backend/app.py

"""FastAPI application — consultant chatbot microservice.

Endpoints:
    POST /chat                       — Main chat endpoint
    GET  /sessions                   — List all sessions
    POST /sessions/new               — Create a new session
    GET  /sessions/{session_id}      — Get session details + history
    DELETE /sessions/{session_id}    — Delete a session
    GET  /health                     — Health check

The frontend is served as static files from ../frontend/.
"""

from __future__ import annotations

import os
import uuid
from contextlib import asynccontextmanager

from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import FileResponse
from fastapi.staticfiles import StaticFiles

from models import (
    ChatRequest,
    ChatResponse,
    Message,
    NewSessionResponse,
    Phase,
    SessionInfo,
    SessionState,
)
from storage import delete_session, init_db, list_sessions, load_session, save_session
from graph import run_consultation


# ---------------------------------------------------------------------------
# Greeting message — shown at the start of every new session
# ---------------------------------------------------------------------------

GREETING_MESSAGE = (
    "**Welcome to Stacklogix.** I'm your consultant for this session. 👋\n\n"
    "Whether you have a **clear request** (e.g. build a product or fix an issue) or a **problem** "
    "(e.g. something isn't working as you'd like), I'll ask a few questions to understand your needs. "
    "Our team will then follow up with you.\n\n"
    "**What would you like to achieve or what do you need help with?**"
)


# ---------------------------------------------------------------------------
# App lifecycle
# ---------------------------------------------------------------------------

@asynccontextmanager
async def lifespan(app: FastAPI):
    await init_db()
    yield


app = FastAPI(
    title="Stacklogix Consultant Chatbot API",
    description="Stacklogix requirement-collection chatbot — gathers client requirements and explains how Stacklogix will address them. LangGraph + Groq.",
    version="1.0.0",
    lifespan=lifespan,
)

# CORS — allow all origins for microservice usage
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


# ---------------------------------------------------------------------------
# Chat endpoint
# ---------------------------------------------------------------------------

@app.post("/chat", response_model=ChatResponse)
async def chat(req: ChatRequest):
    """Process a user message and return the consultant's response."""
    # Load or create session
    session = await load_session(req.session_id)
    if session is None:
        session = SessionState(session_id=req.session_id)

    # Run consultation graph
    result = await run_consultation(session, req.message)

    # Persist updated state
    await save_session(req.session_id, result["session_state"])

    return ChatResponse(
        reply=result["assistant_reply"],
        phase=result["new_phase"],
        confidence=result["new_confidence"],
        understanding=result["new_understanding"],
    )


# ---------------------------------------------------------------------------
# Session management endpoints
# ---------------------------------------------------------------------------

@app.get("/sessions")
async def get_sessions():
    """List all active sessions."""
    sessions = await list_sessions()
    return {"sessions": sessions}


@app.post("/sessions/new")
async def create_session():
    """Create a new session with an opening greeting message."""
    session_id = str(uuid.uuid4())
    state = SessionState(
        session_id=session_id,
        messages=[Message(role="assistant", content=GREETING_MESSAGE)],
    )
    await save_session(session_id, state)
    return {
        "session_id": session_id,
        "greeting": GREETING_MESSAGE,
    }


@app.get("/sessions/{session_id}")
async def get_session(session_id: str):
    """Get full session details including conversation history."""
    session = await load_session(session_id)
    if session is None:
        raise HTTPException(status_code=404, detail="Session not found")
    return session.model_dump()


@app.delete("/sessions/{session_id}")
async def remove_session(session_id: str):
    """Delete a session."""
    deleted = await delete_session(session_id)
    if not deleted:
        raise HTTPException(status_code=404, detail="Session not found")
    return {"status": "deleted", "session_id": session_id}


# ---------------------------------------------------------------------------
# Health check
# ---------------------------------------------------------------------------

@app.get("/health")
async def health():
    return {"status": "healthy", "service": "stacklogix-chatbot"}


# ---------------------------------------------------------------------------
# Serve frontend static files
# ---------------------------------------------------------------------------

FRONTEND_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", "frontend")

if os.path.isdir(FRONTEND_DIR):
    @app.get("/")
    async def serve_index():
        return FileResponse(os.path.join(FRONTEND_DIR, "index.html"))

    app.mount("/static", StaticFiles(directory=FRONTEND_DIR), name="static")