/* ****************************************************************************
 *
 * Copyright (c) Microsoft Corporation. 
 *
 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 
 * copy of the license can be found in the License.html file at the root of this distribution. If 
 * you cannot locate the  Apache License, Version 2.0, please send an email to 
 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 
 * by the terms of the Apache License, Version 2.0.
 *
 * You must not remove this notice, or any other, from this software.
 *
 *
 * ***************************************************************************/
#if FEATURE_REFEMIT

using System;
using System.Collections.Generic;
using System.Dynamic.Utils;
using System.IO;
using System.Reflection;
using System.Reflection.Emit;
using System.Security;
using System.Text;
using System.Threading;

using Microsoft.Scripting.Utils;

#if !FEATURE_CORE_DLR
namespace Microsoft.Scripting.Ast.Compiler {
#else
namespace System.Linq.Expressions.Compiler {
#endif
    internal sealed class AssemblyGen {
        private static AssemblyGen _assembly;

        // Testing options. Only ever set in CLR2 build
        // configurations, see SetSaveAssemblies
#if !FEATURE_CORE_DLR
        private static string _saveAssembliesPath;
        private static bool _saveAssemblies;
#endif

        private readonly AssemblyBuilder _myAssembly;
        private readonly ModuleBuilder _myModule;

#if !FEATURE_CORE_DLR && !SILVERLIGHT
        private readonly string _outFileName;       // can be null iff !SaveAndReloadAssemblies
        private readonly string _outDir;            // null means the current directory
#endif
        private int _index;

        private static AssemblyGen Assembly {
            get {
                if (_assembly == null) {
                    Interlocked.CompareExchange(ref _assembly, new AssemblyGen(), null);
                }
                return _assembly;
            }
        }

        private AssemblyGen() {
            var name = new AssemblyName("Snippets");

#if SILVERLIGHT  // AssemblyBuilderAccess.RunAndSave, Environment.CurrentDirectory
            _myAssembly = AppDomain.CurrentDomain.DefineDynamicAssembly(name, AssemblyBuilderAccess.Run);
            _myModule = _myAssembly.DefineDynamicModule(name.Name, false);
#else

            // mark the assembly transparent so that it works in partial trust:
            var attributes = new[] { 
                new CustomAttributeBuilder(typeof(SecurityTransparentAttribute).GetConstructor(ReflectionUtils.EmptyTypes), new object[0])
            };

#if !FEATURE_CORE_DLR
            if (_saveAssemblies) {
                string outDir = _saveAssembliesPath ?? Directory.GetCurrentDirectory();
                try {
                    outDir = Path.GetFullPath(outDir);
                } catch (Exception) {
                    throw Error.InvalidOutputDir();
                }
                try {
                    Path.Combine(outDir, name.Name + ".dll");
                } catch (ArgumentException) {
                    throw Error.InvalidAsmNameOrExtension();
                }

                _outFileName = name.Name + ".dll";
                _outDir = outDir;
                _myAssembly = AppDomain.CurrentDomain.DefineDynamicAssembly(name, AssemblyBuilderAccess.RunAndSave, outDir,
                    null, null, null, null, false, attributes);

                _myModule = _myAssembly.DefineDynamicModule(name.Name, _outFileName, false);
            } else
#endif
            {
                _myAssembly = AppDomain.CurrentDomain.DefineDynamicAssembly(name, AssemblyBuilderAccess.Run, attributes);
                _myModule = _myAssembly.DefineDynamicModule(name.Name, false);
            }

            _myAssembly.DefineVersionInfoResource();
#endif
        }

        private TypeBuilder DefineType(string name, Type parent, TypeAttributes attr) {
            ContractUtils.RequiresNotNull(name, "name");
            ContractUtils.RequiresNotNull(parent, "parent");

            StringBuilder sb = new StringBuilder(name);

            int index = Interlocked.Increment(ref _index);
            sb.Append("$");
            sb.Append(index);

            // There is a bug in Reflection.Emit that leads to 
            // Unhandled Exception: System.Runtime.InteropServices.COMException (0x80131130): Record not found on lookup.
            // if there is any of the characters []*&+,\ in the type name and a method defined on the type is called.
            sb.Replace('+', '_').Replace('[', '_').Replace(']', '_').Replace('*', '_').Replace('&', '_').Replace(',', '_').Replace('\\', '_');

            name = sb.ToString();

            return _myModule.DefineType(name, attr, parent);
        }

        internal static TypeBuilder DefineDelegateType(string name) {
            return Assembly.DefineType(
                name,
                typeof(MulticastDelegate),
                TypeAttributes.Class | TypeAttributes.Public | TypeAttributes.Sealed | TypeAttributes.AnsiClass | TypeAttributes.AutoClass
            );
        }

#if !FEATURE_CORE_DLR
        //Return the location of the saved assembly file.
        //The file location is used by PE verification in Microsoft.Scripting.
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
        internal string SaveAssembly() {
#if !SILVERLIGHT // AssemblyBuilder.Save
            _myAssembly.Save(_outFileName, PortableExecutableKinds.ILOnly, ImageFileMachine.I386);
            return Path.Combine(_outDir, _outFileName);
#else
            return null;
#endif
        }

        // NOTE: this method is called through reflection from Microsoft.Scripting
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
        internal static void SetSaveAssemblies(bool enable, string directory) {
            _saveAssemblies = enable;
            _saveAssembliesPath = directory;
        }

        // NOTE: this method is called through reflection from Microsoft.Scripting
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
        internal static string[] SaveAssembliesToDisk() {
            if (!_saveAssemblies) {
                return new string[0];
            }

            var assemlyLocations = new List<string>();

            // first save all assemblies to disk:
            if (_assembly != null) {
                string assemblyLocation = _assembly.SaveAssembly();
                if (assemblyLocation != null) {
                    assemlyLocations.Add(assemblyLocation);
                }
                _assembly = null;
            }

            return assemlyLocations.ToArray();
        }
#endif
    }
}
#endif