main.py

from fastapi import FastAPI
# from prometheus_client import metrics
from ai.depth.depth_anything import DepthAnything
from ai.detectors.yolo_detector import YOLO_Detector
from app.config import AppConfig
from backend.api.routers.metrics import metrics_asgi_app
from infra.system_metrics import log_system_metrics
from backend.api.routers import camera_stream
from backend.api.routers import dashboard_stream
from backend.api.routers import health
from contextlib import asynccontextmanager
from infra.logger_structlog import StructLogger
import asyncio

@asynccontextmanager
async def lifespan(app: FastAPI):
    """
    This is on_event("startup") new alternative, Make sure you load models here.
    """
    
    settings = AppConfig()
    logger = StructLogger(settings=settings)

   
    logger.info("Starting Server.... ")
    asyncio.create_task(log_system_metrics(
            logger, 
            logger_interval_sec=settings.intervals.system_metrics_seconds))    
    
    # Using this way to can store data. it is acts as a dict which holds instances
    app.state.detection_model = YOLO_Detector(settings.yolo.model_path)
    app.state.depth_model = DepthAnything(encoder=settings.depth.encoder, depth_model_path=settings.depth.model_path, DEVICE="cuda")

    # safety_detection_path = hg_hub_download(
    #     repo_id="e1250/safety_detection",
    #     filename="yolo_smoke_fire.pt",
    # )
    app.state.safety_detection_model = YOLO_Detector(settings.security_detector.model_path)

    app.state.logger = logger
    app.state.settings = settings
    # Each camera should have its tracker to be able to work fine. 
    # app.state.camera_trackers = {}
    app.state.camera_metadata = {}
    app.state.dashboard_clients = set()
    yield

    logger.warn("Shutting down the server....")
    # You can remove connections and release gpu here .  
    
app = FastAPI(
    title="Tracking System Backend",
    description="real-time frame processing API",
    version="0.1.0",
    lifespan=lifespan
    )

# Routes
app.mount("/metrics", metrics_asgi_app)    # Starting Prometheus server attached to my server.
app.include_router(camera_stream.router, prefix="/detectors")
app.include_router(dashboard_stream.router, prefix="/dashboard")
app.include_router(health.router, prefix="/health")

@app.get("/")
async def root():
    return {"status": "Real-Time tracker backend is running..."}