// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information

namespace log4net.Layout
{
    //
    // 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.
    //
    using System;
    using System.IO;

    using log4net;
    using log4net.Core;

    /// <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="M: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>
        /// Gets 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>
        /// Gets 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>
        /// Gets 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>
        /// Gets a value indicating whether 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; }
    }
}
