"""Typed units and quantity types: what a number IS, not only how large it is.

A rate stored as a decimal (0.0335) can be a margin LEVEL of 3.35%, a margin CHANGE of 335 basis points or a
growth rate of 3.35%. The decimal is the same, the quantity is not. Every rate-like figure therefore carries:

* ``unit`` — the unit it was stated in: PERCENT, PERCENTAGE_POINTS, BASIS_POINTS, DECIMAL_FRACTION, MULTIPLE,
  COUNT, USD, USD_MILLION, USD_BILLION, USD_PER_SHARE;
* ``quantity_type`` — what it measures: LEVEL, CHANGE, GROWTH_RATE, SPREAD, MARGIN_LEVEL, MARGIN_CHANGE, YIELD,
  PROBABILITY.

Canonical values: rates, changes and spreads as decimals (335 bps → 0.0335, 3.35 pp → 0.0335, 3.35% → 0.0335);
money in USD. The canonical number may coincide; the unit and quantity type never collapse, and formatting is
driven by them, never inferred from the size of the stored number.
"""
from __future__ import annotations

# ── units ─────────────────────────────────────────────────────────────────────────────
DECIMAL_FRACTION = "DECIMAL_FRACTION"
PERCENT = "PERCENT"
PERCENTAGE_POINTS = "PERCENTAGE_POINTS"
BASIS_POINTS = "BASIS_POINTS"
MULTIPLE = "MULTIPLE"
COUNT = "COUNT"
USD = "USD"
USD_MILLION = "USD_MILLION"
USD_BILLION = "USD_BILLION"
USD_PER_SHARE = "USD_PER_SHARE"
UNITS = (DECIMAL_FRACTION, PERCENT, PERCENTAGE_POINTS, BASIS_POINTS, MULTIPLE, COUNT, USD, USD_MILLION, USD_BILLION,
         USD_PER_SHARE)
RATE_UNITS = (DECIMAL_FRACTION, PERCENT, PERCENTAGE_POINTS, BASIS_POINTS)
MONEY_UNITS = (USD, USD_MILLION, USD_BILLION, USD_PER_SHARE)

# stated value × factor = canonical value (decimal for rates, USD for money)
TO_CANONICAL = {DECIMAL_FRACTION: 1.0, PERCENT: 0.01, PERCENTAGE_POINTS: 0.01, BASIS_POINTS: 0.0001, MULTIPLE: 1.0,
                COUNT: 1.0, USD: 1.0, USD_MILLION: 1e6, USD_BILLION: 1e9, USD_PER_SHARE: 1.0}

# ── quantity types ────────────────────────────────────────────────────────────────────
LEVEL = "LEVEL"
CHANGE = "CHANGE"
GROWTH_RATE = "GROWTH_RATE"
SPREAD = "SPREAD"
MARGIN_LEVEL = "MARGIN_LEVEL"
MARGIN_CHANGE = "MARGIN_CHANGE"
YIELD = "YIELD"
PROBABILITY = "PROBABILITY"
QUANTITY_TYPES = (LEVEL, CHANGE, GROWTH_RATE, SPREAD, MARGIN_LEVEL, MARGIN_CHANGE, YIELD, PROBABILITY)
CHANGE_TYPES = (CHANGE, MARGIN_CHANGE, SPREAD)
# units a quantity type may be stated in
ALLOWED_UNITS = {
    LEVEL: MONEY_UNITS + (COUNT, MULTIPLE),
    GROWTH_RATE: (PERCENT, DECIMAL_FRACTION),
    MARGIN_LEVEL: (PERCENT, DECIMAL_FRACTION),
    MARGIN_CHANGE: (BASIS_POINTS, PERCENTAGE_POINTS),
    CHANGE: (BASIS_POINTS, PERCENTAGE_POINTS) + MONEY_UNITS,
    SPREAD: (BASIS_POINTS, PERCENTAGE_POINTS),
    YIELD: (PERCENT, DECIMAL_FRACTION),
    PROBABILITY: (PERCENT, DECIMAL_FRACTION),
}

