"""Number / unit / date formatters so every document writes values the same way.
See MPM_Document_Standard.md §5 (Units and numbers)."""
import datetime as _dt
from fractions import Fraction


def ftin(x):
    """Inches -> feet-inches to the nearest 1/16: 154 -> 12'-10", 153.5 -> 12'-9 1/2"."""
    x = round(x * 16) / 16
    ft = int(x // 12)
    rem = x - ft * 12
    whole = int(rem)
    frac = Fraction(rem - whole).limit_denominator(16)
    f = f" {frac.numerator}/{frac.denominator}" if frac else ""
    return f"{ft}'-{whole}{f}\""


def inch(x):
    """Inches to the nearest 1/16: 7.25 -> 7 1/4"."""
    x = round(x * 16) / 16
    whole = int(x)
    frac = Fraction(x - whole).limit_denominator(16)
    if frac and whole:
        return f"{whole} {frac.numerator}/{frac.denominator}\""
    if frac:
        return f"{frac.numerator}/{frac.denominator}\""
    return f"{whole}\""


def mm_in(mm, digits=2):
    """'1448 mm (57.01 in.)' — metric primary with inch conversion."""
    return f"{mm:g} mm ({mm / 25.4:.{digits}f} in.)"


def signed(s, value):
    """Prefix a true minus sign or plus: signed('13\"', -1) -> '−13\"'."""
    return ("−" if value < 0 else "+" if value > 0 else "") + s


def parse_date(d):
    if isinstance(d, _dt.date):
        return d
    return _dt.date.fromisoformat(d)


def show_date(d):
    """Display format used on every page: 'Nov 5, 2026'."""
    d = parse_date(d)
    return f"{d:%b} {d.day}, {d.year}"