import { useState, useEffect, useMemo, useRef, type TouchEventHandler } from 'react';
import { Card, Button, Radio, Checkbox, Input, message, Progress, Modal } from 'antd';
import { useNavigate, useLocation } from 'react-router-dom';
import { useUser, useQuiz } from '../contexts';
import { quizAPI } from '../services/api';
import { questionTypeMap } from '../utils/validation';
import { detectHorizontalSwipe } from '../utils/swipe';
import { UserLayout } from '../layouts/UserLayout';

const { TextArea } = Input;

interface Question {
  id: string;
  content: string;
  type: 'single' | 'multiple' | 'judgment' | 'text';
  options?: string[];
  answer: string | string[];
  analysis?: string;
  score: number;
  createdAt: string;
  category?: string;
}

interface LocationState {
  questions?: Question[];
  totalScore?: number;
  timeLimit?: number;
  subjectId?: string;
  taskId?: string;
}

const QuizPage = () => {
  const navigate = useNavigate();
  const location = useLocation();
  const { user } = useUser();
  const { questions, setQuestions, currentQuestionIndex, setCurrentQuestionIndex, answers, setAnswer, setAnswers, clearQuiz } = useQuiz();
  const [loading, setLoading] = useState(false);
  const [submitting, setSubmitting] = useState(false);
  const [answerSheetOpen, setAnswerSheetOpen] = useState(false);
  const [timeLeft, setTimeLeft] = useState<number | null>(null);
  const [timeLimit, setTimeLimit] = useState<number | null>(null);
  const [subjectId, setSubjectId] = useState<string>('');
  const [taskId, setTaskId] = useState<string>('');
  const lastTickSavedAtMsRef = useRef<number>(0);
  const saveDebounceTimerRef = useRef<number | null>(null);
  const [navDirection, setNavDirection] = useState<'next' | 'prev'>('next');
  const [enterAnimationOn, setEnterAnimationOn] = useState(false);
  const touchStartRef = useRef<{ x: number; y: number; time: number } | null>(null);
  const questionHeadingRef = useRef<HTMLHeadingElement | null>(null);

  useEffect(() => {
    const el = questionHeadingRef.current;
    if (!el) return;
    el.focus();
  }, [currentQuestionIndex]);

  useEffect(() => {
    const onKeyDown = (event: KeyboardEvent) => {
      if (event.defaultPrevented) return;

      const active = document.activeElement as HTMLElement | null;
      const activeTag = (active?.tagName || '').toLowerCase();

      const inputType =
        activeTag === 'input' ? ((active as HTMLInputElement | null)?.type || '').toLowerCase() : '';
      const isTextualInputType =
        activeTag === 'input'
          ? inputType === '' ||
            inputType === 'text' ||
            inputType === 'search' ||
            inputType === 'tel' ||
            inputType === 'url' ||
            inputType === 'email' ||
            inputType === 'password' ||
            inputType === 'number'
          : false;
      const inTextInput =
        activeTag === 'textarea' ||
        active?.getAttribute('role') === 'textbox' ||
        active?.classList.contains('ant-input') ||
        active?.closest?.('.ant-input') ||
        isTextualInputType ||
        active?.isContentEditable;

      if (inTextInput) return;

      if (event.key === 'ArrowLeft') {
        event.preventDefault();
        handlePrevious();
        return;
      }

      if (event.key === 'ArrowRight') {
        event.preventDefault();
        handleNext();
        return;
      }

      if (event.key === 'Escape') {
        if (answerSheetOpen) {
          event.preventDefault();
          setAnswerSheetOpen(false);
        }
      }
    };

    window.addEventListener('keydown', onKeyDown);
    return () => window.removeEventListener('keydown', onKeyDown);
  }, [answerSheetOpen, currentQuestionIndex, questions.length]);

  useEffect(() => {
    if (!user) {
      message.warning('请先填写个人信息');
      navigate('/');
      return;
    }

    const state = location.state as LocationState;

    clearQuiz();

    if (state?.questions) {
      const nextSubjectId = state.subjectId || '';
      const nextTaskId = state.taskId || '';
      const nextTimeLimit = state.timeLimit || 60;

