1 files changed, 105 insertions, 0 deletions
diff --git a/src/SMAPI/Framework/DeprecationManager.cs b/src/SMAPI/Framework/DeprecationManager.cs
new file mode 100644
index 00000000..b07c6c7d
--- /dev/null
+++ b/src/SMAPI/Framework/DeprecationManager.cs
@@ -0,0 +1,105 @@
+using System;
+using System.Collections.Generic;
+
+namespace StardewModdingAPI.Framework
+{
+    /// <summary>Manages deprecation warnings.</summary>
+    internal class DeprecationManager
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The deprecations which have already been logged (as 'mod name::noun phrase::version').</summary>
+        private readonly HashSet<string> LoggedDeprecations = new HashSet<string>(StringComparer.InvariantCultureIgnoreCase);
+
+        /// <summary>Encapsulates monitoring and logging for a given module.</summary>
+        private readonly IMonitor Monitor;
+
+        /// <summary>Tracks the installed mods.</summary>
+        private readonly ModRegistry ModRegistry;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="monitor">Encapsulates monitoring and logging for a given module.</param>
+        /// <param name="modRegistry">Tracks the installed mods.</param>
+        public DeprecationManager(IMonitor monitor, ModRegistry modRegistry)
+        {
+            this.Monitor = monitor;
+            this.ModRegistry = modRegistry;
+        }
+
+        /// <summary>Log a deprecation warning.</summary>
+        /// <param name="nounPhrase">A noun phrase describing what is deprecated.</param>
+        /// <param name="version">The SMAPI version which deprecated it.</param>
+        /// <param name="severity">How deprecated the code is.</param>
+        public void Warn(string nounPhrase, string version, DeprecationLevel severity)
+        {
+            this.Warn(this.ModRegistry.GetModFromStack(), nounPhrase, version, severity);
+        }
+
+        /// <summary>Log a deprecation warning.</summary>
+        /// <param name="source">The friendly mod name which used the deprecated code.</param>
+        /// <param name="nounPhrase">A noun phrase describing what is deprecated.</param>
+        /// <param name="version">The SMAPI version which deprecated it.</param>
+        /// <param name="severity">How deprecated the code is.</param>
+        public void Warn(string source, string nounPhrase, string version, DeprecationLevel severity)
+        {
+            // ignore if already warned
+            if (!this.MarkWarned(source ?? "<unknown>", nounPhrase, version))
+                return;
+
+            // build message
+            string message = $"{source ?? "An unknown mod"} uses deprecated code ({nounPhrase}).";
+            if (source == null)
+                message += $"{Environment.NewLine}{Environment.StackTrace}";
+
+            // log message
+            switch (severity)
+            {
+                case DeprecationLevel.Notice:
+                    this.Monitor.Log(message, LogLevel.Trace);
+                    break;
+
+                case DeprecationLevel.Info:
+                    this.Monitor.Log(message, LogLevel.Debug);
+                    break;
+
+                case DeprecationLevel.PendingRemoval:
+                    this.Monitor.Log(message, LogLevel.Warn);
+                    break;
+
+                default:
+                    throw new NotSupportedException($"Unknown deprecation level '{severity}'");
+            }
+        }
+
+        /// <summary>Mark a deprecation warning as already logged.</summary>
+        /// <param name="nounPhrase">A noun phrase describing what is deprecated (e.g. "the Extensions.AsInt32 method").</param>
+        /// <param name="version">The SMAPI version which deprecated it.</param>
+        /// <returns>Returns whether the deprecation was successfully marked as warned. Returns <c>false</c> if it was already marked.</returns>
+        public bool MarkWarned(string nounPhrase, string version)
+        {
+            return this.MarkWarned(this.ModRegistry.GetModFromStack(), nounPhrase, version);
+        }
+
+        /// <summary>Mark a deprecation warning as already logged.</summary>
+        /// <param name="source">The friendly name of the assembly which used the deprecated code.</param>
+        /// <param name="nounPhrase">A noun phrase describing what is deprecated (e.g. "the Extensions.AsInt32 method").</param>
+        /// <param name="version">The SMAPI version which deprecated it.</param>
+        /// <returns>Returns whether the deprecation was successfully marked as warned. Returns <c>false</c> if it was already marked.</returns>
+        public bool MarkWarned(string source, string nounPhrase, string version)
+        {
+            if (string.IsNullOrWhiteSpace(source))
+                throw new InvalidOperationException("The deprecation source cannot be empty.");
+
+            string key = $"{source}::{nounPhrase}::{version}";
+            if (this.LoggedDeprecations.Contains(key))
+                return false;
+            this.LoggedDeprecations.Add(key);
+            return true;
+        }
+    }
+}