backend/main.py

from fastapi import FastAPI, HTTPException, WebSocket, WebSocketDisconnect
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles
import time
import os
import re
import asyncio
import base64
from datetime import datetime
from typing import List, Optional, Any
from pydantic import BaseModel
from dotenv import load_dotenv

# LangChain / Google GenAI imports
from langchain_google_genai import ChatGoogleGenerativeAI
from langchain_core.messages import HumanMessage, SystemMessage, AIMessage

load_dotenv()

app = FastAPI(title="Socratic Sentiment Chatbot API")

# Enable CORS for frontend integration
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Pydantic Schemas
class ChatMessage(BaseModel):
    role: str  # "user" or "assistant"
    content: str

class ChatRequest(BaseModel):
    message: str
    gemini_api_key: Optional[str] = None
    history: Optional[List[ChatMessage]] = None

class ChatResponse(BaseModel):
    sentiment: str
    response: str
    latency: float
    prompt_context: str
    tokens: int
    cost: float

# Token estimation helper (using standard ~4 characters per token multiplier for English)
def estimate_tokens(text: str) -> int:
    return max(1, int(len(text) / 4.0))

# Cost calculation helper
def calculate_cost(input_tokens: int, output_tokens: int) -> float:
    # Gemini 3.1 Flash Lite pricing ($0.075/1M input tokens, $0.30/1M output tokens)
    input_cost = (input_tokens / 1_000_000.0) * 0.075
    output_cost = (output_tokens / 1_000_000.0) * 0.30
    return input_cost + output_cost

# Helper to extract text from LangChain message content
def get_text_content(content: Any) -> str:
    if isinstance(content, str):
        return content
    elif isinstance(content, list):
        text_parts = []
        for part in content:
            if isinstance(part, dict) and part.get("type") == "text":
                text_parts.append(part.get("text", ""))
            elif isinstance(part, str):
                text_parts.append(part)
        return "".join(text_parts)
    return str(content)

# Regex PII scrubbing helper
def scrub_pii(text: str) -> str:
    if not text:
        return text
    # Email addresses
    text = re.sub(r'[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+', '[EMAIL]', text)
    # Phone numbers
    text = re.sub(r'\b(?:\+?\d{1,3}[-.\s]?)?\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}\b', '[PHONE]', text)
    # IP Addresses
    text = re.sub(r'\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b', '[IP_ADDRESS]', text)
    # SSNs
    text = re.sub(r'\b\d{3}-\d{2}-\d{4}\b', '[SSN]', text)
    return text

# Markdown Logging helper
MD_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "sentiment_log.md")

def log_to_md(question: str, sentiment: str, latency: float, cost: float, tokens_in: int, tokens_out: int, reply: str):
    file_exists = os.path.exists(MD_FILE)
    try:
        with open(MD_FILE, mode="a", encoding="utf-8") as f:
            if not file_exists:
                f.write("# Socratic Chatbot Sentiment & Response Log\n\n")
                f.write("This file tracks detected user sentiments, response latencies, costs, and Socratic replies.\n\n")
            
            timestamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
            f.write(f"## [{timestamp}] Query: \"{question}\"\n\n")
            f.write("<table>\n")
            f.write("  <thead>\n")
            f.write("    <tr><th align=\"left\">Metric</th><th align=\"left\">Value</th></tr>\n")
            f.write("  </thead>\n")
            f.write("  <tbody>\n")
            f.write(f"    <tr><td><strong>Detected Sentiment</strong></td><td><code>{sentiment}</code></td></tr>\n")
            f.write(f"    <tr><td><strong>Latency</strong></td><td>{round(latency, 3)}s</td></tr>\n")
            f.write(f"    <tr><td><strong>Estimated Cost</strong></td><td><code>${cost:.7f}</code></td></tr>\n")
            f.write(f"    <tr><td><strong>Tokens</strong></td><td>{tokens_in + tokens_out} ({tokens_in} in / {tokens_out} out)</td></tr>\n")
            f.write("  </tbody>\n")
            f.write("</table>\n\n")
            f.write(f"### Socratic Tutor Reply\n{reply}\n\n")
            f.write("---\n\n")
    except Exception as e:
        print(f"Error writing to MD log: {e}")

