FB Singleton

//  FacebookManager.h

#import <UIKit/UIKit.h>
#import "Facebook.h"
#import "Constants.h"

@interface FacebookManager : NSObject <FBSessionDelegate, FBRequestDelegate> {
    Facebook *facebook;
    SuccessBlock successBlock;
    FailureBlock failureBlock;
    BOOL doingLogin;
}

@property (nonatomic, retain) Facebook *facebook;

+ (FacebookManager *)sharedFacebook;

- (void)loginWithSuccess:(SuccessBlock)_success andFailure:(FailureBlock)_failure;;
- (void)logout;

@end


// FacebookManager.m

#import "FacebookManager.h"
#import "Constants.h"
#import "UserObject.h"
#import "Utilities.h"

@interface FacebookManager ()
@end

@implementation FacebookManager

@synthesize facebook;

////////////////////////////////////////////////////////////////
#pragma mark Object Lifecycle
////////////////////////////////////////////////////////////////

+ (FacebookManager *)sharedFacebook
{
    static FacebookManager *_sharedFacebook = nil;
    static dispatch_once_t oncePredicate;
    dispatch_once(&oncePredicate, ^{
        _sharedFacebook = [[self alloc] init];
    });

    return _sharedFacebook;
}

- (id)init
{
    self = [super init];
    if (!self) return nil;

    //initialize ivars - for clarity (not necessary)
    doingLogin = NO;
    successBlock = nil;
    failureBlock = nil;

    //initialize Facebook
    facebook = [[Facebook alloc] initWithAppId:facebookAppId andDelegate:self];

    //restore previous session
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    if ([defaults objectForKey:@"FBAccessTokenKey"]
        && [defaults objectForKey:@"FBExpirationDateKey"]) {
        facebook.accessToken = [defaults objectForKey:@"FBAccessTokenKey"];
        facebook.expirationDate = [defaults objectForKey:@"FBExpirationDateKey"];
        [facebook extendAccessTokenIfNeeded];
    }

    return self;
}

- (void)dealloc
{
    //should not be called
    [facebook release];
    [super dealloc];
}

////////////////////////////////////////////////////////////////
#pragma mark Public methods
////////////////////////////////////////////////////////////////

- (void)loginWithSuccess:(SuccessBlock)_success andFailure:(FailureBlock)_failure
{
    if (!doingLogin) {
        if (!facebook.isSessionValid) {
            doingLogin = YES;
            successBlock = [_success copy];
            failureBlock = [_failure copy];
            NSArray *permissions = [[NSArray alloc] initWithObjects:
                                    @"offline_access",
                                    @"publish_stream",
                                    nil];
            [facebook authorize:permissions];
            [permissions release];
            //now wait for the delegate callback
        } else {
            _success(nil);
        }
    } else {
        _failure([Utilities createErrorWithString:NSLocalizedString(@"Login already in progress", "Login already in progress - error message")]);
    }
}

- (void)logout
{
    [facebook logout];
}

////////////////////////////////////////////////////////////////
#pragma mark FBSessionDelegate methods
////////////////////////////////////////////////////////////////

- (void)fbDidLogin
{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:[facebook accessToken] forKey:@"FBAccessTokenKey"];
    [defaults setObject:[facebook expirationDate] forKey:@"FBExpirationDateKey"];
    [defaults synchronize];

    //call the success block
    if (successBlock) {
        successBlock(nil);

        //clean up
        [successBlock release]; successBlock = nil;
        [failureBlock release]; failureBlock = nil;
        doingLogin = NO;
    }

}

- (void)fbDidNotLogin:(BOOL)cancelled
{
    //call the failure block
    if (failureBlock) {
        failureBlock([Utilities createErrorWithString:NSLocalizedString(@"Facebook login failed", @"Facebook login failed - error message")]);

        //clean up
        [successBlock release]; successBlock = nil;
        [failureBlock release]; failureBlock = nil;
        doingLogin = NO;
    }
}

- (void)fbDidLogout
{
    // Remove saved authorization information if it exists
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    if ([defaults objectForKey:@"FBAccessTokenKey"]) {
        [defaults removeObjectForKey:@"FBAccessTokenKey"];
        [defaults removeObjectForKey:@"FBExpirationDateKey"];
        [defaults synchronize];
    }
}

- (void)fbDidExtendToken:(NSString *)accessToken expiresAt:(NSDate *)expiresAt
{
    NSLog(@"token extended until: %@", expiresAt);
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:accessToken forKey:@"FBAccessTokenKey"];
    [defaults setObject:expiresAt forKey:@"FBExpirationDateKey"];
    [defaults synchronize];
}

- (void)fbSessionInvalidated
{
    [[UserObject currentUser] logout];
}

@end