KeychainStore.swift

//
//  KeychainStore.swift
//  NativeAppTemplate
//

import Foundation
import KeychainAccess
import os

protocol KeychainStore {
    associatedtype DataType: NSObject, NSCoding

    var account: String { get set }
    var service: String { get set }

    func remove() throws
    func retrieve() throws -> DataType
    func store(_ data: DataType) throws
}

extension KeychainStore {
    func remove() throws {
        let keychain = Keychain(service: service)

        do {
            try keychain.remove(account)
        } catch {
            throw KeychainStoreError.secCallFailed(error)
        }
    }

    func retrieve() throws -> DataType {
        let keychain = Keychain(service: service)
        let archived: Data?

        archived = try? keychain.getData(account)

        guard archived != nil else {
            throw KeychainStoreError.notFound
        }

        do {
            guard
                let unarchived = try NSKeyedUnarchiver.unarchivedObject(ofClass: DataType.self, from: archived!)
            else {
                throw KeychainStoreError.badData
            }

            return unarchived
        } catch {
            throw KeychainStoreError.archiveFailure(error)
        }
    }

    func store(_ data: DataType) throws {
        let archived: Data
        appLogger.debug("KeychainStore data: \(data, privacy: .private)")
        do {
            archived = try NSKeyedArchiver.archivedData(withRootObject: data, requiringSecureCoding: true)
        } catch {
            throw KeychainStoreError.archiveFailure(error)
        }

        let keychain = Keychain(service: service)

        do {
            try keychain.set(archived, key: account)
        } catch {
            throw KeychainStoreError.secCallFailed(error)
        }
    }
}