"""
Correction API - REST endpoint handlers.

Workflow:
1. Upload: Gescannte Klassenarbeit hochladen
2. OCR: Text aus Handschrift extrahieren
3. Analyse: Antworten analysieren und bewerten
4. Feedback: KI-generiertes Feedback erstellen
5. Export: Korrigierte Arbeit als PDF exportieren
"""

import logging
import uuid
import os
from datetime import datetime
from typing import Dict, Any, Optional
from pathlib import Path

from fastapi import APIRouter, HTTPException, UploadFile, File, BackgroundTasks

from correction_models import (
    CorrectionStatus,
    AnswerEvaluation,
    CorrectionCreate,
    CorrectionUpdate,
    Correction,
    CorrectionResponse,
    AnalysisResponse,
    UPLOAD_DIR,
)
from correction_helpers import (
    corrections_store,
    calculate_grade,
    generate_ai_feedback,
    process_ocr,
    PDFService,
    CorrectionData,
    StudentInfo,
)

logger = logging.getLogger(__name__)

router = APIRouter(
    prefix="/corrections",
    tags=["corrections"],
)


# ============================================================================
# API Endpoints
# ============================================================================

@router.post("/", response_model=CorrectionResponse)
async def create_correction(data: CorrectionCreate):
    """
    Erstellt eine neue Korrektur.

    Noch ohne Datei - diese wird separat hochgeladen.
    """
    correction_id = str(uuid.uuid4())
    now = datetime.utcnow()

    correction = Correction(
        id=correction_id,
        student_id=data.student_id,
        student_name=data.student_name,
        class_name=data.class_name,
        exam_title=data.exam_title,
        subject=data.subject,
        max_points=data.max_points,
        status=CorrectionStatus.UPLOADED,
        created_at=now,
        updated_at=now
    )

    corrections_store[correction_id] = correction
    logger.info(f"Created correction {correction_id} for {data.student_name}")

    return CorrectionResponse(success=True, correction=correction)


@router.post("/{correction_id}/upload", response_model=CorrectionResponse)
async def upload_exam(
    correction_id: str,
    background_tasks: BackgroundTasks,
    file: UploadFile = File(...)
):
    """
    Laedt gescannte Klassenarbeit hoch und startet OCR.

    Unterstuetzte Formate: PDF, PNG, JPG, JPEG
    """
    correction = corrections_store.get(correction_id)
    if not correction:
        raise HTTPException(status_code=404, detail="Korrektur nicht gefunden")

    # Validiere Dateiformat
    allowed_extensions = {".pdf", ".png", ".jpg", ".jpeg"}
    file_ext = Path(file.filename).suffix.lower() if file.filename else ""

    if file_ext not in allowed_extensions:
        raise HTTPException(
            status_code=400,
            detail=f"Ungueltiges Dateiformat. Erlaubt: {', '.join(allowed_extensions)}"
        )

    # Speichere Datei
    file_path = UPLOAD_DIR / f"{correction_id}{file_ext}"

    try:
        content = await file.read()
        with open(file_path, "wb") as f:
            f.write(content)

        correction.file_path = str(file_path)
        correction.updated_at = datetime.utcnow()
        corrections_store[correction_id] = correction

        # Starte OCR im Hintergrund
        background_tasks.add_task(process_ocr, correction_id, str(file_path))

        logger.info(f"Uploaded file for correction {correction_id}: {file.filename}")

        return CorrectionResponse(success=True, correction=correction)

    except Exception as e:
        logger.error(f"Upload error: {e}")
        return CorrectionResponse(success=False, error=str(e))


@router.get("/{correction_id}", response_model=CorrectionResponse)
async def get_correction(correction_id: str):
    """Ruft eine Korrektur ab."""
    correction = corrections_store.get(correction_id)
    if not correction:
        raise HTTPException(status_code=404, detail="Korrektur nicht gefunden")

    return CorrectionResponse(success=True, correction=correction)


@router.get("/", response_model=Dict[str, Any])
async def list_corrections(
    class_name: Optional[str] = None,
    status: Optional[CorrectionStatus] = None,
    limit: int = 50
):
    """Listet Korrekturen auf, optional gefiltert."""
    corrections = list(corrections_store.values())

    if class_name:
        corrections = [c for c in corrections if c.class_name == class_name]

    if status:
        corrections = [c for c in corrections if c.status == status]

    # Sortiere nach Erstellungsdatum (neueste zuerst)
    corrections.sort(key=lambda x: x.created_at, reverse=True)

    return {
        "total": len(corrections),
        "corrections": [c.dict() for c in corrections[:limit]]
    }


@router.post("/{correction_id}/analyze", response_model=AnalysisResponse)
async def analyze_correction(
    correction_id: str,
    expected_answers: Optional[Dict[str, str]] = None
):
    """
    Analysiert die extrahierten Antworten.

