generation/ExamAnswer.py

import logging
from datetime import datetime
from typing import List, Dict, Any 
from celery import shared_task
import json
import re
import httpx

from generation.answer_models import (ExamSubmission,ExamResult,StudentAnswer,GradedAnswer,QuestionType)
from indexing.indexingController import IndexingController
from stores.llm.LLMProviderFactory import LLMProviderFactory
from config import get_settings


def calculate_grade(percentage: float) -> str:
    if percentage >= 90:
        return "A"
    elif percentage >= 80:
        return "B"
    elif percentage >= 70:
        return "C"
    elif percentage >= 60:
        return "D"
    else:
        return "F"


logger = logging.getLogger(__name__)

class ExamGradingService:
    def __init__(self, use_ai_for_essays: bool = True):
        self.use_ai_for_essays = use_ai_for_essays
        
        config = get_settings()
        
        factory = LLMProviderFactory(config)
        provider = factory.create(config.GENERATION_BACKEND)
        provider.set_generation_model(config.GENERATION_MODEL_ID)
        self.llm = provider

        self.semantic_threshold = 0.65
        self.high_confidence = 0.85

    def grade_submission(self, submission: ExamSubmission) -> ExamResult:
        graded_answers: List[GradedAnswer] = []
        total_score = 0
        max_total_score = 0

        for ans in submission.answers:
            correct_answer = None
            if ans.metadata:
                correct_answer = ans.metadata.get("correct_answer")

            graded = self.grade_answer(ans, correct_answer,submission.course_id)
            graded_answers.append(graded)
            total_score += graded.score
            max_total_score += graded.max_score

        percentage = (total_score / max_total_score) * 100 if max_total_score else 0
        grade = calculate_grade(percentage)

        return ExamResult(
            exam_id=submission.exam_id,
            student_id=submission.student_id,
            student_name=submission.student_name,
            graded_answers=graded_answers,
            total_score=total_score,
            max_total_score=max_total_score,
            percentage=percentage,
            grade=grade,
            feedback_summary="RAG based grading using LLM evaluation",
            submission_time=submission.submission_time,
            graded_time=datetime.utcnow().isoformat()
        )

    def grade_answer(self, answer: StudentAnswer, correct_answer: Any, course) -> GradedAnswer:
        if answer.question_type in [QuestionType.MULTIPLE_CHOICE,QuestionType.TRUE_FALSE]:
            student_str = str(answer.student_response).strip().lower()
            if answer.question_type == QuestionType.TRUE_FALSE:    
                if isinstance(correct_answer, bool):
                    correct_bool = correct_answer
                elif isinstance(correct_answer, str):
                    correct_bool = correct_answer.lower() in ['true', 't', '1', 'yes', 'True']
                else:
                    correct_bool = bool(correct_answer)    
                student_bool = student_str in ['true', 't', '1', 'yes']  
                is_correct = student_bool == correct_bool
                score = answer.max_score if is_correct else 0
                feedback = "Exact match grading" 
            else:  # multiple_choice
                correct_str = str(correct_answer).strip().lower() if correct_answer else ""
                is_correct = student_str == correct_str
                score = answer.max_score if is_correct else 0
                feedback = "Exact match grading"
        else:
            if self.use_ai_for_essays and correct_answer:
                score, feedback = self.ai_semantic_grade(
                    answer.question_text,
                    answer.student_response,
                    correct_answer,
                    answer.max_score,
                    course=course
                )
                is_correct = score >= (answer.max_score * self.semantic_threshold)
            else:
                similarity = self.simple_similarity(
                    answer.student_response,
                    correct_answer
                )
                score = similarity * answer.max_score
                is_correct = similarity >= self.semantic_threshold
                feedback = f"Similarity score {similarity:.2f}"

        return GradedAnswer(
            question_no=answer.question_no,
            question_type=answer.question_type,
            question_text=answer.question_text,
            student_response=answer.student_response,
            correct_answer=correct_answer,
            score=score,
            max_score=answer.max_score,
            feedback=feedback,
            is_correct=is_correct
        )

    def simple_similarity(self, student: str, correct: str) -> float:
        if not student or not correct:
            return 0
        student_words = set(student.lower().split())
        correct_words = set(correct.lower().split())
        intersection = student_words.intersection(correct_words)
        union = student_words.union(correct_words)
        return len(intersection) / len(union)

    def retrieve_context(self, question: str, course:str):
        """
        Retrieve relevant context from Qdrant for a given question filtered by course
        Args:   question: The question text to embed and search for // course: Optional course filter        
        Returns:            String containing concatenated context from top 3 chunks
        """
        try:
            controller = IndexingController()
            embedding = controller.embedder.embed_text(question)
            
            # Build metadata filters course 
            filters = []
            if course:
                filters.append({
                    "field": "course", 
                    "op": "eq", 
                    "value": course, 
                    "clause": "must"
                })
            
            # Query Qdrant with filters
            results = controller.vector_store.query_qdrant(embedding=embedding,filters=filters,top_k=5)
            
            context = "\n".join(r["content"] for r in results if r.get("content"))
            
            logger.info(f"Retrieved {len(results)} chunks for question (filtered by course={course})")
            return context

        except Exception as e:
            logger.error(f"Context retrieval failed: {e}")
            return ""

    def build_prompt(self, question, student_answer, correct_answer, context):
        return f"""
You are an academic exam grader.

