"""Session 9 - refresh data.json from the farm database every 10 s so index.html shows live readings.

python export_json.py --db ../smart-farm/farm.db --node greenhouse_01
Then open index.html with VS Code "Live Server" (it must be served over http://, not file://).
"""
import argparse
import json
import sqlite3
import time
from pathlib import Path

ap = argparse.ArgumentParser()
ap.add_argument("--db", default=str(Path(__file__).resolve().parent.parent / "smart-farm" / "farm.db"))
ap.add_argument("--node", default="greenhouse_01")
ap.add_argument("--once", action="store_true")
a = ap.parse_args()
out = Path(__file__).resolve().parent / "data.json"

while True:
    con = sqlite3.connect(a.db)
    con.row_factory = sqlite3.Row
    rows = con.execute("SELECT ts, air_temp_c, air_humidity_pct, soil_moisture_pct FROM readings "
                       "WHERE node_id=? AND air_temp_c IS NOT NULL ORDER BY ts DESC LIMIT 24", (a.node,)).fetchall()
    con.close()
    if rows:
        latest = dict(rows[0])
        data = {"latest": {"node_id": a.node, **{k: latest[k] for k in ("air_temp_c", "air_humidity_pct", "soil_moisture_pct")}},
                "history": [{"t": r["ts"][11:16], "soil": r["soil_moisture_pct"]} for r in reversed(rows)]}
        tmp = out.with_suffix(".tmp")
        tmp.write_text(json.dumps(data, ensure_ascii=False, indent=1), encoding="utf-8")
        tmp.replace(out)                     # atomic: the browser never reads a half-written file
        print(time.strftime("%H:%M:%S"), "updated", data["latest"])
    else:
        print("no readings yet for", a.node)
    if a.once:
        break
    time.sleep(10)