export type ResolvedIcon =
  | { type: 'link'; value: string }
  | { type: 'font-awesome'; name: string; style: string }
  | { type: 'invalid'; reason: string };

const FA_ICON_STYLES = ['solid', 'regular', 'duotone', 'brands'] as string[];
const FA_ICON_NAME_PATTERN = /^[a-z0-9-]+$/i;

/**
 * Resolves an icon value from configuration into a structured object.
 *
 * Supports:
 * - URLs (absolute or relative paths to image files)
 * - Font Awesome icons in formats:
 *    - "solid camera" (style + name)
 *    - "camera" (name only, default style: 'regular')
 *
 * @param icon - The icon string from config.
 * @returns A structured object describing the icon:
 *    - type: 'url' | 'font-awesome' | 'invalid'
 *    - value: for URLs
 *    - name and style: for Font Awesome icons
 *    - reason: for invalid entries
 */
export function resolveIcon(icon?: string): ResolvedIcon {
  if (!icon || typeof icon !== 'string') {
    return { type: 'invalid', reason: 'Icon must be a non-empty string' };
  }

  const trimmed = icon.trim();
  const isLink =
    trimmed.match(/\.(svg|png|jpg|jpeg|gif|ico|webp)$/) || /^https?:\/\//.test(trimmed);

  if (isLink) {
    return { type: 'link', value: trimmed };
  }

  const [first, second] = trimmed.split(/\s+/);

  if (first) {
    if (second) {
      // Format: "style name" (e.g., "solid camera")
      if (FA_ICON_STYLES.includes(first) && FA_ICON_NAME_PATTERN.test(second)) {
        return { type: 'font-awesome', style: first, name: second };
      } else {
        return { type: 'invalid', reason: 'Unrecognized icon format' };
      }
    } else if (!FA_ICON_STYLES.includes(first) && FA_ICON_NAME_PATTERN.test(first)) {
      return {
        type: 'font-awesome',
        name: first,
        style: 'regular',
      };
    }
  }
  return { type: 'invalid', reason: 'Unrecognized icon format' };
}