// massUnitUtils.js
const toGramFactor = {
    'pg': 1e-12,
    'ng': 1e-9,
    'ug': 1e-6,
    'mg': 0.001,
    'g': 1,
    'kg': 1000
};

const validUnits = Object.keys(toGramFactor);

export function isMassUnit(unit) {
    if (typeof unit !== 'string') return false;
    return validUnits.includes(unit.toLowerCase());
}

function toGrams(value, unit) {
    if (typeof value !== 'number' || isNaN(value)) {
        throw new Error('值必须是有效数字');
    }
    const lowerUnit = unit.toLowerCase();
    if (!isMassUnit(lowerUnit)) {
        throw new Error(`无效的质量单位: ${unit}`);
    }
    return value * toGramFactor[lowerUnit];
}

export function compareMass(value1, unit1, value2, unit2) {
    const grams1 = toGrams(value1, unit1);
    const grams2 = toGrams(value2, unit2);
    
    if (grams1 > grams2) return 1;
    if (Math.abs(grams1 - grams2) < 1e-12) return 0;
    return -1;
}