Question:
{question}

Correct Answer:
{correct_answer}

Reference Material:
{context}

Student Answer:
{student_answer}

Evaluate the student answer using semantic similarity.
You may slightly use your knowledge if correct answer not in Reference Material.

Return JSON only:

{{
"score": number between 0 and 1,
"feedback": short explanation
}}
"""

    def parse_llm_output(self, text: str):
        try:
            if isinstance(text, dict):
                if 'response' in text:
                    text = text['response']
                else:
                    text = str(text)
            elif hasattr(text, 'content'):
                text = text.content
            elif hasattr(text, 'text'):
                text = text.text          
            text = str(text).strip()
            if not text:
                return 0, "Empty response from LLM"
            text = re.sub(r'```json\s*|\s*```', '', text)
            try:
                data = json.loads(text)
            except json.JSONDecodeError:
                json_match = re.search(r'\{.*\}', text, re.DOTALL)
                if json_match:
                    data = json.loads(json_match.group())
                else:
                    raise
            
            score = float(data.get("score", 0))
            feedback = data.get("feedback", "") 
            score = max(0, min(score, 1))
            return score, feedback  
        
        except Exception as e:
            logger.error(f"Failed to parse LLM output: {e}, text type: {type(text)}")
            return 0, "Failed to parse AI grading"

    def ai_semantic_grade(self, question, student, correct, max_score, course):
        """
        Grade an answer using AI with context from Qdrant.
        Args: question: The question text // student: Student's answer // correct: Correct answer
            max_score: Maximum score for this question // course: Optional course for filtering context
        Returns: // Tuple of (score, feedback)
        """
        try:
            # Retrieve context filtered by username and course
            context = self.retrieve_context(question, course)
            
            prompt = self.build_prompt(question,student,correct,context)
            
            response = self.llm.generate_text(prompt)
            
            # Log response type for debugging
            logger.info(f"Response type: {type(response)}")
            
            score_ratio, feedback = self.parse_llm_output(response)
            score = score_ratio * max_score
            
            return score, feedback
            
        except Exception as e:
            logger.error(f"AI grading failed: {e}")
            # Fallback to simple similarity
            similarity = self.simple_similarity(student, correct)
            return similarity * max_score, f"Fallback similarity grading: {similarity:.2f}"

@shared_task
def grade_exam_task(submission_dict: Dict[str, Any]):
    submission = None
    try:
        submission = ExamSubmission(**submission_dict)
        service = ExamGradingService()
        result = service.grade_submission(submission)
        result_dict = result.model_dump()

        # Send webhook with grade only
        try:
            webhook_url = get_settings().GRADE_WEBHOOK_URL
            print(f" Webhook URL: {webhook_url}")
            
            if webhook_url:                
                # Create grade-only payload
                grade_only_payload = {
                    "status": "completed",
                    "exam_id": submission.exam_id,
                    "student_id": submission.student_id,
                    "course_id":submission.course_id,
                    "grade": {
                        "total_score": result_dict['total_score'],
                        "max_total_score": result_dict['max_total_score'],
                        "percentage": result_dict['percentage'],
                        "grade": result_dict['grade'],
                        "graded_time": result_dict['graded_time']
                    },
                    "result" : result_dict,
                }
                
                response = httpx.post(
                    webhook_url,
                    json=grade_only_payload,
                    timeout=30.0
                )
                print(f" Response status: {response.status_code}")
                
                if response.status_code == 200:
                    print(" Grade-only webhook sent successfully!")
                else:
                    print(f" Webhook returned status: {response.status_code}")
                    print(f" Response: {response.text[:200]}")
            else:
                print("WEBHOOK_URL is empty or not set!")
                
        except Exception as e:
            print(f" Webhook error: {type(e).__name__}: {e}")
            import traceback
            traceback.print_exc()
        
        print(" Task completed successfully")
        return result_dict
        
    except Exception as e:
        print(f" ERROR in task: {type(e).__name__}: {e}")
        import traceback
        traceback.print_exc()
        raise