import os
import json
import random
import chromadb
import math # ✅ Add the math library for ceiling division
from fastapi import FastAPI, HTTPException, Depends, Query, UploadFile, File
from pydantic import BaseModel, Field
from typing import List, Optional
import firebase_admin
from firebase_admin import credentials, firestore

# --- Local Imports ---
from encoder import SentenceEncoder
from populate_chroma import populate_vector_db
from llm_handler import (
    initialize_llm, get_rag_response, create_chat_session, 
    clear_chat_session, delete_chat_session, get_chat_history,
    get_chat_session_count, clear_all_chat_sessions
)
import llm_handler
from resume_scanner import resume_scanner

# --------------------------------------------------------------------
# Cache & Root Path Setup
# --------------------------------------------------------------------
os.environ["HF_HOME"] = "/data/cache"
os.environ["SENTENCE_TRANSFORMERS_HOME"] = "/data/cache"
root_path = os.getenv("HF_SPACE_ROOT_PATH", "")

# --------------------------------------------------------------------
# Pydantic Models
# --------------------------------------------------------------------
class UserProfile(BaseModel):
    skills: List[str] = Field(..., example=["python", "data analysis"])
    internshipType: str = Field(..., example="Work from Home")

class SearchQuery(BaseModel):
    query: str = Field(..., example="marketing internship in mumbai")

class InternshipData(BaseModel):
    id: str = Field(..., example="int_021")
    title: str
    description: str
    skills: List[str]
    duration: int
    createdAt: str
    stipend: int = None

class SimpleRecommendation(BaseModel):
    internship_id: str
    score: float

class RecommendationResponse(BaseModel):
    recommendations: List[SimpleRecommendation]

class StatusResponse(BaseModel):
    status: str
    internship_id: str

# --- ✅ UPDATED CHAT MODELS ---
class ChatMessage(BaseModel):
    query: str
    session_id: Optional[str] = Field(None, description="Chat session ID (optional - will be auto-created if not provided)")

class ChatResponse(BaseModel):
    response: str
    session_id: str
    is_new_session: bool = Field(default=False, description="True if this was a new session created automatically")

class NewChatSessionResponse(BaseModel):
    session_id: str
    message: str

class ChatHistoryResponse(BaseModel):
    session_id: str
    history: List[dict]

class ClearChatResponse(BaseModel):
    session_id: str
    message: str

class MasterClearResponse(BaseModel):
    message: str
    sessions_cleared: int
    timestamp: str

# --- ✅ RESUME SCANNER MODELS ---
class ResumeExtractionResponse(BaseModel):
    extracted_text: str = Field(..., description="Full extracted text from resume")
    cleaned_text: str = Field(..., description="Cleaned text optimized for search")
    file_info: dict = Field(..., description="File metadata")
    recommendations: List[SimpleRecommendation] = Field(..., description="Internship recommendations")

# --------------------------------------------------------------------
# FastAPI App
# --------------------------------------------------------------------
app = FastAPI(
    title="Internship Recommendation & Chatbot API with Resume Scanner",
    description="An API using Firestore for metadata, ChromaDB for vector search, LLM chatbot with memory, and AI-powered resume analysis.",
    version="4.0.0",
    root_path=root_path
)

# --------------------------------------------------------------------
# Firebase Initialization
# --------------------------------------------------------------------
db = None
try:
    firebase_creds = os.getenv("FIREBASE_CREDS_JSON")
    if firebase_creds:
        creds_dict = json.loads(firebase_creds)
        cred = credentials.Certificate(creds_dict)
        if not firebase_admin._apps:
            firebase_admin.initialize_app(cred)
        db = firestore.client()
        print("✅ Firebase initialized with Hugging Face secret.")
    else:
        raise Exception("FIREBASE_CREDS_JSON not found")
except Exception as e:
    print(f"❌ Could not initialize Firebase: {e}")

def get_db():
    if db is None:
        raise HTTPException(status_code=503, detail="Firestore connection not available.")
    return db

