1 files changed, 121 insertions, 0 deletions
diff --git a/src/StardewModdingAPI/Framework/DeprecationManager.cs b/src/StardewModdingAPI/Framework/DeprecationManager.cs
new file mode 100644
index 00000000..43e82d74
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/DeprecationManager.cs
@@ -0,0 +1,121 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+
+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;
+
+            // show SMAPI 2.0 meta-warning
+            if(this.MarkWarned("SMAPI", "SMAPI 2.0 meta-warning", "2.0"))
+                this.Monitor.Log("Some mods may stop working in SMAPI 2.0 (but they'll work fine for now). Try updating mods with 'deprecated code' warnings; if that doesn't remove the warnings, let the mod authors know about this message or see http://stardewvalleywiki.com/Modding:SMAPI_2.0 for details.", LogLevel.Warn);
+
+            // 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;
+        }
+
+        /// <summary>Get whether a type implements the given virtual method.</summary>
+        /// <param name="subtype">The type to check.</param>
+        /// <param name="baseType">The base type which declares the virtual method.</param>
+        /// <param name="name">The method name.</param>
+        /// <param name="argumentTypes">The expected argument types.</param>
+        internal bool IsVirtualMethodImplemented(Type subtype, Type baseType, string name, Type[] argumentTypes)
+        {
+            MethodInfo method = subtype.GetMethod(nameof(Mod.Entry), argumentTypes);
+            return method.DeclaringType != baseType;
+        }
+    }
+}