using System;
using Google.ProtocolBuffers.DescriptorProtos;
using Google.ProtocolBuffers.Descriptors;

namespace Google.ProtocolBuffers.ProtoGen {
  /// <summary>
  /// Generator for the class describing the .proto file in general,
  /// containing things like the message descriptor.
  /// </summary>
  internal sealed class UmbrellaClassGenerator : SourceGeneratorBase<FileDescriptor>, ISourceGenerator {

    internal UmbrellaClassGenerator(FileDescriptor descriptor)
      : base(descriptor) {
    }

    public void Generate(TextGenerator writer) {
      WriteIntroduction(writer);
      WriteDescriptor(writer);
      WriteChildren(writer, "Extensions", Descriptor.Extensions);
      writer.WriteLine("#region Static variables");
      foreach (MessageDescriptor message in Descriptor.MessageTypes) {
        new MessageGenerator(message).GenerateStaticVariables(writer);
      }
      writer.WriteLine("#endregion");
      // The class declaration either gets closed before or after the children are written.
      if (!DescriptorUtil.NestClasses(Descriptor)) {
        writer.Outdent();
        writer.WriteLine("}");
      }
      WriteChildren(writer, "Enums", Descriptor.EnumTypes);
      WriteChildren(writer, "Messages", Descriptor.MessageTypes);
      WriteChildren(writer, "Services", Descriptor.Services);
      if (DescriptorUtil.NestClasses(Descriptor)) {
        writer.Outdent();
        writer.WriteLine("}");
      }
      if (DescriptorUtil.GetNamespace(Descriptor) != "") {
        writer.Outdent();
        writer.WriteLine("}");
      }
    }

    private void WriteIntroduction(TextGenerator writer) {
      writer.WriteLine("// Generated by the protocol buffer compiler.  DO NOT EDIT!");
      writer.WriteLine();
      Helpers.WriteNamespaces(writer);

      if (DescriptorUtil.GetNamespace(Descriptor) != "") {
        writer.WriteLine("namespace {0} {{", DescriptorUtil.GetNamespace(Descriptor));
        writer.Indent();
        writer.WriteLine();
      }

      writer.WriteLine("{0} static partial class {1} {{", ClassAccessLevel, DescriptorUtil.GetUmbrellaClassName(Descriptor));
      writer.WriteLine();
      writer.Indent();
    }

    private void WriteDescriptor(TextGenerator writer) {
      writer.WriteLine("#region Descriptor");

      writer.WriteLine("public static pbd::FileDescriptor Descriptor {");
      writer.WriteLine("  get { return descriptor; }");
      writer.WriteLine("}");
      writer.WriteLine("private static readonly pbd::FileDescriptor descriptor = pbd::FileDescriptor.InternalBuildGeneratedFileFrom(");
      writer.WriteLine("    global::System.Convert.FromBase64String(");
      writer.Indent();
      writer.Indent();

      // TODO(jonskeet): Consider a C#-escaping format here instead of just Base64.
      byte[] bytes = Descriptor.Proto.ToByteArray();
      string base64 = Convert.ToBase64String(bytes);

      while (base64.Length > 60) {
        writer.WriteLine("\"{0}\" + ", base64.Substring(0, 60));
        base64 = base64.Substring(60);
      }
      writer.WriteLine("\"{0}\"),", base64);

      writer.WriteLine("new pbd::FileDescriptor[] {");
      foreach (FileDescriptor dependency in Descriptor.Dependencies) {
        // TODO(jonskeet): The normal code won't work for the bootstrapping descriptor, because we don't get unknown fields :(
        if (dependency.Package == "google.protobuf" && dependency.Name.EndsWith("descriptor.proto")) {
          writer.WriteLine("  global::" + typeof(DescriptorProtoFile).FullName + ".Descriptor, ");
          continue;
        }
        writer.WriteLine("  {0}.Descriptor, ", DescriptorUtil.GetFullUmbrellaClassName(dependency));
      }
      writer.WriteLine("});");
      writer.Outdent();
      writer.Outdent();
      writer.WriteLine("#endregion");
      writer.WriteLine();
    }
  }
}