# --------------------------------------------------------------------
# Global Variables (encoder + chroma)
# --------------------------------------------------------------------
encoder = None
chroma_collection = None

@app.on_event("startup")
def load_model_and_data():
    global encoder, chroma_collection
    print("🚀 Loading sentence encoder model...")
    encoder = SentenceEncoder()
    chroma_db_path = "/data/chroma_db"
    try:
        client = chromadb.PersistentClient(path=chroma_db_path)
        chroma_collection = client.get_or_create_collection(name="internships")
        print("✅ ChromaDB client initialized and collection is ready.")
        print(f"   - Internships in DB: {chroma_collection.count()}")
        llm_handler.encoder = encoder
        llm_handler.chroma_collection = chroma_collection
        initialize_llm()
    except Exception as e:
        print(f"❌ Error initializing ChromaDB or LLM: {e}")
        raise

# --------------------------------------------------------------------
# Existing Endpoints
# --------------------------------------------------------------------
@app.get("/")
def read_root():
    return {"message": "Welcome to the Internship Recommendation API with Chat Memory and Resume Scanner!"}

# --------------------------------------------------------------------
# ✅ NEW RESUME CONTENT EXTRACTOR ENDPOINT
# --------------------------------------------------------------------

@app.post("/resume-content-extractor", response_model=ResumeExtractionResponse)
async def extract_resume_and_search(file: UploadFile = File(...)):
    """
    Upload resume and get internship recommendations.
    
    This endpoint:
    1. Extracts text from resume (PDF, DOC, DOCX, TXT, Images)
    2. Cleans and optimizes the text for search
    3. Automatically uses the content for internship matching
    4. Returns both extracted content and recommendations
    """
    if chroma_collection is None or encoder is None:
        raise HTTPException(status_code=503, detail="Server is not ready.")
    
    # Validate file
    if file.size and file.size > 10 * 1024 * 1024:
        raise HTTPException(status_code=413, detail="File too large. Maximum size is 10MB.")
    
    allowed_extensions = ['pdf', 'doc', 'docx', 'txt', 'jpg', 'jpeg', 'png', 'bmp', 'tiff']
    file_ext = file.filename.lower().split('.')[-1] if file.filename else ''
    
    if file_ext not in allowed_extensions:
        raise HTTPException(
            status_code=400, 
            detail=f"Unsupported file type. Supported: {', '.join(allowed_extensions)}"
        )
    
    try:
        # Extract text from resume
        file_content = await file.read()
        print(f"📄 Processing resume: {file.filename} ({len(file_content)} bytes)")
        
        extracted_text = resume_scanner.extract_text_from_file(file_content, file.filename)
        if not extracted_text.strip():
            raise HTTPException(status_code=400, detail="Could not extract text from the uploaded file.")
        
        # Clean text for better search
        cleaned_text = resume_scanner.clean_extracted_text(extracted_text)
        print(f"📝 Extracted {len(extracted_text)} chars, cleaned to {len(cleaned_text)} chars")
        
        # Use the cleaned text for search (internal call to search logic)
        query_embedding = encoder.encode([cleaned_text])[0].tolist()
        results = chroma_collection.query(
            query_embeddings=[query_embedding], 
            n_results=random.randint(5, 7)  # Match your existing search logic
        )
        
        # Process results (same as your existing search logic)
        recommendations = []
        ids = results.get('ids', [[]])[0]
        distances = results.get('distances', [[]])[0]
        
        for i, internship_id in enumerate(ids):
            recommendations.append({
                "internship_id": internship_id,
                "score": 1 - distances[i]
            })
        
        print(f"✅ Found {len(recommendations)} recommendations for resume")
        
        return ResumeExtractionResponse(
            extracted_text=extracted_text,
            cleaned_text=cleaned_text,
            file_info={
                "filename": file.filename,
                "file_size": len(file_content),
                "file_type": file_ext,
                "text_length": len(extracted_text)
            },
            recommendations=recommendations
        )
        
    except HTTPException:
        raise
    except Exception as e:
        print(f"❌ Error processing resume: {str(e)}")
        raise HTTPException(status_code=500, detail=f"Error processing resume: {str(e)}")

