using Entities.Contracts; // 假设这些实体合约仍然是必需的
using System.Text.RegularExpressions;
using System.Text;

namespace TechHelper.Client.Exam
{
	public enum ParseErrorType
	{
		Validation = 1,
		DataParsing = 2,
		Structural = 3,
		RegexMatchIssue = 4,
		UnexpectedError = 5
	}

	public class ParseError
	{
		public ParseErrorType Type { get; }
		public string Message { get; }
		public int? Index { get; }
		public string MatchedText { get; }
		public Exception InnerException { get; }

		public ParseError(ParseErrorType type, string message, int? index = null, string matchedText = null, Exception innerException = null)
		{
			Type = type;
			Message = message;
			Index = index;
			MatchedText = matchedText;
			InnerException = innerException;
		}

		public override string ToString()
		{
			var sb = new StringBuilder();
			sb.Append($"[{Type}] {Message}");
			if (Index.HasValue) sb.Append($" (Index: {Index.Value})");
			if (!string.IsNullOrEmpty(MatchedText)) sb.Append($" (MatchedText: '{MatchedText}')");
			if (InnerException != null) sb.Append($" InnerException: {InnerException.Message}");
			return sb.ToString();
		}
	}

	public class AssignmentEx
	{
		public string Title { get; set; } = "Title";
		public string Description { get; set; } = "Description";
		public SubjectAreaEnum SubjectArea { get; set; } = SubjectAreaEnum.Unknown;
		public AssignmentQuestionEx ExamStruct { get; set; } = new AssignmentQuestionEx();
		public List<ParseError> Errors { get; set; } = new List<ParseError>();
	}

	public class AssignmentQuestionEx
	{
		public string Title { get; set; } = string.Empty;
		public string Description { get; set; } = string.Empty;
		public byte Index { get; set; } = 0;
		public float Score { get; set; }
		public QuestionEx? Question { get; set; }
		public AssignmentStructType Type { get; set; }
		public List<AssignmentQuestionEx> ChildrenAssignmentQuestion { get; set; } = new List<AssignmentQuestionEx>();
		public int Priority { get; set; }
	}

	public class QuestionEx
	{
		public string Title { get; set; } = string.Empty;
		public string Answer { get; set; } = string.Empty;
		public List<Option> Options { get; set; } = new List<Option>();
	}

	public class Option
	{
		public string Label { get; set; } = string.Empty;
		public string Text { get; set; } = string.Empty;
	}


	/// <summary>
	/// 表示一个带有优先级的正则表达式配置
	/// </summary>
	public class RegexPatternConfig
	{
		public string Pattern { get; set; }
		public int Priority { get; set; }
		public AssignmentStructType Type { get; set; }
		public Regex Regex { get; private set; }

		public RegexPatternConfig(string pattern, int priority, AssignmentStructType type = AssignmentStructType.Question)
		{
			Pattern = pattern;
			Priority = priority;
			Type = type;
			Regex = new Regex(pattern, RegexOptions.Multiline | RegexOptions.Compiled);
		}
	}

	/// <summary>
	/// 试卷解析的配置类，包含所有正则表达式
	/// </summary>
	public class ExamParserConfig
	{
		public List<RegexPatternConfig> QuestionPatterns { get; set; } = new List<RegexPatternConfig>();
		public List<RegexPatternConfig> OptionPatterns { get; set; } = new List<RegexPatternConfig>();
		public Regex ScoreRegex { get; private set; } // 独立的得分正则表达式

		public ExamParserConfig()
		{
			// 题目/题组模式：只匹配行开头，并按优先级区分
			// Group 1: 编号部分
			// Group 2: 题目/题组标题内容

			// 例如：一. 这是大题一
			QuestionPatterns.Add(new RegexPatternConfig(@"^([一二三四五六七八九十]+)[.\、]\s*(.+)", 1, AssignmentStructType.Struct));

