/**
 * Color utility functions for Zeiterfassung module
 */

/**
 * Generate a consistent color from a string (for avatars, etc.)
 * @param str - The string to generate color from
 * @returns HSL color string
 */
export const stringToColor = (str: string): string => {
  let hash = 0;
  for (let i = 0; i < str.length; i++) {
    hash = str.charCodeAt(i) + ((hash << 5) - hash);
  }
  
  const hue = hash % 360;
  return `hsl(${hue}, 65%, 50%)`;
};

/**
 * Get contrasting text color (black or white) based on background color
 * Uses relative luminance calculation for optimal readability
 * @param hexColor - Hex color code (with or without #)
 * @returns '#000000' for light backgrounds, '#FFFFFF' for dark backgrounds
 */
export const getContrastColor = (hexColor: string): string => {
  // Remove # if present
  const hex = hexColor.replace('#', '');
  
  // Convert to RGB
  const r = parseInt(hex.substr(0, 2), 16);
  const g = parseInt(hex.substr(2, 2), 16);
  const b = parseInt(hex.substr(4, 2), 16);
  
  // Calculate relative luminance using standard formula
  const luminance = (0.299 * r + 0.587 * g + 0.114 * b) / 255;
  
  // Return black for light backgrounds, white for dark backgrounds
  return luminance > 0.5 ? '#000000' : '#FFFFFF';
};