/*******************************************************************************

    Define the base classes for all Appenders

    Appenders are objects that are responsible for emitting messages sent
    to a particular logger. There may be more than one appender attached
    to any logger.
    The actual message is constructed by another class known as an EventLayout.

    Copyright:
        Copyright (c) 2004 Kris Bell.
        Some parts copyright (c) 2009-2016 dunnhumby Germany GmbH.
        All rights reserved.

    License:
        Tango Dual License: 3-Clause BSD License / Academic Free License v3.0.
        See LICENSE_TANGO.txt for details.

*******************************************************************************/

module ocean.util.log.Appender;

import ocean.transition;
import ocean.core.Verify;
import ocean.core.ExceptionDefinitions;
import ocean.io.model.IConduit;
import ocean.util.log.Event;
import ocean.util.log.model.ILogger;


/// Base class for all Appenders
public class Appender
{
    mixin(Typedef!(int, "Mask"));

    private Appender        next_;
    private ILogger.Level   level_;
    private Layout          layout_;
    private static Layout   generic;

    /***************************************************************************

        Interface for all logging layout instances

        Implement this method to perform the formatting of message content.

    ***************************************************************************/

    public interface Layout
    {
        void format (LogEvent event, scope void delegate(cstring) dg);
    }

    /***************************************************************************

        Return the mask used to identify this Appender.

        The mask is used to figure out whether an appender has already been
        invoked for a particular logger.

    ***************************************************************************/

    abstract Mask mask ();

    /// Return the name of this Appender.
    abstract cstring name ();

    /***************************************************************************

        Append a message to the output.

        The event received is only valid for the duration of the `apppend`
        call and shouldn't outlive the scope of `append`.
        Moreover, as `Logger` use a class-local buffer, its tracing functions
        which use formatting are not re-entrant and should not be called
        from here.

        Params:
            event = Event to log

    ***************************************************************************/

    abstract void append (LogEvent event);

    /// Create an Appender and default its layout to LayoutTimer.
    public this ()
    {
        if (generic is null)
            generic = new LayoutTimer;
        this.layout_ = generic;
    }

    /// Return the current Level setting
    final ILogger.Level level ()
    {
        return this.level_;
    }

    /// Return the current Level setting
    final Appender level (ILogger.Level l)
    {
        this.level_ = l;
        return this;
    }

    /***************************************************************************

        Static method to return a mask for identifying the Appender.

        Each Appender class should have a unique fingerprint so that we can
        figure out which ones have been invoked for a given event.
        A bitmask is a simple an efficient way to do that.

    ***************************************************************************/

    protected Mask register (cstring tag)
    {
        static Mask mask = 1;
        static Mask[istring] registry;

        Mask* p = tag in registry;
        if (p)
            return *p;
        else
        {
            auto ret = mask;
            registry [tag] = mask;

            if (mask < 0)
                throw new IllegalArgumentException ("too many unique registrations");

            mask <<= 1;
            return ret;
        }
    }

    /***************************************************************************

        Set the current layout to be that of the argument, or the generic layout
        where the argument is null

    ***************************************************************************/

    void layout (Layout how)
    {
        verify(generic !is null);
        this.layout_ = how ? how : generic;
    }

    /// Return the current Layout
    Layout layout ()
    {
        return this.layout_;
    }

    /// Attach another appender to this one
    void next (Appender appender)
    {
        this.next_ = appender;
    }

    /// Return the next appender in the list
    Appender next ()
    {
        return this.next_;
    }

    /// Close this appender. This would be used for file, sockets, and the like
    void close ()
    {
    }
}


/*******************************************************************************

    An appender that does nothing.

    This is useful for cutting and pasting, and for benchmarking the ocean.log
    environment.

*******************************************************************************/

public class AppendNull : Appender
{
    private Mask mask_;

    /// Create with the given Layout
    this (Layout how = null)
    {
        this.mask_ = this.register(name);
        this.layout(how);
    }

    /// Return the fingerprint for this class
    final override Mask mask ()
    {
        return this.mask_;
    }

    /// Return the name of this class
    final override cstring name ()
    {
        return this.classinfo.name;
    }

    /// Append an event to the output
    final override void append (LogEvent event)
    {
        this.layout.format(event, (cstring) {});
    }
}


/// Append to a configured OutputStream
public class AppendStream : Appender
{
    private Mask            mask_;
    private bool            flush_;
    private OutputStream    stream_;

    ///Create with the given stream and layout
    this (OutputStream stream, bool flush = false, Appender.Layout how = null)
    {
        verify(stream !is null);

        this.mask_ = register (name);
        this.stream_ = stream;
        this.flush_ = flush;
        this.layout(how);
    }

    /// Return the fingerprint for this class
    final override Mask mask ()
    {
        return this.mask_;
    }

    /// Return the name of this class
    override istring name ()
    {
        return this.classinfo.name;
    }

    /// Append an event to the output.
    final override void append (LogEvent event)
    {
        static immutable istring Eol = "\n";

        this.layout.format(event, (cstring content) { this.stream_.write(content); });
        this.stream_.write(Eol);
        if (this.flush_)
            this.stream_.flush;
    }
}


/*******************************************************************************

    A simple layout comprised only of time(ms), level, name, and message

*******************************************************************************/

public class LayoutTimer : Appender.Layout
{
    /***************************************************************************

        Subclasses should implement this method to perform the formatting
         of the actual message content.

    ***************************************************************************/

    public override void format (LogEvent event, scope void delegate(cstring) dg)
    {
        char[20] tmp = void;

        dg(event.toMilli (tmp, event.span));
        dg(" ");
        dg(event.levelName);
        dg(" [");
        dg(event.name);
        dg("] ");
        dg(event.host.label);
        dg("- ");
        dg(event.toString);
    }
}