@app.post("/setup")
def run_initial_setup(secret_key: str = Query(..., example="your_secret_password")):
    correct_key = os.getenv("SETUP_SECRET_KEY")
    if not correct_key or secret_key != correct_key:
        raise HTTPException(status_code=403, detail="Invalid secret key.")
    try:
        print("--- RUNNING DATABASE POPULATION SCRIPT ---")
        populate_vector_db()
        print("--- SETUP COMPLETE ---")
        return {"status": "Setup completed successfully."}
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"An error occurred during setup: {str(e)}")

@app.post("/add-internship", response_model=StatusResponse)
def add_internship(internship: InternshipData, db_client: firestore.Client = Depends(get_db)):
    if chroma_collection is None or encoder is None:
        raise HTTPException(status_code=503, detail="Server is not ready.")
    doc_ref = db_client.collection('internships').document(internship.id)
    if doc_ref.get().exists:
        raise HTTPException(status_code=400, detail="Internship ID already exists.")
    doc_ref.set(internship.dict())
    text_to_encode = f"{internship.title}. {internship.description}. Skills: {', '.join(internship.skills)}"
    embedding = encoder.encode([text_to_encode])[0].tolist()
    metadata_for_chroma = internship.dict()
    metadata_for_chroma['skills'] = json.dumps(metadata_for_chroma['skills'])
    chroma_collection.add(ids=[internship.id], embeddings=[embedding], metadatas=[metadata_for_chroma])
    print(f"✅ Added internship to Firestore and ChromaDB: {internship.id}")
    return {"status": "success", "internship_id": internship.id}

@app.post("/profile-recommendations", response_model=RecommendationResponse)
def get_profile_recommendations(profile: UserProfile):
    if chroma_collection is None or encoder is None:
        raise HTTPException(status_code=503, detail="Server is not ready.")

    query_text = f"Skills: {', '.join(profile.skills)}. Internship Type: {profile.internshipType}"
    query_embedding = encoder.encode([query_text])[0].tolist()
    
    results = chroma_collection.query(
        query_embeddings=[query_embedding], 
        n_results=random.randint(5, 7) # Get 5 to 7 results
    )
    
    recommendations = []
    ids = results.get('ids', [[]])[0]
    distances = results.get('distances', [[]])[0]
    
    for i, internship_id in enumerate(ids):
        recommendations.append({
            "internship_id": internship_id,
            "score": 1 - distances[i]
        })
        
    return {"recommendations": recommendations}

@app.post("/search", response_model=RecommendationResponse)
def search_internships(search: SearchQuery):
    if chroma_collection is None or encoder is None:
        raise HTTPException(status_code=503, detail="Server is not ready.")
        
    query_embedding = encoder.encode([search.query])[0].tolist()
    
    results = chroma_collection.query(
        query_embeddings=[query_embedding], 
        n_results=random.randint(3, 5) # Get 3 to 5 results
    )
    
    recommendations = []
    ids = results.get('ids', [[]])[0]
    distances = results.get('distances', [[]])[0]
    
    for i, internship_id in enumerate(ids):
        recommendations.append({
            "internship_id": internship_id,
            "score": 1 - distances[i]
        })
            
    return {"recommendations": recommendations}

# --------------------------------------------------------------------
# ✅ CHAT ENDPOINTS WITH MEMORY
# --------------------------------------------------------------------

@app.post("/chat/new-session", response_model=NewChatSessionResponse)
def create_new_chat_session():
    """Create a new chat session."""
    session_id = create_chat_session()
    return {
        "session_id": session_id,
        "message": "New chat session created successfully"
    }

@app.post("/chat", response_model=ChatResponse)
def chat_with_bot(message: ChatMessage):
    """
    Chat with the bot. Automatically creates a session if none provided.
    
