from datetime import datetime

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session
from sqlalchemy import func

from app.database import get_db
from app.models.quiz import Quiz
from app.models.question import Question
from app.models.attempt import QuizAttempt, AttemptAnswer
from app.models.pdf_document import PDFDocument
from app.models.user import User
from app.schemas.attempt import (
    AttemptSubmit,
    AttemptResponse,
    AttemptDetail,
    AnswerDetail,
    DashboardStats,
    QuizStats,
)
from app.utils.auth import get_current_user
from app.utils.quiz_questions import get_quiz_questions

router = APIRouter()


@router.post("/start", response_model=AttemptResponse)
def start_attempt(
    quiz_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    quiz = db.query(Quiz).filter(Quiz.id == quiz_id).first()
    if not quiz:
        raise HTTPException(status_code=404, detail="Quiz not found")

    attempt = QuizAttempt(
        quiz_id=quiz_id,
        user_id=current_user.id,
        total_questions=quiz.questions_count,
    )
    db.add(attempt)
    db.commit()
    db.refresh(attempt)
    return AttemptResponse(
        id=attempt.id,
        quiz_id=attempt.quiz_id,
        score=0,
        total_questions=attempt.total_questions,
        percentage=0.0,
        started_at=attempt.started_at,
        completed_at=None,
    )


@router.post("/{attempt_id}/submit", response_model=AttemptDetail)
def submit_attempt(
    attempt_id: int,
    submission: AttemptSubmit,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    attempt = db.query(QuizAttempt).filter(
        QuizAttempt.id == attempt_id,
        QuizAttempt.user_id == current_user.id,
    ).first()
    if not attempt:
        raise HTTPException(status_code=404, detail="Attempt not found")
    if attempt.completed_at:
        raise HTTPException(status_code=400, detail="Attempt already submitted")

    # Get all questions for this quiz via junction table
    questions = {q.id: q for q in get_quiz_questions(db, attempt.quiz_id)}

    score = 0
    submitted = {ans.question_id: ans.user_answer for ans in submission.answers}

    # Save submitted answers
    for ans in submission.answers:
        question = questions.get(ans.question_id)
        if not question:
            continue
        is_correct = ans.user_answer.strip().lower() == question.correct_answer.strip().lower()
        if is_correct:
            score += 1
        db.add(AttemptAnswer(
            attempt_id=attempt_id,
            question_id=ans.question_id,
            user_answer=ans.user_answer,
            is_correct=is_correct,
        ))

    # Build full review — include ALL questions, unanswered marked as incorrect
    answer_details = []
    for q in get_quiz_questions(db, attempt.quiz_id):
        user_answer = submitted.get(q.id, "")
        is_correct = bool(user_answer) and user_answer.strip().lower() == q.correct_answer.strip().lower()
        answer_details.append(AnswerDetail(
            question_id=q.id,
            question_text=q.question_text,
            question_type=q.question_type,
            options=q.options,
            user_answer=user_answer,
            correct_answer=q.correct_answer,
            is_correct=is_correct,
            explanation=q.explanation,
        ))

    attempt.score = score
    attempt.completed_at = datetime.utcnow()
    db.commit()

    percentage = (score / attempt.total_questions * 100) if attempt.total_questions > 0 else 0

    # Update reminder schedule
    try:
        from app.services.reminder_service import update_reminder_schedule
        update_reminder_schedule(db, current_user.id, attempt.quiz_id, percentage)
    except Exception:
        pass  # Don't fail submission if reminder update fails

    return AttemptDetail(
        id=attempt.id,
        quiz_id=attempt.quiz_id,
        score=score,
        total_questions=attempt.total_questions,
        percentage=round(percentage, 1),
        started_at=attempt.started_at,
        completed_at=attempt.completed_at,
        answers=answer_details,
    )


@router.get("/", response_model=list[AttemptResponse])
def list_attempts(
    quiz_id: int | None = None,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    query = db.query(QuizAttempt).filter(QuizAttempt.user_id == current_user.id)
    if quiz_id:
        query = query.filter(QuizAttempt.quiz_id == quiz_id)
    attempts = query.order_by(QuizAttempt.started_at.desc()).all()

    return [
        AttemptResponse(
            id=a.id,
            quiz_id=a.quiz_id,
            score=a.score,
            total_questions=a.total_questions,
            percentage=round((a.score / a.total_questions * 100) if a.total_questions > 0 else 0, 1),
            started_at=a.started_at,
            completed_at=a.completed_at,
        )
        for a in attempts
    ]


