Google Api

Yavsc/GoogleApiSupport/Google.Apis.Core/ApplicationContext.cs

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+/*
+Copyright 2011 Google Inc
+
+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
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+using Google.Apis.Logging;
+using System;
+
+namespace Google
+{
+    /// <summary>Defines the context in which this library runs. It allows setting up custom loggers.</summary>
+    public static class ApplicationContext
+    {
+        private static ILogger logger;
+
+        // For testing
+        internal static void Reset() => logger = null;
+
+        /// <summary>Returns the logger used within this application context.</summary>
+        /// <remarks>It creates a <see cref="NullLogger"/> if no logger was registered previously</remarks>
+        public static ILogger Logger
+        {
+            get
+            {
+                // Register the default null-logger if no other one was set.
+                return logger ?? (logger = new NullLogger());
+            }
+        }
+
+        /// <summary>Registers a logger with this application context.</summary>
+        /// <exception cref="InvalidOperationException">Thrown if a logger was already registered.</exception>
+        public static void RegisterLogger(ILogger loggerToRegister)
+        {
+            // TODO(peleyal): Reconsider why the library should contain only one logger. Also consider using Tracing!
+            if (logger != null && !(logger is NullLogger))
+            {
+                throw new InvalidOperationException("A logger was already registered with this context.");
+            }
+            logger = loggerToRegister;
+        }
+    }
+}