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();
    }
}