    - If session_id is not provided: Creates a new session automatically
    - If session_id is provided but doesn't exist: Creates a new session with that ID
    - If session_id exists: Continues the existing conversation
    """
    print(f"📨 Received chat request:")
    print(f"   Query: {message.query}")
    print(f"   Session ID: {message.session_id}")
    
    try:
        is_new_session = message.session_id is None or message.session_id == ""
        
        response, session_id = get_rag_response(message.query, message.session_id)
        
        print(f"📤 Sending response:")
        print(f"   Session ID: {session_id}")
        print(f"   Is New Session: {is_new_session}")
        print(f"   Response: {response[:100]}...")
        
        return {
            "response": response,
            "session_id": session_id,
            "is_new_session": is_new_session
        }
    except Exception as e:
        print(f"❌ Error in chat endpoint: {str(e)}")
        raise HTTPException(status_code=500, detail=f"Error processing chat: {str(e)}")

@app.get("/chat/{session_id}/history", response_model=ChatHistoryResponse)
def get_session_history(session_id: str):
    """Get the chat history for a specific session."""
    history = get_chat_history(session_id)
    if history is None:
        raise HTTPException(status_code=404, detail="Chat session not found")
    return {
        "session_id": session_id,
        "history": history
    }

@app.delete("/chat/{session_id}/clear", response_model=ClearChatResponse)
def clear_session_history(session_id: str):
    """Clear the chat history for a specific session."""
    success = clear_chat_session(session_id)
    if not success:
        raise HTTPException(status_code=404, detail="Chat session not found")
    return {
        "session_id": session_id,
        "message": "Chat history cleared successfully"
    }

@app.delete("/chat/{session_id}/delete", response_model=ClearChatResponse)
def delete_session(session_id: str):
    """
    Delete a chat session completely.
    
    ⭐ RECOMMENDED: Call this when user closes the chatbot to free up memory.
    This helps keep the server efficient by cleaning up unused sessions.
    """
    success = delete_chat_session(session_id)
    if not success:
        raise HTTPException(status_code=404, detail="Chat session not found")
    print(f"🗑️ Session deleted by user: {session_id}")
    return {
        "session_id": session_id,
        "message": "Chat session deleted successfully"
    }

@app.delete("/chat/sessions/clear-all", response_model=MasterClearResponse)
def clear_all_sessions(secret_key: str = Query(..., example="your_admin_secret")):
    """
    🚨 MASTER ENDPOINT: Clear all chat sessions at once.
    
    This endpoint requires an admin secret key and will:
    - Clear ALL active chat sessions
    - Free up memory immediately
    - Useful for maintenance and preventing memory bloating
    
    ⚠️ WARNING: This will terminate all ongoing conversations!
    """
    # Check admin secret key
    admin_secret = os.getenv("ADMIN_SECRET_KEY")
    if not admin_secret or secret_key != admin_secret:
        raise HTTPException(status_code=403, detail="Invalid admin secret key.")
    
    from datetime import datetime
    
    sessions_cleared = clear_all_chat_sessions()
    timestamp = datetime.now().isoformat()
    
    return {
        "message": f"Successfully cleared all chat sessions. Memory freed.",
        "sessions_cleared": sessions_cleared,
        "timestamp": timestamp
    }

@app.get("/chat/sessions/count")
def get_active_sessions():
    """Get the number of active chat sessions."""
    count = get_chat_session_count()
    return {
        "active_sessions": count,
        "message": f"There are {count} active chat sessions",
        "memory_status": "healthy" if count <= 15 else "high_usage"
    }

# Health check endpoint
@app.get("/healthz")
def health_check():
    status = {
        "status": "healthy",
        "encoder_ready": encoder is not None,
        "chroma_ready": chroma_collection is not None,
        "firebase_ready": db is not None,
        "active_chat_sessions": get_chat_session_count()
    }
    return status