FilteringTargetWrapper.cs

// 
// Copyright (c) 2004-2019 Jaroslaw Kowalski <jaak@jkowalski.net>, Kim Christensen, Julian Verdurmen
// 
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namespace NLog.Targets.Wrappers
{
    using System.Collections.Generic;
    using NLog.Common;
    using NLog.Conditions;
    using NLog.Config;
    using NLog.Filters;

    /// <summary>
    /// Filters log entries based on a condition.
    /// </summary>
    /// <seealso href="https://github.com/nlog/nlog/wiki/FilteringWrapper-target">Documentation on NLog Wiki</seealso>
    /// <example>
    /// <p>This example causes the messages not contains the string '1' to be ignored.</p>
    /// <p>
    /// To set up the target in the <a href="config.html">configuration file</a>, 
    /// use the following syntax:
    /// </p>
    /// <code lang="XML" source="examples/targets/Configuration File/FilteringWrapper/NLog.config" />
    /// <p>
    /// The above examples assume just one target and a single rule. See below for
    /// a programmatic configuration that's equivalent to the above config file:
    /// </p>
    /// <code lang="C#" source="examples/targets/Configuration API/FilteringWrapper/Simple/Example.cs" />
    /// </example>
    [Target("FilteringWrapper", IsWrapper = true)]
    public class FilteringTargetWrapper : WrapperTargetBase
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="FilteringTargetWrapper" /> class.
        /// </summary>
        public FilteringTargetWrapper()
            : this(null, null)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="FilteringTargetWrapper" /> class.
        /// </summary>
        /// <param name="name">Name of the target.</param>
        /// <param name="wrappedTarget">The wrapped target.</param>
        /// <param name="condition">The condition.</param>
        public FilteringTargetWrapper(string name, Target wrappedTarget, ConditionExpression condition)
            : this(wrappedTarget, condition)
        {
            Name = name;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="FilteringTargetWrapper" /> class.
        /// </summary>
        /// <param name="wrappedTarget">The wrapped target.</param>
        /// <param name="condition">The condition.</param>
        public FilteringTargetWrapper(Target wrappedTarget, ConditionExpression condition)
        {
            WrappedTarget = wrappedTarget;
            Condition = condition;
        }

        /// <summary>
        /// Gets or sets the condition expression. Log events who meet this condition will be forwarded 
        /// to the wrapped target.
        /// </summary>
        /// <docgen category='Filtering Options' order='10' />
        public ConditionExpression Condition { get => (Filter as ConditionBasedFilter)?.Condition; set => Filter = value != null ? new ConditionBasedFilter() { Condition = value, DefaultFilterResult = FilterResult.Ignore } : null; }

        /// <summary>
        /// Gets or sets the filter. Log events who evaluates to <see cref="FilterResult.Ignore"/> will be discarded
        /// </summary>
        /// <docgen category='Filtering Options' order='10' />
        [RequiredParameter]
        public Filter Filter { get; set; }

        /// <inheritdoc/>
        protected override void InitializeTarget()
        {
            base.InitializeTarget();

            if (!OptimizeBufferReuse && WrappedTarget != null && WrappedTarget.OptimizeBufferReuse)
            {
                OptimizeBufferReuse = GetType() == typeof(FilteringTargetWrapper); // Class not sealed, reduce breaking changes
            }
        }

        /// <summary>
        /// Checks the condition against the passed log event.
        /// If the condition is met, the log event is forwarded to
        /// the wrapped target.
        /// </summary>
        /// <param name="logEvent">Log event.</param>
        protected override void Write(AsyncLogEventInfo logEvent)
        {
            if (FilterIncludeLogEvent(logEvent.LogEvent))
            {
                WrappedTarget.WriteAsyncLogEvent(logEvent);
            }
            else
            {
                logEvent.Continuation(null);
            }
        }

        /// <inheritdoc/>
        protected override void Write(IList<AsyncLogEventInfo> logEvents)
        {
            bool hasIgnoredLogEvents = false;
            IList<AsyncLogEventInfo> filterLogEvents = null;
            AsyncLogEventInfo filterLogEvent = default(AsyncLogEventInfo);
            for (int i = 0; i < logEvents.Count; ++i)
            {
                if (FilterIncludeLogEvent(logEvents[i].LogEvent))
                {
                    if (hasIgnoredLogEvents && filterLogEvents == null)
                    {
                        if (filterLogEvent.LogEvent != null)
                        {
                            filterLogEvents = new List<AsyncLogEventInfo>();
                            filterLogEvents.Add(filterLogEvent);
                            filterLogEvent = default(AsyncLogEventInfo);
                        }
                        else
                        {
                            filterLogEvent = logEvents[i];
                        }
                    }

                    if (filterLogEvents != null)
                        filterLogEvents.Add(logEvents[i]);
                }
                else
                {
                    if (!hasIgnoredLogEvents && i > 0)
                    {
                        filterLogEvents = new List<AsyncLogEventInfo>();
                        for (int j = 0; j < i; ++j)
                            filterLogEvents.Add(logEvents[j]);
                    }
                    hasIgnoredLogEvents = true;
                    logEvents[i].Continuation(null);
                }
            }

            if (!hasIgnoredLogEvents)
                WrappedTarget.WriteAsyncLogEvents(logEvents);
            else if (filterLogEvents != null)
                WrappedTarget.WriteAsyncLogEvents(filterLogEvents);
            else if (filterLogEvent.LogEvent != null)
                WrappedTarget.WriteAsyncLogEvent(filterLogEvent);
        }

        private bool FilterIncludeLogEvent(LogEventInfo logEvent)
        {
            var filterResult = Filter.GetFilterResult(logEvent);
            if (filterResult == FilterResult.Ignore || filterResult == FilterResult.IgnoreFinal)
                return false;
            else
                return true;
        }
    }
}