app.py

"""
Building Detection API — FastAPI Backend for Hugging Face Spaces.

Endpoints:
    GET  /          → Health check + model info
    GET  /health    → Health check
    POST /detect    → Detect buildings in a polygon area
"""

from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel, Field
from typing import List, Optional
import uvicorn

from model_manager import load_model, get_model_info
from inference import detect_buildings

# ==========================================
# === App Setup ===
# ==========================================
app = FastAPI(
    title="🏗️ Building Detection API",
    description="Detect buildings from satellite imagery using Mask R-CNN V5",
    version="1.0.0",
)

# Allow CORS for Vercel frontend
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],  # In production, restrict to your Vercel domain
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


# ==========================================
# === Request / Response Models ===
# ==========================================
class DetectRequest(BaseModel):
    coordinates: List[List[float]] = Field(
        ...,
        description="Polygon coordinates as [[lng, lat], ...] in GeoJSON format",
        example=[[31.24, 30.04], [31.25, 30.04], [31.25, 30.05], [31.24, 30.05]],
    )
    threshold: Optional[float] = Field(
        default=0.5,
        ge=0.1,
        le=0.95,
        description="Detection confidence threshold",
    )
    use_v51: Optional[bool] = Field(
        default=True,
        description="Enable V5.1 pipeline (MobileSAM + SigLIP) for better accuracy",
    )


class DetectResponse(BaseModel):
    geojson: dict
    stats: dict


class HealthResponse(BaseModel):
    status: str
    model: dict


# ==========================================
# === Startup Event ===
# ==========================================
@app.on_event("startup")
async def startup():
    """Load model when the server starts."""
    print("🚀 Starting Building Detection API...")
    load_model()
    print("✅ API ready!")


# ==========================================
# === Endpoints ===
# ==========================================
@app.get("/", response_model=HealthResponse)
async def root():
    """Health check and model info."""
    return {
        "status": "🟢 online",
        "model": get_model_info(),
    }


@app.get("/health", response_model=HealthResponse)
async def health():
    """Health check endpoint."""
    return {
        "status": "🟢 online",
        "model": get_model_info(),
    }


@app.post("/detect", response_model=DetectResponse)
async def detect(request: DetectRequest):
    """
    Detect buildings in the specified polygon area.

    Send polygon coordinates in GeoJSON format [[lng, lat], ...].
    Returns a GeoJSON FeatureCollection with detected building polygons.
    """
    try:
        result = detect_buildings(
            coordinates=request.coordinates,
            threshold=request.threshold,
            use_v51=request.use_v51,
        )

        if "error" in result:
            raise HTTPException(status_code=400, detail=result["error"])

        return result

    except HTTPException:
        raise
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"Processing error: {str(e)}")


# ==========================================
# === Run ===
# ==========================================
if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=7860)