// 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.

part of '../protoc.dart';

class EnumAlias {
  final EnumValueDescriptorProto value;
  final EnumValueDescriptorProto canonicalValue;
  EnumAlias(this.value, this.canonicalValue);
}

class EnumGenerator extends ProtobufContainer {
  /// For top-level enums: [FileGenerator]. For nested enums:
  /// [MessageGenerator].
  @override
  final ProtobufContainer parent;

  @override
  final FeatureSet features;

  @override
  final String classname;

  @override
  final String fullName;

  final EnumDescriptorProto _descriptor;

  final List<EnumValueDescriptorProto> _canonicalValues =
      <EnumValueDescriptorProto>[];

  final List<int> _originalCanonicalIndices = <int>[];

  final List<EnumAlias> _aliases = <EnumAlias>[];

  /// Maps the name of an enum value to the Dart name we will use for it.
  final Map<String, String> dartNames = <String, String>{};

  final List<int> _originalAliasIndices = <int>[];

  final List<int> _fieldPathSegment;

  @override
  late final List<int> fieldPath = [...parent.fieldPath, ..._fieldPathSegment];

  EnumGenerator._(
    EnumDescriptorProto descriptor,
    this.parent,
    Set<String> usedClassNames,
    int repeatedFieldIndex,
    int fieldIdTag,
  ) : _fieldPathSegment = [fieldIdTag, repeatedFieldIndex],
      classname = messageOrEnumClassName(
        descriptor.name,
        usedClassNames,
        parent: parent.classname ?? '',
      ),
      fullName =
          parent.fullName == ''
              ? descriptor.name
              : '${parent.fullName}.${descriptor.name}',
      _descriptor = descriptor,
      features = resolveFeatures(parent.features, descriptor.options.features) {
    final usedNames = {...reservedEnumNames};
    for (var i = 0; i < descriptor.value.length; i++) {
      final value = descriptor.value[i];
      final canonicalValue = descriptor.value.firstWhere(
        (v) => v.number == value.number,
      );
      if (value == canonicalValue) {
        _canonicalValues.add(value);
        _originalCanonicalIndices.add(i);
      } else {
        _aliases.add(EnumAlias(value, canonicalValue));
        _originalAliasIndices.add(i);
      }
      dartNames[value.name] = disambiguateName(
        avoidInitialUnderscore(value.name),
        usedNames,
        enumSuffixes(),
      );
    }
  }

  static const _topLevelFieldTag = 5;
  static const _nestedFieldTag = 4;

  EnumGenerator.topLevel(
    EnumDescriptorProto descriptor,
    ProtobufContainer parent,
    Set<String> usedClassNames,
    int repeatedFieldIndex,
  ) : this._(
        descriptor,
        parent,
        usedClassNames,
        repeatedFieldIndex,
        _topLevelFieldTag,
      );

  EnumGenerator.nested(
    EnumDescriptorProto descriptor,
    ProtobufContainer parent,
    Set<String> usedClassNames,
    int repeatedFieldIndex,
  ) : this._(
        descriptor,
        parent,
        usedClassNames,
        repeatedFieldIndex,
        _nestedFieldTag,
      );

  @override
  String get package => parent.package;

  @override
  FileGenerator? get fileGen => parent.fileGen;

  /// Make this enum available as a field type.
  void register(GenerationContext ctx) {
    ctx.registerFieldType(this);
  }

  /// Returns a const expression that evaluates to the JSON for this message.
  ///
  /// [context] represents the .pb.dart file where the expression will be used.
  String getJsonConstant(FileGenerator context) {
    final name = '$classname\$json';
    if (context.protoFileUri == fileGen!.protoFileUri) {
      return name;
    }
    return '${context.importPrefix(this)}.$name';
  }

  static const int _enumValueTag = 2;

