import {
  AREA_DECIMALS,
  BDFT_DECIMALS,
  INCH_STEP,
  PRICE_DECIMALS,
} from "./constants.js";

/** Half-up at .5 (away from zero). */
export function roundHalfUp(value: number, decimals: number): number {
  if (!Number.isFinite(value)) {
    return value;
  }
  const factor = 10 ** decimals;
  const scaled = Math.abs(value) * factor;
  const rounded = Math.floor(scaled + 0.5) / factor;
  return value < 0 ? -rounded : rounded;
}

/** Nearest INCH_STEP (1/8"). */
export function roundLengthIn(lengthIn: number): number {
  return Math.round(lengthIn / INCH_STEP) * INCH_STEP;
}

export function roundSqft(sqft: number): number {
  return roundHalfUp(sqft, AREA_DECIMALS);
}

export function roundBdft(bdft: number): number {
  return roundHalfUp(bdft, BDFT_DECIMALS);
}

export function roundPrice(price: number): number {
  return roundHalfUp(price, PRICE_DECIMALS);
}

/** bdft = sqft × thickness_in. No divide-by-12. */
export function computeBdft(sqft: number, thicknessIn: number): number {
  return roundBdft(sqft * thicknessIn);
}