import csv, os
f = {"mm": 1, "cm": 10, "in": 25.4}
latest = {}
for r in csv.DictReader(open("readings.csv")):
    latest[(r["station"], r["date"])] = float(r["amount"]) * f[r["unit"]]
gauges = list(csv.DictReader(open("gauges.csv"))) if os.path.exists("gauges.csv") else []
rejected = {(r["station"], r["date"]) for r in csv.DictReader(open("qc.csv")) if r["decision"] == "reject"} if os.path.exists("qc.csv") else set()
def scale(s, d):
    rows = sorted((g["installed"], float(g["scale"])) for g in gauges if g["station"] == s and g["installed"] <= d)
    return rows[-1][1] if rows else 1.0
st = {}
for (s, d), v in latest.items():
    if (s, d) in rejected:
        st.setdefault(s, [])
        continue
    st.setdefault(s, []).append(v * scale(s, d))
w = csv.writer(open("rainfall.csv", "w", newline=""))
w.writerow(["station", "total_mm", "wet_days", "mean_mm_per_wet_day"])
for s, vals in st.items():
    wet = [v for v in vals if v > 0]
    w.writerow([s, f"{sum(vals):.1f}", len(wet), f"{sum(vals) / len(wet):.2f}"])