#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.Collections.Generic;
using System.Reflection;
using System.IO;

using log4net.Util;
using log4net.Repository;
using log4net.Repository.Hierarchy;

namespace log4net.Config;

/// <summary>
/// Assembly level attribute to configure the <see cref="XmlConfigurator"/>.
/// </summary>
/// <remarks>
/// <para>
/// This attribute may only be used at the assembly scope and can only
/// be used once per assembly.
/// </para>
/// <para>
/// Use this attribute to configure the <see cref="XmlConfigurator"/>
/// without calling one of the <see cref="XmlConfigurator.Configure()"/>
/// methods.
/// </para>
/// <para>
/// If neither of the <see cref="ConfigFile"/> or <see cref="ConfigFileExtension"/>
/// properties are set the configuration is loaded from the application's .config file.
/// If set the <see cref="ConfigFile"/> property takes priority over the
/// <see cref="ConfigFileExtension"/> property. The <see cref="ConfigFile"/> property
/// specifies a path to a file to load the config from. The path is relative to the
/// application's base directory; <see cref="AppDomain.BaseDirectory"/>.
/// The <see cref="ConfigFileExtension"/> property is used as a postfix to the assembly file name.
/// The config file must be located in the  application's base directory; <see cref="AppDomain.BaseDirectory"/>.
/// For example in a console application setting the <see cref="ConfigFileExtension"/> to
/// <c>config</c> has the same effect as not specifying the <see cref="ConfigFile"/> or 
/// <see cref="ConfigFileExtension"/> properties.
/// </para>
/// <para>
/// The <see cref="Watch"/> property can be set to cause the <see cref="XmlConfigurator"/>
/// to watch the configuration file for changes.
/// </para>
/// <note>
/// <para>
/// Log4net will only look for assembly level configuration attributes once.
/// When using the log4net assembly level attributes to control the configuration 
/// of log4net you must ensure that the first call to any of the 
/// <see cref="Core.LoggerManager"/> methods is made from the assembly with the configuration
/// attributes. 
/// </para>
/// <para>
/// If you cannot guarantee the order in which log4net calls will be made from 
/// different assemblies you must use programmatic configuration instead, i.e.
/// call the <see cref="XmlConfigurator.Configure()"/> method directly.
/// </para>
/// </note>
/// </remarks>
/// <author>Nicko Cadell</author>
/// <author>Gert Driesen</author>
[AttributeUsage(AttributeTargets.Assembly)]
[Log4NetSerializable]
public sealed class XmlConfiguratorAttribute : ConfiguratorAttribute
{
  /// <summary>
  /// Default constructor
  /// </summary>
  /// <remarks>
  /// <para>
  /// Default constructor
  /// </para>
  /// </remarks>
  public XmlConfiguratorAttribute() : base(0) /* configurator priority 0 */
  {
  }

  /// <summary>
  /// Gets or sets the filename of the configuration file.
  /// </summary>
  /// <value>
  /// The filename of the configuration file.
  /// </value>
  /// <remarks>
  /// <para>
  /// If specified, this is the name of the configuration file to use with
  /// the <see cref="XmlConfigurator"/>. This file path is relative to the
  /// <b>application base</b> directory (<see cref="AppDomain.BaseDirectory"/>).
  /// </para>
  /// <para>
  /// The <see cref="ConfigFile"/> takes priority over the <see cref="ConfigFileExtension"/>.
  /// </para>
  /// </remarks>
  public string? ConfigFile { get; set; }

  /// <summary>
  /// Gets or sets the extension of the configuration file.
  /// </summary>
  /// <remarks>
  /// <para>
  /// If specified this is the extension for the configuration file.
  /// The path to the config file is built by using the <b>application 
  /// base</b> directory (<see cref="AppDomain.BaseDirectory"/>),
  /// the <b>assembly file name</b> and the config file extension.
  /// </para>
  /// <para>
  /// If the <see cref="ConfigFileExtension"/> is set to <c>MyExt</c> then
  /// possible config file names would be: <c>MyConsoleApp.exe.MyExt</c> or
  /// <c>MyClassLibrary.dll.MyExt</c>.
  /// </para>
  /// <para>
  /// The <see cref="ConfigFile"/> takes priority over the <see cref="ConfigFileExtension"/>.
  /// </para>
  /// </remarks>
  public string? ConfigFileExtension { get; set; }

