// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:io' hide BytesBuilder;
import 'dart:typed_data' show BytesBuilder;

import 'package:collection/collection.dart';
import 'package:fixnum/fixnum.dart';
import 'package:protobuf/protobuf.dart';

import '../names.dart' show lowerCaseFirstLetter;
import '../protoc.dart' show FileGenerator;
import 'gen/dart_options.pb.dart';
import 'gen/google/api/client.pb.dart';
import 'gen/google/protobuf/compiler/plugin.pb.dart';
import 'linker.dart';
import 'options.dart';
import 'output_config.dart';

abstract class ProtobufContainer {
  // A map of proto file paths to import prefix aliases.
  final Map<String, String> _prefixes = {};

  String get package;
  String? get classname;
  String get fullName;

  /// The field path contains the field IDs and indices (for repeated fields)
  /// that lead to the proto member corresponding to a piece of generated code.
  /// Repeated fields in the descriptor are further identified by the index of
  /// the message in question.
  /// For more information see
  /// https://github.com/protocolbuffers/protobuf/blob/master/src/google/protobuf/descriptor.proto#L728
  List<int> get fieldPath;

  /// The fully qualified name with a leading '.'.
  ///
  /// This exists because names from protoc come like this.
  String get dottedName => '.$fullName';

  String get binaryDescriptorName =>
      '${lowerCaseFirstLetter(classname!)}Descriptor';

  String importPrefix({required FileGenerator context}) {
    final protoFilePath = fileGen!.protoFileUri.toString();
    return context._calculateImportPrefix(protoFilePath);
  }

  String _calculateImportPrefix(String protoImportPath) =>
      _prefixes.putIfAbsent(protoImportPath, () => '\$${_prefixes.length}');

  /// The generator of the .pb.dart file defining this entity.
  ///
  /// (Represents the .pb.dart file that we need to import in order to use it.)
  FileGenerator? get fileGen;

  // The generator containing this entity.
  ProtobufContainer? get parent;

  /// The top-level parent of this entity, or itself if it is a top-level
  /// entity.
  ProtobufContainer? get toplevelParent {
    if (parent == null) {
      return null;
    }
    if (parent is FileGenerator) {
      return this;
    }
    return parent?.toplevelParent;
  }
}

class CodeGenerator {
  final Stream<List<int>> _streamIn;
  final IOSink _streamOut;

  CodeGenerator(this._streamIn, this._streamOut);

  /// Runs the code generator. The optional [optionParsers] can be used to
  /// change how command line options are parsed (see [parseGenerationOptions]
  /// for details), and [config] can be used to override where
  /// generated files are created and how imports between generated files are
  /// constructed (see [OutputConfiguration] for details).
  Future<void> generate({
    Map<String, SingleOptionParser>? optionParsers,
    OutputConfiguration config = const DefaultOutputConfiguration(),
  }) async {
    final extensions = ExtensionRegistry();

    Dart_options.registerAllExtensions(extensions);
    Client.registerAllExtensions(extensions);

    final builder = await _streamIn.fold(
      BytesBuilder(),
      (builder, data) => builder..add(data),
    );
    final bytes = builder.takeBytes();
    // Suppress CodedBufferReader builtin size limitation when reading the
    // request; protobuf definitions can be larger than default limit of 64Mb.
    final reader = CodedBufferReader(bytes, sizeLimit: bytes.length);
    final request = CodeGeneratorRequest();
    request.mergeFromCodedBufferReader(reader, extensions);
    reader.checkLastTagWas(0);

    request.protoFile.sortBy((desc) => desc.name);

    final response = CodeGeneratorResponse();

    // Parse the options in the request. Return the errors if any.
    final options = parseGenerationOptions(request, response, optionParsers);
    if (options == null) {
      _streamOut.add(response.writeToBuffer());
      return;
    }

    // Create a syntax tree for each .proto file given to us.
    // (We may import it even if we don't generate the .pb.dart file.)
    final generators = <FileGenerator>[];
    for (final file in request.protoFile) {
      generators.add(FileGenerator(file, options));
    }

    // Collect field types and importable files.
    link(options, generators);

    // Generate the .pb.dart file if requested.
    for (final gen in generators) {
      final name = gen.descriptor.name;
      if (request.fileToGenerate.contains(name)) {
        response.file.addAll(gen.generateFiles(config));
      }
    }
    response.supportedFeatures = Int64(
      CodeGeneratorResponse_Feature.FEATURE_PROTO3_OPTIONAL.value,
    );
    _streamOut.add(response.writeToBuffer());
  }
}