#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.Reflection;

using log4net.Repository;

namespace log4net.Config;

/// <summary>
/// Base class for all log4net configuration attributes.
/// </summary>
/// <remarks>
/// This is an abstract class that must be extended by 
/// specific configurators. This attribute allows the
/// configurator to be parameterized by an assembly level
/// attribute.
/// </remarks>
/// <author>Nicko Cadell</author>
/// <author>Gert Driesen</author>
[AttributeUsage(AttributeTargets.Assembly)]
public abstract class ConfiguratorAttribute : Attribute, IComparable
{
  private readonly int _priority;

  /// <summary>
  /// Constructor used by subclasses.
  /// </summary>
  /// <param name="priority">the ordering priority for this configurator</param>
  /// <remarks>
  /// <para>
  /// The <paramref name="priority"/> is used to order the configurator
  /// attributes before they are invoked. Higher priority configurators are executed
  /// before lower priority ones.
  /// </para>
  /// </remarks>
  protected ConfiguratorAttribute(int priority) => this._priority = priority;

  /// <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>
  /// Abstract method implemented by a subclass. When this method is called
  /// the subclass should configure the <paramref name="targetRepository"/>.
  /// </para>
  /// </remarks>
  public abstract void Configure(Assembly sourceAssembly, ILoggerRepository targetRepository);

  /// <summary>
  /// Compare this instance to another ConfiguratorAttribute
  /// </summary>
  /// <param name="obj">the object to compare to</param>
  /// <returns>see <see cref="IComparable.CompareTo"/></returns>
  /// <remarks>
  /// <para>
  /// Compares the priorities of the two <see cref="ConfiguratorAttribute"/> instances.
  /// Sorts by priority in descending order. Objects with the same priority are
  /// randomly ordered.
  /// </para>
  /// </remarks>
  public int CompareTo(object? obj)
  {
    if (ReferenceEquals(this, obj))
    {
      return 0;
    }

    int result = -1;

    if (obj is ConfiguratorAttribute target)
    {
      // Compare the priorities
      result = target._priority.CompareTo(_priority);
      if (result == 0)
      {
        // Same priority, so have to provide some ordering
        result = -1;
      }
    }
    return result;
  }
}