kira/backend/main.py

"""Kira — AI body double backend

Cheapest pipeline: gpt-4o-mini-transcribe STT → gpt-5.4-nano LLM → OpenAI TTS
~$0.019/min total, simple 3-step chat completions.
"""

import json
import base64
import uuid
import logging
import asyncio

from fastapi import FastAPI, WebSocket, WebSocketDisconnect
from fastapi.middleware.cors import CORSMiddleware

from config import settings
from services.memory import kira_memory

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger("kira")

app = FastAPI(title="Kira Backend")

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# System prompt
BASE_SYSTEM_PROMPT = (
    "You are Kira, a warm, kind, and encouraging AI body double. "
    "You speak in a friendly, girly-pop tone. You are helping someone with ADHD "
    "stay focused and on task. Keep responses short, supportive, and uplifting. "
    "Check in on them. Remind them to take breaks. Celebrate small wins. "
    "Use occasional emoji but don't overdo it. Never be judgmental."
)

_openai = None


def get_openai():
    global _openai
    if _openai is None:
        from openai import AsyncOpenAI
        _openai = AsyncOpenAI(api_key=settings.openai_api_key)
    return _openai


@app.on_event("startup")
async def startup():
    if kira_memory.init():
        logger.info("Honcho memory initialized")
    else:
        logger.info("Honcho memory not configured")


@app.get("/api/health")
async def health():
    mem_status = "active" if kira_memory.enabled else "disabled"
    return {"status": "ok", "name": "kira", "memory": mem_status}


def build_system_prompt(user_id: str) -> str:
    prompt = BASE_SYSTEM_PROMPT
    if kira_memory.enabled:
        try:
            kira_memory.ensure_peers(user_id)
            suffix = kira_memory.build_system_prompt_suffix()
            if suffix:
                prompt += suffix
        except Exception as e:
            logger.warning(f"Memory context failed: {e}")
    return prompt


async def run_conversation(text: str, user_id: str) -> str:
    """STT → LLM → TTS using the cheapest models."""
    system_prompt = build_system_prompt(user_id)
    client = get_openai()

    # LLM
    resp = await client.chat.completions.create(
        model="gpt-5.4-nano",
        messages=[
            {"role": "system", "content": system_prompt},
            {"role": "user", "content": text},
        ],
        max_tokens=300,
        temperature=0.7,
    )
    kira_text = resp.choices[0].message.content or "Mhm, I'm here!"
    return kira_text


async def transcribe_audio(audio_bytes: bytes) -> str | None:
    """Transcribe audio bytes using cheapest STT model."""
    client = get_openai()
    try:
        transcript = await client.audio.transcriptions.create(
            model="gpt-4o-mini-transcribe",
            file=("audio.webm", audio_bytes, "audio/webm"),
            response_format="text",
        )
        return transcript.strip() if transcript and transcript.strip() else None
    except Exception as e:
        logger.warning(f"STT error: {e}")
        return None


async def synthesize_speech(text: str) -> bytes:
    """Generate TTS audio from text."""
    client = get_openai()
    try:
        resp = await client.audio.speech.create(
            model="tts-1",
            voice="nova",
            input=text,
            response_format="opus",
        )
        return resp.content
    except Exception as e:
        logger.warning(f"TTS error: {e}")
        return b""


@app.websocket("/api/ws")
async def conversation_ws(websocket: WebSocket):
    await websocket.accept()
    session_id = str(uuid.uuid4())[:8]
    user_id = "default-user"
    identified = False
    logger.info(f"[{session_id}] WebSocket connected")

    audio_buffer = bytearray()
    conversation_history: list[dict] = []

    try:
        while True:
            raw = await websocket.receive_text()
            msg = json.loads(raw)
            msg_type = msg.get("type", "")

            # ── Identity & Preferences ──
            if msg_type == "identify":
                user_id = msg.get("user_id", "").strip()
                user_name = msg.get("name", "").strip()
                if user_name and user_id:
                    kira_memory.set_user_preference(user_id, "name", user_name)

                prefs = kira_memory.get_user_preferences(user_id)
                identified = True

                if kira_memory.enabled:
                    kira_memory.ensure_peers(user_id)
                    kira_memory.ensure_session(session_id)

                await websocket.send_json({
                    "type": "identified",
                    "user_id": user_id,
                    "preferences": prefs,
                })
                continue

            if msg_type == "set_preference":
                key = msg.get("key", "").strip()
                value = msg.get("value", "").strip()
                if key and user_id and user_id != "default-user":
                    kira_memory.set_user_preference(user_id, key, value)
                await websocket.send_json({
                    "type": "preference_saved",
                    "key": key,
                    "success": True,
                })
                continue

            # ── Conversation ──
            if msg_type == "audio":
                # Accumulate PCM16 audio chunks
                chunk = base64.b64decode(msg["data"])
                audio_buffer.extend(chunk)

            elif msg_type == "transcribe":
                if not audio_buffer:
                    await websocket.send_json({"type": "error", "message": "No audio data"})
                    continue

                logger.info(f"[{session_id}] Transcribing {len(audio_buffer)} bytes...")

                # 1. STT
                transcript = await transcribe_audio(bytes(audio_buffer))
                audio_buffer.clear()

                if not transcript:
                    await websocket.send_json({"type": "error", "message": "Could not transcribe"})
                    continue

                await websocket.send_json({"type": "transcript", "role": "user", "text": transcript})
                conversation_history.append({"role": "user", "content": transcript})

                # 2. LLM
                logger.info(f"[{session_id}] User: {transcript}")
                kira_text = await run_conversation(transcript, user_id)
                conversation_history.append({"role": "assistant", "content": kira_text})
                logger.info(f"[{session_id}] Kira: {kira_text}")

                # Store in Honcho
                if kira_memory.enabled and identified:
                    try:
                        kira_memory.store_messages(transcript, kira_text)
                    except Exception:
                        pass

                # 3. TTS
                await websocket.send_json({"type": "speaking_start", "text": kira_text})
                audio_bytes = await synthesize_speech(kira_text)
                audio_b64 = base64.b64encode(audio_bytes).decode("utf-8")
                await websocket.send_json({"type": "audio", "data": audio_b64, "text": kira_text})
                await websocket.send_json({"type": "speaking_end"})

            elif msg_type == "conversation_text":
                user_text = msg.get("text", "").strip()
                if not user_text:
                    continue

                conversation_history.append({"role": "user", "content": user_text})
                logger.info(f"[{session_id}] User (text): {user_text}")

                kira_text = await run_conversation(user_text, user_id)
                conversation_history.append({"role": "assistant", "content": kira_text})
                logger.info(f"[{session_id}] Kira: {kira_text}")

                if kira_memory.enabled and identified:
                    try:
                        kira_memory.store_messages(user_text, kira_text)
                    except Exception:
                        pass

                await websocket.send_json({"type": "speaking_start", "text": kira_text})
                audio_bytes = await synthesize_speech(kira_text)
                audio_b64 = base64.b64encode(audio_bytes).decode("utf-8")
                await websocket.send_json({"type": "audio", "data": audio_b64, "text": kira_text})
                await websocket.send_json({"type": "speaking_end"})

            elif msg_type == "ping":
                await websocket.send_json({"type": "pong"})

    except WebSocketDisconnect:
        logger.info(f"[{session_id}] Disconnected")
    except Exception as e:
        logger.error(f"[{session_id}] Error: {e}")
        try:
            await websocket.send_json({"type": "error", "message": str(e)})
        except Exception:
            pass