1 files changed, 194 insertions, 0 deletions
diff --git a/src/SMAPI/Framework/Monitor.cs b/src/SMAPI/Framework/Monitor.cs
new file mode 100644
index 00000000..bf338386
--- /dev/null
+++ b/src/SMAPI/Framework/Monitor.cs
@@ -0,0 +1,194 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using StardewModdingAPI.Framework.Logging;
+
+namespace StardewModdingAPI.Framework
+{
+    /// <summary>Encapsulates monitoring and logic for a given module.</summary>
+    internal class Monitor : IMonitor
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The name of the module which logs messages using this instance.</summary>
+        private readonly string Source;
+
+        /// <summary>Manages access to the console output.</summary>
+        private readonly ConsoleInterceptionManager ConsoleManager;
+
+        /// <summary>The log file to which to write messages.</summary>
+        private readonly LogFileManager LogFile;
+
+        /// <summary>The maximum length of the <see cref="LogLevel"/> values.</summary>
+        private static readonly int MaxLevelLength = (from level in Enum.GetValues(typeof(LogLevel)).Cast<LogLevel>() select level.ToString().Length).Max();
+
+        /// <summary>The console text color for each log level.</summary>
+        private static readonly IDictionary<LogLevel, ConsoleColor> Colors = Monitor.GetConsoleColorScheme();
+
+        /// <summary>Propagates notification that SMAPI should exit.</summary>
+        private readonly CancellationTokenSource ExitTokenSource;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>Whether SMAPI is aborting. Mods don't need to worry about this unless they have background tasks.</summary>
+        public bool IsExiting => this.ExitTokenSource.IsCancellationRequested;
+
+        /// <summary>Whether to show the full log stamps (with time/level/logger) in the console. If false, shows a simplified stamp with only the logger.</summary>
+        internal bool ShowFullStampInConsole { get; set; }
+
+        /// <summary>Whether to show trace messages in the console.</summary>
+        internal bool ShowTraceInConsole { get; set; }
+
+        /// <summary>Whether to write anything to the console. This should be disabled if no console is available.</summary>
+        internal bool WriteToConsole { get; set; } = true;
+
+        /// <summary>Whether to write anything to the log file. This should almost always be enabled.</summary>
+        internal bool WriteToFile { get; set; } = true;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="source">The name of the module which logs messages using this instance.</param>
+        /// <param name="consoleManager">Manages access to the console output.</param>
+        /// <param name="logFile">The log file to which to write messages.</param>
+        /// <param name="exitTokenSource">Propagates notification that SMAPI should exit.</param>
+        public Monitor(string source, ConsoleInterceptionManager consoleManager, LogFileManager logFile, CancellationTokenSource exitTokenSource)
+        {
+            // validate
+            if (string.IsNullOrWhiteSpace(source))
+                throw new ArgumentException("The log source cannot be empty.");
+
+            // initialise
+            this.Source = source;
+            this.LogFile = logFile ?? throw new ArgumentNullException(nameof(logFile), "The log file manager cannot be null.");
+            this.ConsoleManager = consoleManager;
+            this.ExitTokenSource = exitTokenSource;
+        }
+
+        /// <summary>Log a message for the player or developer.</summary>
+        /// <param name="message">The message to log.</param>
+        /// <param name="level">The log severity level.</param>
+        public void Log(string message, LogLevel level = LogLevel.Debug)
+        {
+            this.LogImpl(this.Source, message, level, Monitor.Colors[level]);
+        }
+
+        /// <summary>Immediately exit the game without saving. This should only be invoked when an irrecoverable fatal error happens that risks save corruption or game-breaking bugs.</summary>
+        /// <param name="reason">The reason for the shutdown.</param>
+        public void ExitGameImmediately(string reason)
+        {
+            this.LogFatal($"{this.Source} requested an immediate game shutdown: {reason}");
+            this.ExitTokenSource.Cancel();
+        }
+
