//
//  FacebookService.m
//  NineSpot
//
//  Created by Nick Dalton on 11/28/14.
//  Copyright (c) 2014 NineSpot. All rights reserved.
//

#import <FacebookSDK/FacebookSDK.h>
#import <CommonCrypto/CommonCrypto.h>

#import "FacebookService.h"

#import "AppDelegate.h"
#import "EndUser.h"


NSString *const kNotificationLoginFacebookSuccess = @"NotificationLoginFacebookSuccess";


@implementation FacebookService


#pragma mark - AppDelegate handlers

- (BOOL)handleOpenURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication
{
    return [FBAppCall handleOpenURL:url
                  sourceApplication:sourceApplication
                    fallbackHandler:^(FBAppCall *call) {
                        DDLogDebug(@"In fallback handler");
                    }];
}

- (void)handleApplicationDidBecomeActive
{
    // Call the 'activateApp' method to log an app event for use in analytics and advertising reporting.
    [FBAppEvents activateApp];

    // We need to properly handle activation of the application with regards to SSO
    //  (e.g., returning from iOS 6.0 authorization dialog or from fast app switching).
    [FBAppCall handleDidBecomeActive];
}

- (void)handleApplicationWillTerminate
{
    // If the app is going away, we close the session object.
    [FBSession.activeSession close];
}


#pragma mark - Facebook session

- (BOOL)isSessionOpen
{
    BOOL isOpen = FBSession.activeSession.isOpen;
    DDLogDebug(@"Facebook Session is %@", isOpen ? @"open" : @"not open");

    DDLogDebug(@"Facebook access token expires: %@", FBSession.activeSession.accessTokenData.expirationDate);

    return isOpen;
}

- (void)openSessionFromTokenCache
{
    DDLogDebug(@"Facebook openSessionFromTokenCache");

    // Try to open a Facebook session from a token cache
    if (FBSession.activeSession.state == FBSessionStateCreatedTokenLoaded) {
        // Yes, so just open the session (this won't display any UX).
        [FBSession openActiveSessionWithReadPermissions:@[@"public_profile", @"email"]
                                           allowLoginUI:NO
                                      completionHandler:^(FBSession *session,
                                                          FBSessionState status,
                                                          NSError *error) {
                                          // Respond to session state changes
                                          [self facebookSessionStateChanged:session state:status error:error];
                                      }];
    }
}

- (void)login
{
    DDLogDebug(@"Facebook login");

    [FBSession openActiveSessionWithReadPermissions:@[@"public_profile", @"email"]
                                       allowLoginUI:YES
                                  completionHandler:^(FBSession *session,
                                                      FBSessionState status,
                                                      NSError *error) {
                                      // Respond to session state changes
                                      [self facebookSessionStateChanged:session state:status error:error];
                                  }];
}

- (void)logout
{
    DDLogDebug(@"Facebook logout");
    [FBSession.activeSession closeAndClearTokenInformation];
}

- (void)facebookSessionStateChanged:(FBSession *)session
                              state:(FBSessionState) state
                              error:(NSError *)error
{
    DDLogDebug(@"FBSessionState changed to: %lu", (unsigned long)state);

    // Capture demographic data
    if ([session isOpen]) {
        [[FBRequest requestForMe] startWithCompletionHandler:
         ^(FBRequestConnection *connection,
           NSDictionary<FBGraphUser> *user,
           NSError *connectionError) {
             if (!connectionError) {
                 DDLogDebug(@"FBGraphUser: %@", user);
                 EndUser *endUser = [self endUserFromFacebookUser:user];
                 [ApplicationDelegate.webService saveEndUser:endUser];
                 [[NSNotificationCenter defaultCenter] postNotificationName:kNotificationLoginFacebookSuccess object:endUser];
             } else {
                 DDLogError(@"Error in FBRequest requestForMe: %@", [connectionError localizedDescription]);
             }
         }];
    }

}


#pragma mark - EndUser helper methods

- (EndUser *)endUserFromFacebookUser:(id<FBGraphUser>)user
{
    EndUser *endUser = [[EndUser alloc] init];

    endUser.name = user.name;
    endUser.emailAddress = [user objectForKey:@"email"];
    endUser.userId = user.objectID;

    NSString *genderString = [user objectForKey:@"gender"];
    if (genderString) {
        NSString *genderCharacter = [[genderString substringToIndex:1] uppercaseString];
        endUser.gender = genderCharacter;
    }

    endUser.accessToken = FBSession.activeSession.accessTokenData.accessToken;
    endUser.password = [self generatedPasswordForFacebookUser:user];
    endUser.isFacebookUser = YES;

    // Get profile picture
    [[FBRequest requestForMe] startWithCompletionHandler:^(FBRequestConnection *connection, NSDictionary<FBGraphUser> *FBuser, NSError *error) {
        if (error) {
            DDLogError(@"Error fetching Facebook profile picture: %@", [error localizedDescription]);
        } else {
            NSString *urlString = [NSString stringWithFormat:@"https://graph.facebook.com/%@/picture?type=normal", [FBuser objectID]];
            if (urlString) {
                @try {
                    endUser.mediumThumbnailURL = [NSURL URLWithString:urlString];
                    [[NSNotificationCenter defaultCenter] postNotificationName:kNotificationEndUserUpdated object:endUser];
                }
                @catch (NSException *exception) {
                    DDLogError(@"Error cretating URL for Facebook thumbnail %@ : %@", urlString, [exception description]);
                }
            }
        }
    }];

    return endUser;
}

- (NSString *)generatedPasswordForFacebookUser:(id<FBGraphUser>)user
{
    NSString *password = nil;

    NSString *userId = user.objectID;
    if (userId) {
        NSString *hash = [self computeSHA256DigestForString:userId withSalt:@"42"];
        NSString *trimmedHash = [hash substringToIndex:16];
        password = [NSString stringWithFormat:@"fb%@.", trimmedHash];
    }

    return password;
}

- (NSString *)computeSHA256DigestForString:(NSString *)input
{
    const char *cstr = [input cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:input.length];
    uint8_t digest[CC_SHA256_DIGEST_LENGTH];

    CC_SHA256(data.bytes, (unsigned int)data.length, digest);

    NSMutableString *output = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 2];
    for (int i = 0; i < CC_SHA256_DIGEST_LENGTH; i++) {
        [output appendFormat:@"%02x", digest[i]];
    }
    return output;
}

- (NSString *)computeSHA256DigestForString:(NSString *)input withSalt:(NSString *)salt
{
    const char *cData = [input cStringUsingEncoding:NSUTF8StringEncoding];
    const char *cKey = [salt cStringUsingEncoding:NSUTF8StringEncoding];
    uint8_t cHMAC[CC_SHA256_DIGEST_LENGTH];

    CCHmac(kCCHmacAlgSHA256, cKey, strlen(cKey), cData, strlen(cData), cHMAC);

    NSMutableString *output = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 2];
    for (int i = 0; i < CC_SHA256_DIGEST_LENGTH; i++) {
        [output appendFormat:@"%02x", cHMAC[i]];
    }
    return output;
}

@end