"""Cross-check the ApsisRS rain height against ITU-R P.839-4.

Reads the values written by ``cargo run -p apsis-rs --features rf --example
dump_p839`` and recomputes each one with the ``itur`` package, which
implements the recommendation directly.

The reference implementation returns a not-a-number value outside the region
its bilinear interpolator covers, which happens near the poles and at the
seam. Those points are reported separately rather than counted as failures,
because the tabulated grid does cover them and the Rust model interpolates
from it.

The script needs no network access.

Usage:

    pixi run python validation/python/atmosphere/check_p839.py [path]

Exit status is zero when every compared value agrees within tolerance and one
otherwise.

用 ITU-R P.839-4 交叉核对 ApsisRS 的雨顶高度。

读取由 ``cargo run -p apsis-rs --features rf --example dump_p839`` 写出的
值，并用 ``itur`` 包逐个重算，后者直接实现该建议书。

参考实现在其双线性插值器所覆盖区域之外返回非数（NaN），这发生在两极附近
与接缝处。那些点被分开报告而不计为失败，因为所列网格确实覆盖它们，而
Rust 模型是由该网格插值的。

本脚本不需要网络访问。

用法：

    pixi run python validation/python/atmosphere/check_p839.py [path]

每个被比较的值都在容差内一致时退出状态为零，否则为一。
"""

from __future__ import annotations

import csv
import math
import sys
from pathlib import Path

import numpy as np

from itur.models.itu839 import _ITU839_4_

# The table is stored in metres, so the interpolation reproduces the
# tabulated values to that resolution.
# 该表以米存储，故插值把所列值复现到该分辨率。
TOLERANCE_KM = 1e-9

DEFAULT_INPUT = Path("validation/data/expected/rust_p839.csv")


def read_rows(path: Path) -> list[dict[str, str]]:
    """Reads the CSV rows.

    读取 CSV 各行。
    """
    with path.open(newline="") as handle:
        reader = csv.DictReader(handle)
        return [row for row in reader if row.get("latitude_deg")]


def main(argv: list[str]) -> int:
    path = Path(argv[1]) if len(argv) > 1 else DEFAULT_INPUT
    if not path.exists():
        print(f"missing input file: {path}", file=sys.stderr)
        print(
            "generate it with: cargo run -p apsis-rs --features rf "
            "--example dump_p839 > " + str(path),
            file=sys.stderr,
        )
        return 2

    rows = read_rows(path)
    if not rows:
        print("input file has no data rows", file=sys.stderr)
        return 2

    model = _ITU839_4_()
    worst = 0.0
    worst_at = None
    compared = 0
    outside = 0

    for row in rows:
        latitude = float(row["latitude_deg"])
        longitude = float(row["longitude_deg"])
        reference = float(
            np.asarray(
                model.isoterm_0(
                    np.array([[latitude]]), np.array([[longitude]])
                )
            ).ravel()[0]
        )
        if math.isnan(reference):
            # The reference interpolator does not cover this point.
            # 参考插值器不覆盖该点。
            outside += 1
            continue

        actual = float(row["isotherm_km"])
        error = abs(actual - reference)
        if error > worst:
            worst = error
            worst_at = (latitude, longitude)
        compared += 1

    print(f"points compared:      {compared}")
    print(f"outside the reference: {outside}")
    print(f"worst difference:     {worst:.3e} km at {worst_at}")
    print(f"tolerance:            {TOLERANCE_KM:.3e} km")

    if compared > 0 and worst <= TOLERANCE_KM:
        print("result:               pass")
        return 0
    print("result:               FAIL")
    return 1


if __name__ == "__main__":
    raise SystemExit(main(sys.argv))