# Option B response helper doing both sentiment detection and response generation in one pass
def run_flow_b(message: str, api_key: str, history: Optional[List[ChatMessage]] = None):
    import json
    
    # Enforce structural JSON natively.
    llm = ChatGoogleGenerativeAI(
        model="gemini-3.1-flash-lite",
        google_api_key=api_key,
        temperature=0.5,
        max_tokens=450,
        generation_config={"response_mime_type": "application/json"}
    )
    
    custom_system = (
        "Socratic tutor: guide with clear, substantial hints. Continue unless close. "
        "If close: give answer & ask: 'Do you want to learn something else?'"
    )
    
    tone_instruction = (
        "JSON: {\"s\":\"sentiment\",\"r\":\"reply\"}\n"
        "s values: confusion|frustration|confused_but_engaged|confused_and_frustrated|starting_to_get_bored|confident_and_engaged|neutral\n"
        "Rules:\n"
        "- Sympathize with s implicitly (tone/style); never name or mention the sentiment/emotion itself.\n"
        "- NEVER use 'if you' (use direct phrasing: 'think about', 'imagine').\n"
        "- Ask 1 question max.\n"
        "Responses:\n"
        "- frustration: acknowledge sentiment indirectly + simplify + question.\n"
        "- starting_to_get_bored: acknowledge sentiment indirectly + puzzle/analogy + question.\n"
        "- other: hint + question."
    )
    
    messages = [SystemMessage(content=f"{custom_system}\n\n{tone_instruction}")]
    
    # Minimize tokens: slice history to last 4 messages and truncate to 60 characters
    if history:
        compact_history = history[-4:]
        for msg in compact_history:
            content = msg.content
            if len(content) > 60:
                content = content[:60] + "..."
            
            if msg.role == "user":
                messages.append(HumanMessage(content=content))
            else:
                messages.append(AIMessage(content=content))
                
    messages.append(HumanMessage(content=message))
    
    res = llm.invoke(messages)
    raw_response = get_text_content(res.content)
    cleaned_json = raw_response.strip()
    
    try:
        parsed = json.loads(cleaned_json)
        state_val = parsed.get("s", "neutral")
        reply_val = parsed.get("r", "")
    except Exception as e:
        print(f"Failed to parse LLM JSON response: {e}. Raw response: {raw_response}")
        state_val = "neutral"
        reply_val = "Let's take a look at this concept step by step. What do you think is the first part?"
        
    prompt_context = f"{custom_system}\n{tone_instruction}\nUser Query: {message}"
    est_in = estimate_tokens(prompt_context)
    est_out = estimate_tokens(raw_response)
    
    return state_val, reply_val, prompt_context, est_in, est_out

# API Routes
@app.get("/api/status")
def get_status():
    return {
        "status": "ready",
        "gemini_api_key_configured": bool(os.environ.get("GEMINI_API_KEY"))
    }

@app.post("/api/chat", response_model=ChatResponse)
def chat_endpoint(request: ChatRequest):
    # Retrieve Gemini API Key
    api_key = request.gemini_api_key or os.environ.get("GEMINI_API_KEY")
    if not api_key:
        raise HTTPException(
            status_code=400,
            detail="Gemini API Key is missing. Please provide it in the Settings panel or environment."
        )
    
    start_time = time.time()
    
    # Scrub PII
    scrubbed_message = scrub_pii(request.message)
    
    try:
        sentiment, reply, prompt_context, est_in, est_out = run_flow_b(
            message=scrubbed_message,
            api_key=api_key,
            history=request.history
        )
        latency = time.time() - start_time
        cost = calculate_cost(est_in, est_out)
        tokens = est_in + est_out
        
        # Log to Markdown
        log_to_md(
            question=request.message,
            sentiment=sentiment,
            latency=latency,
            cost=cost,
            tokens_in=est_in,
            tokens_out=est_out,
            reply=reply
        )
        
        return ChatResponse(
            sentiment=sentiment,
            response=reply,
            latency=round(latency, 3),
            prompt_context=prompt_context,
            tokens=tokens,
            cost=cost
        )
    except Exception as e:
        print(f"Chat endpoint error: {e}")
        raise HTTPException(
            status_code=500,
            detail=f"An error occurred: {str(e)}"
        )

