#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.IO;

using log4net.Core;

namespace log4net.Layout;

/// <summary>
/// Interface implemented by layout objects
/// </summary>
/// <remarks>
/// <para>
/// An <see cref="ILayout"/> object is used to format a <see cref="LoggingEvent"/>
/// as text. The <see cref="Format(TextWriter,LoggingEvent)"/> method is called by an
/// appender to transform the <see cref="LoggingEvent"/> into a string.
/// </para>
/// <para>
/// The layout can also supply <see cref="Header"/> and <see cref="Footer"/>
/// text that is appender before any events and after all the events respectively.
/// </para>
/// </remarks>
/// <author>Nicko Cadell</author>
/// <author>Gert Driesen</author>
public interface ILayout
{
  /// <summary>
  /// Implement this method to create your own layout format.
  /// </summary>
  /// <param name="writer">The TextWriter to write the formatted event to</param>
  /// <param name="loggingEvent">The event to format</param>
  /// <remarks>
  /// <para>
  /// This method is called by an appender to format
  /// the <paramref name="loggingEvent"/> as text and output to a writer.
  /// </para>
  /// <para>
  /// If the caller does not have a <see cref="TextWriter"/> and prefers the
  /// event to be formatted as a <see cref="string"/> then the following
  /// code can be used to format the event into a <see cref="StringWriter"/>.
  /// </para>
  /// <code lang="C#">
  /// StringWriter writer = new StringWriter();
  /// Layout.Format(writer, loggingEvent);
  /// string formattedEvent = writer.ToString();
  /// </code>
  /// </remarks>
  void Format(TextWriter writer, LoggingEvent loggingEvent);

  /// <summary>
  /// The content type output by this layout. 
  /// </summary>
  /// <value>The content type</value>
  /// <remarks>
  /// <para>
  /// The content type output by this layout.
  /// </para>
  /// <para>
  /// This is a MIME type e.g. <c>"text/plain"</c>.
  /// </para>
  /// </remarks>
  string ContentType { get; }

  /// <summary>
  /// The header for the layout format.
  /// </summary>
  /// <value>the layout header</value>
  /// <remarks>
  /// <para>
  /// The Header text will be appended before any logging events
  /// are formatted and appended.
  /// </para>
  /// </remarks>
  string? Header { get; }

  /// <summary>
  /// The footer for the layout format.
  /// </summary>
  /// <value>the layout footer</value>
  /// <remarks>
  /// <para>
  /// The Footer text will be appended after all the logging events
  /// have been formatted and appended.
  /// </para>
  /// </remarks>
  string? Footer { get; }

  /// <summary>
  /// Flag indicating if this layout handle exceptions
  /// </summary>
  /// <value><c>false</c> if this layout handles exceptions</value>
  /// <remarks>
  /// <para>
  /// If this layout handles the exception object contained within
  /// <see cref="LoggingEvent"/>, then the layout should return
  /// <c>false</c>. Otherwise, if the layout ignores the exception
  /// object, then the layout should return <c>true</c>.
  /// </para>
  /// </remarks>
  bool IgnoresException { get; }
}