      setQuestions(state.questions);
      setAnswers({});
      setCurrentQuestionIndex(0);
      setTimeLimit(nextTimeLimit);
      setTimeLeft(nextTimeLimit * 60);
      setSubjectId(nextSubjectId);
      setTaskId(nextTaskId);

      const progressKey = buildProgressKey(user.id, nextSubjectId, nextTaskId);
      setActiveProgress(user.id, progressKey);
      saveProgress(progressKey, {
        questions: state.questions,
        answers: {},
        currentQuestionIndex: 0,
        timeLeftSeconds: nextTimeLimit * 60,
        timeLimitMinutes: nextTimeLimit,
        subjectId: nextSubjectId,
        taskId: nextTaskId,
      });
      return;
    }

    const restored = restoreActiveProgress(user.id);
    if (restored) {
      setQuestions(restored.questions);
      setAnswers(restored.answers);
      setCurrentQuestionIndex(restored.currentQuestionIndex);
      setTimeLimit(restored.timeLimitMinutes);
      setTimeLeft(restored.timeLeftSeconds);
      setSubjectId(restored.subjectId);
      setTaskId(restored.taskId);
      return;
    }

    generateQuiz();
  }, [user, navigate, location]);

  // 倒计时逻辑
  useEffect(() => {
    if (timeLeft === null || timeLeft <= 0) return;

    const timer = setInterval(() => {
      setTimeLeft(prev => {
        if (prev === null || prev <= 1) {
          clearInterval(timer);
          handleTimeUp();
          return 0;
        }
        return prev - 1;
      });
    }, 1000);

    return () => clearInterval(timer);
  }, [timeLeft]);

  const generateQuiz = async () => {
    try {
      setLoading(true);
      const response = await quizAPI.generateQuiz(user!.id);
      setQuestions(response.data.questions);
      setCurrentQuestionIndex(0);
      setAnswers({});
      setTimeLimit(60);
      setTimeLeft(60 * 60);
      setSubjectId('');
      setTaskId('');

      const progressKey = buildProgressKey(user!.id, '', '');
      setActiveProgress(user!.id, progressKey);
      saveProgress(progressKey, {
        questions: response.data.questions,
        answers: {},
        currentQuestionIndex: 0,
        timeLeftSeconds: 60 * 60,
        timeLimitMinutes: 60,
        subjectId: '',
        taskId: '',
      });
    } catch (error: any) {
      message.error(error.message || '生成试卷失败');
    } finally {
      setLoading(false);
    }
  };

  const handleTimeUp = () => {
    message.warning('考试时间已到，将自动提交答案');
    setTimeout(() => {
      handleSubmit(true);
    }, 1000);
  };

  const formatTime = (seconds: number) => {
    const minutes = Math.floor(seconds / 60);
    const remainingSeconds = seconds % 60;
    return `${minutes}:${remainingSeconds.toString().padStart(2, '0')}`;
  };

  const getTagColor = (type: string) => {
    switch (type) {
      case 'single':
        return 'bg-blue-100 text-blue-800';
      case 'multiple':
        return 'bg-purple-100 text-purple-800';
      case 'judgment':
        return 'bg-orange-100 text-orange-800';
      case 'text':
        return 'bg-green-100 text-green-800';
      default:
        return 'bg-gray-100 text-gray-800';
    }
  };

  const handleAnswerChange = (questionId: string, value: string | string[]) => {
    setAnswer(questionId, value);
  };

  useEffect(() => {
    if (!user) return;
    if (!questions.length) return;
    if (timeLeft === null) return;

    if (saveDebounceTimerRef.current !== null) {
      window.clearTimeout(saveDebounceTimerRef.current);
    }

    saveDebounceTimerRef.current = window.setTimeout(() => {
      const progressKey = getActiveProgressKey(user.id);
      if (!progressKey) return;
      saveProgress(progressKey, {
        questions,
        answers,
        currentQuestionIndex,
        timeLeftSeconds: timeLeft,
        timeLimitMinutes: timeLimit || 60,
        subjectId,
        taskId,
      });
      saveDebounceTimerRef.current = null;
    }, 300);

