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

 *

 * Copyright (c) Microsoft Corporation. 

 *

 * This source code is subject to terms and conditions of the Microsoft Public License. A 

 * copy of the license can be found in the License.html file at the root of this distribution. If 

 * you cannot locate the  Microsoft Public License, 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 Microsoft Public License.

 *

 * You must not remove this notice, or any other, from this software.

 *

 *

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



using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.IO;

using System.Reflection;

using System.Reflection.Emit;



using Microsoft.Contracts;

using Microsoft.Scripting.Ast;

using Microsoft.Scripting.Generation;

using Microsoft.Scripting.Runtime;

using Microsoft.Scripting.Utils;



namespace Microsoft.Scripting {

    /// <summary>

    /// ScriptCode is an instance of compiled code that is bound to a specific LanguageContext

    /// but not a specific ScriptScope.  The code can be re-executed multiple times in different

    /// contexts. Hosting API counterpart for this class is <c>CompiledCode</c>.

    /// </summary>

    public sealed partial class ScriptCode {

        private readonly LambdaExpression/*!*/ _code;

        private readonly LanguageContext/*!*/ _languageContext;

        private readonly CompilerContext/*!*/ _compilerContext;



        private DlrMainCallTarget _simpleTarget;



        private DlrMainCallTarget _optimizedTarget;

        private Scope _optimizedScope;



        private ScriptCode(DlrMainCallTarget callTarget, LanguageContext context, Scope optimizedScope, CompilerContext compilerContext) {

            if (optimizedScope != null) {

                _optimizedTarget = callTarget;

            } else {

                _simpleTarget = callTarget;

            }



            _optimizedScope = optimizedScope;

            _languageContext = context;

            _compilerContext = compilerContext;

        }



        internal ScriptCode(LambdaExpression/*!*/ code, LanguageContext/*!*/ languageContext, CompilerContext/*!*/ compilerContext) {

            Assert.NotNull(code, languageContext, compilerContext);

            

            _code = code;

            _languageContext = languageContext;

            _compilerContext = compilerContext;

        }



        public LanguageContext/*!*/ LanguageContext {

            get { return _languageContext; }

        }



        public CompilerContext/*!*/ CompilerContext {

            get { return _compilerContext; }

        }



        public SourceUnit/*!*/ SourceUnit {

            get { return _compilerContext.SourceUnit; }

        }



        public LambdaExpression/*!*/ Lambda {

            get {

                return _code;

            }

        }



        private bool EmitDebugSymbols {

            get {

                return SourceUnit.HasPath && _languageContext.DomainManager.GlobalOptions.DebugMode;

            }

        }



        public void EnsureCompiled() {            

            if (_simpleTarget != null) {

                return;

            }



            lock (this) { // TODO: mutex object

                if (_simpleTarget == null) {

                    // Rewrite globals to runtime lookups on the Scope

                    LambdaExpression lambda = new GlobalLookupRewriter().RewriteLambda(_code, "Initialize");



                    _simpleTarget = LambdaCompiler.CompileLambda<DlrMainCallTarget>(lambda, EmitDebugSymbols);

                }

            }

        }



        public object Run() {

            return Run(MakeOptimizedScope());

        }



        public object Run(Scope/*!*/ scope) {       

            ContractUtils.RequiresNotNull(scope, "scope");



            return Run(GetContextForScope(scope));

        }



        public object Run(CodeContext/*!*/ context) {

            ContractUtils.RequiresNotNull(context, "context");



            if (context.GlobalScope == _optimizedScope) {

                return _optimizedTarget(context);

            }



            EnsureCompiled();

            return _simpleTarget(context);

        }



        [Confined]

        public override string/*!*/ ToString() {

            return string.Format("ScriptCode '{0}' from {1}", SourceUnit, _languageContext.DisplayName);

        }



        public Scope/*!*/ MakeOptimizedScope() {

            if (_optimizedScope != null) {

                return _optimizedScope;

            }



            return CompileOptimizedScope();

        }



        private CodeContext GetContextForScope(Scope scope) {

            ScopeExtension scopeExtension = _languageContext.EnsureScopeExtension(scope.ModuleScope);



            return new CodeContext(scope, _languageContext);

        }

   



        /// <summary>

        /// This takes an assembly name including extension and saves the provided ScriptCode objects into the assembly.  