    Optional mit Musterloesung fuer automatische Bewertung.
    """
    correction = corrections_store.get(correction_id)
    if not correction:
        raise HTTPException(status_code=404, detail="Korrektur nicht gefunden")

    if correction.status not in [CorrectionStatus.OCR_COMPLETE, CorrectionStatus.ANALYZED]:
        raise HTTPException(
            status_code=400,
            detail=f"Korrektur im falschen Status: {correction.status}"
        )

    if not correction.extracted_text:
        raise HTTPException(status_code=400, detail="Kein extrahierter Text vorhanden")

    try:
        correction.status = CorrectionStatus.ANALYZING
        corrections_store[correction_id] = correction

        # Einfache Analyse ohne LLM
        # Teile Text in Abschnitte (simuliert Aufgabenerkennung)
        text_parts = correction.extracted_text.split('\n\n')
        evaluations = []

        for i, part in enumerate(text_parts[:10], start=1):  # Max 10 Aufgaben
            if len(part.strip()) < 5:
                continue

            # Simulierte Bewertung
            # In Produktion wuerde hier LLM-basierte Analyse stattfinden
            expected = expected_answers.get(str(i), "") if expected_answers else ""

            # Einfacher Textvergleich (in Produktion: semantischer Vergleich)
            is_correct = bool(expected and expected.lower() in part.lower())
            points = correction.max_points / len(text_parts) if text_parts else 0

            evaluation = AnswerEvaluation(
                question_number=i,
                extracted_text=part[:200],  # Kuerzen fuer Response
                points_possible=points,
                points_awarded=points if is_correct else points * 0.5,  # Teilpunkte
                feedback=f"Antwort zu Aufgabe {i}" + (" korrekt." if is_correct else " mit Verbesserungsbedarf."),
                is_correct=is_correct,
                confidence=0.7  # Simulierte Confidence
            )
            evaluations.append(evaluation)

        # Berechne Gesamtergebnis
        total_points = sum(e.points_awarded for e in evaluations)
        percentage = (total_points / correction.max_points * 100) if correction.max_points > 0 else 0
        suggested_grade = calculate_grade(percentage)

        # Generiere Feedback
        ai_feedback = generate_ai_feedback(
            evaluations, total_points, correction.max_points, correction.subject
        )

        # Aktualisiere Korrektur
        correction.evaluations = evaluations
        correction.total_points = total_points
        correction.percentage = percentage
        correction.grade = suggested_grade
        correction.ai_feedback = ai_feedback
        correction.status = CorrectionStatus.ANALYZED
        correction.updated_at = datetime.utcnow()
        corrections_store[correction_id] = correction

        logger.info(f"Analysis complete for {correction_id}: {total_points}/{correction.max_points}")

        return AnalysisResponse(
            success=True,
            evaluations=evaluations,
            total_points=total_points,
            percentage=percentage,
            suggested_grade=suggested_grade,
            ai_feedback=ai_feedback
        )

    except Exception as e:
        logger.error(f"Analysis error: {e}")
        correction.status = CorrectionStatus.ERROR
        corrections_store[correction_id] = correction
        return AnalysisResponse(success=False, error=str(e))


@router.put("/{correction_id}", response_model=CorrectionResponse)
async def update_correction(correction_id: str, data: CorrectionUpdate):
    """
    Aktualisiert eine Korrektur.

    Ermoeglicht manuelle Anpassungen durch die Lehrkraft.
    """
    correction = corrections_store.get(correction_id)
    if not correction:
        raise HTTPException(status_code=404, detail="Korrektur nicht gefunden")

    if data.evaluations is not None:
        correction.evaluations = data.evaluations
        correction.total_points = sum(e.points_awarded for e in data.evaluations)
        correction.percentage = (
            correction.total_points / correction.max_points * 100
        ) if correction.max_points > 0 else 0

    if data.total_points is not None:
        correction.total_points = data.total_points
        correction.percentage = (
            data.total_points / correction.max_points * 100
        ) if correction.max_points > 0 else 0

    if data.grade is not None:
        correction.grade = data.grade

    if data.teacher_notes is not None:
        correction.teacher_notes = data.teacher_notes

    if data.status is not None:
        correction.status = data.status

    correction.updated_at = datetime.utcnow()
    corrections_store[correction_id] = correction

    return CorrectionResponse(success=True, correction=correction)


@router.post("/{correction_id}/complete", response_model=CorrectionResponse)
async def complete_correction(correction_id: str):
    """Markiert Korrektur als abgeschlossen."""
    correction = corrections_store.get(correction_id)
    if not correction:
        raise HTTPException(status_code=404, detail="Korrektur nicht gefunden")

    correction.status = CorrectionStatus.COMPLETED
    correction.updated_at = datetime.utcnow()
    corrections_store[correction_id] = correction

    logger.info(f"Correction {correction_id} completed: {correction.grade}")

    return CorrectionResponse(success=True, correction=correction)


@router.get("/{correction_id}/export-pdf")
async def export_correction_pdf(correction_id: str):
    """
    Exportiert korrigierte Arbeit als PDF.