			// 例如：(一) 这是第一子题组
			QuestionPatterns.Add(new RegexPatternConfig(@"^\(([一二三四五六七八九十]{1,2}|十[一二三四五六七八九])\)\s*(.+)", 2, AssignmentStructType.Composite));

			// 例如：1. 这是第一道题目 或 1 这是第一道题目
			QuestionPatterns.Add(new RegexPatternConfig(@"^(\d+)\.?\s*(.+)", 3, AssignmentStructType.Question));

			// 例如：(1). 这是小问一 或 (1) 这是小问一
			QuestionPatterns.Add(new RegexPatternConfig(@"^\((\d+)\)\.?\s*(.+)", 4, AssignmentStructType.Question));

			// 例如：① 这是另一种小问 或 ①. 这是另一种小问 (如果 ① 后面会跟点，这个更通用)
			// 如果 ① 后面通常没有点，但您希望它也能匹配，则保留原样或根据实际情况调整
			QuestionPatterns.Add(new RegexPatternConfig(@"^[①②③④⑤⑥⑦⑧⑨⑩]+\.?\s*(.+)", 5, AssignmentStructType.Question));



			// 选项模式 (保持不变，使用 AssignmentStructType.Option 区分)
			OptionPatterns.Add(new RegexPatternConfig(@"([A-Z]\.)\s*(.*?)(?=[A-Z]\.|$)", 1, AssignmentStructType.Option));
			OptionPatterns.Add(new RegexPatternConfig(@"([a-z]\.)\s*(.*?)(?=[a-z]\.|$)", 2, AssignmentStructType.Option));

			// 独立的得分正则表达式：匹配行末尾的 "(X分)" 格式
			// Group 1: 捕获分数（如 "10" 或 "0.5"）
			ScoreRegex = new Regex(@"(?:\s*\(((\d+(?:\.\d+)?))\s*分\)\s*$)", RegexOptions.Multiline | RegexOptions.Compiled);
		}
	}

	public class PotentialMatch
	{
		public int StartIndex { get; set; }
		public int EndIndex { get; set; }
		public string MatchedText { get; set; }
		public Match RegexMatch { get; set; }
		public RegexPatternConfig PatternConfig { get; set; }
	}

	public class ExamDocumentScanner
	{
		private readonly ExamParserConfig _config;

		public ExamDocumentScanner(ExamParserConfig config)
		{
			_config = config ?? throw new ArgumentNullException(nameof(config));
		}

		public List<PotentialMatch> Scan(string text, List<ParseError> errors)
		{
			if (string.IsNullOrEmpty(text))
			{
				return new List<PotentialMatch>();
			}

			var allPotentialMatches = new List<PotentialMatch>();
			var allPatternConfigs = new List<RegexPatternConfig>();
			allPatternConfigs.AddRange(_config.QuestionPatterns);
			allPatternConfigs.AddRange(_config.OptionPatterns);

			foreach (var patternConfig in allPatternConfigs)
			{
				try
				{
					foreach (Match match in patternConfig.Regex.Matches(text))
					{
						allPotentialMatches.Add(new PotentialMatch
						{
							StartIndex = match.Index,
							EndIndex = match.Index + match.Length,
							MatchedText = match.Value,
							RegexMatch = match,
							PatternConfig = patternConfig,
						});
					}
				}
				catch (Exception ex)
				{
					errors.Add(new ParseError(ParseErrorType.UnexpectedError,
						$"An error occurred during regex matching for pattern: '{patternConfig.Pattern}'.",
						innerException: ex));
				}
			}
			return allPotentialMatches.OrderBy(pm => pm.StartIndex).ToList();
		}
	}

	public class ExamStructureBuilder
	{
		private readonly ExamParserConfig _config;

		public ExamStructureBuilder(ExamParserConfig config)
		{
			_config = config ?? throw new ArgumentNullException(nameof(config), "ExamParserConfig cannot be null.");
		}

