#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2016 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using System.CodeDom;
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Text.RegularExpressions;
using HeuristicLab.Collections;
using HeuristicLab.Common;
using HeuristicLab.Common.Resources;
using HeuristicLab.Core;
using HeuristicLab.Persistence.Auxiliary;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
using HeuristicLab.PluginInfrastructure;
using Microsoft.CSharp;

namespace HeuristicLab.Operators.Programmable {

  [Item("ProgrammableOperator", "An operator that can be programmed for arbitrary needs.")]
  [StorableClass]
  public class ProgrammableOperator : Operator, IParameterizedNamedItem, IStorableContent, IProgrammableItem {

    #region Fields & Properties

    public string Filename { get; set; }

    public new ParameterCollection Parameters {
      get { return base.Parameters; }
    }

    public static new System.Drawing.Image StaticItemImage { get { return VSImageLibrary.Script; } }

    private MethodInfo executeMethod;
    public CompilerErrorCollection CompileErrors { get; private set; }
    public string CompilationUnitCode { get; private set; }

    [Storable]
    private string code;
    public string Code {
      get { return code; }
      set {
        if (value != code) {
          code = value;
          executeMethod = null;
          OnCodeChanged();
        }
      }
    }

    private object syncRoot = new object();

    private static object initLock = new object();
    private static Dictionary<string, List<Assembly>> defaultPluginDict;
    private static Dictionary<Assembly, bool> defaultAssemblyDict;

    public readonly Dictionary<string, List<Assembly>> Plugins;
    protected Dictionary<Assembly, bool> Assemblies;

    [Storable(Name = "SelectedAssemblies")]
    private List<string> _selectedAssemblyNames_persistence {
      get {
        return Assemblies.Where(a => a.Value).Select(a => a.Key.FullName).ToList();
      }
      set {
        var selectedAssemblyNames = new HashSet<string>(value.Select(n => new AssemblyName(n).Name));
        foreach (var a in Assemblies.Keys.ToList()) {
          Assemblies[a] = selectedAssemblyNames.Contains(new AssemblyName(a.FullName).Name);
        }
      }
    }

    public IEnumerable<Assembly> AvailableAssemblies {
      get { return Assemblies.Keys; }
    }

    public IEnumerable<Assembly> SelectedAssemblies {
      get { return Assemblies.Where(kvp => kvp.Value).Select(kvp => kvp.Key); }
    }

    [Storable]
    private HashSet<string> namespaces;
    public IEnumerable<string> Namespaces {
      get { return namespaces; }
    }

    public override bool CanChangeDescription {
      get { return true; }
    }

    #endregion

    #region Extended Accessors

    public void SelectAssembly(Assembly a) {
      if (a != null && Assemblies.ContainsKey(a) && !Assemblies[a]) {
        Assemblies[a] = true;
      }
    }

    public void UnselectAssembly(Assembly a) {
      if (a != null && Assemblies.ContainsKey(a) && Assemblies[a]) {
        Assemblies[a] = false;
      }
    }

    public void SelectNamespace(string ns) {
      namespaces.Add(ns);
      OnSignatureChanged();
    }

    public void UnselectNamespace(string ns) {
      namespaces.Remove(ns);
      OnSignatureChanged();
    }

    public IEnumerable<string> GetAllNamespaces(bool selectedAssembliesOnly) {
      var namespaces = new HashSet<string>();
      foreach (var a in Assemblies) {
        if (!selectedAssembliesOnly || a.Value) {
          foreach (var t in a.Key.GetTypes()) {
            if (t.IsPublic) {
              foreach (string ns in GetNamespaceHierachy(t.Namespace)) {
                namespaces.Add(ns);
              }
            }
          }
        }
      }
      return namespaces;
    }

    private IEnumerable<string> GetNamespaceHierachy(string ns) {
      if (ns != null) {
        for (int i = ns.Length; i != -1; i = ns.LastIndexOf('.', i - 1)) {
          yield return ns.Substring(0, i);
        }
      }
    }

