using Entities.DTO;
using System.Text.Json.Serialization;
using System.Text.Json;

namespace TechHelper.Client.Exam
{
	public static class ExamPaperExtensions
	{
		public static ExamDto ConvertToExamDTO(this ExamPaper examPaper)
		{
			ExamDto dto = new ExamDto();

			dto.AssignmentTitle = examPaper.AssignmentTitle;
			dto.Description = examPaper.Description;
			dto.SubjectArea = examPaper.SubjectArea;
			dto.QuestionGroups.Title = examPaper.AssignmentTitle;
			dto.QuestionGroups.Descript = examPaper.Description;

			foreach (var qg in examPaper.QuestionGroups)
			{
				var qgd = new QuestionGroupDto();
				ParseMajorQuestionGroup(qg, qgd, false);
				dto.QuestionGroups.SubQuestionGroups.Add(qgd);
			}


			foreach (var question in examPaper.TopLevelQuestions)
			{
				if (question.SubQuestions != null && question.SubQuestions.Any())
				{
					var qgDto = new QuestionGroupDto
					{
						Title = question.Stem,
						Score = (int)question.Score,
						Descript = "",
					};

					qgDto.ValidQuestionGroup = !string.IsNullOrEmpty(qgDto.Descript);


					ParseQuestionWithSubQuestions(question, qgDto, qgDto.ValidQuestionGroup);
					dto.QuestionGroups.SubQuestionGroups.Add(qgDto);
				}
				else
				{
					var qgDto = new QuestionGroupDto
					{
						Title = question.Stem,
						Score = (int)question.Score,
						Descript = "",
					};

					qgDto.ValidQuestionGroup = !string.IsNullOrEmpty(qgDto.Descript);

					var subQuestionDto = new SubQuestionDto();
					ParseSingleQuestion(question, subQuestionDto, !qgDto.ValidQuestionGroup);
					qgDto.SubQuestions.Add(subQuestionDto);
					dto.QuestionGroups.SubQuestionGroups.Add(qgDto);
				}
			}

			return dto;
		}

		private static void ParseMajorQuestionGroup(MajorQuestionGroup qg, QuestionGroupDto qgd, bool isParentGroupValidChain)
		{
			qgd.Title = qg.Title;
			qgd.Score = (int)qg.Score;
			qgd.Descript = qg.Descript;


			qgd.ValidQuestionGroup = !string.IsNullOrEmpty(qg.Descript) && !isParentGroupValidChain;


			bool nextIsParentGroupValidChain = qgd.ValidQuestionGroup || isParentGroupValidChain;


			if (qg.SubQuestionGroups != null)
			{
				qg.SubQuestionGroups.ForEach(sqg =>
				{
					var sqgd = new QuestionGroupDto();
					sqgd.Index = (byte)qg.SubQuestionGroups.IndexOf(sqg);
					ParseMajorQuestionGroup(sqg, sqgd, nextIsParentGroupValidChain);
					qgd.SubQuestionGroups.Add(sqgd);
				});
			}

			// 处理 MajorQuestionGroup 下的 SubQuestions
			if (qg.SubQuestions != null)
			{
				qg.SubQuestions.ForEach(sq =>
				{
					// 如果 MajorQuestionGroup 下的 Question 包含子问题，则转为 QuestionGroupDto
					if (sq.SubQuestions != null && sq.SubQuestions.Any())
					{
						var subQgd = new QuestionGroupDto
						{
							Title = sq.Stem,
							Index = (byte)qg.SubQuestions.IndexOf(sq),
							Score = (int)sq.Score,
							Descript = "" // 默认为空
						};
						// 判断当前组是否有效：如果有描述，并且其父级链中没有任何一个组是有效组，则当前组有效
						subQgd.ValidQuestionGroup = !string.IsNullOrEmpty(subQgd.Descript) && !nextIsParentGroupValidChain;

						ParseQuestionWithSubQuestions(sq, subQgd, subQgd.ValidQuestionGroup || nextIsParentGroupValidChain);
						qgd.SubQuestionGroups.Add(subQgd);
					}
					else // 如果 MajorQuestionGroup 下的 Question 没有子问题，则转为 SubQuestionDto
					{
						var subQd = new SubQuestionDto();
						// 只有当所有父组（包括当前组）都不是有效组时，这个题目才有效
						ParseSingleQuestion(sq, subQd, !nextIsParentGroupValidChain);
						subQd.Index = (byte)qg.SubQuestions.IndexOf(sq);
						qgd.SubQuestions.Add(subQd);
					}
				});
			}
		}

