"""측점 표기 한 벌 — 파이썬 짝(TS `common_util/common_util_station.ts` · 거울 시험 `test_545_1`).

`station_label` ↔ `stationLabel` · `infer_station_interval` ↔ `inferStationInterval` — 한쪽을 고치면 다른 쪽도.
가져오는 것이 없는 순수 함수(E05 보고서 등 무거운 모듈 없이 씀).
"""

from __future__ import annotations

import math
from typing import Any


def station_label(chainage: float, interval: float, decimals: int = 1) -> str:
    """`측점번호+잔여거리`(예 `61+14.5` · `decimals=0` 이면 거리 정수)."""
    safe = interval if interval > 0 else 1.0
    number = math.floor((chainage + 1e-6) / safe)
    rest = chainage - number * safe
    if abs(rest) < 0.05:
        rest = 0.0
    if rest >= safe - 0.05:
        number, rest = number + 1, 0.0
    scale = 10 if decimals else 1
    shown = math.floor(rest * scale + 0.5) / scale  # JS Math.round
    return f"{number}+{int(shown) if shown == int(shown) else shown}"


def infer_station_interval(stations: list[dict[str, Any]]) -> float:
    """측점 목록의 최빈 간격(0.1 m 반올림 · 같으면 큰 쪽 · 없으면 1)."""
    counts: dict[float, int] = {}
    for prev, cur in zip(stations, stations[1:]):
        difference = float(cur["chainage_m"]) - float(prev["chainage_m"])
        if difference <= 0:
            continue
        rounded = math.floor(difference * 10 + 0.5) / 10
        counts[rounded] = counts.get(rounded, 0) + 1
    if not counts:
        return 1
    return max(counts.items(), key=lambda item: (item[1], item[0]))[0]