  /// <summary>
  /// Gets or sets a value indicating whether to watch the configuration file.
  /// </summary>
  /// <value>
  /// <see langword="true"/> if the configuration should be watched, <see langword="false"/> otherwise.
  /// </value>
  /// <remarks>
  /// <para>
  /// If this flag is specified and set to <see langword="true"/> then the framework
  /// will watch the configuration file and will reload the config each time 
  /// the file is modified.
  /// </para>
  /// <para>
  /// The config file can only be watched if it is loaded from local disk.
  /// In a No-Touch (Smart Client) deployment where the application is downloaded
  /// from a web server the config file may not reside on the local disk
  /// and therefore it may not be able to watch it.
  /// </para>
  /// <note>
  /// Watching configuration is not supported on the SSCLI.
  /// </note>
  /// </remarks>
  public bool Watch { get; set; }

  /// <summary>
  /// Configures the <see cref="ILoggerRepository"/> for the specified assembly.
  /// </summary>
  /// <param name="sourceAssembly">The assembly that this attribute was defined on.</param>
  /// <param name="targetRepository">The repository to configure.</param>
  /// <remarks>
  /// <para>
  /// Configure the repository using the <see cref="XmlConfigurator"/>.
  /// The <paramref name="targetRepository"/> specified must extend the <see cref="Hierarchy"/>
  /// class otherwise the <see cref="XmlConfigurator"/> will not be able to
  /// configure it.
  /// </para>
  /// </remarks>
  /// <exception cref="ArgumentOutOfRangeException">The <paramref name="targetRepository" /> does not extend <see cref="Hierarchy"/>.</exception>
  public override void Configure(Assembly sourceAssembly, ILoggerRepository targetRepository)
  {
    List<LogLog> configurationMessages = new();

    using (new LogLog.LogReceivedAdapter(configurationMessages))
    {
      string? applicationBaseDirectory = null;
      try
      {
        applicationBaseDirectory = SystemInfo.ApplicationBaseDirectory;
      }
      catch (Exception e) when (!e.IsFatal())
      {
        // Ignore this exception because it is only thrown when ApplicationBaseDirectory is a file
        // and the application does not have PathDiscovery permission
      }

      if (applicationBaseDirectory is null || new Uri(applicationBaseDirectory).IsFile)
      {
        ConfigureFromFile(sourceAssembly, targetRepository);
      }
      else
      {
        ConfigureFromUri(targetRepository);
      }
    }

    targetRepository.ConfigurationMessages = configurationMessages;
  }

  /// <summary>
  /// Attempt to load configuration from the local file system
  /// </summary>
  /// <param name="sourceAssembly">The assembly that this attribute was defined on.</param>
  /// <param name="targetRepository">The repository to configure.</param>
  private void ConfigureFromFile(Assembly sourceAssembly, ILoggerRepository targetRepository)
  {
    // Work out the full path to the config file
    string? fullPath2ConfigFile = null;

    // Select the config file
    if (string.IsNullOrEmpty(ConfigFile))
    {
      if (string.IsNullOrEmpty(ConfigFileExtension))
      {
        // Use the default .config file for the AppDomain
        try
        {
          fullPath2ConfigFile = SystemInfo.ConfigurationFileLocation;
        }
        catch (Exception e) when (!e.IsFatal())
        {
          LogLog.Error(_declaringType, "XmlConfiguratorAttribute: Exception getting ConfigurationFileLocation. Must be able to resolve ConfigurationFileLocation when ConfigFile and ConfigFileExtension properties are not set.", e);
        }
      }
      else
      {
        // Force the extension to start with a '.'
        if (ConfigFileExtension![0] != '.')
        {
          ConfigFileExtension = '.' + ConfigFileExtension;
        }

        string? applicationBaseDirectory = null;
        try
        {
          applicationBaseDirectory = SystemInfo.ApplicationBaseDirectory;
        }
        catch (Exception e) when (!e.IsFatal())
        {
          LogLog.Error(_declaringType, "Exception getting ApplicationBaseDirectory. Must be able to resolve ApplicationBaseDirectory and AssemblyFileName when ConfigFileExtension property is set.", e);
        }

        if (applicationBaseDirectory is not null)
        {
          fullPath2ConfigFile = Path.Combine(applicationBaseDirectory, SystemInfo.AssemblyFileName(sourceAssembly) + ConfigFileExtension);
        }
      }
    }
    else
    {
      string? applicationBaseDirectory = null;
      try
      {
        applicationBaseDirectory = SystemInfo.ApplicationBaseDirectory;
      }
      catch (Exception e) when (!e.IsFatal())
      {
        LogLog.Warn(_declaringType, $"Exception getting ApplicationBaseDirectory. ConfigFile property path [{ConfigFile}] will be treated as an absolute path.", e);
      }

      if (applicationBaseDirectory is not null)
      {
        // Just the base dir + the config file
        fullPath2ConfigFile = Path.Combine(applicationBaseDirectory, ConfigFile!);
      }
      else
      {
        fullPath2ConfigFile = ConfigFile;
      }
    }

    if (fullPath2ConfigFile is not null)
    {
      ConfigureFromFile(targetRepository, new FileInfo(fullPath2ConfigFile));
    }
  }