		public AssignmentEx BuildExam(string fullExamText, List<PotentialMatch> allPotentialMatches)
		{
			if (string.IsNullOrWhiteSpace(fullExamText))
			{
				throw new ArgumentException("Full exam text cannot be null or empty.", nameof(fullExamText));
			}
			if (allPotentialMatches == null)
			{
				throw new ArgumentNullException(nameof(allPotentialMatches), "Potential matches list cannot be null.");
			}

			var assignment = new AssignmentEx();
			try
			{
				assignment.Title = GetExamTitle(fullExamText);
			}
			catch (Exception ex)
			{
				assignment.Errors.Add(new ParseError(ParseErrorType.UnexpectedError, "Failed to extract exam title.", innerException: ex));
				assignment.Title = "未识别试卷标题";
			}

			var assignmentQuestionStack = new Stack<AssignmentQuestionEx>();
			var rootAssignmentQuestion = new AssignmentQuestionEx { Type = AssignmentStructType.Struct, Priority = 0, Title = "Root Exam Structure" };
			assignmentQuestionStack.Push(rootAssignmentQuestion);
			assignment.ExamStruct = rootAssignmentQuestion;

			int currentContentStart = 0;

			if (allPotentialMatches.Any() && allPotentialMatches[0].StartIndex > 0)
			{
				string introText = fullExamText.Substring(0, allPotentialMatches[0].StartIndex).Trim();
				if (!string.IsNullOrWhiteSpace(introText))
				{
					assignment.Description += (string.IsNullOrWhiteSpace(assignment.Description) ? "" : "\n") + introText;
				}
			}
			currentContentStart = allPotentialMatches.Any() ? allPotentialMatches[0].StartIndex : 0;

			for (int i = 0; i < allPotentialMatches.Count; i++)
			{
				var pm = allPotentialMatches[i];

				try
				{
					if (!IsValidPotentialMatch(pm, i, fullExamText.Length, currentContentStart, assignment.Errors))
					{
						currentContentStart = Math.Max(currentContentStart, pm.EndIndex);
						continue;
					}

					string precedingText = fullExamText.Substring(currentContentStart, pm.StartIndex - currentContentStart).Trim();
					if (!string.IsNullOrWhiteSpace(precedingText))
					{
						if (assignmentQuestionStack.Peek().Question != null)
						{
							ProcessQuestionContent(assignmentQuestionStack.Peek(), precedingText, assignment.Errors);
						}
						else
						{
							assignment.Description += (string.IsNullOrWhiteSpace(assignment.Description) ? "" : "\n") + precedingText;
						}
					}

					if (pm.PatternConfig.Type == AssignmentStructType.Option)
					{
						HandleOptionMatch(pm, i, assignmentQuestionStack.Peek(), assignment.Errors);
					}
					else
					{
						HandleQuestionGroupMatch(pm, i, assignmentQuestionStack, assignment.Errors);
					}

					currentContentStart = pm.EndIndex;
				}
				catch (Exception ex)
				{
					assignment.Errors.Add(new ParseError(ParseErrorType.UnexpectedError,
						$"An unexpected error occurred during main loop processing of PotentialMatch at index {i}.",
						index: i, matchedText: pm.MatchedText, innerException: ex));
					currentContentStart = Math.Max(currentContentStart, pm.EndIndex);
				}
			}

			if (currentContentStart < fullExamText.Length)
			{
				try
				{
					string remainingText = fullExamText.Substring(currentContentStart).Trim();
					if (!string.IsNullOrWhiteSpace(remainingText))
					{
						if (assignmentQuestionStack.Peek().Question != null)
						{
							ProcessQuestionContent(assignmentQuestionStack.Peek(), remainingText, assignment.Errors);
						}
						else
						{
							assignment.Description += (string.IsNullOrWhiteSpace(assignment.Description) ? "" : "\n") + remainingText;
						}
					}
				}
				catch (Exception ex)
				{
					assignment.Errors.Add(new ParseError(ParseErrorType.UnexpectedError,
						"An unexpected error occurred while processing remaining text after all potential matches.",
						innerException: ex));
				}
			}

