/*

 Copyright (C) 2015 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Table view controller that displays events occuring within the next 24 hours. Prompts a user for access to their Calendar, then updates its UI according to their response.

 */

#import "RootViewController.h"

@interface RootViewController () <EKEventEditViewDelegate>

// EKEventStore instance associated with the current Calendar application

@property (nonatomic, strong) EKEventStore *eventStore;

// Default calendar associated with the above event store

@property (nonatomic, strong) EKCalendar *defaultCalendar;

// Array of all events happening within the next 24 hours

@property (nonatomic, strong) NSMutableArray *eventsList;

// Used to add events to Calendar

@property (weak, nonatomic) IBOutlet UIBarButtonItem *addButton;

@end

@implementation RootViewController

#pragma mark -

#pragma mark View lifecycle

- (void)viewDidLoad

{

    [super viewDidLoad];

    // Initialize the event store  

    self.eventStore = [[EKEventStore alloc] init];

    // Initialize the events list

    self.eventsList = [[NSMutableArray alloc] initWithCapacity:0];

    // The Add button is initially disabled

    self.addButton.enabled = NO;

}

-(void)viewDidAppear:(BOOL)animated

{

    [super viewDidAppear:animated];

    // Check whether we are authorized to access Calendar

    [self checkEventStoreAccessForCalendar];

}

// This method is called when the user selects an event in the table view. It configures the destination

// event view controller with this event.

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender

{

    if ([segue.identifier isEqualToString:@"showEventViewController"])

    {

        // Configure the destination event view controller

        EKEventViewController* eventViewController = (EKEventViewController *)segue.destinationViewController;

        // Fetch the index path associated with the selected event

        NSIndexPath *indexPath = (self.tableView).indexPathForSelectedRow;

        // Set the view controller to display the selected event

        eventViewController.event = (self.eventsList)[indexPath.row];

        // Allow event editing

        eventViewController.allowsEditing = YES;

    }

}

#pragma mark -

#pragma mark Table View

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section

{

    return self.eventsList.count;

}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

{

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"eventCell" forIndexPath:indexPath];

    // Get the event at the row selected and display its title

    cell.textLabel.text = [(self.eventsList)[indexPath.row] title];

    return cell;

}

#pragma mark -

#pragma mark Access Calendar

// Check the authorization status of our application for Calendar 

-(void)checkEventStoreAccessForCalendar

{

    EKAuthorizationStatus status = [EKEventStore authorizationStatusForEntityType:EKEntityTypeEvent];    

    switch (status)

    {

        // Update our UI if the user has granted access to their Calendar

        case EKAuthorizationStatusAuthorized: [self accessGrantedForCalendar];

            break;

        // Prompt the user for access to Calendar if there is no definitive answer

        case EKAuthorizationStatusNotDetermined: [self requestCalendarAccess];

            break;

        // Display a message if the user has denied or restricted access to Calendar

        case EKAuthorizationStatusDenied:

        case EKAuthorizationStatusRestricted:

        {

            UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Privacy Warning" message:@"Permission was not granted for Calendar"

                                                                    preferredStyle:UIAlertControllerStyleAlert];

            UIAlertAction *defaultAction = [UIAlertAction actionWithTitle:@"OK"

                                                                    style:UIAlertActionStyleDefault

                                                                  handler:^(UIAlertAction * action) {}];

            [alert addAction:defaultAction];

            [self presentViewController:alert animated:YES completion:nil];

        }

            break;

        default:

            break;

    }

}

// Prompt the user for access to their Calendar

-(void)requestCalendarAccess

{

    [self.eventStore requestAccessToEntityType:EKEntityTypeEvent completion:^(BOOL granted, NSError *error)

    {

         if (granted)

         {

             RootViewController * __weak weakSelf = self;

             // Let's ensure that our code will be executed from the main queue

             dispatch_async(dispatch_get_main_queue(), ^{

             // The user has granted access to their Calendar; let's populate our UI with all events occuring in the next 24 hours.

                 [weakSelf accessGrantedForCalendar];

             });

         }

     }];

}

// This method is called when the user has granted permission to Calendar

-(void)accessGrantedForCalendar

{

    // Let's get the default calendar associated with our event store

    self.defaultCalendar = self.eventStore.defaultCalendarForNewEvents;

    // Enable the Add button  

    self.addButton.enabled = YES;

    // Fetch all events happening in the next 24 hours and put them into eventsList

    self.eventsList = [self fetchEvents];

    // Update the UI with the above events

    [self.tableView reloadData];

}

#pragma mark -

#pragma mark Fetch events

// Fetch all events happening in the next 24 hours 

- (NSMutableArray *)fetchEvents

{

    NSDate *startDate = [NSDate date];

    //Create the end date components

    NSDateComponents *tomorrowDateComponents = [[NSDateComponents alloc] init];

    tomorrowDateComponents.day = 1;

    NSDate *endDate = [[NSCalendar currentCalendar] dateByAddingComponents:tomorrowDateComponents

                                                                    toDate:startDate

                                                                   options:0];

    // We will only search the default calendar for our events

    NSArray *calendarArray = @[self.defaultCalendar];

    // Create the predicate

    NSPredicate *predicate = [self.eventStore predicateForEventsWithStartDate:startDate

                                                                      endDate:endDate

                                                                    calendars:calendarArray];

    // Fetch all events that match the predicate

    NSMutableArray *events = [NSMutableArray arrayWithArray:[self.eventStore eventsMatchingPredicate:predicate]];

    return events;

}

#pragma mark -

#pragma mark Add a new event

// Display an event edit view controller when the user taps the "+" button.

// A new event is added to Calendar when the user taps the "Done" button in the above view controller.

- (IBAction)addEvent:(id)sender

{

    // Create an instance of EKEventEditViewController 

    EKEventEditViewController *addController = [[EKEventEditViewController alloc] init];

    // Set addController's event store to the current event store

    addController.eventStore = self.eventStore;

    addController.editViewDelegate = self;

    [self presentViewController:addController animated:YES completion:nil];

}

#pragma mark -

#pragma mark EKEventEditViewDelegate

// Overriding EKEventEditViewDelegate method to update event store according to user actions.

- (void)eventEditViewController:(EKEventEditViewController *)controller 

          didCompleteWithAction:(EKEventEditViewAction)action

{

    RootViewController * __weak weakSelf = self;

    // Dismiss the modal view controller

    [self dismissViewControllerAnimated:YES completion:^

     {

         if (action != EKEventEditViewActionCanceled)

         {

             dispatch_async(dispatch_get_main_queue(), ^{

                 // Re-fetch all events happening in the next 24 hours

                 weakSelf.eventsList = [self fetchEvents];

                 // Update the UI with the above events

                 [weakSelf.tableView reloadData];

             });

         }

     }];

}

// Set the calendar edited by EKEventEditViewController to our chosen calendar - the default calendar.

- (EKCalendar *)eventEditViewControllerDefaultCalendarForNewEvents:(EKEventEditViewController *)controller

{

    return self.defaultCalendar;

}

@end