Rewrite UserSession for proto files.

client/src/main/kotlin/io/spine/examples/pingh/client/UserSessionExts.kt

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2024, TeamDev. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Redistribution and use in source and/or binary forms, with or without
+ * modification, must retain the above copyright notice and the following
+ * disclaimer.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package io.spine.examples.pingh.client
+
+import io.spine.examples.pingh.github.Username
+import io.spine.examples.pingh.github.of
+import kotlin.reflect.KClass
+
+/**
+ * The username to which the current session belongs.
+ */
+internal val UserSession.username: Username
+    get() = this.id?.username ?: Guest.username
+
+/**
+ * Returns `true` if the session is authenticated, and `false` if it is a guest session.
+ */
+internal fun UserSession.isAuthenticated() = this != Guest.session
+
+/**
+ * Saves the user session data to a file in the user's data directory.
+ */
+internal fun UserSession.save() {
+    FileStorage.save(FileLocation.Session, this)
+}
+
+/**
+ * Loads the user session data from a file in the user's data directory.
+ *
+ * Returns a guest session if the file is empty.
+ */
+@Suppress("UnusedReceiverParameter" /* Associated with the class but doesn't use its data. */)
+internal fun KClass<UserSession>.loadOrDefault(): UserSession =
+    FileStorage.loadOrDefault(FileLocation.Session) { Guest.session }
+
+internal object Guest {
+    internal val session = UserSession.getDefaultInstance()!!
+    internal val username = Username::class.of("unauthenticated-guest")
+}