from __future__ import annotations

from decimal import Decimal, InvalidOperation, ROUND_HALF_UP


FUEL_FACTORS: list[tuple[str, Decimal]] = [
    ("HTPB", Decimal("0.00177")),
    ("Solid", Decimal("0.00178")),
    ("PBAN", Decimal("0.001772")),
    ("Kerolox", Decimal("0.0010290673")),
    ("Hydrolox", Decimal("0.00036235886")),
    ("Methalox", Decimal("0.000845043157")),
    ("Hydrazine", Decimal("0.001004")),
    ("MMH/NTO", Decimal("0.00116557")),
]

FUEL_DENSITY_T_PER_LITER = dict(FUEL_FACTORS)
VALUE_STEP = Decimal("0.000001")


def list_fuel_factors() -> list[dict[str, float | str]]:
    return [
        {"fuel": fuel, "tonnes_per_liter": _to_float(factor)}
        for fuel, factor in FUEL_FACTORS
    ]


def convert_value(mode: str, raw_value: object) -> dict[str, object]:
    value = _parse_positive_decimal(raw_value)
    normalized_mode = mode.strip().lower()

    if normalized_mode == "volume":
        results = [
            {
                "fuel": fuel,
                "value": _to_float(value * factor),
                "unit": "t",
            }
            for fuel, factor in FUEL_FACTORS
        ]
        return {
            "mode": normalized_mode,
            "input_value": _to_float(value),
            "input_unit": "L",
            "results": results,
        }

    if normalized_mode == "mass":
        results = [
            {
                "fuel": fuel,
                "value": _to_float(value / factor),
                "unit": "L",
            }
            for fuel, factor in FUEL_FACTORS
        ]
        return {
            "mode": normalized_mode,
            "input_value": _to_float(value),
            "input_unit": "t",
            "results": results,
        }

    raise ValueError("mode must be either 'volume' or 'mass'")


def _parse_positive_decimal(raw_value: object) -> Decimal:
    try:
        value = Decimal(str(raw_value))
    except (InvalidOperation, ValueError, TypeError) as exc:
        raise ValueError("value must be numeric") from exc

    if value <= 0:
        raise ValueError("value must be greater than zero")

    return value


def _to_float(value: Decimal) -> float:
    return float(value.quantize(VALUE_STEP, rounding=ROUND_HALF_UP))