@router.get("/history")
def get_quiz_history(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Return per-quiz attempt history for the performance line graph."""
    completed = db.query(QuizAttempt).filter(
        QuizAttempt.user_id == current_user.id,
        QuizAttempt.completed_at.isnot(None),
    ).order_by(QuizAttempt.completed_at).all()

    # Group by quiz
    from collections import defaultdict
    by_quiz: dict = defaultdict(list)
    quiz_titles: dict = {}
    for a in completed:
        pct = round((a.score / a.total_questions * 100) if a.total_questions > 0 else 0, 1)
        by_quiz[a.quiz_id].append({
            "date": a.completed_at.isoformat(),
            "percentage": pct,
            "score": a.score,
            "total": a.total_questions,
        })
        if a.quiz_id not in quiz_titles:
            quiz = db.query(Quiz).filter(Quiz.id == a.quiz_id).first()
            quiz_titles[a.quiz_id] = quiz.title if quiz else f"Quiz {a.quiz_id}"

    return [
        {"quiz_id": qid, "title": quiz_titles[qid], "attempts": attempts}
        for qid, attempts in by_quiz.items()
    ]


@router.get("/stats/dashboard", response_model=DashboardStats)
def get_dashboard_stats(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    total_docs = db.query(PDFDocument).filter(PDFDocument.user_id == current_user.id).count()
    # Count distinct quizzes the user has attempted (not created)
    total_quizzes = db.query(QuizAttempt.quiz_id).filter(
        QuizAttempt.user_id == current_user.id,
        QuizAttempt.completed_at.isnot(None),
    ).distinct().count()

    completed_attempts = db.query(QuizAttempt).filter(
        QuizAttempt.user_id == current_user.id,
        QuizAttempt.completed_at.isnot(None),
    ).all()

    total_attempts = len(completed_attempts)
    avg_score = 0.0
    if completed_attempts:
        scores = [(a.score / a.total_questions * 100) if a.total_questions > 0 else 0 for a in completed_attempts]
        avg_score = round(sum(scores) / len(scores), 1)

    # Per-quiz stats — based on quizzes the user has attempted, not created
    quiz_stats = []
    attempted_quiz_ids = {a.quiz_id for a in completed_attempts}
    quizzes = db.query(Quiz).filter(Quiz.id.in_(attempted_quiz_ids)).all() if attempted_quiz_ids else []
    for quiz in quizzes:
        quiz_attempts = [a for a in completed_attempts if a.quiz_id == quiz.id]
        if quiz_attempts:
            pcts = [(a.score / a.total_questions * 100) if a.total_questions > 0 else 0 for a in quiz_attempts]
            quiz_stats.append(QuizStats(
                quiz_id=quiz.id,
                quiz_title=quiz.title,
                attempts_count=len(quiz_attempts),
                best_score=round(max(pcts), 1),
                latest_score=round(pcts[-1], 1),
                average_score=round(sum(pcts) / len(pcts), 1),
            ))

    return DashboardStats(
        total_documents=total_docs,
        total_quizzes=total_quizzes,
        total_attempts=total_attempts,
        average_score=avg_score,
        quiz_stats=quiz_stats,
    )


@router.get("/{attempt_id}", response_model=AttemptDetail)
def get_attempt(
    attempt_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    attempt = db.query(QuizAttempt).filter(
        QuizAttempt.id == attempt_id,
        QuizAttempt.user_id == current_user.id,
    ).first()
    if not attempt:
        raise HTTPException(status_code=404, detail="Attempt not found")

    # Show ALL questions in review, not just answered ones
    submitted_map = {ans.question_id: ans for ans in attempt.answers}
    answer_details = []
    for q in get_quiz_questions(db, attempt.quiz_id):
        ans = submitted_map.get(q.id)
        answer_details.append(AnswerDetail(
            question_id=q.id,
            question_text=q.question_text,
            question_type=q.question_type,
            options=q.options,
            user_answer=ans.user_answer if ans else "",
            correct_answer=q.correct_answer,
            is_correct=ans.is_correct if ans else False,
            explanation=q.explanation,
        ))

    percentage = (attempt.score / attempt.total_questions * 100) if attempt.total_questions > 0 else 0
    return AttemptDetail(
        id=attempt.id,
        quiz_id=attempt.quiz_id,
        score=attempt.score,
        total_questions=attempt.total_questions,
        percentage=round(percentage, 1),
        started_at=attempt.started_at,
        completed_at=attempt.completed_at,
        answers=answer_details,
    )