			return assignment;
		}

		private bool IsValidPotentialMatch(PotentialMatch pm, int index, int fullTextLength, int currentContentStart, List<ParseError> errors)
		{
			if (pm.StartIndex < currentContentStart || pm.EndIndex > fullTextLength || pm.StartIndex > pm.EndIndex)
			{
				errors.Add(new ParseError(ParseErrorType.Validation,
					$"PotentialMatch at index {index} has invalid start/end indices. Start: {pm.StartIndex}, End: {pm.EndIndex}, CurrentContentStart: {currentContentStart}, FullTextLength: {fullTextLength}",
					index: index, matchedText: pm.MatchedText));
				return false;
			}
			if (pm.RegexMatch == null || pm.PatternConfig == null)
			{
				errors.Add(new ParseError(ParseErrorType.Validation,
					$"PotentialMatch at index {index} is missing RegexMatch or PatternConfig.",
					index: index, matchedText: pm.MatchedText));
				return false;
			}
			return true;
		}

		private void HandleQuestionGroupMatch(PotentialMatch pm, int index, Stack<AssignmentQuestionEx> assignmentQuestionStack, List<ParseError> errors)
		{
			try
			{
				while (assignmentQuestionStack.Count > 1 && pm.PatternConfig.Priority <= assignmentQuestionStack.Peek().Priority)
				{
					assignmentQuestionStack.Pop();
				}

				// 验证捕获组：Group 1 是编号，Group 2 是题目内容
				if (pm.RegexMatch.Groups.Count < 3 || !pm.RegexMatch.Groups[1].Success || string.IsNullOrWhiteSpace(pm.RegexMatch.Groups[2].Value))
				{
					errors.Add(new ParseError(ParseErrorType.RegexMatchIssue,
						$"Question/Group match at index {index} does not have enough regex groups (expected 3 for number and title) or a valid title group (Group 2). Skipping this group.",
						index: index, matchedText: pm.MatchedText));
					return;
				}

				float score = 0;
				// 尝试从 MatchedText 的末尾匹配分数
				Match scoreMatch = _config.ScoreRegex.Match(pm.MatchedText);
				if (scoreMatch.Success && scoreMatch.Groups.Count > 1 && scoreMatch.Groups[1].Success)
				{
					if (!float.TryParse(scoreMatch.Groups[1].Value, out score))
					{
						errors.Add(new ParseError(ParseErrorType.DataParsing,
							$"Failed to parse score '{scoreMatch.Groups[1].Value}' for match at index {index}. Defaulting to 0.",
							index: index, matchedText: pm.MatchedText));
					}
					// 从 MatchedText 中移除分数部分，使其只包含编号和标题
					// 注意：这里修改的是pm.MatchedText，这不会影响原始文本，只是当前匹配项的“内容”
					pm.MatchedText = pm.MatchedText.Substring(0, scoreMatch.Index).Trim();
				}

				// 提取标题，这里使用 Group 2 的值，它不包含分数
				string title = pm.RegexMatch.Groups[2].Value.Trim();


				AssignmentQuestionEx newAssignmentQuestion;
				if (pm.PatternConfig.Type == AssignmentStructType.Struct)
				{
					newAssignmentQuestion = new AssignmentQuestionEx
					{
						Title = title,
						Score = score,
						Priority = pm.PatternConfig.Priority,
						Type = pm.PatternConfig.Type
					};
				}
				else // AssignmentStructType.Question 类型
				{
					newAssignmentQuestion = new AssignmentQuestionEx
					{
						Priority = pm.PatternConfig.Priority,
						Type = pm.PatternConfig.Type,
						Score = score,
						Question = new QuestionEx
						{
							Title = title,
						}
					};
				}