    return () => {
      if (saveDebounceTimerRef.current !== null) {
        window.clearTimeout(saveDebounceTimerRef.current);
        saveDebounceTimerRef.current = null;
      }
    };
  }, [user, questions, answers, currentQuestionIndex, subjectId, taskId, timeLeft, timeLimit]);

  useEffect(() => {
    if (!user) return;
    if (!questions.length) return;
    if (timeLeft === null) return;

    const now = Date.now();
    if (now - lastTickSavedAtMsRef.current < 5000) return;
    lastTickSavedAtMsRef.current = now;

    const progressKey = getActiveProgressKey(user.id);
    if (!progressKey) return;

    saveProgress(progressKey, {
      questions,
      answers,
      currentQuestionIndex,
      timeLeftSeconds: timeLeft,
      timeLimitMinutes: timeLimit || 60,
      subjectId,
      taskId,
    });
  }, [user, questions.length, timeLeft]);

  const handleNext = () => {
    if (currentQuestionIndex < questions.length - 1) {
      setNavDirection('next');
      setCurrentQuestionIndex(currentQuestionIndex + 1);
    }
  };

  const handlePrevious = () => {
    if (currentQuestionIndex > 0) {
      setNavDirection('prev');
      setCurrentQuestionIndex(currentQuestionIndex - 1);
    }
  };

  const handleJumpTo = (index: number) => {
    if (index < 0 || index >= questions.length) return;
    if (index === currentQuestionIndex) return;
    setNavDirection(index > currentQuestionIndex ? 'next' : 'prev');
    setCurrentQuestionIndex(index);
  };

  const handleSubmit = async (forceSubmit = false) => {
    try {
      setSubmitting(true);

      if (!forceSubmit) {
        // 检查是否所有题目都已回答
        const unansweredQuestions = questions.filter(q => !answers[q.id]);
        if (unansweredQuestions.length > 0) {
          message.warning(`还有 ${unansweredQuestions.length} 道题未作答`);
          return;
        }
      }

      // 准备答案数据
      const answersData = questions.map(question => {
        const isCorrect = checkAnswer(question, answers[question.id]);
        return {
          questionId: question.id,
          userAnswer: answers[question.id],
          score: isCorrect ? question.score : 0,
          isCorrect
        };
      });

      const response = await quizAPI.submitQuiz({
        userId: user!.id,
        subjectId: subjectId || undefined,
        taskId: taskId || undefined,
        answers: answersData
      });

      message.success('答题提交成功！');
      clearActiveProgress(user!.id);
      navigate(`/result/${response.data.recordId}`);
    } catch (error: any) {
      message.error(error.message || '提交失败');
    } finally {
      setSubmitting(false);
    }
  };

  const handleGiveUp = () => {
    if (!user) return;
    Modal.confirm({
      title: '确认弃考？',
      content: '弃考将清空本次答题进度与计时信息，且不计入考试次数。',
      okText: '确认弃考',
      cancelText: '继续答题',
      okButtonProps: { danger: true },
      onOk: () => {
        clearActiveProgress(user.id);
        clearQuiz();
        navigate('/tasks');
      },
    });
  };

  const checkAnswer = (question: Question, userAnswer: string | string[]): boolean => {
    if (!userAnswer) return false;

    if (question.type === 'multiple') {
      const correctAnswers = Array.isArray(question.answer) ? question.answer : [question.answer];
      const userAnswers = Array.isArray(userAnswer) ? userAnswer : [userAnswer];
      return correctAnswers.length === userAnswers.length && 
             correctAnswers.every(answer => userAnswers.includes(answer));
    } else {
      return userAnswer === question.answer;
    }
  };

  const renderQuestion = (question: Question) => {
    const currentAnswer = answers[question.id];

    switch (question.type) {
      case 'single':
        return (
          <Radio.Group
            value={currentAnswer as string}
            onChange={(e) => handleAnswerChange(question.id, e.target.value)}
            className="w-full"
          >
            {question.options?.map((option, index) => (
              <Radio key={index} value={option} className="block mb-3 p-4 min-h-12 rounded-lg border border-gray-200 hover:bg-gray-50 hover:border-mars-200 transition-colors">
                {String.fromCharCode(65 + index)}. {option}
              </Radio>
            ))}
          </Radio.Group>
        );

