Exploring the CallKit blocking feature

CallDirectoryHandler.swift

//
//  CallDirectoryHandler.swift
//  SelectiveHearing.BlockEveryone
//
//  Created by Michael Sepcot on 4/14/17.
//  Copyright © 2017 Michael Sepcot. All rights reserved.
//

import Foundation
import CallKit

struct USPhoneNumber: Sequence, IteratorProtocol {
    let areaCodes = [
        201, 202, 203, 205, 206, 207, 208, 209, 210, 212, 213, 214, 215, 216, 217, 218, 219, 224, 225, 228, 229, 231, 234, 239, 240,
        248, 251, 252, 253, 254, 256, 260, 262, 267, 269, 270, 272, 276, 281, 301, 302, 303, 304, 305, 307, 308, 309, 310, 312, 313,
        314, 315, 316, 317, 318, 319, 320, 321, 323, 325, 330, 331, 334, 336, 337, 339, 340, 346, 347, 351, 352, 360, 361, 385, 386,
        401, 402, 404, 405, 406, 407, 408, 409, 410, 412, 413, 414, 415, 417, 419, 423, 424, 425, 430, 432, 434, 435, 440, 442, 443,
        458, 469, 470, 475, 478, 479, 480, 484, 501, 502, 503, 504, 505, 507, 508, 509, 510, 512, 513, 515, 516, 517, 518, 520, 530,
        531, 534, 539, 540, 541, 551, 559, 561, 562, 563, 567, 570, 571, 573, 574, 575, 580, 585, 586, 601, 602, 603, 605, 606, 607,
        608, 609, 610, 612, 614, 615, 616, 617, 618, 619, 620, 623, 626, 630, 631, 636, 641, 646, 650, 651, 657, 660, 661, 662, 667,
        669, 670, 671, 678, 681, 682, 684, 701, 702, 703, 704, 706, 707, 708, 712, 713, 714, 715, 716, 717, 718, 719, 720, 724, 725,
        727, 731, 732, 734, 737, 740, 747, 754, 757, 760, 762, 763, 765, 769, 770, 772, 773, 774, 775, 779, 781, 785, 786, 787, 801,
        802, 803, 804, 805, 806, 808, 810, 812, 813, 814, 815, 816, 817, 818, 828, 830, 831, 832, 843, 845, 847, 848, 850, 856, 857,
        858, 859, 860, 862, 863, 864, 865, 870, 872, 878, 901, 903, 904, 906, 907, 908, 909, 910, 912, 913, 914, 915, 916, 917, 918,
        919, 920, 925, 928, 929, 931, 936, 937, 938, 939, 940, 941, 947, 949, 951, 952, 954, 956, 970, 971, 972, 973, 978, 979, 980,
        984, 985, 989
    ]

    var index = 0
    var phoneNumber = 0

    mutating func next() -> CXCallDirectoryPhoneNumber? {
        if phoneNumber > 999_9999 {
            phoneNumber = 0
            index += 1
        }

        if index == areaCodes.count {
            return nil
        } else {
            defer { phoneNumber += 1 }

            if let phoneNumber11 = NumberFormatter().number(from: String(format: "1%.3d%.7d", areaCodes[index], phoneNumber)) {
                return CXCallDirectoryPhoneNumber(phoneNumber11)
            }

            return nil
        }
    }
}

class CallDirectoryHandler: CXCallDirectoryProvider {

    override func beginRequest(with context: CXCallDirectoryExtensionContext) {
        context.delegate = self

        do {
            try addBlockingPhoneNumbers(to: context)
        } catch {
            NSLog("Unable to add blocking phone numbers")
            let error = NSError(domain: "CallDirectoryHandler", code: 1, userInfo: nil)
            context.cancelRequest(withError: error)
            return
        }

        context.completeRequest()
    }

    private func addBlockingPhoneNumbers(to context: CXCallDirectoryExtensionContext) throws {
        // Retrieve phone numbers to block from data store. For optimal performance and memory usage when there are many phone numbers,
        // consider only loading a subset of numbers at a given time and using autorelease pool(s) to release objects allocated during each batch of numbers which are loaded.
        //
        // Numbers must be provided in numerically ascending order.

        let phoneNumbers = USPhoneNumber()
        for phoneNumber in phoneNumbers {
            context.addBlockingEntry(withNextSequentialPhoneNumber: phoneNumber)
        }
    }

}

extension CallDirectoryHandler: CXCallDirectoryExtensionContextDelegate {

    func requestFailed(for extensionContext: CXCallDirectoryExtensionContext, withError error: Error) {
        // An error occurred while adding blocking or identification entries, check the NSError for details.
        // For Call Directory error codes, see the CXErrorCodeCallDirectoryManagerError enum in <CallKit/CXError.h>.
        //
        // This may be used to store the error details in a location accessible by the extension's containing app, so that the
        // app may be notified about errors which occured while loading data even if the request to load data was initiated by
        // the user in Settings instead of via the app itself.
    }

}

Turns out CallKit doesn't like it when you try to add 3 billion numbers to the block list. Go figure.

It was a fun exercise to build the USPhoneNumber war dialer as a sequence iterator.

There's less than ten million numbers in the US and you forgot to put them in ascending order, which is why it won't work.