using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Threading;

namespace Python.Runtime
{
    /// 
    /// Several places in the runtime generate code on the fly to support
    /// dynamic functionality. The CodeGenerator class manages the dynamic
    /// assembly used for code generation and provides utility methods for
    /// certain repetitive tasks.
    /// 
    internal class CodeGenerator
    {
        private AssemblyBuilder _aBuilder = null;

        private AssemblyBuilder aBuilder
        {
            get
            {
                if (_aBuilder == null)
                {
                    var aname = new AssemblyName { Name = "__CodeGenerator_Assembly" };
                    var aa = AssemblyBuilderAccess.Run;

                    _aBuilder = Thread.GetDomain().DefineDynamicAssembly(aname, aa);
                }

                return _aBuilder;
            }
        }

        private ModuleBuilder _mBuilder = null;
        private ModuleBuilder mBuilder
        {
            get
            {
                if (_mBuilder == null)
                {
                    _mBuilder = aBuilder.DefineDynamicModule("__CodeGenerator_Module");
                }

                return _mBuilder;
            }
        }

        internal CodeGenerator()
        {
        }

        /// 
        /// DefineType is a shortcut utility to get a new TypeBuilder.
        /// 
        internal TypeBuilder DefineType(string name)
        {
            var attrs = TypeAttributes.Public;
            return mBuilder.DefineType(name, attrs);
        }

        /// 
        /// DefineType is a shortcut utility to get a new TypeBuilder.
        /// 
        internal TypeBuilder DefineType(string name, Type basetype)
        {
            var attrs = TypeAttributes.Public;
            return mBuilder.DefineType(name, attrs, basetype);
        }
    }
}