      case 'multiple':
        return (
          <Checkbox.Group
            value={currentAnswer as string[] || []}
            onChange={(checkedValues) => handleAnswerChange(question.id, checkedValues)}
            className="w-full"
          >
            {question.options?.map((option, index) => (
              <Checkbox key={index} value={option} className="block mb-3 p-4 min-h-12 rounded-lg border border-gray-200 hover:bg-gray-50 hover:border-mars-200 transition-colors w-full">
                {String.fromCharCode(65 + index)}. {option}
              </Checkbox>
            ))}
          </Checkbox.Group>
        );

      case 'judgment':
        return (
          <Radio.Group
            value={currentAnswer as string}
            onChange={(e) => handleAnswerChange(question.id, e.target.value)}
            className="w-full"
          >
            <Radio value="正确" className="block mb-3 p-4 min-h-12 rounded-lg border border-gray-200 hover:bg-gray-50 hover:border-mars-200 transition-colors">
              正确
            </Radio>
            <Radio value="错误" className="block mb-3 p-4 min-h-12 rounded-lg border border-gray-200 hover:bg-gray-50 hover:border-mars-200 transition-colors">
              错误
            </Radio>
          </Radio.Group>
        );

      case 'text':
        return (
          <TextArea
            rows={6}
            value={currentAnswer as string || ''}
            onChange={(e) => handleAnswerChange(question.id, e.target.value)}
            placeholder="请输入您的答案..."
            className="rounded-lg border-gray-300 focus:border-mars-500 focus:ring-mars-500"
          />
        );

      default:
        return <div>未知题型</div>;
    }
  };

  const answeredCount = useMemo(() => {
    return questions.reduce((count, q) => (answers[q.id] ? count + 1 : count), 0);
  }, [questions, answers]);

  useEffect(() => {
    if (!questions.length) return;
    setEnterAnimationOn(false);
    const rafId = requestAnimationFrame(() => setEnterAnimationOn(true));
    return () => cancelAnimationFrame(rafId);
  }, [currentQuestionIndex, questions.length]);

  if (loading || !questions.length) {
    return (
      <UserLayout>
        <div className="flex items-center justify-center h-full min-h-[500px]">
          <div className="text-center">
            <div className="animate-spin rounded-full h-12 w-12 border-b-2 border-mars-600 mx-auto mb-4"></div>
            <p className="text-gray-700">正在生成试卷...</p>
          </div>
        </div>
      </UserLayout>
    );
  }

  const currentQuestion = questions[currentQuestionIndex];
  const progress = ((currentQuestionIndex + 1) / questions.length) * 100;

  const handleTouchStart: TouchEventHandler = (e) => {
    if (e.touches.length !== 1) return;
    const target = e.target as HTMLElement | null;
    if (target?.closest('textarea,input,[role="textbox"],.ant-input,.ant-checkbox-wrapper,.ant-radio-wrapper')) return;
    const touch = e.touches[0];
    touchStartRef.current = { x: touch.clientX, y: touch.clientY, time: Date.now() };
  };

  const handleTouchEnd: TouchEventHandler = (e) => {
    const start = touchStartRef.current;
    touchStartRef.current = null;
    if (!start) return;

    const touch = e.changedTouches[0];
    if (!touch) return;

    const direction = detectHorizontalSwipe({
      startX: start.x,
      startY: start.y,
      endX: touch.clientX,
      endY: touch.clientY,
      elapsedMs: Date.now() - start.time,
    });

    if (direction === 'left') {
      handleNext();
      return;
    }
    if (direction === 'right') {
      handlePrevious();
    }
  };

  return (
    <UserLayout>
      <div className="max-w-4xl mx-auto pb-24">
        {/* 头部信息 */}
        <div className="bg-white rounded-xl shadow-sm p-4 md:p-6 mb-4 md:mb-6 border border-gray-100">
          <div className="flex flex-col md:flex-row md:justify-between md:items-center gap-3 mb-4">
            <div>
              <h1 className="text-xl md:text-2xl font-bold text-gray-900">在线答题</h1>
              <p className="text-gray-700 mt-1">
                第 {currentQuestionIndex + 1} 题 / 共 {questions.length} 题
              </p>
            </div>
            <div className="flex items-center justify-between md:justify-end gap-3">
              <Button danger onClick={handleGiveUp} className="h-12 px-4 focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:ring-red-500">
                弃考
              </Button>
              {timeLeft !== null && (
                <div className="text-right">
                  <div className="text-sm text-gray-700">剩余时间</div>
                  <div className={`text-2xl font-bold tabular-nums ${
                    timeLeft < 300 ? 'text-red-600' : 'text-mars-600'
                  }`}>
                    {formatTime(timeLeft)}
                  </div>
                </div>
              )}
            </div>
          </div>
          
