLEXSystemLogMessage+Private.h"
#import "FLEXSystemLogTableViewCell.h"
#import <asl.h>

@interface FLEXSystemLogTableViewController () <UISearchDisplayDelegate>

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
@property (nonatomic, strong) UISearchDisplayController *searchController;
#pragma clang diagnostic pop
@property (nonatomic, copy) NSArray *logMessages;
@property (nonatomic, copy) NSArray *filteredLogMessages;
@property (nonatomic, strong) NSTimer *logUpdateTimer;

@end

@implementation FLEXSystemLogTableViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self.tableView registerClass:[FLEXSystemLogTableViewCell class] forCellReuseIdentifier:kFLEXSystemLogTableViewCellIdentifier];
    self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
    self.title = @"Loading...";
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@" ⬇︎ " style:UIBarButtonItemStylePlain target:self action:@selector(scrollToLastRow)];

    UISearchBar *searchBar = [[UISearchBar alloc] init];
    [searchBar sizeToFit];
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    self.searchController = [[UISearchDisplayController alloc] initWithSearchBar:searchBar contentsController:self];
#pragma clang diagnostic pop
    self.searchController.delegate = self;
    self.searchController.searchResultsDataSource = self;
    self.searchController.searchResultsDelegate = self;
    [self.searchController.searchResultsTableView registerClass:[FLEXSystemLogTableViewCell class] forCellReuseIdentifier:kFLEXSystemLogTableViewCellIdentifier];
    self.searchController.searchResultsTableView.separatorStyle = UITableViewCellSeparatorStyleNone;
    self.tableView.tableHeaderView = self.searchController.searchBar;

    [self updateLogMessages];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    NSTimeInterval updateInterval = 1.0;

#if TARGET_IPHONE_SIMULATOR
    // Querrying the ASL is much slower in the simulator. We need a longer polling interval to keep things repsonsive.
    updateInterval = 5.0;
#endif

    self.logUpdateTimer = [NSTimer scheduledTimerWithTimeInterval:updateInterval target:self selector:@selector(updateLogMessages) userInfo:nil repeats:YES];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    [self.logUpdateTimer invalidate];
}

- (void)updateLogMessages
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSArray *logMessages = [[self class] allLogMessagesForCurrentProcess];
        dispatch_async(dispatch_get_main_queue(), ^{
            self.title = @"System Log";
            self.logMessages = logMessages;

            // "Follow" the log as new messages stream in if we were previously near the bottom.
            BOOL wasNearBottom = self.tableView.contentOffset.y >= self.tableView.contentSize.height - self.tableView.frame.size.height - 100.0;
            [self.tableView reloadData];
            if (wasNearBottom) {
                [self scrollToLastRow];
            }
        });
    });
}

- (void)scrollToLastRow
{
    NSInteger numberOfRows = [self.tableView numberOfRowsInSection:0];
    if (numberOfRows > 0) {
        NSIndexPath *lastIndexPath = [NSIndexPath indexPathForRow:numberOfRows - 1 inSection:0];
        [self.tableView scrollToRowAtIndexPath:lastIndexPath atScrollPosition:UITableViewScrollPositionBottom animated:YES];
    }
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    NSInteger numberOfRows = 0;
    if (tableView == self.tableView) {
        numberOfRows = [self.logMessages count];
    } else if (tableView == self.searchController.searchResultsTableView) {
        numberOfRows = [self.filteredLogMessages count];
    }
    return numberOfRows;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{
    FLEXSystemLogTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:kFLEXSystemLogTableViewCellIdentifier forIndexPath:indexPath];
    if (tableView == self.tableView) {
        cell.logMessage = [self.logMessages objectAtIndex:indexPath.row];
        cell.highlightedText = nil;
    } else if (tableView == self.searchController.searchResultsTableView) {
        cell.logMessage = [self.filteredLogMessages objectAtIndex:indexPath.row];
        cell.highlightedText = self.searchController.searchBar.text;
    }
    if (indexPath.row % 2 == 0) {
        cell.backgroundColor = [UIColor colorWithWhite:0.95 alpha:1.0];
    } else {
        cell.backgroundColor = [UIColor whiteColor];
    }
    
    return cell;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    FLEXSystemLogMessage *logMessage = nil;
    if (tableView == self.tableView) {
        logMessage = [self.logMessages objectAtIndex:indexPath.row];
    } else if (tableView == self.searchController.searchResultsTableView) {
        logMessage = [self.filteredLogMessages objectAtIndex:indexPath.row];
    }
    return [FLEXSystemLogTableViewCell 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:)) {
        FLEXSystemLogMessage *logMessage = nil;
        if (tableView == self.tableView) {
            logMessage = [self.logMessages objectAtIndex:indexPath.row];
        } else if (tableView == self.searchController.searchResultsTableView) {
            logMessage = [self.filteredLogMessages objectAtIndex:indexPath.row];
        }

        NSString *stringToCopy = [FLEXSystemLogTableViewCell displayedTextForLogMessage:logMessage] ?: @"";
        [[UIPasteboard generalPasteboard] setString:stringToCopy];
    }
}

#pragma mark - Search display delegate

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSArray *filteredLogMessages = [self.logMessages filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(FLEXSystemLogMessage *logMessage, NSDictionary *bindings) {
            NSString *displayedText = [FLEXSystemLogTableViewCell displayedTextForLogMessage:logMessage];
            return [displayedText rangeOfString:searchString options:NSCaseInsensitiveSearch].length > 0;
        }]];
        dispatch_async(dispatch_get_main_queue(), ^{
            if ([self.searchDisplayController.searchBar.text isEqual:searchString]) {
                self.filteredLogMessages = filteredLogMessages;
                [self.searchDisplayController.searchResultsTableView reloadData];
            }
        });
    });

    // Reload done after the data fetches asynchronously
    return NO;
}

#pragma mark - Log Message Fetching

// Due to a mistake in asl.h, things get a little messy. We need to mark these symbols as weak since they won't exist on iOS 7 despite the compiler thinking otherwise.
// asl.h in the iOS 8.1 SDK claims that asl_next() and asl_release() were introduced in iOS 7 to replace aslresponse_next() and aslresponse_free(). However, they were actually added in iOS 8.0.
extern aslmsg asl_next(asl_object_t obj) __attribute__((weak_import));
extern void asl_release(asl_object_t obj) __attribute__((weak_import));

+ (NSArray *)allLogMessagesForCurrentProcess
{
    asl_object_t query = asl_new(ASL_TYPE_QUERY);

    // Filter for messages from the current process. Note that this appears to happen by default on device, but is required in the simulator.
    NSString *pidString = [NSString stringWithFormat:@"%d", [[NSProcessInfo processInfo] processIdentifier]];
    asl_set_query(query, ASL_KEY_PID, [pidString UTF8String], ASL_QUERY_OP_EQUAL);

    aslresponse response = asl_search(NULL, query);
    aslmsg aslMessage = NULL;

    NSMutableArray *logMessages = [NSMutableArray array];

    if (&asl_next != NULL && &asl_release != NULL) {
        while ((aslMessage = asl_next(response))) {
            [logMessages addObject:[FLEXSystemLogMessage logMessageFromASLMessage:aslMessage]];
        }
        asl_release(response);
    } else {
        // Mute incorrect deprecated warnings. We'll need the "deprecated" functions on iOS 7, where their replacements don't yet exist.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
        while ((aslMessage = aslresponse_next(response))) {
            [logMessages addObject:[FLEXSystemLogMessage logMessageFromASLMessage:aslMessage]];
        }
        aslresponse_free(response);
#pragma clang diagnostic pop
    }

    return logMessages;
}

@end