  /// <summary>
  /// Configure the specified repository using a <see cref="FileInfo"/>
  /// </summary>
  /// <param name="targetRepository">The repository to configure.</param>
  /// <param name="configFile">the FileInfo pointing to the config file</param>
  private void ConfigureFromFile(ILoggerRepository targetRepository, FileInfo configFile)
  {
    // Do we configure just once or do we configure and then watch?
    if (Watch)
    {
      XmlConfigurator.ConfigureAndWatch(targetRepository, configFile);
    }
    else
    {
      XmlConfigurator.Configure(targetRepository, configFile);
    }
  }

  /// <summary>
  /// Attempt to load configuration from a URI
  /// </summary>
  /// <param name="targetRepository">The repository to configure.</param>
  private void ConfigureFromUri(ILoggerRepository targetRepository)
  {
    // Work out the full path to the config file
    Uri? fullPath2ConfigFile = null;

    // Select the config file
    if (string.IsNullOrEmpty(ConfigFile))
    {
      if (string.IsNullOrEmpty(ConfigFileExtension))
      {
        string? systemConfigFilePath = null;
        try
        {
          systemConfigFilePath = SystemInfo.ConfigurationFileLocation;
        }
        catch (Exception e) when (!e.IsFatal())
        {
          LogLog.Error(_declaringType, "XmlConfiguratorAttribute: Exception getting ConfigurationFileLocation. Must be able to resolve ConfigurationFileLocation when ConfigFile and ConfigFileExtension properties are not set.", e);
        }

        if (systemConfigFilePath is not null)
        {
          // Use the default .config file for the AppDomain
          fullPath2ConfigFile = new Uri(systemConfigFilePath);
        }
      }
      else
      {
        // Force the extension to start with a '.'
        if (ConfigFileExtension![0] != '.')
        {
          ConfigFileExtension = '.' + ConfigFileExtension;
        }

        string? systemConfigFilePath = null;
        try
        {
          systemConfigFilePath = SystemInfo.ConfigurationFileLocation;
        }
        catch (Exception e) when (!e.IsFatal())
        {
          LogLog.Error(_declaringType, "XmlConfiguratorAttribute: Exception getting ConfigurationFileLocation. Must be able to resolve ConfigurationFileLocation when the ConfigFile property are not set.", e);
        }

        if (systemConfigFilePath is not null)
        {
          UriBuilder builder = new(new Uri(systemConfigFilePath));

          // Remove the current extension from the systemConfigFileUri path
          string path = builder.Path;
          int startOfExtension = path.LastIndexOf('.');
          if (startOfExtension >= 0)
          {
            path = path.Substring(0, startOfExtension);
          }
          path += ConfigFileExtension;

          builder.Path = path;
          fullPath2ConfigFile = builder.Uri;
        }
      }
    }
    else
    {
      string? applicationBaseDirectory = null;
      try
      {
        applicationBaseDirectory = SystemInfo.ApplicationBaseDirectory;
      }
      catch (Exception e) when (!e.IsFatal())
      {
        LogLog.Warn(_declaringType, $"Exception getting ApplicationBaseDirectory. ConfigFile property path [{ConfigFile}] will be treated as an absolute URI.", e);
      }

      if (applicationBaseDirectory is not null)
      {
        // Just the base dir + the config file
        fullPath2ConfigFile = new Uri(new Uri(applicationBaseDirectory), ConfigFile!);
      }
      else
      {
        fullPath2ConfigFile = new Uri(ConfigFile!);
      }
    }

    if (fullPath2ConfigFile is not null)
    {
      if (fullPath2ConfigFile.IsFile)
      {
        // The ConfigFile could be an absolute local path, therefore we have to be
        // prepared to switch back to using FileInfos here
        ConfigureFromFile(targetRepository, new FileInfo(fullPath2ConfigFile.LocalPath));
      }
      else
      {
        if (Watch)
        {
          LogLog.Warn(_declaringType, "XmlConfiguratorAttribute: Unable to watch config file loaded from a URI");
        }
        XmlConfigurator.Configure(targetRepository, fullPath2ConfigFile);
      }
    }
  }

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