    #endregion

    #region Construction & Initialization

    [StorableConstructor]
    protected ProgrammableOperator(bool deserializing)
      : base(deserializing) {
      ProgrammableOperator.StaticInitialize();
      Assemblies = defaultAssemblyDict.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
      Plugins = defaultPluginDict.ToDictionary(kvp => kvp.Key, kvp => kvp.Value.ToList());
    }

    protected ProgrammableOperator(ProgrammableOperator original, Cloner cloner)
      : base(original, cloner) {
      code = original.Code;
      executeMethod = original.executeMethod;
      Assemblies = original.Assemblies.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
      Plugins = original.Plugins.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
      namespaces = new HashSet<string>(original.namespaces);
      CompilationUnitCode = original.CompilationUnitCode;
      if (original.CompileErrors != null)
        CompileErrors = new CompilerErrorCollection(original.CompileErrors);
      RegisterEvents();
    }

    public ProgrammableOperator() {
      code = "";
      executeMethod = null;
      ProgrammableOperator.StaticInitialize();
      Assemblies = defaultAssemblyDict.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
      Plugins = defaultPluginDict.ToDictionary(kvp => kvp.Key, kvp => kvp.Value.ToList());
      namespaces = new HashSet<string>(DiscoverNamespaces());
      RegisterEvents();
    }

    [StorableHook(HookType.AfterDeserialization)]
    private void AfterDeserialization() {
      // ensure default namespaces and assemblies are present if deserializing old operators
      namespaces.Add("HeuristicLab.Operators.Programmable");
      Assemblies[typeof(HeuristicLab.Operators.Operator).Assembly] = true;
      Assemblies[typeof(HeuristicLab.Operators.Programmable.ProgrammableOperator).Assembly] = true;
      Assemblies[typeof(System.Threading.Barrier).Assembly] = true; // ensure new System assembly is selected (4.0.0.0)
      RegisterEvents();
    }

    public override IDeepCloneable Clone(Cloner cloner) {
      return new ProgrammableOperator(this, cloner);
    }

    private void RegisterEvents() {
      Parameters.ItemsAdded += Parameters_Changed;
      Parameters.ItemsRemoved += Parameters_Changed;
      Parameters.ItemsReplaced += Parameters_Changed;
      Parameters.CollectionReset += Parameters_Changed;
    }

    private void Parameters_Changed(object sender, CollectionItemsChangedEventArgs<IParameter> args) {
      OnSignatureChanged();
    }

    protected void OnSignatureChanged() {
      executeMethod = null;
      EventHandler handler = SignatureChanged;
      if (handler != null) handler(this, EventArgs.Empty);
    }

    private static void StaticInitialize() {
      lock (initLock) {
        if (defaultPluginDict != null && defaultAssemblyDict != null)
          return;
        defaultAssemblyDict = DiscoverAssemblies();
        defaultPluginDict = GroupAssemblies(defaultAssemblyDict.Keys);
      }
    }

    private static Dictionary<string, List<Assembly>> GroupAssemblies(IEnumerable<Assembly> assemblies) {
      var plugins = new Dictionary<string, List<Assembly>>();
      var locationTable = assemblies.ToDictionary(a => a.Location, a => a);

      foreach (var plugin in ApplicationManager.Manager.Plugins) {
        var aList = new List<Assembly>();
        foreach (var aName in from file in plugin.Files
                              where file.Type == PluginFileType.Assembly
                              select file.Name) {
          Assembly a;
          locationTable.TryGetValue(aName, out a);
          if (a != null) {
            aList.Add(a);
            locationTable.Remove(aName);
          }
        }
        plugins[plugin.Name] = aList;
      }