				assignmentQuestionStack.Peek().ChildrenAssignmentQuestion.Add(newAssignmentQuestion);
				assignmentQuestionStack.Push(newAssignmentQuestion);
			}
			catch (Exception ex)
			{
				errors.Add(new ParseError(ParseErrorType.UnexpectedError,
					$"An unexpected error occurred during processing a non-option match (type: {pm.PatternConfig.Type}) at index {index}.",
					index: index, matchedText: pm.MatchedText, innerException: ex));
			}
		}

		private void HandleOptionMatch(PotentialMatch pm, int index, AssignmentQuestionEx currentAssignmentQuestion, List<ParseError> errors)
		{
			try
			{
				if (currentAssignmentQuestion.Question == null)
				{
					errors.Add(new ParseError(ParseErrorType.Structural,
						$"Found isolated Option at index {index}. Options must belong to a 'Question' type structure. Ignoring this option.",
						index: index, matchedText: pm.MatchedText));
					return;
				}

				if (pm.RegexMatch.Groups.Count < 3 || !pm.RegexMatch.Groups[1].Success || string.IsNullOrWhiteSpace(pm.RegexMatch.Groups[2].Value))
				{
					errors.Add(new ParseError(ParseErrorType.RegexMatchIssue,
						$"Option match at index {index} does not have enough regex groups or valid label/text groups (Group 1/2). Skipping this option.",
						index: index, matchedText: pm.MatchedText));
					return;
				}

				Option newOption = new Option
				{
					Label = pm.RegexMatch.Groups[1].Value.Trim(),
					Text = pm.RegexMatch.Groups[2].Value.Trim()
				};
				currentAssignmentQuestion.Question.Options.Add(newOption);
			}
			catch (Exception ex)
			{
				errors.Add(new ParseError(ParseErrorType.UnexpectedError,
					$"An unexpected error occurred during processing Option at index {index}.",
					index: index, matchedText: pm.MatchedText, innerException: ex));
			}
		}

		private void ProcessQuestionContent(AssignmentQuestionEx question, string contentText, List<ParseError> errors)
		{
			if (question?.Question == null)
			{
				errors.Add(new ParseError(ParseErrorType.Structural,
					$"Attempted to process content for a non-question type AssignmentQuestionEx (Type: {question?.Type}). Content: '{contentText}'",
					matchedText: contentText));
				return;
			}

			if (!string.IsNullOrWhiteSpace(contentText))
			{
				question.Question.Title += (string.IsNullOrWhiteSpace(question.Question.Title) ? "" : "\n") + contentText;
			}
		}

		private string GetExamTitle(string examPaperText)
		{
			var firstLine = examPaperText.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries)
										.FirstOrDefault(line => !string.IsNullOrWhiteSpace(line));
			return firstLine ?? "未识别试卷标题";
		}
	}

	public class ExamParser
	{
		private readonly ExamParserConfig _config;
		private readonly ExamDocumentScanner _scanner;
		private readonly ExamStructureBuilder _builder;

		public ExamParser(ExamParserConfig config)
		{
			_config = config ?? throw new ArgumentNullException(nameof(config));
			_scanner = new ExamDocumentScanner(_config);
			_builder = new ExamStructureBuilder(_config);
		}

		/// <summary>
		/// 解析给定的试卷文本，返回结构化的 AssignmentEx 对象。
		/// </summary>
		/// <param name="examPaperText">完整的试卷文本</param>
		/// <returns>解析后的 AssignmentEx 对象</returns>
		public AssignmentEx ParseExamPaper(string examPaperText)
		{
			var assignment = new AssignmentEx();
			List<PotentialMatch> allPotentialMatches = _scanner.Scan(examPaperText, assignment.Errors);
			assignment = _builder.BuildExam(examPaperText, allPotentialMatches);
			return assignment;
		}
	}
}