"""Path and naming helpers for NPZ snapshot storage."""

from __future__ import annotations

import re
from collections.abc import Sequence


def radar_key_from_config(
    model_name: str,
    serial: str,
    sweep_start_hz: float,
    sweep_stop_hz: float,
    sweep_points: int,
    ifbw_hz: float,
    power_dbm: float,
    extra_serials: Sequence[str] | None = None,
) -> str:
    """Build deterministic key for calibration/reference set lookup."""
    serial_parts = [serial or "no_serial"]
    if extra_serials:
        serial_parts.extend(str(value).strip() or "no_serial" for value in extra_serials)
    serial_part = "_".join(sanitize_path_component(value) for value in serial_parts)
    start_token = format_float_for_key(sweep_start_hz)
    stop_token = format_float_for_key(sweep_stop_hz)
    points_token = "adc" if model_name.strip().lower() == "kamil_adc" else str(int(sweep_points))
    ifbw_token = format_float_for_key(ifbw_hz)
    power_token = format_float_for_key(power_dbm)
    return (
        f"{model_name}_{serial_part}"
        f"_st{start_token}_sp{stop_token}"
        f"_p{points_token}_if{ifbw_token}_pw{power_token}"
    )


def radar_config_filename_prefix(
    model_name: str,
    sweep_start_hz: float,
    sweep_stop_hz: float,
    sweep_points: int,
    power_dbm: float,
) -> str:
    """Build a readable, filesystem-safe prefix describing the radar acquisition setup.

    Encodes the radar model, sweep frequency span, point count, and power so a saved
    dataset's name carries the configuration it was captured with. ADC-mode radars have
    no fixed sweep, so the point count is reported as ``adc``.
    """
    points_token = "adc" if model_name.strip().lower() == "kamil_adc" else f"{int(sweep_points)}pts"
    tokens = (
        model_name,
        _format_frequency_span(sweep_start_hz, sweep_stop_hz),
        points_token,
        f"{power_dbm:g}dBm",
    )
    return sanitize_path_component("_".join(tokens))


def _format_frequency_span(start_hz: float, stop_hz: float) -> str:
    """Format a frequency span compactly, both bounds sharing the larger bound's unit."""
    unit, scale = _frequency_unit(max(start_hz, stop_hz))
    return f"{start_hz / scale:g}-{stop_hz / scale:g}{unit}"


def _frequency_unit(hz: float) -> tuple[str, float]:
    """Pick the largest unit (GHz/MHz/kHz/Hz) that keeps the magnitude at or above one."""
    for unit, scale in (("GHz", 1e9), ("MHz", 1e6), ("kHz", 1e3)):
        if hz >= scale:
            return unit, scale
    return "Hz", 1.0


def collection_dir_name(index: int, collection_id: int, monotonic_ns: int) -> str:
    """Build canonical collection directory name for snapshot stages."""
    return f"{index:04d}_id{int(collection_id)}_ns{int(monotonic_ns)}"


def sanitize_path_component(name: str) -> str:
    """Convert arbitrary string into filesystem-safe component."""
    cleaned = re.sub(r"[^A-Za-z0-9._-]+", "_", name.strip())
    cleaned = cleaned.strip("._")
    return cleaned or "snapshot"


def format_float_for_key(value: float) -> str:
    """Format float compactly for deterministic key serialization."""
    integer = int(round(value))
    if abs(value - float(integer)) < 1e-6:
        return str(integer)
    return f"{value:.6f}".rstrip("0").rstrip(".")