using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Text;

namespace Newtonsoft.Json.Serialization
{
    /// <summary>
    /// Represents a trace writer that writes to memory. When the trace message limit is
    /// reached then old trace messages will be removed as new messages are added.
    /// </summary>
    public class MemoryTraceWriter : ITraceWriter
    {
        private readonly Queue<string> _traceMessages;

        /// <summary>
        /// Gets the <see cref="TraceLevel"/> that will be used to filter the trace messages passed to the writer.
        /// For example a filter level of <code>Info</code> will exclude <code>Verbose</code> messages and include <code>Info</code>,
        /// <code>Warning</code> and <code>Error</code> messages.
        /// </summary>
        /// <value>
        /// The <see cref="TraceLevel"/> that will be used to filter the trace messages passed to the writer.
        /// </value>
        public TraceLevel LevelFilter { get; set; }

        /// <summary>
        /// Initializes a new instance of the <see cref="MemoryTraceWriter"/> class.
        /// </summary>
        public MemoryTraceWriter()
        {
            LevelFilter = TraceLevel.Verbose;
            _traceMessages = new Queue<string>();
        }

        /// <summary>
        /// Writes the specified trace level, message and optional exception.
        /// </summary>
        /// <param name="level">The <see cref="TraceLevel"/> at which to write this trace.</param>
        /// <param name="message">The trace message.</param>
        /// <param name="ex">The trace exception. This parameter is optional.</param>
        public void Trace(TraceLevel level, string message, Exception ex)
        {
            if (_traceMessages.Count >= 1000)
            {
                _traceMessages.Dequeue();
            }

            StringBuilder sb = new StringBuilder();
            sb.Append(DateTime.Now.ToString("yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fff", CultureInfo.InvariantCulture));
            sb.Append(" ");
            sb.Append(level.ToString("g"));
            sb.Append(" ");
            sb.Append(message);

            _traceMessages.Enqueue(sb.ToString());
        }

        /// <summary>
        /// Returns an enumeration of the most recent trace messages.
        /// </summary>
        /// <returns>An enumeration of the most recent trace messages.</returns>
        public IEnumerable<string> GetTraceMessages()
        {
            return _traceMessages;
        }

        /// <summary>
        /// Returns a <see cref="String"/> of the most recent trace messages.
        /// </summary>
        /// <returns>
        /// A <see cref="String"/> of the most recent trace messages.
        /// </returns>
        public override string ToString()
        {
            StringBuilder sb = new StringBuilder();
            foreach (string traceMessage in _traceMessages)
            {
                if (sb.Length > 0)
                {
                    sb.AppendLine();
                }

                sb.Append(traceMessage);
            }

            return sb.ToString();
        }
    }
}