      plugins["other"] = locationTable.Values.ToList();
      return plugins;
    }

    protected static List<Assembly> defaultAssemblies = new List<Assembly>() {
      // mscorlib automatically included (would cause duplicate)
      typeof(System.ComponentModel.INotifyPropertyChanged).Assembly, // System.dll
      typeof(System.Linq.Enumerable).Assembly,  // System.Core.dll
      typeof(System.Data.Linq.DataContext).Assembly, // System.Data.Linq.dll
      typeof(HeuristicLab.Common.IDeepCloneable).Assembly,
      typeof(HeuristicLab.Core.Item).Assembly,
      typeof(HeuristicLab.Data.IntValue).Assembly,
      typeof(HeuristicLab.Parameters.ValueParameter<IItem>).Assembly,
      typeof(HeuristicLab.Collections.ObservableList<IItem>).Assembly,
      typeof(HeuristicLab.Operators.Operator).Assembly,
      typeof(HeuristicLab.Operators.Programmable.ProgrammableOperator).Assembly,
    };

    protected static Dictionary<Assembly, bool> DiscoverAssemblies() {
      var assemblies = new Dictionary<Assembly, bool>();
      foreach (var a in AppDomain.CurrentDomain.GetAssemblies()) {
        try {
          if (File.Exists(a.Location)) {
            assemblies.Add(a, false);
          }
        } catch (NotSupportedException) {
          // NotSupportedException is thrown while accessing 
          // the Location property of the anonymously hosted
          // dynamic methods assembly, which is related to
          // LINQ queries
        }
      }
      foreach (var a in defaultAssemblies) {
        if (assemblies.ContainsKey(a)) {
          assemblies[a] = true;
        } else {
          assemblies.Add(a, true);
        }
      }
      return assemblies;
    }

    protected static List<string> DiscoverNamespaces() {
      return new List<string>() {
        "HeuristicLab.Common",
        "HeuristicLab.Core",
        "HeuristicLab.Data",
        "HeuristicLab.Parameters",
        "HeuristicLab.Operators.Programmable",
        "System",
        "System.Collections.Generic",
        "System.Text",
        "System.Linq",
        "System.Data.Linq",
      };
    }

    #endregion

    #region Compilation

    private static CSharpCodeProvider codeProvider =
      new CSharpCodeProvider(
        new Dictionary<string, string>() {
          { "CompilerVersion", "v4.0" },  // support C# 4.0 syntax
        });

    private CompilerResults DoCompile() {
      CompilerParameters parameters = new CompilerParameters();
      parameters.GenerateExecutable = false;
      parameters.GenerateInMemory = true;
      parameters.IncludeDebugInformation = false;
      parameters.ReferencedAssemblies.AddRange(SelectedAssemblies.Select(a => a.Location).ToArray());
      var unit = CreateCompilationUnit();
      var writer = new StringWriter();
      codeProvider.GenerateCodeFromCompileUnit(
        unit,
        writer,
        new CodeGeneratorOptions() {
          BracingStyle = "C",
          ElseOnClosing = true,
          IndentString = "  ",
        });
      CompilationUnitCode = writer.ToString();
      return codeProvider.CompileAssemblyFromDom(parameters, unit);
    }

    public virtual void Compile() {
      var results = DoCompile();
      executeMethod = null;
      CompileErrors = results.Errors;
      if (results.Errors.HasErrors) {
        StringBuilder sb = new StringBuilder();
        foreach (CompilerError error in results.Errors) {
          sb.Append(error.Line).Append(':')
            .Append(error.Column).Append(": ")
            .AppendLine(error.ErrorText);
        }
        throw new Exception(string.Format(
          "Compilation of \"{0}\" failed:{1}{2}",
          Name, Environment.NewLine,
          sb.ToString()));
      } else {
        Assembly assembly = results.CompiledAssembly;
        Type[] types = assembly.GetTypes();
        executeMethod = types[0].GetMethod("Execute");
      }
    }

