/**
 * Y bounds of filled grain volume — matches GrainFillFlat / GrainCableFill fallback volume math.
 */
export interface GrainYBounds {
    minY: number;
    maxY: number;
}

export function grainYBoundsFromFillPercent(
    diameter: number,
    sidewallHeight: number,
    hopperHeight: number,
    fillPercent: number
): GrainYBounds {
    const radius = diameter / 2;
    const sidewallBaseY = -sidewallHeight / 2;
    const hopperTipY = sidewallBaseY - hopperHeight;

    if (fillPercent <= 0) {
        return { minY: sidewallBaseY, maxY: sidewallBaseY };
    }

    const cylinderVolume = Math.PI * radius * radius * sidewallHeight;
    const hopperVolume =
        hopperHeight > 0 ? (1 / 3) * Math.PI * radius * radius * hopperHeight : 0;
    const totalVolume = cylinderVolume + hopperVolume;
    const filledVolume = totalVolume * fillPercent;

    if (hopperHeight > 0 && filledVolume <= hopperVolume) {
        const ratio = filledVolume / hopperVolume;
        const hopperFillHeight = hopperHeight * Math.pow(ratio, 1 / 3);
        return {
            minY: hopperTipY,
            maxY: hopperTipY + hopperFillHeight,
        };
    }

    const hopperFillHeight = hopperHeight;
    const remainingVolume = filledVolume - hopperVolume;
    const cylinderFillHeight = Math.max(
        0,
        remainingVolume / (Math.PI * radius * radius)
    );

    return {
        minY: hopperHeight > 0 ? hopperTipY : sidewallBaseY,
        maxY: sidewallBaseY + cylinderFillHeight,
    };
}