backend/app/api/fleet.py

"""Fleet Mode telemetry ingestion.

Mounted phones run inference locally and send only compact hazard telemetry plus an optional
privacy-processed thumbnail. This endpoint intentionally does no model inference and no DBSCAN in
the request path.
"""
from __future__ import annotations

import base64
import io
import uuid
from datetime import datetime, timedelta, timezone

from fastapi import APIRouter, Depends, HTTPException
from PIL import Image, UnidentifiedImageError
from sqlmodel import Session

from app.config import settings
from app.db.repository import Repository
from app.db.session import get_session
from app.models.schemas import (
    FleetTelemetryIn,
    FleetTelemetryResponse,
    GeoSource,
    HazardType,
    Severity,
    Source,
)
from app.models.tables import HazardReport

router = APIRouter(prefix="/fleet", tags=["fleet"])


def _utc(dt: datetime) -> datetime:
    if dt.tzinfo is None:
        return dt.replace(tzinfo=timezone.utc)
    return dt.astimezone(timezone.utc)


def _severity_from_area(area_frac: float | None) -> Severity:
    if area_frac is None:
        return Severity.low
    if area_frac >= settings.SEV_HIGH:
        return Severity.high
    if area_frac >= settings.SEV_MED:
        return Severity.medium
    return Severity.low


def _validate_timestamp(ts: datetime) -> datetime:
    observed_at = _utc(ts)
    now = datetime.now(timezone.utc)
    if observed_at < now - timedelta(hours=settings.FLEET_MAX_EVENT_AGE_HOURS):
        raise HTTPException(status_code=422, detail="Telemetry timestamp is too old.")
    if observed_at > now + timedelta(minutes=settings.FLEET_MAX_CLOCK_SKEW_MINUTES):
        raise HTTPException(status_code=422, detail="Telemetry timestamp is in the future.")
    return observed_at


def _store_thumbnail(thumbnail_b64: str | None) -> str | None:
    if not thumbnail_b64:
        return None

    raw_b64 = thumbnail_b64.split(",", 1)[1] if "," in thumbnail_b64 else thumbnail_b64
    if len(raw_b64) > settings.FLEET_MAX_THUMBNAIL_BYTES * 2:
        raise HTTPException(status_code=413, detail="Thumbnail payload is too large.")

    try:
        data = base64.b64decode(raw_b64, validate=True)
    except ValueError as exc:
        raise HTTPException(status_code=422, detail="Thumbnail is not valid Base64.") from exc

    if len(data) > settings.FLEET_MAX_THUMBNAIL_BYTES:
        raise HTTPException(status_code=413, detail="Thumbnail payload is too large.")

    try:
        img = Image.open(io.BytesIO(data)).convert("RGB")
    except (UnidentifiedImageError, OSError) as exc:
        raise HTTPException(status_code=422, detail="Thumbnail is not a valid image.") from exc

    img.thumbnail((320, 320))
    out = io.BytesIO()
    img.save(out, format="JPEG", quality=62, optimize=True)

    fleet_dir = settings.MEDIA_DIR / "fleet"
    fleet_dir.mkdir(parents=True, exist_ok=True)
    filename = f"{uuid.uuid4().hex}.jpg"
    path = fleet_dir / filename
    path.write_bytes(out.getvalue())
    return f"media/fleet/{filename}"


@router.post("/telemetry", response_model=FleetTelemetryResponse)
async def ingest_telemetry(
    payload: FleetTelemetryIn,
    session: Session = Depends(get_session),
) -> FleetTelemetryResponse:
    if payload.hazard_type == HazardType.other:
        raise HTTPException(status_code=422, detail="Fleet telemetry requires a concrete hazard type.")
    if payload.confidence < settings.FLEET_MIN_CONFIDENCE:
        raise HTTPException(status_code=422, detail="Detection confidence is below the fleet threshold.")
    if payload.bbox is not None and len(payload.bbox) != 4:
        raise HTTPException(status_code=422, detail="bbox must contain [x1, y1, x2, y2].")

    observed_at = _validate_timestamp(payload.timestamp)
    repo = Repository(session)
    if payload.client_event_id:
        duplicate = repo.get_report_by_client_event(payload.client_event_id)
        if duplicate is not None:
            return FleetTelemetryResponse(
                status="accepted",
                report_id=duplicate.id,
                queued_for_cluster=False,
            )

    thumbnail_path = _store_thumbnail(payload.thumbnail_b64)
    report = HazardReport(
        observed_at=observed_at,
        source=Source.fleet_stream,
        hazard_type=payload.hazard_type,
        severity=_severity_from_area(payload.bbox_area_frac),
        confidence=round(payload.confidence, 4),
        lat=payload.lat,
        lon=payload.lon,
        geo_source=GeoSource.device,
        media_path=thumbnail_path or "",
        thumbnail_path=thumbnail_path,
        bbox=payload.bbox or [],
        bbox_area_frac=payload.bbox_area_frac,
        device_speed=payload.speed,
        client_event_id=payload.client_event_id,
        auto_validated=True,
    )
    report = repo.add_report(report)
    return FleetTelemetryResponse(status="accepted", report_id=report.id, queued_for_cluster=True)