# main.py
import os
import uuid
import json
import traceback
import threading
from datetime import datetime
from flask import Flask, request, jsonify
from flask_cors import CORS
import firebase_admin
from firebase_admin import credentials, db, storage, auth

from lesson_gen import (
    fetch_arxiv_papers, generate_knowledge_base,
    generate_lesson_from_knowledge_base, generate_remedial_lesson,
    create_lesson_video, deepgram_tts
)
import logging

# --- Configuration & Initialization ---
app = Flask(__name__)
CORS(app)

try:
    credentials_json_string = os.environ.get("FIREBASE")
    if not credentials_json_string: raise ValueError("FIREBASE env var not set.")
    credentials_json = json.loads(credentials_json_string)
    firebase_db_url = os.environ.get("Firebase_DB")
    firebase_storage_bucket = os.environ.get("Firebase_Storage")
    if not all([firebase_db_url, firebase_storage_bucket]): raise ValueError("Firebase DB/Storage env vars must be set.")
    cred = credentials.Certificate(credentials_json)
    firebase_admin.initialize_app(cred, {'databaseURL': firebase_db_url, 'storageBucket': firebase_storage_bucket})
    logging.info("Firebase Admin SDK initialized successfully for ProfAI.")
except Exception as e:
    logging.fatal(f"FATAL: Error initializing Firebase: {e}")

bucket = storage.bucket()
logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(levelname)s - %(message)s')

# --- Helper Functions & Workers ---
def verify_token(token):
    try: return auth.verify_id_token(token)['uid']
    except Exception as e:
        logging.error(f"Token verification failed: {e}")
        return None

def generation_worker(course_id, user_id, topic, level, goal):
    """Worker for the entire initial course generation process."""
    logging.info(f"WORKER [{course_id}]: Starting for topic '{topic}'.")
    course_ref = db.reference(f'profai_courses/{course_id}')
    try:
        arxiv_docs = fetch_arxiv_papers(topic)
        knowledge_base = generate_knowledge_base(topic, level, goal, arxiv_docs)
        learning_path = knowledge_base.get("learning_path", [])
        course_ref.update({"knowledgeBase": knowledge_base, "learningPath": learning_path})

        first_concept = learning_path[0] if learning_path else "Introduction"
        lesson_content = generate_lesson_from_knowledge_base(knowledge_base, first_concept)
        
        narration_bytes = deepgram_tts(lesson_content['script'])
        if not narration_bytes: raise Exception("TTS failed, cannot proceed.")
        video_bytes = create_lesson_video(lesson_content['script'], narration_bytes)

        blob_name = f"profai_courses/{user_id}/{course_id}/lesson_1.mp4"
        blob = bucket.blob(blob_name)
        blob.upload_from_string(video_bytes, content_type="video/mp4")

        steps = [{
            "step": 1, "type": "video", "concept": first_concept,
            "videoUrl": blob.public_url, "status": "unlocked"
        }, {
            "step": 2, "type": "quiz", "concept": first_concept,
            "quizData": lesson_content['quiz'], "status": "locked"
        }]
        
        course_ref.update({"status": "ready", "steps": steps})
        
        user_ref = db.reference(f'users/{user_id}')
        user_credits = user_ref.child('credits').get()
        user_ref.update({'credits': user_credits - 8})
        logging.info(f"WORKER [{course_id}]: Success. Charged 8 credits.")
    except Exception as e:
        logging.error(f"WORKER [{course_id}]: Failed: {traceback.format_exc()}")
        course_ref.update({"status": "failed", "error": str(e)})

def lesson_worker(course_id, user_id, concept, current_steps, is_remedial=False, regenerate_step_num=None):
    """Worker for generating subsequent, remedial, or regenerated lessons."""
    action = "Regenerating" if regenerate_step_num else "Generating"
    logging.info(f"WORKER [{course_id}]: {action} lesson for concept '{concept}'. Remedial: {is_remedial}")
    course_ref = db.reference(f'profai_courses/{course_id}')
    try:
        knowledge_base = course_ref.child('knowledgeBase').get()
        if not knowledge_base: raise Exception("Knowledge base not found for course.")

