From d40c7c63a8070fbfc2bfc7dc7b289aa04805b0ec Mon Sep 17 00:00:00 2001
From: Jonas Arnold <jonas.arnold@live.de>
Date: Sat, 8 Apr 2023 14:02:42 +0200
Subject: [PATCH] implemented interface for a generic logger

---
 Common/Logging/ILogger.cs              |  90 +++++++++++++++++++++
 Common/Logging/LogEntry.cs             | 103 +++++++++++++++++++++++++
 Common/Logging/LogLevel.cs             |  14 ++++
 Common/Logging/NewLogEntryEventArgs.cs |  14 ++++
 4 files changed, 221 insertions(+)
 create mode 100644 Common/Logging/ILogger.cs
 create mode 100644 Common/Logging/LogEntry.cs
 create mode 100644 Common/Logging/LogLevel.cs
 create mode 100644 Common/Logging/NewLogEntryEventArgs.cs

diff --git a/Common/Logging/ILogger.cs b/Common/Logging/ILogger.cs
new file mode 100644
index 0000000..766525f
--- /dev/null
+++ b/Common/Logging/ILogger.cs
@@ -0,0 +1,90 @@
+namespace Common.Logging;
+
+/// <summary>
+/// Generalized interface for a logger.
+/// Contains Initialization and Stopping methods, an event for when a new log entry is entered.
+/// Contains various methods to create a log entry.
+/// </summary>
+public interface ILogger
+{
+    /// <summary>
+    /// Event that is thrown whenever a new log entry was entered with any Log method.
+    /// </summary>
+    event EventHandler<NewLogEntryEventArgs> NewLogEntry;
+
+    /// <summary>
+    /// Initialize the Logger once before using it. 
+    /// Sets the minimum<see cref="Logging.LogLevel"/> to <see cref="Logging.LogLevel.Trace"/>. Therefore all log entries will be logged.
+    /// </summary>
+    void Initialize();
+
+    /// <summary>
+    /// Initialize the Logger once before using it.
+    /// </summary>
+    /// <param name="minimumLogLevel">log entries with a lower level than this will not be logged</param>
+    void Initialize(LogLevel minimumLogLevel);
+
+    /// <summary>
+    /// Empties queue and closes logging stream.
+    /// </summary>
+    void StopLogging();
+
+    /// <summary>
+    /// Changes minimum<see cref="Logging.LogLevel"/> to the given level.
+    /// </summary>
+    /// <param name="newMinimumLogLevel">log entries with a lower level than this will not be logged anymore</param>
+    void SetMinimumLogLevel(LogLevel newMinimumLogLevel);
+
+    #region Logging methods
+    /// <summary>
+    /// Create a Log entry with the level <see cref="Logging.LogLevel.Trace"/>.
+    /// </summary>
+    /// <param name="category">Category of the log entry. Example: Location in Software</param>
+    /// <param name="message">Message to describe what to log.</param>
+    void LogTrace(string message, string category);
+
+    /// <summary>
+    /// Create a Log entry with the level <see cref="Logging.LogLevel.Debug"/>.
+    /// </summary>
+    /// <param name="category">Category of the log entry. Example: Location in Software</param>
+    /// <param name="message">Message to describe what to log.</param>
+    void LogDebug(string message, string category);
+
+    /// <summary>
+    /// Create a Log entry with the level <see cref="Logging.LogLevel.Info"/>.
+    /// </summary>
+    /// <param name="category">Category of the log entry. Example: Location in Software</param>
+    /// <param name="message">Message to describe what to log.</param>
+    void LogInfo(string message, string category);
+
+    /// <summary>
+    /// Create a Log entry with the level <see cref="Logging.LogLevel.Warn"/>.
+    /// </summary>
+    /// <param name="category">Category of the log entry. Example: Location in Software</param>
+    /// <param name="message">Message to describe what to log.</param>
+    void LogWarn(string message, string category);
+
+    /// <summary>
+    /// Create a Log entry with the level <see cref="Logging.LogLevel.Error"/>.
+    /// </summary>
+    /// <param name="category">Category of the log entry. Example: Location in Software</param>
+    /// <param name="message">Message to describe what to log.</param>
+    void LogError(string message, string category);
+
+    /// <summary>
+    /// Create a Log entry with a <see cref="System.Exception"/> assigned. No message provided.
+    /// </summary>
+    /// <param name="exception">Exception associated with the log entry.</param>
+    /// <param name="category">Category of the log entry. Example: Location in Software</param>
+    void LogException(Exception exception, string category);
+
+    /// <summary>
+    /// Create a Log entry with a <see cref="System.Exception"/> assigned.
+    /// </summary>
+    /// <param name="exception">Exception associated with the log entry.</param>
+    /// <param name="message">Message to describe what to log.</param>
+    /// <param name="category">Category of the log entry. Example: Location in Software</param>
+    void LogException(Exception exception, string message, string category);
+
+    #endregion
+}
diff --git a/Common/Logging/LogEntry.cs b/Common/Logging/LogEntry.cs
new file mode 100644
index 0000000..a79e795
--- /dev/null
+++ b/Common/Logging/LogEntry.cs
@@ -0,0 +1,103 @@
+using System.Text;
+
+namespace Common.Logging;
+
+/// <summary>
+/// A generalized class that represents a single log entry.
