using System;
using JD.Kernel.StaticHelpers;

namespace JD.LogService
{
    /// <summary>
    /// Basic logging facilities.
    /// </summary>
    public static class Logger
    {
        private static ILogger m_emptyLogger;
        
        /// <summary>
        /// Gets a logger that does nothing except not being null :)
        /// </summary>
        public static ILogger Empty
        {
            get { return m_emptyLogger = m_emptyLogger ?? new EmptyLogger(); }
        }

        /// <summary>
        /// Creates and return a delegated logger.
        /// </summary>
        /// <param name="logAction">Will be used as the logging action of the logger.</param>
        public static ILogger FromAction(Action<LogEvent> logAction)
        {
            return new DelegatedLogger(logAction);
        }

        /// <summary>
        /// Returns a wrapper logger that locks each log call individually.
        /// </summary>
        public static ILogger Locked(ILogger logger)
        {
            return new LockedLogger(logger);
        }

        public static ILogger CreateConsoleLogger()
        {
            return new ConsoleLogger();
        }

        #region Nested

        private class EmptyLogger : ILogger
        {
            public void Log(LogEvent @event)
            {
                // Do nothing!
            }
        }

        private class DelegatedLogger : ILogger
        {
            private readonly Action<LogEvent> m_logAction;

            public DelegatedLogger(Action<LogEvent> logAction)
            {
                Throw.IfNull(logAction, "logAction");
                m_logAction = logAction;
            }

            public void Log(LogEvent @event)
            {
                m_logAction(@event);
            }
        }

        private class LockedLogger : ILogger
        {
            private readonly object m_lock = new object();
            private readonly ILogger m_logger;

            public LockedLogger(ILogger logger)
            {
                Throw.IfNull(logger, "logger");
                m_logger = logger;
            }

            public void Log(LogEvent @event)
            {
                lock (m_lock)
                {
                    m_logger.Log(@event);
                }
            }
        }

        private class ConsoleLogger : ILogger
        {
            public void Log(LogEvent @event)
            {
                if (@event.Category == LogCategory.Error)
                {
                    Console.Error.WriteLine(@event.ToCanonicalString());
                }
                else if (@event.Category == LogCategory.Warning)
                {
                    Console.Out.WriteLine(@event.ToCanonicalString());
                }
                else
                {
                    Console.Out.WriteLine(@event.Message);
                }
            }
        }

        #endregion
    }
}