    Enthaelt:
    - Originalscan
    - Bewertungen
    - Feedback
    - Gesamtergebnis
    """
    correction = corrections_store.get(correction_id)
    if not correction:
        raise HTTPException(status_code=404, detail="Korrektur nicht gefunden")

    try:
        pdf_service = PDFService()

        # Erstelle CorrectionData
        correction_data = CorrectionData(
            student=StudentInfo(
                student_id=correction.student_id,
                name=correction.student_name,
                class_name=correction.class_name
            ),
            exam_title=correction.exam_title,
            subject=correction.subject,
            date=correction.created_at.strftime("%d.%m.%Y"),
            max_points=correction.max_points,
            achieved_points=correction.total_points,
            grade=correction.grade or "",
            percentage=correction.percentage,
            corrections=[
                {
                    "question": f"Aufgabe {e.question_number}",
                    "answer": e.extracted_text,
                    "points": f"{e.points_awarded}/{e.points_possible}",
                    "feedback": e.feedback
                }
                for e in correction.evaluations
            ],
            teacher_notes=correction.teacher_notes or "",
            ai_feedback=correction.ai_feedback or ""
        )

        # Generiere PDF
        pdf_bytes = pdf_service.generate_correction_pdf(correction_data)

        from fastapi.responses import Response

        return Response(
            content=pdf_bytes,
            media_type="application/pdf",
            headers={
                "Content-Disposition": f'attachment; filename="korrektur_{correction.student_name}_{correction.exam_title}.pdf"'
            }
        )

    except Exception as e:
        logger.error(f"PDF export error: {e}")
        raise HTTPException(status_code=500, detail=f"PDF-Export fehlgeschlagen: {str(e)}")


@router.delete("/{correction_id}")
async def delete_correction(correction_id: str):
    """Loescht eine Korrektur."""
    if correction_id not in corrections_store:
        raise HTTPException(status_code=404, detail="Korrektur nicht gefunden")

    correction = corrections_store[correction_id]

    # Loesche auch die hochgeladene Datei
    if correction.file_path and os.path.exists(correction.file_path):
        try:
            os.remove(correction.file_path)
        except Exception as e:
            logger.warning(f"Could not delete file {correction.file_path}: {e}")

    del corrections_store[correction_id]
    logger.info(f"Deleted correction {correction_id}")

    return {"status": "deleted", "id": correction_id}


@router.get("/class/{class_name}/summary")
async def get_class_summary(class_name: str):
    """
    Gibt Zusammenfassung fuer eine Klasse zurueck.

    Enthaelt Statistiken ueber alle Korrekturen der Klasse.
    """
    class_corrections = [
        c for c in corrections_store.values()
        if c.class_name == class_name and c.status == CorrectionStatus.COMPLETED
    ]

    if not class_corrections:
        return {
            "class_name": class_name,
            "total_students": 0,
            "average_percentage": 0,
            "grade_distribution": {},
            "corrections": []
        }

    # Berechne Statistiken
    percentages = [c.percentage for c in class_corrections]
    average_percentage = sum(percentages) / len(percentages) if percentages else 0

    # Notenverteilung
    grade_distribution = {}
    for c in class_corrections:
        grade = c.grade or "?"
        grade_distribution[grade] = grade_distribution.get(grade, 0) + 1

    return {
        "class_name": class_name,
        "total_students": len(class_corrections),
        "average_percentage": round(average_percentage, 1),
        "average_points": round(
            sum(c.total_points for c in class_corrections) / len(class_corrections), 1
        ),
        "grade_distribution": grade_distribution,
        "corrections": [
            {
                "id": c.id,
                "student_name": c.student_name,
                "total_points": c.total_points,
                "percentage": c.percentage,
                "grade": c.grade
            }
            for c in sorted(class_corrections, key=lambda x: x.student_name)
        ]
    }


@router.post("/{correction_id}/ocr/retry", response_model=CorrectionResponse)
async def retry_ocr(correction_id: str, background_tasks: BackgroundTasks):
    """
    Wiederholt OCR-Verarbeitung.

    Nuetzlich wenn erste Verarbeitung fehlgeschlagen ist.
    """
    correction = corrections_store.get(correction_id)
    if not correction:
        raise HTTPException(status_code=404, detail="Korrektur nicht gefunden")

    if not correction.file_path:
        raise HTTPException(status_code=400, detail="Keine Datei vorhanden")

    if not os.path.exists(correction.file_path):
        raise HTTPException(status_code=400, detail="Datei nicht mehr vorhanden")

    # Starte OCR erneut
    correction.status = CorrectionStatus.UPLOADED
    correction.extracted_text = None
    correction.updated_at = datetime.utcnow()
    corrections_store[correction_id] = correction

    background_tasks.add_task(process_ocr, correction_id, correction.file_path)

    return CorrectionResponse(success=True, correction=correction)