+        /// <summary>Write a newline to the console and log file.</summary>
+        internal void Newline()
+        {
+            if (this.WriteToConsole)
+                this.ConsoleManager.ExclusiveWriteWithoutInterception(Console.WriteLine);
+            if (this.WriteToFile)
+                this.LogFile.WriteLine("");
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Log a fatal error message.</summary>
+        /// <param name="message">The message to log.</param>
+        private void LogFatal(string message)
+        {
+            this.LogImpl(this.Source, message, LogLevel.Error, ConsoleColor.White, background: ConsoleColor.Red);
+        }
+
+        /// <summary>Write a message line to the log.</summary>
+        /// <param name="source">The name of the mod logging the message.</param>
+        /// <param name="message">The message to log.</param>
+        /// <param name="level">The log level.</param>
+        /// <param name="color">The console foreground color.</param>
+        /// <param name="background">The console background color (or <c>null</c> to leave it as-is).</param>
+        private void LogImpl(string source, string message, LogLevel level, ConsoleColor color, ConsoleColor? background = null)
+        {
+            // generate message
+            string levelStr = level.ToString().ToUpper().PadRight(Monitor.MaxLevelLength);
+
+            string fullMessage = $"[{DateTime.Now:HH:mm:ss} {levelStr} {source}] {message}";
+            string consoleMessage = this.ShowFullStampInConsole ? fullMessage : $"[{source}] {message}";
+
+            // write to console
+            if (this.WriteToConsole && (this.ShowTraceInConsole || level != LogLevel.Trace))
+            {
+                this.ConsoleManager.ExclusiveWriteWithoutInterception(() =>
+                {
+                    if (this.ConsoleManager.SupportsColor)
+                    {
+                        if (background.HasValue)
+                            Console.BackgroundColor = background.Value;
+                        Console.ForegroundColor = color;
+                        Console.WriteLine(consoleMessage);
+                        Console.ResetColor();
+                    }
+                    else
+                        Console.WriteLine(consoleMessage);
+                });
+            }
+
+            // write to log file
+            if (this.WriteToFile)
+                this.LogFile.WriteLine(fullMessage);
+        }
+
+        /// <summary>Get the color scheme to use for the current console.</summary>
+        private static IDictionary<LogLevel, ConsoleColor> GetConsoleColorScheme()
+        {
+            // scheme for dark console background
+            if (Monitor.IsDark(Console.BackgroundColor))
+            {
+                return new Dictionary<LogLevel, ConsoleColor>
+                {
+                    [LogLevel.Trace] = ConsoleColor.DarkGray,
+                    [LogLevel.Debug] = ConsoleColor.DarkGray,
+                    [LogLevel.Info] = ConsoleColor.White,
+                    [LogLevel.Warn] = ConsoleColor.Yellow,
+                    [LogLevel.Error] = ConsoleColor.Red,
+                    [LogLevel.Alert] = ConsoleColor.Magenta
+                };
+            }
+
+            // scheme for light console background
+            return new Dictionary<LogLevel, ConsoleColor>
+            {
+                [LogLevel.Trace] = ConsoleColor.DarkGray,
+                [LogLevel.Debug] = ConsoleColor.DarkGray,
+                [LogLevel.Info] = ConsoleColor.Black,
+                [LogLevel.Warn] = ConsoleColor.DarkYellow,
+                [LogLevel.Error] = ConsoleColor.Red,
+                [LogLevel.Alert] = ConsoleColor.DarkMagenta
+            };
+        }
+
+        /// <summary>Get whether a console color should be considered dark, which is subjectively defined as 'white looks better than black on this text'.</summary>
+        /// <param name="color">The color to check.</param>
+        private static bool IsDark(ConsoleColor color)
+        {
+            switch (color)
+            {
+                case ConsoleColor.Black:
+                case ConsoleColor.Blue:
+                case ConsoleColor.DarkBlue:
+                case ConsoleColor.DarkRed:
+                case ConsoleColor.Red:
+                    return true;
+
+                default:
+                    return false;
+            }
+        }
+    }
+}