import "dart:io";

import "package:build/build.dart";
import "package:yaml/yaml.dart";

String joinString(List<String> strings, String sep) {
  String joined = "";

  for (final str in strings) {
    joined += "$str$sep";
  }

  return joined;
}

String _getAttributeType(dynamic data) {
  if (data is String) {
    return data;
  }

  return (data as YamlMap)["type"]!;
}

bool _getAttributeDeserialise(dynamic data) {
  if (data is YamlMap) {
    return data["deserialise"] ?? false;
  }

  return false;
}

String _generateAttributes(YamlMap data) {
  if (data["attributes"] == null) {
    return "";
  }

  List<String> attrs = [];
  data["attributes"].forEach((key, value) {
      final type_ = _getAttributeType(value);
      assert(!type_.endsWith(" "));
      attrs.add("\tfinal $type_ $key;");
  });

  final joined = joinString(attrs, "\n");
  return joined.substring(0, joined.length - 1);
}

String _generateInitializers(YamlMap data) {
  if (data["attributes"] == null) {
    return "";
  }

  List<String> attrs = [];
  data["attributes"].forEach((key, value) {
      final type_ = _getAttributeType(value);
      final defaultValue = value is YamlMap
        ? value["default"]
        : null;
      final defaultString = defaultValue != null
        ? " = const $defaultValue"
        : "";
      final isRequired = !type_.endsWith("?") && defaultValue == null;
      final requiredString = isRequired ? "required " : "";

      attrs.add("\t\t${requiredString}this.$key$defaultString,");
  });

  final joined = joinString(attrs, "\n");
  return joined.substring(0, joined.length - 1);
}

String _generateToJson(YamlMap data) {
  String json = '''
\t@override
\tMap<String, dynamic> toJson() => {\n
''';

  if (data["attributes"] != null) {
    data["attributes"].forEach((key, _) {
        json += "\t\t\"$key\": $key,\n";
    });
  }

  json += '''
\t\t"type": "${data["name"]!}"
\t};\n
''';
  return json;
}

String _generateFromJson(YamlMap data) {
  final name = data["name"]!;
  String json = "\tstatic $name fromJson(Map<String, dynamic> json) => $name(";

  if (data["attributes"] != null) {
    json += "\n";
    data["attributes"].forEach((key, value) {
        final type_ = _getAttributeType(value);
        if (type_.startsWith("List<")) {
          final exp = RegExp(r"List\<(.*?)\>");
          final listType = exp.firstMatch(type_)!.group(1)!;

          final suffix = type_.endsWith("?") ? " ?? []" : "!";
          String attr = '(json["$key"]$suffix)';
          if (_getAttributeDeserialise(value)) {
            attr += ".map((item) => $listType.fromJson(item))";
          }

          json += "\t\t$key: List<$listType>.from($attr),\n";
        } else {
          if (_getAttributeDeserialise(value)) {
            if (type_.endsWith("?")) {
              final attrTypeNoNull = type_.substring(0, type_.length - 1);
              json += '\t\t$key: json["$key"] != null ? $attrTypeNoNull.fromJson(json["$key"]) : null,\n';
            } else {
              json += '\t\t$key: $type_.fromJson(json["$key"]!),\n';
            }
          } else {
            final nullString = type_.endsWith("?")
              ? "" : "!";
            json += '\t\t$key: json["$key"]$nullString,\n';
          }
        }
    });
    json += "\t);";
  } else {
    json += ");";
  }

  return json;
}

String generateClassFromData(YamlMap data) {
  String impls = "";
  for (final impl in data["implements"]) {
    impls += "$impl, ";
  }
  final constructor = data["attributes"] != null
    ? '''
\t${data["name"]!}({
${_generateInitializers(data)}
\t});
    '''
    : '\t${data["name"]!}();';
  return '''
class ${data["name"]!} extends ${data["extends"]} implements ${impls.substring(0, impls.length - 2)} {
${_generateAttributes(data)}
$constructor

\t// JSON Stuff
${_generateToJson(data)}
${_generateFromJson(data)}
}

''';
}

String _generateBuilder(String name, String baseClass, YamlList classes) {
  String func = '''
$baseClass? get${name}FromJson(Map<String, dynamic> json) {
\tswitch(json["type"]!) {
''';

  for (final class_ in classes) {
    final name = class_["name"]!;
    func += '\t\tcase "$name": return $name.fromJson(json);\n';
  }

  func += "\t\tdefault: return null;\n";
  func += "\t}\n}";
  return func;
}

String generateFileFromData(YamlMap data) {
  String file = '''
//// AUTO-GENERATED by build_runner ////
/// DO NOT EDIT BY HAND
part of "${data["partof"]!}";

''';

  data["classes"].forEach((attributes) {
      file += generateClassFromData(attributes);
  });
  if (data["generate_builder"]) {
    file += "\n\n";
    file += _generateBuilder(
      data["builder_name"],
      data["builder_baseclass"],
      data["classes"]
    );
  }
  
  return file;
}

class DataClassBuilder implements Builder {
  @override
  Future build(BuildStep step) async {
    final file = File(step.inputId.path);
    final data = loadYaml(await file.readAsString());
    
    for (final asset in step.allowedOutputs) {
      if (asset.path.endsWith("commands.moxxy.dart")) {
        await step.writeAsString(
          asset,
          generateFileFromData(data["files"]["commands"]!)
        );
      } else if (asset.path.endsWith("events.moxxy.dart")) {
        await step.writeAsString(
          asset,
          generateFileFromData(data["files"]["events"]!)
        );
      }
    }
  }

  @override
  final buildExtensions = const {
    "data_classes.yaml": [
      "shared/commands.moxxy.dart",
      "shared/events.moxxy.dart"
    ]
  };
}

Builder dataClassBuilder(BuilderOptions options) => DataClassBuilder();