using System.Diagnostics;
using System.IO;
using System.Threading;

namespace winsw
{
    // ReSharper disable once InconsistentNaming
    public interface EventLogger
    {
        void LogEvent(string message);
        void LogEvent(string message, EventLogEntryType type);
    }

    /// <summary>
    /// Abstraction for handling log.
    /// </summary>
    public abstract class LogHandler
    {
        // ReSharper disable once InconsistentNaming
        public abstract void log(Stream outputStream, Stream errorStream);

        /// <summary>
        /// Error and information about logging should be reported here.
        /// </summary>
        public EventLogger EventLogger { set; get; }

        /// <summary>
        /// Convenience method to copy stuff from StreamReader to StreamWriter
        /// </summary>
        protected void CopyStream(Stream i, Stream o)
        {
            byte[] buf = new byte[1024];
            while (true)
            {
                int sz = i.Read(buf, 0, buf.Length);
                if (sz == 0) break;
                o.Write(buf, 0, sz);
                o.Flush();
            }
            i.Close();
            o.Close();
        }

        /// <summary>
        /// File replacement.
        /// </summary>
        protected void CopyFile(string sourceFileName, string destFileName)
        {
            try
            {
                File.Delete(destFileName);
                File.Move(sourceFileName, destFileName);
            }
            catch (IOException e)
            {
                EventLogger.LogEvent("Failed to copy :" + sourceFileName + " to " + destFileName + " because " + e.Message);
            }
        }
    }

    /// <summary>
    /// Base class for file-based loggers
    /// </summary>
    public abstract class AbstractFileLogAppender : LogHandler
    {
        protected string BaseLogFileName { private set; get; }

        public AbstractFileLogAppender(string logDirectory, string baseName)
        {
            BaseLogFileName = Path.Combine(logDirectory, baseName);
        }
    }

    public abstract class SimpleLogAppender : AbstractFileLogAppender
    {
        public FileMode FileMode { private set; get; }
        public string OutputLogFileName { private set; get; }
        public string ErrorLogFileName { private set; get; }

        public SimpleLogAppender(string logDirectory, string baseName, FileMode fileMode)
            : base(logDirectory, baseName)
        {
            FileMode = fileMode;
            OutputLogFileName = BaseLogFileName + ".out.log";
            ErrorLogFileName = BaseLogFileName + ".err.log";
        }

        public override void log(Stream outputStream, Stream errorStream)
        {
            new Thread(delegate() { CopyStream(outputStream, new FileStream(OutputLogFileName, FileMode)); }).Start();
            new Thread(delegate() { CopyStream(errorStream, new FileStream(ErrorLogFileName, FileMode)); }).Start();
        }
    }

    public class DefaultLogAppender : SimpleLogAppender
    {
        public DefaultLogAppender(string logDirectory, string baseName)
            : base(logDirectory, baseName, FileMode.Append)
        {
        }
    }

    public class ResetLogAppender : SimpleLogAppender
    {
        public ResetLogAppender(string logDirectory, string baseName)
            : base(logDirectory, baseName, FileMode.Create)
        {
        }
    }
    
    /// <summary>
    /// LogHandler that throws away output
    /// </summary>
    public class IgnoreLogAppender : LogHandler
    {
        public override void log(Stream outputStream, Stream errorStream)
        {
            new Thread(delegate() { CopyStream(outputStream, Stream.Null); }).Start();
            new Thread(delegate() { CopyStream(errorStream, Stream.Null); }).Start();
        }
    }

    public class TimeBasedRollingLogAppender : AbstractFileLogAppender
    {
        public string Pattern { get; private set; }
        public int Period { get; private set; }

        public TimeBasedRollingLogAppender(string logDirectory, string baseName, string pattern, int period)
            : base(logDirectory, baseName)
        {
            Pattern = pattern;
            Period = period;
        }

        public override void log(Stream outputStream, Stream errorStream)
        {
            new Thread(delegate() { CopyStreamWithDateRotation(outputStream, ".out.log"); }).Start();
            new Thread(delegate() { CopyStreamWithDateRotation(errorStream, ".err.log"); }).Start();
        }

        /// <summary>
        /// Works like the CopyStream method but does a log rotation based on time.
        /// </summary>
        private void CopyStreamWithDateRotation(Stream data, string ext)
        {
            PeriodicRollingCalendar periodicRollingCalendar = new PeriodicRollingCalendar(Pattern, Period);
            periodicRollingCalendar.init();

            byte[] buf = new byte[1024];
            FileStream w = new FileStream(BaseLogFileName + "_" + periodicRollingCalendar.format + ext, FileMode.Append);
            while (true)
            {
                int len = data.Read(buf, 0, buf.Length);
                if (len == 0) break;    // EOF

                if (periodicRollingCalendar.shouldRoll)
                {// rotate at the line boundary
                    int offset = 0;
                    bool rolled = false;
                    for (int i = 0; i < len; i++)
                    {
                        if (buf[i] == 0x0A)
                        {// at the line boundary.
                            // time to rotate.
                            w.Write(buf, offset, i + 1);
                            w.Close();
                            offset = i + 1;