          <Progress
            percent={Math.round(progress)}
            strokeColor="#008C8C"
            trailColor="#f0fcfc"
            showInfo={false}
            className="mt-2"
          />
        </div>

        {/* 题目卡片 */}
        <Card className="shadow-sm border border-gray-100 rounded-xl">
          <div
            onTouchStart={handleTouchStart}
            onTouchEnd={handleTouchEnd}
            className="mb-6 md:mb-8"
          >
            <div className="flex items-center justify-between mb-4">
              <span className={`inline-block px-3 py-1 rounded-full text-sm font-medium ${getTagColor(currentQuestion.type)}`}>
                {questionTypeMap[currentQuestion.type]}
              </span>
            </div>
            {currentQuestion.category && (
              <div className="mb-3">
                <span className="inline-block px-2 py-1 bg-gray-50 text-gray-700 text-xs rounded border border-gray-100">
                  {currentQuestion.category}
                </span>
              </div>
            )}
            <h2
              ref={questionHeadingRef}
              tabIndex={-1}
              className={`text-lg md:text-xl font-medium text-gray-900 leading-relaxed transition-all duration-200 ease-out ${
                enterAnimationOn
                  ? 'opacity-100 translate-x-0'
                  : navDirection === 'next'
                    ? 'opacity-0 translate-x-2'
                    : 'opacity-0 -translate-x-2'
              }`}
            >
              {currentQuestion.content}
            </h2>
          </div>

          <div
            className={`mb-6 md:mb-8 transition-all duration-200 ease-out ${
              enterAnimationOn
                ? 'opacity-100 translate-x-0'
                : navDirection === 'next'
                  ? 'opacity-0 translate-x-2'
                  : 'opacity-0 -translate-x-2'
            }`}
          >
            {renderQuestion(currentQuestion)}
          </div>
        </Card>

        <div className="fixed left-0 right-0 bottom-0 z-20">
          <div className="bg-white/95 backdrop-blur border-t border-gray-200">
            <div className="max-w-4xl mx-auto px-4 py-3">
              <div className="flex items-center gap-3">
                <Button
                  onClick={handlePrevious}
                  disabled={currentQuestionIndex === 0}
                  className="h-12 min-w-12 px-4 rounded-lg hover:border-mars-500 hover:text-mars-600 focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:ring-mars-500"
                >
                  上一题
                </Button>

                <Button
                  onClick={() => setAnswerSheetOpen(true)}
                  className="h-12 flex-1 rounded-lg border-gray-200 text-gray-900 hover:border-mars-400 hover:text-mars-600 focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:ring-mars-500"
                >
                  答题卡（{answeredCount}/{questions.length}）
                </Button>

                {currentQuestionIndex === questions.length - 1 ? (
                  <Button
                    type="primary"
                    onClick={() => handleSubmit()}
                    loading={submitting}
                    className="h-12 min-w-12 px-4 rounded-lg bg-mars-600 hover:bg-mars-700 border-none shadow-sm focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:ring-mars-500"
                  >
                    提交
                  </Button>
                ) : (
                  <Button
                    type="primary"
                    onClick={handleNext}
                    className="h-12 min-w-12 px-4 rounded-lg bg-mars-500 hover:bg-mars-600 border-none shadow-sm focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:ring-mars-500"
                  >
                    下一题
                  </Button>
                )}
              </div>
            </div>
          </div>
        </div>