+/// </summary>
+public class LogEntry
+{
+    /// <summary>
+    /// Category of the <see cref="LogEntry"/>.
+    /// Example: Location in Software
+    /// </summary>
+    public string Category { get; set; }
+
+    /// <summary>
+    /// Message to describe what to log.
+    /// </summary>
+    public string Message { get; set; }
+
+    /// <summary>
+    /// Time when the <see cref="LogEntry"/> was created.
+    /// </summary>
+    public DateTime Time { get; }
+
+    /// <summary>
+    /// Time when the <see cref="LogEntry"/> was created as a formatted string.
+    /// </summary>
+    public string TimeString => this.Time.ToString("dd.MM.yyyy HH:mm:ss.fff");
+
+    /// <summary>
+    /// <see cref="System.Exception"/> associated with the <see cref="LogEntry"/>, may be null.
+    /// </summary>
+    public Exception? Exception { get; set; }
+
+    /// <summary>
+    /// <see cref="Logging.LogLevel"/> associated with the <see cref="LogEntry"/>.
+    /// </summary>
+    public LogLevel LogLevel { get; set; }
+
+    /// <summary>
+    /// Creates an empty <see cref="LogEntry"/> with no <see cref="Category"/> and <see cref="Message"/>.
+    /// </summary>
+    public LogEntry()
+    {
+        this.Time = DateTime.Now;
+        this.Category = string.Empty;
+        this.Message = string.Empty;
+    }
+
+    /// <summary>
+    /// Creates a <see cref="LogEntry"/> with the information given as parameters.
+    /// </summary>
+    /// <param name="level"><see cref="Logging.LogLevel"/> associated with the <see cref="LogEntry"/></param>
+    /// <param name="category">Category of the <see cref="LogEntry"/>. Example: Location in Software</param>
+    /// <param name="message">Message to describe what to log.</param>
+    /// <param name="ex"><see cref="System.Exception"/> associated with the <see cref="LogEntry"/>, may be null.</param>
+    public LogEntry(LogLevel level, string category, string message, Exception? ex)
+    {
+        this.Time = DateTime.Now;
+        this.LogLevel = level;
+        this.Category = category;
+        this.Message = message;
+        this.Exception = ex;
+    }
+
+    /// <summary>
+    /// Creates a <see cref="LogEntry"/> with the information given as parameters.
+    /// Sets the category of the <see cref="LogEntry"/> to an empty string.
+    /// No <see cref="System.Exception"/> is assigned to the <see cref="LogEntry"/>.
+    /// </summary>
+    /// <param name="level"><see cref="Logging.LogLevel"/> associated with the <see cref="LogEntry"/></param>
+    /// <param name="message">Message to describe what to log.</param>
+    public LogEntry(LogLevel level, string message)
+      : this(level, string.Empty, message, null) { }
+
+    /// <summary>
+    /// Creates a <see cref="LogEntry"/> with the information given as parameters.
+    /// No <see cref="System.Exception"/> is assigned to the <see cref="LogEntry"/>.
+    /// </summary>
+    /// <param name="level"><see cref="Logging.LogLevel"/> associated with the <see cref="LogEntry"/></param>
+    /// <param name="category">Category of the <see cref="LogEntry"/>. Example: Location in Software</param>
+    /// <param name="message">Message to describe what to log.</param>
+    public LogEntry(LogLevel level, string category, string message)
+       : this(level, category, message, null) { }
+
+    /// <summary>
+    /// Builds the string that is to log for this entry.
+    /// </summary>
+    /// <returns>string with complete log entry</returns>
+    public override string ToString()
+    {
+        StringBuilder sb = new();
+
+        sb.AppendLine($"{this.TimeString} {this.LogLevel.ToString().ToUpper()} {this.Category}: {this.Message}");
+        if (this.Exception != null)
+        {
+            sb.AppendLine($"Exception: {this.Exception}");
+        }
+
+        return sb.ToString();
+    }
+}
diff --git a/Common/Logging/LogLevel.cs b/Common/Logging/LogLevel.cs
new file mode 100644
index 0000000..bd02a1c
--- /dev/null
+++ b/Common/Logging/LogLevel.cs
@@ -0,0 +1,14 @@
+namespace Common.Logging;
+
+/// <summary>
+/// Level of a log entry.
+/// </summary>
+public enum LogLevel
+{ 
+    Undefined = 0,
+    Error = 1,
+    Warn = 2,
+    Info = 3,
+    Debug = 4,
+    Trace = 5
+}
diff --git a/Common/Logging/NewLogEntryEventArgs.cs b/Common/Logging/NewLogEntryEventArgs.cs
new file mode 100644
index 0000000..82a9f55
--- /dev/null
+++ b/Common/Logging/NewLogEntryEventArgs.cs
@@ -0,0 +1,14 @@
+namespace Common.Logging;
+
+/// <summary>
+/// EventArgs for when a new log entry is present.
+/// </summary>
+public class NewLogEntryEventArgs : EventArgs
+{ 
+    public LogEntry LogEntry { get; }
+
+    public NewLogEntryEventArgs(LogEntry logEntry)
+    {
+        this.LogEntry = logEntry;
+    }
+}