                            // create a new file and write everything to the new file.
                            w = new FileStream(BaseLogFileName + "_" + periodicRollingCalendar.format + ext, FileMode.Create);
                            rolled = true;
                            if (offset < len)
                            {
                                w.Write(buf, offset, len - offset);
                                break;
                            }
                        }
                    }

                    if (!rolled)
                    {// we didn't roll - most likely as we didnt find a line boundary, so we should log what we read and roll anyway.
                        w.Write(buf, 0, len);
                        w.Close();
                        w = new FileStream(BaseLogFileName + "_" + periodicRollingCalendar.format + ext, FileMode.Create);
                    }

                }
                else
                {// typical case. write the whole thing into the current file
                    w.Write(buf, 0, len);
                }

                w.Flush();
            }
            data.Close();
            w.Close();
        }

    }

    public class SizeBasedRollingLogAppender : AbstractFileLogAppender
    {
        // ReSharper disable once InconsistentNaming
        public static int BYTES_PER_KB = 1024;
        // ReSharper disable once InconsistentNaming
        public static int BYTES_PER_MB = 1024 * BYTES_PER_KB;
        // ReSharper disable once InconsistentNaming
        public static int DEFAULT_SIZE_THRESHOLD = 10 * BYTES_PER_MB; // rotate every 10MB.
        // ReSharper disable once InconsistentNaming
        public static int DEFAULT_FILES_TO_KEEP = 8;

        public int SizeTheshold { private set; get; }

        public int FilesToKeep { private set; get; }

        public SizeBasedRollingLogAppender(string logDirectory, string baseName, int sizeThreshold, int filesToKeep)
            : base(logDirectory, baseName)
        {
            SizeTheshold = sizeThreshold;
            FilesToKeep = filesToKeep;
        }

        public SizeBasedRollingLogAppender(string logDirectory, string baseName)
            : this(logDirectory, baseName, DEFAULT_SIZE_THRESHOLD, DEFAULT_FILES_TO_KEEP) { }

        public override void log(Stream outputStream, Stream errorStream)
        {
            new Thread(delegate() { CopyStreamWithRotation(outputStream, ".out.log"); }).Start();
            new Thread(delegate() { CopyStreamWithRotation(errorStream, ".err.log"); }).Start();
        }

        /// <summary>
        /// Works like the CopyStream method but does a log rotation.
        /// </summary>
        private void CopyStreamWithRotation(Stream data, string ext)
        {
            byte[] buf = new byte[1024];
            FileStream w = new FileStream(BaseLogFileName + ext, FileMode.Append);
            long sz = new FileInfo(BaseLogFileName + ext).Length;

            while (true)
            {
                int len = data.Read(buf, 0, buf.Length);
                if (len == 0) break;    // EOF
                if (sz + len < SizeTheshold)
                {// typical case. write the whole thing into the current file
                    w.Write(buf, 0, len);
                    sz += len;
                }
                else
                {
                    // rotate at the line boundary
                    int s = 0;
                    for (int i = 0; i < len; i++)
                    {
                        if (buf[i] != 0x0A) continue;
                        if (sz + i < SizeTheshold) continue;

                        // at the line boundary and exceeded the rotation unit.
                        // time to rotate.
                        w.Write(buf, s, i + 1);
                        w.Close();
                        s = i + 1;

                        try
                        {
                            for (int j = FilesToKeep; j >= 1; j--)
                            {
                                string dst = BaseLogFileName + "." + (j - 1) + ext;
                                string src = BaseLogFileName + "." + (j - 2) + ext;
                                if (File.Exists(dst))
                                    File.Delete(dst);
                                if (File.Exists(src))
                                    File.Move(src, dst);
                            }
                            File.Move(BaseLogFileName + ext, BaseLogFileName + ".0" + ext);
                        }
                        catch (IOException e)
                        {
                            EventLogger.LogEvent("Failed to rotate log: " + e.Message);
                        }

                        // even if the log rotation fails, create a new one, or else
                        // we'll infinitely try to rotate.
                        w = new FileStream(BaseLogFileName + ext, FileMode.Create);
                        sz = new FileInfo(BaseLogFileName + ext).Length;
                    }
                }

                w.Flush();
            }
            data.Close();
            w.Close();
        }
    }

    /// <summary>
    /// Rotate log when a service is newly started.
    /// </summary>
    public class RollingLogAppender : SimpleLogAppender
    {
        public RollingLogAppender(string logDirectory, string baseName)
            : base(logDirectory, baseName, FileMode.Append)
        {
        }

        public override void log(Stream outputStream, Stream errorStream)
        {
            CopyFile(OutputLogFileName, OutputLogFileName + ".old");
            CopyFile(ErrorLogFileName, ErrorLogFileName + ".old");
            base.log(outputStream, errorStream);
        }
    }
}