        {answerSheetOpen && (
          <Modal
            title="答题卡"
            open={answerSheetOpen}
            onCancel={() => setAnswerSheetOpen(false)}
            footer={null}
            centered
            width={560}
            destroyOnClose
          >
            <div className="flex items-center justify-between mb-4">
              <div className="text-sm text-gray-700">
                已答 {answeredCount} / 共 {questions.length}
              </div>
              <Button
                type="primary"
                onClick={() => setAnswerSheetOpen(false)}
                className="h-10 px-4 bg-mars-600 hover:bg-mars-700 border-none"
              >
                回到当前题
              </Button>
            </div>

            <div className="grid grid-cols-5 sm:grid-cols-6 gap-2">
              {questions.map((q, idx) => {
                const isCurrent = idx === currentQuestionIndex;
                const isAnswered = !!answers[q.id];

                const baseClassName = 'h-12 w-12 rounded-lg border focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:ring-mars-500';
                const className = isCurrent
                  ? `${baseClassName} border-mars-500 text-mars-700 bg-mars-50`
                  : isAnswered
                    ? `${baseClassName} border-green-200 text-green-700 bg-green-50 hover:border-green-300`
                    : `${baseClassName} border-gray-200 text-gray-800 bg-white hover:border-mars-200`;

                return (
                  <button
                    key={q.id}
                    type="button"
                    className={className}
                    onClick={() => {
                      setAnswerSheetOpen(false);
                      handleJumpTo(idx);
                    }}
                    aria-label={`跳转到第 ${idx + 1} 题`}
                  >
                    {idx + 1}
                  </button>
                );
              })}
            </div>
          </Modal>
        )}
      </div>
    </UserLayout>
  );
};

export default QuizPage;

const QUIZ_PROGRESS_ACTIVE_PREFIX = 'quiz_progress_active_v1:';
const QUIZ_PROGRESS_PREFIX = 'quiz_progress_v1:';

type QuizProgressV1 = {
  questions: Question[];
  answers: Record<string, string | string[]>;
  currentQuestionIndex: number;
  timeLeftSeconds: number;
  timeLimitMinutes: number;
  subjectId: string;
  taskId: string;
  savedAt: string;
};

const buildProgressKey = (userId: string, subjectId: string, taskId: string) => {
  const scope = taskId ? `task:${taskId}` : `subject:${subjectId || 'none'}`;
  return `${QUIZ_PROGRESS_PREFIX}${userId}:${scope}`;
};

const setActiveProgress = (userId: string, progressKey: string) => {
  localStorage.setItem(`${QUIZ_PROGRESS_ACTIVE_PREFIX}${userId}`, progressKey);
};

const removeActiveProgress = (userId: string) => {
  localStorage.removeItem(`${QUIZ_PROGRESS_ACTIVE_PREFIX}${userId}`);
};

const getActiveProgressKey = (userId: string) => {
  return localStorage.getItem(`${QUIZ_PROGRESS_ACTIVE_PREFIX}${userId}`) || '';
};

const saveProgress = (progressKey: string, input: Omit<QuizProgressV1, 'savedAt'>) => {
  const payload: QuizProgressV1 = {
    ...input,
    savedAt: new Date().toISOString(),
  };
  localStorage.setItem(progressKey, JSON.stringify(payload));
};

const restoreActiveProgress = (userId: string): QuizProgressV1 | null => {
  const progressKey = getActiveProgressKey(userId);
  if (!progressKey) return null;

  const raw = localStorage.getItem(progressKey);
  if (!raw) return null;

  try {
    const parsed = JSON.parse(raw) as QuizProgressV1;
    if (!parsed || !Array.isArray(parsed.questions)) return null;
    if (!parsed.answers || typeof parsed.answers !== 'object') return null;
    if (typeof parsed.currentQuestionIndex !== 'number') return null;
    if (typeof parsed.timeLeftSeconds !== 'number') return null;
    if (typeof parsed.timeLimitMinutes !== 'number') return null;
    if (typeof parsed.subjectId !== 'string') return null;
    if (typeof parsed.taskId !== 'string') return null;
    return parsed;
  } catch {
    return null;
  }
};

const clearActiveProgress = (userId: string) => {
  const progressKey = getActiveProgressKey(userId);
  if (progressKey) {
    localStorage.removeItem(progressKey);
  }
  removeActiveProgress(userId);
};