Dactyloidae iOS initial commit

mobile/ios/Shared/KeychainCache.swift

@@ -0,0 +1,65 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import Foundation
+import XCGLogger
+import SwiftKeychainWrapper
+import SwiftyJSON
+
+private let log = Logger.keychainLogger
+
+public protocol JSONLiteralConvertible {
+    func asJSON() -> JSON
+}
+
+open class KeychainCache<T: JSONLiteralConvertible> {
+    open let branch: String
+    open let label: String
+
+    open var value: T? {
+        didSet {
+            checkpoint()
+        }
+    }
+
+    public init(branch: String, label: String, value: T?) {
+        self.branch = branch
+        self.label = label
+        self.value = value
+    }
+
+    open class func fromBranch(_ branch: String, withLabel label: String?, withDefault defaultValue: T? = nil, factory: (JSON) -> T?) -> KeychainCache<T> {
+        if let l = label {
+            let key = "\(branch).\(l)"
+            KeychainWrapper.sharedAppContainerKeychain.ensureStringItemAccessibility(.afterFirstUnlock, forKey: key)
+            if let s = KeychainWrapper.sharedAppContainerKeychain.string(forKey: key) {
+                if let t = factory(JSON(parseJSON: s)) {
+                    log.info("Read \(branch) from Keychain with label \(branch).\(l).")
+                    return KeychainCache(branch: branch, label: l, value: t)
+                } else {
+                    log.warning("Found \(branch) in Keychain with label \(branch).\(l), but could not parse it.")
+                }
+            } else {
+                log.warning("Did not find \(branch) in Keychain with label \(branch).\(l).")
+            }
+        } else {
+            log.warning("Did not find \(branch) label in Keychain.")
+        }
+        // Fall through to missing.
+        log.warning("Failed to read \(branch) from Keychain.")
+        let label = label ?? Bytes.generateGUID()
+        return KeychainCache(branch: branch, label: label, value: defaultValue)
+    }
+
+    open func checkpoint() {
+        log.info("Storing \(self.branch) in Keychain with label \(self.branch).\(self.label).")
+        // TODO: PII logging.
+        if let value = value,
+            let jsonString = value.asJSON().stringValue() {
+            KeychainWrapper.sharedAppContainerKeychain.set(jsonString, forKey: "\(branch).\(label)", withAccessibility: .afterFirstUnlock)
+        } else {
+            KeychainWrapper.sharedAppContainerKeychain.removeObject(forKey: "\(branch).\(label)")
+        }
+    }
+}