/*

     File: DirectoryWatcher.m 

 Abstract: 

 Object used to monitor the contents of a given directory by using

 "kqueue": a kernel event notification mechanism.

  Version: 1.6 

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 */ 

#import "DirectoryWatcher.h"

#include <sys/types.h>

#include <sys/event.h>

#include <sys/time.h>

#include <fcntl.h>

#include <unistd.h>

#import <CoreFoundation/CoreFoundation.h>

@interface DirectoryWatcher (DirectoryWatcherPrivate)

- (BOOL)startMonitoringDirectory:(NSString *)dirPath;

- (void)kqueueFired;

@end

#pragma mark -

@implementation DirectoryWatcher

@synthesize delegate;

- (instancetype)init

{

    self = [super init];

    delegate = NULL;

    dirFD = -1;

    kq = -1;

    dirKQRef = NULL;

    return self;

}

- (void)dealloc

{

    [self invalidate];

}

+ (DirectoryWatcher *)watchFolderWithPath:(NSString *)watchPath delegate:(id)watchDelegate

{

    DirectoryWatcher *retVal = NULL;

    if ((watchDelegate != NULL) && (watchPath != NULL))

    {

        DirectoryWatcher *tempManager = [[DirectoryWatcher alloc] init];

        tempManager.delegate = watchDelegate;       

        if ([tempManager startMonitoringDirectory: watchPath])

        {

            // Everything appears to be in order, so return the DirectoryWatcher.  

            // Otherwise we'll fall through and return NULL.

            retVal = tempManager;

        }

    }

    return retVal;

}

- (void)invalidate

{

    if (dirKQRef != NULL)

    {

        CFFileDescriptorInvalidate(dirKQRef);

        CFRelease(dirKQRef);

        dirKQRef = NULL;

        // We don't need to close the kq, CFFileDescriptorInvalidate closed it instead.

        // Change the value so no one thinks it's still live.

        kq = -1;

    }

    if(dirFD != -1)

    {

        close(dirFD);

        dirFD = -1;

    }

}

@end

#pragma mark -

@implementation DirectoryWatcher (DirectoryWatcherPrivate)

- (void)kqueueFired

{

    assert(kq >= 0);

    struct kevent   event;

    struct timespec timeout = {0, 0};

    int             eventCount;

    eventCount = kevent(kq, NULL, 0, &event, 1, &timeout);

    assert((eventCount >= 0) && (eventCount < 2));

    // call our delegate of the directory change

    [delegate directoryDidChange:self];

    CFFileDescriptorEnableCallBacks(dirKQRef, kCFFileDescriptorReadCallBack);

}

static void KQCallback(CFFileDescriptorRef kqRef, CFOptionFlags callBackTypes, void *info)

{

    DirectoryWatcher *obj;

    obj = (__bridge DirectoryWatcher *)info;

    assert([obj isKindOfClass:[DirectoryWatcher class]]);

    assert(kqRef == obj->dirKQRef);

    assert(callBackTypes == kCFFileDescriptorReadCallBack);

    [obj kqueueFired];

}

- (BOOL)startMonitoringDirectory:(NSString *)dirPath

{

    // Double initializing is not going to work...

    if ((dirKQRef == NULL) && (dirFD == -1) && (kq == -1))

    {

        // Open the directory we're going to watch

        dirFD = open([dirPath fileSystemRepresentation], O_EVTONLY);

        if (dirFD >= 0)

        {

            // Create a kqueue for our event messages...

            kq = kqueue();

            if (kq >= 0)

            {

                struct kevent eventToAdd;

                eventToAdd.ident  = dirFD;

                eventToAdd.filter = EVFILT_VNODE;

                eventToAdd.flags  = EV_ADD | EV_CLEAR;

                eventToAdd.fflags = NOTE_WRITE;

                eventToAdd.data   = 0;

                eventToAdd.udata  = NULL;

                int errNum = kevent(kq, &eventToAdd, 1, NULL, 0, NULL);

                if (errNum == 0)

                {

                    CFFileDescriptorContext context = { 0, (__bridge void *)(self), NULL, NULL, NULL };

                    CFRunLoopSourceRef      rls;

                    // Passing true in the third argument so CFFileDescriptorInvalidate will close kq.

                    dirKQRef = CFFileDescriptorCreate(NULL, kq, true, KQCallback, &context);

                    if (dirKQRef != NULL)

                    {

                        rls = CFFileDescriptorCreateRunLoopSource(NULL, dirKQRef, 0);

                        if (rls != NULL)

                        {

                            CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopDefaultMode);

                            CFRelease(rls);

                            CFFileDescriptorEnableCallBacks(dirKQRef, kCFFileDescriptorReadCallBack);

                            // If everything worked, return early and bypass shutting things down

                            return YES;

                        }

                        // Couldn't create a runloop source, invalidate and release the CFFileDescriptorRef

                        CFFileDescriptorInvalidate(dirKQRef);

                        CFRelease(dirKQRef);

                        dirKQRef = NULL;

                    }

                }

                // kq is active, but something failed, close the handle...

                close(kq);

                kq = -1;

            }

            // file handle is open, but something failed, close the handle...

            close(dirFD);

            dirFD = -1;

        }

    }

    return NO;

}

@end