  void generate(IndentingWriter out) {
    final commentBlock = fileGen?.commentBlock(fieldPath);
    if (commentBlock != null) {
      out.println(commentBlock);
    }
    if (_descriptor.options.deprecated) {
      out.println('@$coreImportPrefix.Deprecated(\'This enum is deprecated\')');
    }
    out.addAnnotatedBlock(
      'class $classname extends $protobufImportPrefix.ProtobufEnum {',
      '}\n',
      [
        NamedLocation(
          name: classname,
          fieldPathSegment: fieldPath,
          start: 'class '.length,
        ),
      ],
      () {
        // -----------------------------------------------------------------
        // Define enum types.
        final omitEnumNames = ConditionalConstDefinition('omit_enum_names');
        for (var i = 0; i < _canonicalValues.length; i++) {
          final val = _canonicalValues[i];
          final name = dartNames[val.name]!;
          out.addSuffix(
            omitEnumNames.constFieldName,
            omitEnumNames.constDefinition,
          );
          final conditionalValName = omitEnumNames.createTernary(val.name);
          final fieldPathSegment = <int>[
            ...fieldPath,
            _enumValueTag,
            _originalCanonicalIndices[i],
          ];

          final commentBlock = fileGen?.commentBlock(fieldPathSegment);
          if (commentBlock != null) {
            out.println(commentBlock);
          }

          if (val.options.deprecated) {
            out.println(
              '@$coreImportPrefix.Deprecated(\'This enum value is deprecated\')',
            );
          }

          out.printlnAnnotated(
            'static const $classname $name = '
            '$classname._(${val.number}, $conditionalValName);',
            [
              NamedLocation(
                name: name,
                fieldPathSegment: fieldPathSegment,
                start: 'static const $classname '.length,
              ),
            ],
          );
        }
        if (_aliases.isNotEmpty) {
          out.println();
          for (var i = 0; i < _aliases.length; i++) {
            final alias = _aliases[i];
            final name = dartNames[alias.value.name]!;
            out.printlnAnnotated(
              'static const $classname $name ='
              ' ${dartNames[alias.canonicalValue.name]};',
              [
                NamedLocation(
                  name: name,
                  fieldPathSegment: List.from(fieldPath)
                    ..addAll([_enumValueTag, _originalAliasIndices[i]]),
                  start: 'static const $classname '.length,
                ),
              ],
            );
          }
        }
        out.println();

        out.println(
          'static const $coreImportPrefix.List<$classname> values ='
          ' <$classname> [',
        );
        for (final val in _canonicalValues) {
          final name = dartNames[val.name];
          out.println('  $name,');
        }
        out.println('];');
        out.println();

        var maxEnumValue = -1;
        for (final valueDescriptor in _canonicalValues) {
          if (valueDescriptor.number.isNegative) {
            maxEnumValue = -1; // don't use list
            break;
          }
          if (valueDescriptor.number > maxEnumValue) {
            maxEnumValue = valueDescriptor.number;
          }
        }

        final useList =
            _canonicalValues.isEmpty ||
            (maxEnumValue >= 0 &&
                _canonicalValues.length / (maxEnumValue + 1) >= 0.7);

        if (useList) {
          out.println(
            'static final $coreImportPrefix.List<$classname?> _byValue ='
            ' $protobufImportPrefix.ProtobufEnum.\$_initByValueList(values, $maxEnumValue);',
          );

          out.println(
            'static $classname? valueOf($coreImportPrefix.int value) =>'
            '  value < 0 || value >= _byValue.length ? null : _byValue[value];',
          );
        } else {
          out.println(
            'static final $coreImportPrefix.Map<$coreImportPrefix.int, $classname> _byValue ='
            ' $protobufImportPrefix.ProtobufEnum.initByValue(values);',
          );

          out.println(
            'static $classname? valueOf($coreImportPrefix.int value) =>'
            ' _byValue[value];',
          );
        }

        out.println();

        out.println('const $classname._(super.value, super.name);');
      },
    );
  }

  /// Writes a Dart constant containing the JSON for the [EnumDescriptorProto].
  void generateConstants(IndentingWriter out) {
    final name = getJsonConstant(fileGen!);
    final json = _descriptor.writeToJsonMap();

    out.println(
      '@$coreImportPrefix.Deprecated'
      '(\'Use ${toplevelParent!.binaryDescriptorName} instead\')',
    );
    out.print('const $name = ');
    writeJsonConst(out, json);
    out.println(';');
    out.println();
  }
}
