using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;
using Server;

namespace Server.Commands.Generic
{
public sealed class OrderInfo
{
private Property m_Property;
private int m_Order;

public Property Property
{
get { return m_Property; }
set { m_Property = value; }
}

public bool IsAscending
{
get { return ( m_Order > 0 ); }
set { m_Order = ( value ? +1 : -1 ); }
}

public bool IsDescending
{
get { return ( m_Order < 0 ); }
set { m_Order = ( value ? -1 : +1 ); }
}

public int Sign
{
get { return Math.Sign( m_Order ); }
set
{
m_Order = Math.Sign( value );

if ( m_Order == 0 )
throw new InvalidOperationException( "Sign cannot be zero." );
}
}

public OrderInfo( Property property, bool isAscending )
{
m_Property = property;

this.IsAscending = isAscending;
}
}

public static class SortCompiler
{
public static IComparer Compile( AssemblyEmitter assembly, Type objectType, OrderInfo[] orders )
{
TypeBuilder typeBuilder = assembly.DefineType(
"__sort",
TypeAttributes.Public,
typeof( object )
);

#region Constructor
{
ConstructorBuilder ctor = typeBuilder.DefineConstructor(
MethodAttributes.Public,
CallingConventions.Standard,
Type.EmptyTypes
);

ILGenerator il = ctor.GetILGenerator();

// : base()
il.Emit( OpCodes.Ldarg_0 );
il.Emit( OpCodes.Call, typeof( object ).GetConstructor( Type.EmptyTypes ) );

// return;
il.Emit( OpCodes.Ret );
}
#endregion

#region IComparer
typeBuilder.AddInterfaceImplementation( typeof( IComparer ) );

MethodBuilder compareMethod;

#region Compare
{
MethodEmitter emitter = new MethodEmitter( typeBuilder );

emitter.Define(
/*  name  */ "Compare",
/*  attr  */ MethodAttributes.Public | MethodAttributes.Virtual,
/* return */ typeof( int ),
/* params */ new Type[] { typeof( object ), typeof( object ) } );

LocalBuilder a = emitter.CreateLocal( objectType );
LocalBuilder b = emitter.CreateLocal( objectType );

LocalBuilder v = emitter.CreateLocal( typeof( int ) );

emitter.LoadArgument( 1 );
emitter.CastAs( objectType );
emitter.StoreLocal( a );

emitter.LoadArgument( 2 );
emitter.CastAs( objectType );
emitter.StoreLocal( b );

emitter.Load( 0 );
emitter.StoreLocal( v );

Label end = emitter.CreateLabel();

for ( int i = 0; i < orders.Length; ++i )
{
if ( i > 0 )
{
emitter.LoadLocal( v );
emitter.BranchIfTrue( end ); // if ( v != 0 ) return v;
}

OrderInfo orderInfo = orders[i];

Property prop = orderInfo.Property;
int sign = orderInfo.Sign;

emitter.LoadLocal( a );
emitter.Chain( prop );

bool couldCompare =
emitter.CompareTo( sign, delegate()
{
emitter.LoadLocal( b );
emitter.Chain( prop );
} );

if ( !couldCompare )
throw new InvalidOperationException( "Property is not comparable." );

emitter.StoreLocal( v );
}

emitter.MarkLabel( end );

emitter.LoadLocal( v );
emitter.Return();

typeBuilder.DefineMethodOverride(
emitter.Method,
typeof( IComparer ).GetMethod(
"Compare",
new Type[]
{
typeof( object ),
typeof( object )
}
)
);

compareMethod = emitter.Method;
}
#endregion
#endregion

Type comparerType = typeBuilder.CreateType();

return (IComparer) Activator.CreateInstance( comparerType );
}
}
}