"""Tag-schema value transforms for miniDLNA folder names.

Applied when building a folder name from a tag value — the tag keeps its exact
value (e.g. rating 87 → tag "Hodnocení/87"), while the folder groups it
(→ "…/80–89 %"). Config-driven and extensible via ``TAG_TRANSFORMS``.
"""
import re
from typing import Optional


def rating_band(rating: int) -> str:
    """Bucket a 0–100 rating into a ten-point band label (e.g. "80–89 %").

    The top bucket spans 90–100 % so a perfect 100 still lands in a band.
    """
    low = min((rating // 10) * 10, 90)
    high = 100 if low == 90 else low + 9
    return f"{low}–{high} %"


def _decade_band(value) -> str:
    """``decade_band`` transform: pull the leading integer and bucket it."""
    match = re.search(r"\d+", str(value))
    return rating_band(int(match.group())) if match else str(value)


# Named value transforms usable from the tag schema (config-driven, extensible).
TAG_TRANSFORMS = {
    None: str,
    "identity": str,
    "decade_band": _decade_band,
}


def apply_transform(value: str, transform: Optional[str]) -> str:
    """Apply a named tag-schema transform to a value, returning a string."""
    fn = TAG_TRANSFORMS.get(transform, str)
    try:
        return str(fn(value))
    except (ValueError, TypeError, AttributeError):
        return str(value)