		// 解析包含子问题的 Question，将其转换为 QuestionGroupDto
		// isParentGroupValidChain 参数表示从顶层到当前组的任一父组是否已经是“有效组”
		private static void ParseQuestionWithSubQuestions(Question question, QuestionGroupDto qgd, bool isParentGroupValidChain)
		{
			qgd.Title = question.Stem;
			qgd.Score = (int)question.Score;
			qgd.Descript = ""; // 默认为空

			// 判断当前组是否有效：如果有描述，并且其父级链中没有任何一个组是有效组，则当前组有效
			qgd.ValidQuestionGroup = !string.IsNullOrEmpty(qgd.Descript) && !isParentGroupValidChain;

			// 更新传递给子项的 isParentGroupValidChain 状态
			bool nextIsParentGroupValidChain = qgd.ValidQuestionGroup || isParentGroupValidChain;


			if (question.SubQuestions != null)
			{
				question.SubQuestions.ForEach(subQ =>
				{
					// 如果子问题本身还有子问题（多层嵌套），则继续创建 QuestionGroupDto
					if (subQ.SubQuestions != null && subQ.SubQuestions.Any())
					{
						var nestedQgd = new QuestionGroupDto
						{
							Title = subQ.Stem,
							Score = (int)subQ.Score,
							Descript = "" // 默认为空
						};
						// 判断当前组是否有效：如果有描述，并且其父级链中没有任何一个组是有效组，则当前组有效
						nestedQgd.ValidQuestionGroup = !string.IsNullOrEmpty(nestedQgd.Descript) && !nextIsParentGroupValidChain;

						ParseQuestionWithSubQuestions(subQ, nestedQgd, nestedQgd.ValidQuestionGroup || nextIsParentGroupValidChain);
						qgd.SubQuestionGroups.Add(nestedQgd);
					}
					else // 如果子问题没有子问题，则直接创建 SubQuestionDto
					{
						var subQd = new SubQuestionDto();
						// 只有当所有父组（包括当前组）都不是有效组时，这个题目才有效
						ParseSingleQuestion(subQ, subQd, !nextIsParentGroupValidChain);
						qgd.SubQuestions.Add(subQd);
					}
				});
			}
		}

		// 解析单个 Question (没有子问题) 为 SubQuestionDto
		private static void ParseSingleQuestion(Question question, SubQuestionDto subQd, bool validQ)
		{
			subQd.Stem = question.Stem;
			subQd.Score = (int)question.Score;
			subQd.ValidQuestion = validQ; // 根据传入的 validQ 确定是否是“有效题目”
			subQd.SampleAnswer = question.SampleAnswer;
			subQd.QuestionType = question.QuestionType;
			// 注意：DifficultyLevel 在本地 Question 中没有，如果服务器需要，可能需要补充默认值或从其他地方获取
			// subQd.DifficultyLevel = ...;

			if (question.Options != null)
			{
				question.Options.ForEach(o =>
				{
					subQd.Options.Add(new OptionDto { Value = o.Label + o.Text });
				});
			}
		}


		public static void SeqIndex(this ExamDto dto)
		{
			dto.QuestionGroups.SeqQGroupIndex();
		}


		public static void SeqQGroupIndex(this QuestionGroupDto dto)
		{
			dto.SubQuestions?.ForEach(sq =>
			{
				sq.Index = (byte)dto.SubQuestions.IndexOf(sq);
			});

			dto.SubQuestionGroups?.ForEach(sqg =>
			{
				sqg.Index = (byte)dto.SubQuestionGroups.IndexOf(sqg);
				sqg.SeqQGroupIndex();
			});
		}


		public static string SerializeExamDto(this ExamDto dto)
		{
			// 配置序列化选项（可选）
			var options = new JsonSerializerOptions
			{
				WriteIndented = true,
				PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
				DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
			};

			return JsonSerializer.Serialize(dto, options);
		}

		public static ExamDto DeserializeExamDto(string jsonString)
		{

			var options = new JsonSerializerOptions
			{
				PropertyNamingPolicy = JsonNamingPolicy.CamelCase
			};

			return JsonSerializer.Deserialize<ExamDto>(jsonString, options);
		}

	}
}