"""Staged constraint discovery for s2s-reforecasts: progressively fix fields and
read back the EXACT valid values (untruncated), so the minimal request uses real
model-version days, hindcast dates and leadtime windows -- no guessing."""
import json
import os

import datapi

ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
ECDS_URL = "https://ecds.ecmwf.int/api"
DATASET = "s2s-reforecasts"


def _get_key():
    k = os.environ.get("CDSAPI_KEY")
    if k:
        return k
    rc = os.environ.get("CDSAPI_RC", os.path.expanduser("~/.cdsapirc"))
    if os.path.exists(rc):
        for line in open(rc):
            if line.strip().startswith("key"):
                return line.split(":", 1)[1].strip()
    return None


c = datapi.ApiClient(url=ECDS_URL, key=_get_key())
proc = c.get_process(DATASET)
KEYS = ["year", "month", "day", "hyear", "hmonth", "hday", "leadtime_hour", "variable"]

stages = {
    "base": {"origin": "ecmwf", "forecast_type": "control_forecast", "level_type": "single_level"},
    "var_2t": {"origin": "ecmwf", "forecast_type": "control_forecast", "level_type": "single_level",
               "variable": ["2_m_temperature"]},
    "var_2t_2015_01": {"origin": "ecmwf", "forecast_type": "control_forecast", "level_type": "single_level",
                       "variable": ["2_m_temperature"], "year": "2015", "month": "01"},
}
out = {}
for name, sel in stages.items():
    try:
        con = proc.apply_constraints(sel)
        out[name] = {"selection": sel,
                     "valid": {k: con.get(k) for k in KEYS if k in con}}
        print(f"\n===== {name} =====", flush=True)
        for k in KEYS:
            if k in con:
                v = con[k]
                print(f"  {k}: {v if not isinstance(v,list) or len(v)<=40 else v[:40]+['...']}", flush=True)
    except Exception as e:
        out[name] = {"selection": sel, "error": f"{type(e).__name__}: {e}"}
        print(f"{name}: ERROR {e}", flush=True)

with open(os.path.join(ROOT, "metadata", "ecds_constraints_staged.json"), "w") as f:
    json.dump(out, f, indent=2, default=str)
print("\nwrote metadata/ecds_constraints_staged.json", flush=True)