# WebSocket Endpoint for Socratic voice dialogue via Gemini Multimodal Live API
@app.websocket("/api/live-ws")
async def websocket_live_endpoint(websocket: WebSocket):
    await websocket.accept()
    
    # Retrieve Gemini API Key from query params or environment
    api_key = websocket.query_params.get("api_key") or os.environ.get("GEMINI_API_KEY")
    if not api_key:
        await websocket.close(code=4000, reason="GEMINI_API_KEY is missing.")
        return
        
    try:
        from google import genai
        from google.genai import types
    except ImportError:
        await websocket.close(code=4001, reason="google-genai SDK not installed.")
        return

    client = genai.Client(api_key=api_key)
    
    # Configure Socratic Tutor instruction for Gemini Live API
    config = types.LiveConnectConfig(
        response_modalities=["AUDIO"], # Audio modality
        system_instruction=types.Content(
            parts=[types.Part.from_text(
                text="Socratic tutor: guide with clear, substantial hints (no tiny nudges) to solve faster. "
                     "Confidence is not mastery—continue Socratic hints unless they are close. "
                     "Only when close to the solution, give the final answer & ask: 'Do you want to learn something else?' "
                     "NEVER use the phrase 'if you' anywhere in your response (e.g. do not say 'if you think', 'if you were', etc.). Instead, frame instructions or scenarios directly (e.g., say 'think about', 'imagine', 'when looking at', or 'sometimes'). "
                     "Only ask one question at a time to avoid overwhelming the user. "
                     "Keep replies extremely concise (maximum 3 brief sentences) and conversational."
            )]
        )
    )
    
    try:
        # Establish async WebSocket connection to Gemini Live using the Gemini 3.1 Flash Live model
        async with client.aio.live.connect(model="gemini-3.1-flash-live-preview", config=config) as session:
            
            async def receive_from_client():
                try:
                    while True:
                        # Receive JSON from browser client
                        message = await websocket.receive_json()
                        msg_type = message.get("type")
                        
                        if msg_type == "audio":
                            # Decode base64 PCM audio chunk sent from frontend
                            audio_bytes = base64.b64decode(message["data"])
                            # Stream real-time audio (using 'audio' instead of deprecated 'media')
                            await session.send_realtime_input(
                                audio=types.Blob(data=audio_bytes, mime_type="audio/pcm;rate=16000")
                            )
                        elif msg_type == "text":
                            # Send real-time text input
                            await session.send_realtime_input(text=message["data"])
                except WebSocketDisconnect:
                    pass
                except Exception as e:
                    print(f"[WebSocket Proxy Client -> Gemini] Error: {e}")

            async def send_to_client():
                try:
                    async for response in session.receive():
                        server_content = response.server_content
                        if server_content is not None:
                            model_turn = server_content.model_turn
                            if model_turn is not None:
                                for part in model_turn.parts:
                                    if part.inline_data is not None:
                                        # Stream PCM audio output back to client as Base64
                                        audio_b64 = base64.b64encode(part.inline_data.data).decode('utf-8')
                                        await websocket.send_json({
                                            "type": "audio",
                                            "data": audio_b64
                                        })
                                    elif part.text is not None:
                                        # Stream text transcription back to client
                                        await websocket.send_json({
                                            "type": "text",
                                            "data": part.text
                                        })
                            
                            # Handle turn completion (model finished speaking)
                            if server_content.turn_complete:
                                await websocket.send_json({"type": "turn_complete"})
                except Exception as e:
                    print(f"[WebSocket Proxy Gemini -> Client] Error: {e}")

            # Run both tasks concurrently
            await asyncio.gather(receive_from_client(), send_to_client())
            
    except Exception as e:
        print(f"WebSocket Gemini Live connection failed: {e}")
    finally:
        try:
            await websocket.close()
        except Exception:
            pass

# Mount frontend static files in production if dist folder is built
frontend_dist_path = os.path.join(os.path.dirname(os.path.dirname(os.path.abspath(__file__))), "frontend", "dist")
if os.path.exists(frontend_dist_path):
    app.mount("/", StaticFiles(directory=frontend_dist_path, html=True), name="frontend")