/**
 * Unit formatting and parsing utilities for CAD distance values.
 * All internal CAD coordinates are stored in world units.
 * scaleFactor converts world units to millimeters (1 world unit = scaleFactor mm).
 */

export type UnitType = 'mm' | 'cm' | 'm';

/**
 * Format a raw world-unit distance into a human-readable string with the given unit.
 * @param raw - distance in world units
 * @param unit - target display unit ('mm' | 'cm' | 'm')
 * @param scaleFactor - millimeters per world unit (default 1)
 * @returns formatted string like "500 mm", "5.0 cm", "0.05 m"
 */
export function formatDistance(
  raw: number,
  unit: UnitType,
  scaleFactor: number = 1,
): string {
  const mm = raw * scaleFactor;
  switch (unit) {
    case 'mm':
      return `${mm.toFixed(0)} mm`;
    case 'cm':
      return `${(mm / 10).toFixed(1)} cm`;
    case 'm':
      return `${(mm / 1000).toFixed(2)} m`;
  }
}

/**
 * Parse a user-entered distance string back into world units.
 * @param input - numeric string (e.g. "500", "5.5", "0.05")
 * @param unit - the unit the user is entering values in
 * @param scaleFactor - millimeters per world unit (default 1)
 * @returns world-unit distance, or 0 if input is invalid
 */
export function parseDistance(
  input: string,
  unit: UnitType,
  scaleFactor: number = 1,
): number {
  const value = parseFloat(input);
  if (isNaN(value)) return 0;
  switch (unit) {
    case 'mm':
      return value / scaleFactor;
    case 'cm':
      return (value * 10) / scaleFactor;
    case 'm':
      return (value * 1000) / scaleFactor;
  }
}

/**
 * Format a raw world-unit coordinate value for compact display (e.g. status bar).
 * Uses fewer decimal places than formatDistance.
 */
export function formatCoordinate(
  raw: number,
  unit: UnitType,
  scaleFactor: number = 1,
): string {
  const mm = raw * scaleFactor;
  switch (unit) {
    case 'mm':
      return `${mm.toFixed(0)}`;
    case 'cm':
      return `${(mm / 10).toFixed(1)}`;
    case 'm':
      return `${(mm / 1000).toFixed(3)}`;
  }
}

/**
 * Format a raw world-unit value for an input field (without unit suffix).
 * This is what the user sees in text inputs so they can edit the numeric value.
 */
export function formatInputValue(
  raw: number,
  unit: UnitType,
  scaleFactor: number = 1,
): string {
  const mm = raw * scaleFactor;
  switch (unit) {
    case 'mm':
      return `${mm.toFixed(0)}`;
    case 'cm':
      return `${(mm / 10).toFixed(1)}`;
    case 'm':
      return `${(mm / 1000).toFixed(3)}`;
  }
}

/**
 * Format a raw world-unit squared area value (Task H5).
 * @param rawSquared squared world-units (e.g. polygonArea result)
 * @param unit target display unit
 * @param scaleFactor world-units → mm conversion (like formatDistance)
 * @returns formatted string like "5000 mm²", "50.0 cm²", "5.00 m²"
 */
export function formatArea(
  rawSquared: number,
  unit: UnitType,
  scaleFactor: number = 1,
): string {
  const mmSquared = rawSquared * scaleFactor * scaleFactor;
  switch (unit) {
    case 'mm':
      return `${mmSquared.toFixed(0)} mm²`;
    case 'cm':
      return `${(mmSquared / 100).toFixed(1)} cm²`;
    case 'm':
      return `${(mmSquared / 1000000).toFixed(2)} m²`;
    default:
      return `${mmSquared.toFixed(0)} mm²`;
  }
}