#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with 
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

using System;
using System.IO;

using log4net.Util;
using log4net.Core;

namespace log4net.Layout.Pattern;

/// <summary>
/// Write the caller stack frames to the output
/// </summary>
/// <remarks>
/// <para>
/// Writes the <see cref="LocationInfo.StackFrames"/> to the output writer, using format:
/// type3.MethodCall3 > type2.MethodCall2 > type1.MethodCall1
/// </para>
/// </remarks>
/// <author>Michael Cromwell</author>
internal class StackTracePatternConverter : PatternLayoutConverter, IOptionHandler
{
  private int _stackFrameLevel = 1;

  /// <summary>
  /// Initialize the converter
  /// </summary>
  /// <remarks>
  /// <para>
  /// This is part of the <see cref="IOptionHandler"/> delayed object
  /// activation scheme. The <see cref="ActivateOptions"/> method must 
  /// be called on this object after the configuration properties have
  /// been set. Until <see cref="ActivateOptions"/> is called this
  /// object is in an undefined state and must not be used. 
  /// </para>
  /// <para>
  /// If any of the configuration properties are modified then 
  /// <see cref="ActivateOptions"/> must be called again.
  /// </para>
  /// </remarks>
  public void ActivateOptions()
  {
    if (Option is null)
    {
      return;
    }

    string optStr = Option.Trim();
    if (optStr.Length != 0)
    {
      if (SystemInfo.TryParse(optStr, out int stackLevelVal))
      {
        if (stackLevelVal <= 0)
        {
          LogLog.Error(_declaringType, $"StackTracePatternConverter: StackeFrameLevel option ({optStr}) isn't a positive integer.");
        }
        else
        {
          _stackFrameLevel = stackLevelVal;
        }
      }
      else
      {
        LogLog.Error(_declaringType, $"StackTracePatternConverter: StackFrameLevel option \"{optStr}\" not a decimal integer.");
      }
    }
  }

  /// <summary>
  /// Write the strack frames to the output
  /// </summary>
  /// <param name="writer"><see cref="TextWriter" /> that will receive the formatted result.</param>
  /// <param name="loggingEvent">the event being logged</param>
  /// <remarks>
  /// <para>
  /// Writes the <see cref="LocationInfo.StackFrames"/> to the output writer.
  /// </para>
  /// </remarks>
  protected override void Convert(TextWriter writer, LoggingEvent loggingEvent)
  {
    StackFrameItem[]? stackframes = loggingEvent.LocationInformation?.StackFrames;
    if ((stackframes is null) || (stackframes.Length <= 0))
    {
      LogLog.Error(_declaringType, "loggingEvent.LocationInformation.StackFrames was null or empty.");
      return;
    }

    int stackFrameIndex = _stackFrameLevel - 1;
    while (stackFrameIndex >= 0)
    {
      if (stackFrameIndex >= stackframes.Length)
      {
        stackFrameIndex--;
        continue;
      }

      StackFrameItem stackFrame = stackframes[stackFrameIndex];
      writer.Write("{0}.{1}", stackFrame.ClassName, GetMethodInformation(stackFrame.Method));
      if (stackFrameIndex > 0)
      {
        // TODO: make this user settable?
        writer.Write(" > ");
      }
      stackFrameIndex--;
    }
  }

  /// <summary>
  /// Returns the Name of the method
  /// </summary>
  /// <param name="method"></param>
  /// <remarks>This method was created, so this class could be used as a base class for StackTraceDetailPatternConverter</remarks>
  /// <returns>string</returns>
  internal virtual string GetMethodInformation(MethodItem method) => method.Name;

  /// <summary>
  /// The fully qualified type of the StackTracePatternConverter class.
  /// </summary>
  /// <remarks>
  /// Used by the internal logger to record the Type of the
  /// log message.
  /// </remarks>
  private static readonly Type _declaringType = typeof(StackTracePatternConverter);
}