import Contacts       // CNContactStore, CNSaveRequest, CNContact
import ContactsUI     // CNContactPickerViewController

let store = CNContactStore()

func requestAccess() async throws -> Bool {
    return try await store.requestAccess(for: .contacts)
}

// Check current status without prompting
func checkStatus() -> CNAuthorizationStatus {
    CNContactStore.authorizationStatus(for: .contacts)
}

func fetchContacts(named name: String) throws -> [CNContact] {
    let predicate = CNContact.predicateForContacts(matchingName: name)
    let keys: [CNKeyDescriptor] = [
        CNContactGivenNameKey as CNKeyDescriptor,
        CNContactFamilyNameKey as CNKeyDescriptor,
        CNContactPhoneNumbersKey as CNKeyDescriptor
    ]
    return try store.unifiedContacts(matching: predicate, keysToFetch: keys)
}

func fetchContact(identifier: String) throws -> CNContact {
    let keys: [CNKeyDescriptor] = [
        CNContactGivenNameKey as CNKeyDescriptor,
        CNContactFamilyNameKey as CNKeyDescriptor,
        CNContactEmailAddressesKey as CNKeyDescriptor
    ]
    return try store.unifiedContact(withIdentifier: identifier, keysToFetch: keys)
}

func fetchAllContacts() throws -> [CNContact] {
    let keys: [CNKeyDescriptor] = [
        CNContactGivenNameKey as CNKeyDescriptor,
        CNContactFamilyNameKey as CNKeyDescriptor
    ]
    let request = CNContactFetchRequest(keysToFetch: keys)
    request.sortOrder = .givenName

    var contacts: [CNContact] = []
    try store.enumerateContacts(with: request) { contact, _ in
        contacts.append(contact)
    }
    return contacts
}

let nameKeys = CNContactFormatter.descriptorForRequiredKeys(for: .fullName)
let keys: [CNKeyDescriptor] = [nameKeys, CNContactPhoneNumbersKey as CNKeyDescriptor]

func createContact(givenName: String, familyName: String, phone: String) throws {
    let contact = CNMutableContact()
    contact.givenName = givenName
    contact.familyName = familyName
    contact.phoneNumbers = [
        CNLabeledValue(
            label: CNLabelPhoneNumberMobile,
            value: CNPhoneNumber(stringValue: phone)
        )
    ]

    let saveRequest = CNSaveRequest()
    saveRequest.add(contact, toContainerWithIdentifier: nil) // nil = default container
    try store.execute(saveRequest)
}

func updateContactEmail(identifier: String, email: String) throws {
    let keys: [CNKeyDescriptor] = [
        CNContactEmailAddressesKey as CNKeyDescriptor
    ]
    let contact = try store.unifiedContact(withIdentifier: identifier, keysToFetch: keys)
    guard let mutable = contact.mutableCopy() as? CNMutableContact else { return }

    mutable.emailAddresses.append(
        CNLabeledValue(label: CNLabelWork, value: email as NSString)
    )

    let saveRequest = CNSaveRequest()
    saveRequest.update(mutable)
    try store.execute(saveRequest)
}

func deleteContact(identifier: String) throws {
    let keys: [CNKeyDescriptor] = [CNContactIdentifierKey as CNKeyDescriptor]
    let contact = try store.unifiedContact(withIdentifier: identifier, keysToFetch: keys)
    guard let mutable = contact.mutableCopy() as? CNMutableContact else { return }

    let saveRequest = CNSaveRequest()
    saveRequest.delete(mutable)
    try store.execute(saveRequest)
}

import SwiftUI
import ContactsUI

struct ContactPicker: UIViewControllerRepresentable {
    @Binding var selectedContact: CNContact?

    func makeUIViewController(context: Context) -> CNContactPickerViewController {
        let picker = CNContactPickerViewController()
        picker.delegate = context.coordinator
        return picker
    }

    func updateUIViewController(_ uiViewController: CNContactPickerViewController, context: Context) {}

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    final class Coordinator: NSObject, CNContactPickerDelegate {
        let parent: ContactPicker

        init(_ parent: ContactPicker) {
            self.parent = parent
        }

        func contactPicker(_ picker: CNContactPickerViewController, didSelect contact: CNContact) {
            parent.selectedContact = contact
        }

        func contactPickerDidCancel(_ picker: CNContactPickerViewController) {
            parent.selectedContact = nil
        }
    }
}

struct ContactSelectionView: View {
    @State private var selectedContact: CNContact?
    @State private var showPicker = false

    var body: some View {
        VStack {
            if let contact = selectedContact {
                Text("\(contact.givenName) \(contact.familyName)")
            }
            Button("Select Contact") {
                showPicker = true
            }
        }
        .sheet(isPresented: $showPicker) {
            ContactPicker(selectedContact: $selectedContact)
        }
    }
}

let picker = CNContactPickerViewController()
// Only show contacts that have an email address
picker.predicateForEnablingContact = NSPredicate(format: "emailAddresses.@count > 0")
// Selecting a contact returns it directly (no detail card)
picker.predicateForSelectionOfContact = NSPredicate(value: true)

func observeContactChanges() {
    NotificationCenter.default.addObserver(
        forName: .CNContactStoreDidChange,
        object: nil,
        queue: .main
    ) { _ in
        // Refetch contacts -- cached CNContact objects are stale
        refreshContacts()
    }
}

// WRONG: Fetches everything including full-resolution photos
let keys: [CNKeyDescriptor] = [CNContactCompleteNameKey as CNKeyDescriptor,
    CNContactImageDataKey as CNKeyDescriptor,
    CNContactPhoneNumbersKey as CNKeyDescriptor,
    CNContactEmailAddressesKey as CNKeyDescriptor,
    CNContactPostalAddressesKey as CNKeyDescriptor,
    CNContactBirthdayKey as CNKeyDescriptor]

// CORRECT: Fetch only what you display
let keys: [CNKeyDescriptor] = [
    CNContactGivenNameKey as CNKeyDescriptor,
    CNContactFamilyNameKey as CNKeyDescriptor
]

// WRONG: Only fetched name keys, now accessing phone
let keys: [CNKeyDescriptor] = [CNContactGivenNameKey as CNKeyDescriptor]
let contact = try store.unifiedContact(withIdentifier: id, keysToFetch: keys)
let phone = contact.phoneNumbers.first // CRASH

// CORRECT: Include the key you need
let keys: [CNKeyDescriptor] = [
    CNContactGivenNameKey as CNKeyDescriptor,
    CNContactPhoneNumbersKey as CNKeyDescriptor
]

// WRONG: CNContact has no setter
let contact = try store.unifiedContact(withIdentifier: id, keysToFetch: keys)
contact.givenName = "New Name" // Compile error

// CORRECT: Create mutable copy
guard let mutable = contact.mutableCopy() as? CNMutableContact else { return }
mutable.givenName = "New Name"

// WRONG: Jump straight to fetch
let contacts = try store.unifiedContacts(matching: predicate, keysToFetch: keys)

// CORRECT: Check or request access first
let granted = try await store.requestAccess(for: .contacts)
guard granted else { return }
let contacts = try store.unifiedContacts(matching: predicate, keysToFetch: keys)

// WRONG: Main thread enumeration
func loadContacts() {
    try store.enumerateContacts(with: request) { contact, _ in ... }
}

// CORRECT: Run on a background thread
func loadContacts() async throws -> [CNContact] {
    try await Task.detached {
        var results: [CNContact] = []
        try store.enumerateContacts(with: request) { contact, _ in
            results.append(contact)
        }
        return results
    }.value
}