# economic concepts for guidance and claims: a change or a growth rate is never stored under a level concept
CONCEPT_QUANTITY = {
    "REVENUE": LEVEL, "REVENUE_GROWTH": GROWTH_RATE, "ORGANIC_REVENUE_GROWTH": GROWTH_RATE,
    "OPERATING_MARGIN": MARGIN_LEVEL, "OPERATING_MARGIN_CHANGE": MARGIN_CHANGE,
    "NET_MARGIN": MARGIN_LEVEL, "GROSS_MARGIN": MARGIN_LEVEL, "GROSS_MARGIN_CHANGE": MARGIN_CHANGE,
    "EPS": LEVEL, "EPS_GROWTH": GROWTH_RATE, "OPERATING_INCOME": LEVEL, "OPERATING_EXPENSES": LEVEL,
    "INTEREST_EXPENSE": LEVEL, "AMORTIZATION": LEVEL, "TAX_RATE": MARGIN_LEVEL, "FREE_CASH_FLOW": LEVEL,
    "CAPEX": LEVEL, "SHARE_REPURCHASE": LEVEL, "DIVIDEND": LEVEL, "NET_INTEREST_INCOME": LEVEL,
    "NET_INTEREST_MARGIN": MARGIN_LEVEL, "OTHER": None,
}


class QuantityError(ValueError):
    """A unit or quantity type that does not describe the figure."""


def to_canonical(value, unit):
    if value is None:
        return None
    if unit not in TO_CANONICAL:
        raise QuantityError(f"unknown unit {unit!r}")
    return float(value) * TO_CANONICAL[unit]


def check(unit, quantity_type):
    """(ok, reason): is this unit a valid way to state this quantity type?"""
    if unit not in UNITS:
        return False, f"unknown unit {unit!r}"
    if quantity_type not in QUANTITY_TYPES:
        return False, f"unknown quantity type {quantity_type!r}"
    if unit not in ALLOWED_UNITS[quantity_type]:
        return False, f"{quantity_type} cannot be stated in {unit}"
    return True, ""


def _num(x, dec):
    s = f"{x:,.{dec}f}"
    return s.rstrip("0").rstrip(".") if dec and "." in s else s


def format_value(value, unit, quantity_type=None, *, signed=False):
    """One canonical value, formatted from its unit and quantity type (never from its magnitude)."""
    if value is None:
        return None
    v = float(value)
    sg = "+" if (signed and v > 0) else ""
    if unit == BASIS_POINTS:
        return f"{sg}{_num(v * 10000.0, 0)} bps"
    if unit == PERCENTAGE_POINTS:
        return f"{sg}{_num(v * 100.0, 2)} percentage points"
    if unit in (PERCENT, DECIMAL_FRACTION):
        return f"{sg}{v * 100.0:,.1f}%"
    if unit == MULTIPLE:
        return f"{v:,.1f}x"
    if unit == COUNT:
        return f"{int(round(v)):,}"
    if unit == USD_PER_SHARE:
        return f"{sg}${v:,.2f}"
    if unit in (USD, USD_MILLION, USD_BILLION):
        a = abs(v)
        s = "-" if v < 0 else sg
        if a >= 1e12:
            return f"{s}${a / 1e12:,.2f}T"
        if a >= 1e9:
            return f"{s}${a / 1e9:,.2f}B"
        if a >= 1e6:
            return f"{s}${a / 1e6:,.0f}M" if a >= 1e8 else f"{s}${a / 1e6:,.1f}M"
        return f"{s}${a:,.0f}"
    raise QuantityError(f"cannot format unit {unit!r}")


def format_range(low, high, unit, quantity_type=None):
    lo, hi = format_value(low, unit, quantity_type), format_value(high, unit, quantity_type)
    if lo is None and hi is None:
        return None
    if lo is None or hi is None or lo == hi:
        return lo or hi
    if unit == BASIS_POINTS:
        return f"{_num(float(low) * 10000.0, 0)}–{_num(float(high) * 10000.0, 0)} bps"
    if unit == PERCENTAGE_POINTS:
        return f"{_num(float(low) * 100.0, 2)}–{_num(float(high) * 100.0, 2)} percentage points"
    return f"{lo}–{hi}"


MAGNITUDE_BAND = (0.2, 5.0)


def magnitude_ok(value, low, high=None):
    """(ok, reason): is a threshold measured against a source of the same unit of the same order of magnitude?
    A threshold of 3.6 bps against guidance of 335–360 bps is the same number in the wrong unit, not a judgement."""
    refs = [abs(float(x)) for x in (low, high) if x is not None and float(x) != 0.0]
    if value is None or not refs:
        return True, ""
    v = abs(float(value))
    ratio = min((v / r for r in refs), key=lambda q: abs(q - 1.0) if q else float("inf")) if v else 0.0
    lo, hi = MAGNITUDE_BAND
    if lo <= ratio <= hi:
        return True, ""
    return False, f"threshold is {ratio:.3g}× its source value (outside {lo}–{hi}×): a unit slip, not a judgement"