        /// 

        /// The provided script codes can constitute code from multiple languages.  The assemblyName can be either a fully qualified 

        /// or a relative path.  The DLR will simply save the assembly to the desired location.  The assembly is created by the DLR and 

        /// if a file already exists than an exception is raised.  

        /// 

        /// The DLR determines the internal format of the ScriptCode and the DLR can feel free to rev this as appropriate.  

        /// </summary>

        public static void SaveToDisk(string/*!*/ assemblyName, params ScriptCode/*!*/[]/*!*/ codes) {

            ContractUtils.RequiresNotNull(assemblyName, "assemblyName");

            ContractUtils.RequiresNotNullItems(codes, "codes");



            // break the assemblyName into it's dir/name/extension

            string dir = Path.GetDirectoryName(assemblyName);

            if (String.IsNullOrEmpty(dir)) {

                dir = Environment.CurrentDirectory;

            }



            string name = Path.GetFileNameWithoutExtension(assemblyName);

            string ext = Path.GetExtension(assemblyName);



            // build the assembly & type gen that all the script codes will live in...

            AssemblyGen ag = new AssemblyGen(new AssemblyName(name), dir, ext, /*emitSymbols*/false);            

            TypeBuilder tb = ag.DefinePublicType("DLRCachedCode", typeof(object), true);

            TypeGen tg = new TypeGen(ag, tb);

            

            // then compile all of the code

            foreach (ScriptCode sc in codes) {

                sc.CompileToDisk(tg);

            }



            tg.FinishType();



            ag.Dump();

        }





        /// <summary>

        /// This will take an assembly object which the user has loaded and return a new set of ScriptCode’s which have 

        /// been loaded into the provided ScriptDomainManager.  

        /// 

        /// If the language associated with the ScriptCode’s has not already been loaded the DLR will load the 

        /// LanguageContext into the ScriptDomainManager based upon the saved LanguageContext type.  

        /// 

        /// If the LanguageContext or the version of the DLR the language was compiled against is unavailable a 

        /// TypeLoadException will be raised unless policy has been applied by the administrator to redirect bindings.

        /// </summary>

        public static ScriptCode[] LoadFromAssembly(ScriptDomainManager/*!*/ runtime, Assembly/*!*/ assembly) {

            ContractUtils.RequiresNotNull(runtime, "runtime");

            ContractUtils.RequiresNotNull(assembly, "assembly");



            // get the type which has our cached code...

            Type t = assembly.GetType("DLRCachedCode");

            if (t == null) {

                return new ScriptCode[0];

            }



            List<ScriptCode> codes = new List<ScriptCode>();



            // look for methods which are associated with a saved ScriptCode...

            foreach (MethodInfo mi in t.GetMethods()) {

                // we mark the methods as special name when we generate them because the 

                // method name implies the filename.

                if (!mi.IsSpecialName) {

                    continue;

                }



                // we also put an attribute which contains additional information

                DlrCachedCodeAttribute[] code = (DlrCachedCodeAttribute[])mi.GetCustomAttributes(typeof(DlrCachedCodeAttribute), false);

                if (code.Length == 0) {

                    continue;

                }



                LanguageContext lc = runtime.GetLanguageContext(code[0].LanguageContextType);

                Scope scope;



                if (code[0].Names != null) {



                    // create the storage for the global scope

                    GlobalsDictionary dict = new GlobalsDictionary(SymbolTable.StringsToIds(code[0].Names));



                    // create the CodeContext for the code from the storage

                    scope = new Scope(dict);

                    CodeContext context = new CodeContext(scope, lc);



                    // initialize the tuple

                    IModuleDictionaryInitialization ici = dict as IModuleDictionaryInitialization;

                    if (ici != null) {

                        ici.InitializeModuleDictionary(context);

                    }

                } else {

                    scope = null;

                }



                // create the CompilerContext for the ScriptCode

                SourceUnit su = new SourceUnit(lc, NullTextContentProvider.Null, mi.Name, SourceCodeKind.File);

                CompilerContext ctx = new CompilerContext(su, lc.GetCompilerOptions(), ErrorSink.Null);



                // finally generate the ScriptCode

                ScriptCode sc = new ScriptCode(

                    (DlrMainCallTarget)Delegate.CreateDelegate(typeof(DlrMainCallTarget), mi),

                    lc,

                    scope,

                    ctx

                );



                codes.Add(sc);

            }



            return codes.ToArray();

        }

    }      

}