import { useState } from "react";
import { useParams, useNavigate } from "react-router-dom";
import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
import { Button } from "@/components/ui/button";
import { Progress } from "@/components/ui/progress";
import { RadioGroup, RadioGroupItem } from "@/components/ui/radio-group";
import { Label } from "@/components/ui/label";
import { Badge } from "@/components/ui/badge";
import { Loader2, CheckCircle2, ArrowRight, Clock } from "lucide-react";
import { useStartDiagnostic, useAnswerDiagnostic } from "@/hooks/queries";
import { useToast } from "@/hooks/use-toast";
import type { DiagnosticQuestion } from "@/types";

export default function DiagnosticTest() {
  const { subjectId } = useParams<{ subjectId: string }>();
  const navigate = useNavigate();
  const { toast } = useToast();
  const startMutation = useStartDiagnostic();
  const answerMutation = useAnswerDiagnostic();

  const [sessionId, setSessionId] = useState<number | null>(null);
  const [currentQuestion, setCurrentQuestion] = useState<DiagnosticQuestion | null>(null);
  const [selectedAnswer, setSelectedAnswer] = useState("");
  const [questionIndex, setQuestionIndex] = useState(0);
  const [totalQuestions, setTotalQuestions] = useState(0);
  const [completed, setCompleted] = useState(false);

  const handleStart = () => {
    startMutation.mutate(Number(subjectId), {
      onSuccess: (data) => {
        setSessionId(data.session.id);
        setCurrentQuestion(data.first_question);
        setTotalQuestions(data.session.total_questions);
        setQuestionIndex(1);
      },
      onError: () => toast({ title: "Error", description: "Failed to start diagnostic", variant: "destructive" }),
    });
  };

  const handleAnswer = () => {
    if (!sessionId || !currentQuestion || !selectedAnswer) return;
    answerMutation.mutate(
      { session_id: sessionId, question_id: currentQuestion.id, answer: selectedAnswer },
      {
        onSuccess: (data) => {
          setSelectedAnswer("");
          if (data.completed) {
            setCompleted(true);
          } else if (data.next_question) {
            setCurrentQuestion(data.next_question);
            setQuestionIndex((i) => i + 1);
          }
        },
        onError: () => toast({ title: "Error", description: "Failed to submit answer", variant: "destructive" }),
      }
    );
  };

  if (completed) {
    return (
      <div className="max-w-lg mx-auto text-center py-16 space-y-6">
        <CheckCircle2 className="h-16 w-16 text-green-500 mx-auto" />
        <h1 className="text-2xl font-bold">Diagnostic Complete!</h1>
        <p className="text-muted-foreground">Your proficiency profile has been generated.</p>
        <div className="flex gap-3 justify-center">
          <Button onClick={() => navigate(`/student/proficiency/${subjectId}`)}>View Proficiency</Button>
          <Button variant="outline" onClick={() => navigate(`/student/plan/${subjectId}`)}>See Learning Plan</Button>
        </div>
      </div>
    );
  }

  if (!sessionId) {
    return (
      <div className="max-w-lg mx-auto text-center py-16 space-y-6">
        <Clock className="h-16 w-16 text-primary mx-auto opacity-60" />
        <h1 className="text-2xl font-bold">Diagnostic Assessment</h1>
        <p className="text-muted-foreground">This adaptive test will assess your current knowledge across all topics. Questions adapt to your performance in real time.</p>
        <Button size="lg" onClick={handleStart} disabled={startMutation.isPending}>
          {startMutation.isPending && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
          Begin Assessment
        </Button>
      </div>
    );
  }

  return (
    <div className="max-w-2xl mx-auto space-y-6">
      <div className="space-y-2">
        <div className="flex justify-between text-sm text-muted-foreground">
          <span>Question {questionIndex} of ~{totalQuestions}</span>
          <Badge variant="outline">{currentQuestion?.difficulty}</Badge>
        </div>
        <Progress value={(questionIndex / totalQuestions) * 100} className="h-2" />
      </div>

      {currentQuestion && (
        <Card>
          <CardHeader>
            <div className="flex items-center gap-2 text-sm text-muted-foreground mb-2">
              <span>{currentQuestion.domain_name}</span>
              <span>·</span>
              <span>{currentQuestion.topic_name}</span>
            </div>
            <CardTitle className="text-lg">{currentQuestion.question_text}</CardTitle>
          </CardHeader>
          <CardContent className="space-y-4">
            {currentQuestion.options && (
              <RadioGroup value={selectedAnswer} onValueChange={setSelectedAnswer}>
                {currentQuestion.options.map((opt, i) => (
                  <div key={i} className="flex items-center space-x-3 rounded-lg border p-3 hover:bg-accent/50 transition-colors">
                    <RadioGroupItem value={opt} id={`opt-${i}`} />
                    <Label htmlFor={`opt-${i}`} className="flex-1 cursor-pointer">{opt}</Label>
                  </div>
                ))}
              </RadioGroup>
            )}
            <Button className="w-full" onClick={handleAnswer} disabled={!selectedAnswer || answerMutation.isPending}>
              {answerMutation.isPending && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
              Submit Answer <ArrowRight className="ml-1 h-4 w-4" />
            </Button>
          </CardContent>
        </Card>
      )}
    </div>
  );
}