        if is_remedial:
            lesson_content = generate_remedial_lesson(concept)
            cost = 5
        else: # Standard or Regenerated lesson
            lesson_content = generate_lesson_from_knowledge_base(knowledge_base, concept)
            cost = 8
        
        narration_bytes = deepgram_tts(lesson_content['script'])
        if not narration_bytes: raise Exception("TTS failed.")
        video_bytes = create_lesson_video(lesson_content['script'], narration_bytes)
        
        step_num = regenerate_step_num if regenerate_step_num else len(current_steps) + 1
        blob_name = f"profai_courses/{user_id}/{course_id}/lesson_{step_num}_{uuid.uuid4().hex[:4]}.mp4"
        blob = bucket.blob(blob_name)
        blob.upload_from_string(video_bytes, content_type="video/mp4")
        
        new_video_step = {
            "step": step_num, "type": "video", "concept": concept,
            "videoUrl": blob.public_url, "status": "unlocked"
        }
        new_quiz_step = {
            "step": step_num + 1, "type": "quiz", "concept": concept,
            "quizData": lesson_content['quiz'], "status": "locked"
        }

        if regenerate_step_num:
            # Replace existing steps
            current_steps[regenerate_step_num - 1] = new_video_step
            if (regenerate_step_num < len(current_steps)) and current_steps[regenerate_step_num]['type'] == 'quiz':
                 current_steps[regenerate_step_num] = new_quiz_step
        else:
            # Append new steps
            current_steps.extend([new_video_step, new_quiz_step])
        
        course_ref.child('steps').set(current_steps)
        
        user_ref = db.reference(f'users/{user_id}')
        user_credits = user_ref.child('credits').get()
        user_ref.update({'credits': user_credits - cost})
        logging.info(f"WORKER [{course_id}]: Lesson '{concept}' processed. Charged {cost} credits.")

    except Exception as e:
        logging.error(f"WORKER [{course_id}]: Lesson generation for '{concept}' failed: {e}")
        # Mark the last unlocked step as failed to signal the frontend
        current_steps[-1]['status'] = 'generation_failed'
        course_ref.child('steps').set(current_steps)

# --- USER AUTHENTICATION (EXPANDED) ---
@app.route('/api/auth/signup', methods=['POST'])
def signup():
    try:
        data = request.get_json()
        email = data.get('email')
        password = data.get('password')
        if not email or not password: return jsonify({'error': 'Email and password are required'}), 400
        user = auth.create_user(email=email, password=password)
        user_ref = db.reference(f'users/{user.uid}')
        user_data = {'email': email, 'credits': 20, 'created_at': datetime.utcnow().isoformat()} # Default credits
        user_ref.set(user_data)
        return jsonify({'success': True, 'user': {'uid': user.uid, **user_data}}), 201
    except Exception as e: return jsonify({'error': str(e)}), 400

@app.route('/api/auth/google-signin', methods=['POST'])
def google_signin():
    try:
        auth_header = request.headers.get('Authorization', '')
        if not auth_header.startswith('Bearer '): return jsonify({'error': 'Missing or invalid token'}), 401
        
        token = auth_header.split(' ')[1]
        decoded_token = auth.verify_id_token(token)
        uid = decoded_token['uid']
        email = decoded_token.get('email')
        
        user_ref = db.reference(f'users/{uid}')
        user_data = user_ref.get()
        if not user_data:
            logging.info(f"New user signed in with Google: {email}, UID: {uid}. Creating profile.")
            user_data = {'email': email, 'credits': 20, 'created_at': datetime.utcnow().isoformat()}
            user_ref.set(user_data)
        else:
            logging.info(f"Existing user signed in with Google: {email}, UID: {uid}.")
            
        return jsonify({'success': True, 'user': {'uid': uid, **user_data}}), 200
    except Exception as e:
        logging.error(f"Google Sign-in failed: {traceback.format_exc()}")
        return jsonify({'error': str(e)}), 400

