"""Bits and bytes related humanization."""

from __future__ import annotations

from math import log

suffixes = {
    "decimal": (
        " kB",
        " MB",
        " GB",
        " TB",
        " PB",
        " EB",
        " ZB",
        " YB",
        " RB",
        " QB",
    ),
    "binary": (
        " KiB",
        " MiB",
        " GiB",
        " TiB",
        " PiB",
        " EiB",
        " ZiB",
        " YiB",
        " RiB",
        " QiB",
    ),
    "gnu": "KMGTPEZYRQ",
}


def naturalsize(
    value: float | str,
    binary: bool = False,
    gnu: bool = False,
    format: str = "%.1f",
) -> str:
    """Format a number of bytes like a human-readable filesize (e.g. 10 kB).

    By default, decimal suffixes (kB, MB) are used.

    Non-GNU modes are compatible with jinja2's `filesizeformat` filter.

    Examples:
        ```pycon
        >>> naturalsize(3000000)
        '3.0 MB'
        >>> naturalsize(300, False, True)
        '300B'
        >>> naturalsize(3000, False, True)
        '2.9K'
        >>> naturalsize(3000, False, True, "%.3f")
        '2.930K'
        >>> naturalsize(3000, True)
        '2.9 KiB'
        >>> naturalsize(10**28)
        '10.0 RB'
        >>> naturalsize(10**34 * 3)
        '30000.0 QB'
        >>> naturalsize(-4096, True)
        '-4.0 KiB'

        ```

    Args:
        value (int, float, str): Integer to convert.
        binary (bool): If `True`, uses binary suffixes (KiB, MiB) with base
            2<sup>10</sup> instead of 10<sup>3</sup>.
        gnu (bool): If `True`, the binary argument is ignored and GNU-style
            (`ls -sh` style) prefixes are used (K, M) with the 2**10 definition.
        format (str): Custom formatter.

    Returns:
        str: Human readable representation of a filesize.
    """
    if gnu:
        suffix = suffixes["gnu"]
    elif binary:
        suffix = suffixes["binary"]
    else:
        suffix = suffixes["decimal"]

    base = 1024 if (gnu or binary) else 1000
    bytes_ = float(value)
    abs_bytes = abs(bytes_)

    if abs_bytes == 1 and not gnu:
        return f"{int(bytes_)} Byte"

    if abs_bytes < base:
        return f"{int(bytes_)}B" if gnu else f"{int(bytes_)} Bytes"

    exp = int(min(log(abs_bytes, base), len(suffix)))
    ret: str = format % (bytes_ / (base**exp)) + suffix[exp - 1]
    return ret