    private CodeCompileUnit CreateCompilationUnit() {
      CodeNamespace ns = new CodeNamespace("HeuristicLab.Operators.Programmable.CustomOperators");
      ns.Types.Add(CreateType());
      ns.Imports.AddRange(
        GetSelectedAndValidNamespaces()
        .Select(n => new CodeNamespaceImport(n))
        .ToArray());
      CodeCompileUnit unit = new CodeCompileUnit();
      unit.Namespaces.Add(ns);
      return unit;
    }

    public IEnumerable<string> GetSelectedAndValidNamespaces() {
      var possibleNamespaces = new HashSet<string>(GetAllNamespaces(true));
      foreach (var ns in Namespaces)
        if (possibleNamespaces.Contains(ns))
          yield return ns;
    }

    public static readonly Regex SafeTypeNameCharRegex = new Regex("[_a-zA-Z0-9]+");
    public static readonly Regex SafeTypeNameRegex = new Regex("[_a-zA-Z][_a-zA-Z0-9]*");

    public string CompiledTypeName {
      get {
        var sb = new StringBuilder();
        foreach (string s in SafeTypeNameCharRegex.Matches(Name).Cast<Match>().Select(m => m.Value)) {
          sb.Append(s);
        }
        return SafeTypeNameRegex.Match(sb.ToString()).Value;
      }
    }

    private CodeTypeDeclaration CreateType() {
      CodeTypeDeclaration typeDecl = new CodeTypeDeclaration(CompiledTypeName) {
        IsClass = true,
        TypeAttributes = TypeAttributes.Public,
      };
      typeDecl.Members.Add(CreateMethod());
      return typeDecl;
    }

    public string Signature {
      get {
        var sb = new StringBuilder()
        .Append("public static IOperation Execute(")
        .Append(TypeNameParser.Parse(GetType().FullName).GetTypeNameInCode(namespaces))
        .Append(" op, ")
        .Append(TypeNameParser.Parse(typeof(IExecutionContext).FullName).GetTypeNameInCode(namespaces))
        .Append(" context");
        foreach (IParameter param in Parameters) {
          sb.Append(String.Format(", {0} {1}",
            TypeNameParser.Parse(param.GetType().FullName).GetTypeNameInCode(namespaces),
            param.Name));
        }
        return sb.Append(")").ToString();
      }
    }

    public event EventHandler SignatureChanged;

    private static Regex lineSplitter = new Regex(@"\r\n|\r|\n");

    private CodeMemberMethod CreateMethod() {
      CodeMemberMethod method = new CodeMemberMethod();
      method.Name = "Execute";
      method.ReturnType = new CodeTypeReference(typeof(IOperation));
      method.Attributes = MemberAttributes.Public | MemberAttributes.Static;
      method.Parameters.Add(new CodeParameterDeclarationExpression(GetType(), "op"));
      method.Parameters.Add(new CodeParameterDeclarationExpression(typeof(IExecutionContext), "context"));
      foreach (var param in Parameters)
        method.Parameters.Add(new CodeParameterDeclarationExpression(param.GetType(), param.Name));
      string[] codeLines = lineSplitter.Split(code);
      for (int i = 0; i < codeLines.Length; i++) {
        codeLines[i] = string.Format("#line {0} \"ProgrammableOperator\"{1}{2}", i + 1, "\r\n", codeLines[i]);
      }
      method.Statements.Add(new CodeSnippetStatement(string.Join("\r\n", codeLines) + MethodSuffix));
      return method;
    }

    public virtual string MethodSuffix {
      get { return "return null;"; }
    }

    #endregion

    #region HeuristicLab interfaces

    public override IOperation Apply() {
      lock (syncRoot) {
        if (executeMethod == null) {
          Compile();
        }
      }

      var parameters = new List<object>() { this, ExecutionContext };
      parameters.AddRange(Parameters.Select(p => (object)p));
      return (IOperation)executeMethod.Invoke(null, parameters.ToArray());
    }

    public event EventHandler CodeChanged;
    protected virtual void OnCodeChanged() {
      EventHandler handler = CodeChanged;
      if (handler != null) handler(this, EventArgs.Empty);
    }

    #endregion
  }
}