# --- ProfAI CRUD ENDPOINTS ---
@app.route('/api/profai/courses', methods=['GET'])
def get_user_courses():
    """Lists all courses created by the authenticated user."""
    try:
        token = request.headers.get('Authorization', '').split(' ')[1]
        uid = verify_token(token)
        if not uid: return jsonify({'error': 'Unauthorized'}), 401

        courses_ref = db.reference('profai_courses')
        user_courses = courses_ref.order_by_child('uid').equal_to(uid).get()
        
        if not user_courses: return jsonify([]), 200

        # Convert dict to a list sorted by creation date
        courses_list = sorted(user_courses.values(), key=lambda x: x.get('createdAt', ''), reverse=True)
        return jsonify(courses_list), 200
    except Exception as e:
        return jsonify({'error': str(e)}), 500

@app.route('/api/profai/start-course', methods=['POST'])
def start_course():
    try:
        token = request.headers.get('Authorization', '').split(' ')[1]
        uid = verify_token(token)
        if not uid: return jsonify({'error': 'Unauthorized'}), 401
        
        user_credits = db.reference(f'users/{uid}/credits').get()
        if not isinstance(user_credits, (int, float)) or user_credits < 8:
            return jsonify({'error': 'Insufficient credits. Requires 8 credits to start a new course.'}), 402

        data = request.get_json()
        topic, level, goal = data.get('topic'), data.get('level'), data.get('goal')
        if not all([topic, level, goal]):
            return jsonify({'error': 'topic, level, and goal are required'}), 400

        course_id = uuid.uuid4().hex
        course_data = {
            'id': course_id, 'uid': uid, 'topic': topic,
            'status': 'generating', 'createdAt': datetime.utcnow().isoformat(),
        }
        db.reference(f'profai_courses/{course_id}').set(course_data)

        thread = threading.Thread(target=generation_worker, args=(course_id, uid, topic, level, goal))
        thread.daemon = True
        thread.start()

        return jsonify({'success': True, 'message': 'Your personalized course is being generated!', 'courseId': course_id}), 202
    except Exception as e:
        return jsonify({'error': str(e)}), 500

@app.route('/api/profai/course-status/<string:course_id>', methods=['GET'])
def get_course_status(course_id):
    try:
        token = request.headers.get('Authorization', '').split(' ')[1]
        uid = verify_token(token)
        if not uid: return jsonify({'error': 'Unauthorized'}), 401

        course_data = db.reference(f'profai_courses/{course_id}').get()
        if not course_data or course_data.get('uid') != uid:
            return jsonify({'error': 'Course not found or unauthorized'}), 404
        
        return jsonify(course_data), 200
    except Exception as e:
        return jsonify({'error': str(e)}), 500

@app.route('/api/profai/courses/<string:course_id>', methods=['DELETE'])
def delete_course(course_id):
    """Deletes a course and all associated videos from storage."""
    try:
        token = request.headers.get('Authorization', '').split(' ')[1]
        uid = verify_token(token)
        if not uid: return jsonify({'error': 'Unauthorized'}), 401

        course_ref = db.reference(f'profai_courses/{course_id}')
        course_data = course_ref.get()
        if not course_data or course_data.get('uid') != uid:
            return jsonify({'error': 'Course not found or unauthorized'}), 404
        
        # Delete associated files from Firebase Storage
        storage_prefix = f"profai_courses/{uid}/{course_id}/"
        blobs_to_delete = bucket.list_blobs(prefix=storage_prefix)
        for blob in blobs_to_delete:
            logging.info(f"Deleting file from storage: {blob.name}")
            blob.delete()
            
        # Delete course record from database
        course_ref.delete()
        logging.info(f"Deleted course {course_id} for user {uid}")
        
        return jsonify({'success': True, 'message': 'Course deleted successfully.'}), 200
    except Exception as e:
        return jsonify({'error': str(e)}), 500

@app.route('/api/profai/courses/<string:course_id>/steps/<int:step_num>/regenerate', methods=['POST'])
def regenerate_step(course_id, step_num):
    """Regenerates a specific lesson video and its quiz."""
    try:
        token = request.headers.get('Authorization', '').split(' ')[1]
        uid = verify_token(token)
        if not uid: return jsonify({'error': 'Unauthorized'}), 401
        
        user_credits = db.reference(f'users/{uid}/credits').get()
        if user_credits < 8: return jsonify({'error': 'Insufficient credits. Regeneration requires 8 credits.'}), 402

        course_ref = db.reference(f'profai_courses/{course_id}')
        course_data = course_ref.get()
        if not course_data or course_data.get('uid') != uid:
            return jsonify({'error': 'Course not found or unauthorized'}), 404

        steps = course_data.get('steps', [])
        if not (0 < step_num <= len(steps) and steps[step_num - 1]['type'] == 'video'):
            return jsonify({'error': 'Invalid step number. You can only regenerate video steps.'}), 400

        concept_to_regenerate = steps[step_num - 1]['concept']
        steps[step_num - 1]['status'] = 'regenerating' # Update UI state
        course_ref.child('steps').set(steps)

        thread = threading.Thread(target=lesson_worker, args=(course_id, uid, concept_to_regenerate, steps, False, step_num))
        thread.daemon = True
        thread.start()
        
        return jsonify({'success': True, 'message': f"Regenerating lesson for '{concept_to_regenerate}'."}), 202
    except Exception as e:
        return jsonify({'error': str(e)}), 500

@app.route('/api/profai/submit-quiz/<string:course_id>', methods=['POST'])
def submit_quiz(course_id):
    try:
        token = request.headers.get('Authorization', '').split(' ')[1]
        uid = verify_token(token)
        if not uid: return jsonify({'error': 'Unauthorized'}), 401
        
        data = request.get_json()
        answers = data.get('answers', {})
        
        course_ref = db.reference(f'profai_courses/{course_id}')
        course_data = course_ref.get()
        if not course_data or course_data.get('uid') != uid:
            return jsonify({'error': 'Course not found'}), 404
        
        steps = course_data.get('steps', [])
        learning_path = course_data.get('learningPath', [])
        
        quiz_step_index = next((i for i, step in enumerate(steps) if step.get('status') == 'unlocked' and step.get('type') == 'quiz'), -1)
        if quiz_step_index == -1: return jsonify({'error': 'No active quiz found'}), 400

        quiz_data = steps[quiz_step_index]['quizData']
        correct_count = sum(1 for q in quiz_data if answers.get(q['question']) == q['answer'])
        score = correct_count / len(quiz_data)
        
        steps[quiz_step_index]['status'] = 'completed'
        next_action_message = ""

        if score > 0.6: # Pass
            user_credits = db.reference(f'users/{uid}/credits').get()
            if user_credits < 8: return jsonify({'error': 'Insufficient credits for next lesson (requires 8).'}), 402

            last_concept = steps[quiz_step_index]['concept']
            try:
                next_concept_index = learning_path.index(last_concept) + 1
                if next_concept_index < len(learning_path):
                    next_concept = learning_path[next_concept_index]
                    thread = threading.Thread(target=lesson_worker, args=(course_id, uid, next_concept, steps, False))
                    thread.daemon = True
                    thread.start()
                    next_action_message = f"Passed! Generating your next lesson on '{next_concept}'."
                else:
                    steps.append({"step": len(steps) + 1, "type": "course_complete", "status": "unlocked"})
                    next_action_message = "Congratulations! You've completed the course."
            except (ValueError, IndexError):
                return jsonify({'error': 'Could not determine the next lesson step.'}), 500
        else: # Struggle
            user_credits = db.reference(f'users/{uid}/credits').get()
            if user_credits < 5: return jsonify({'error': 'Insufficient credits for remedial lesson (requires 5).'}), 402
            
            failed_concept = steps[quiz_step_index]['concept']
            thread = threading.Thread(target=lesson_worker, args=(course_id, uid, failed_concept, steps, True))
            thread.daemon = True
            thread.start()
            next_action_message = f"Let's review. Generating a remedial lesson on '{failed_concept}'."

        course_ref.child('steps').set(steps)
        return jsonify({'success': True, 'score': score, 'message': next_action_message}), 202

    except Exception as e:
        return jsonify({'error': str(e)}), 500

# --- Main Execution ---
if __name__ == '__main__':
    port = int(os.environ.get("PORT", 7860))
    app.run(debug=True, host="0.0.0.0", port=port)