/**
 * Normalize an Instagram handle from various input formats to a pure username.
 *
 * Handles these formats:
 *  - "https://www.instagram.com/banobagi_ps/"      → "banobagi_ps"
 *  - "https://instagram.com/banobagi_ps?hl=en"     → "banobagi_ps"
 *  - "http://instagram.com/banobagi_ps"             → "banobagi_ps"
 *  - "instagram.com/banobagi_ps"                    → "banobagi_ps"
 *  - "@banobagi_ps"                                 → "banobagi_ps"
 *  - "banobagi_ps"                                  → "banobagi_ps"
 *  - null / undefined / ""                          → null
 */
export function normalizeInstagramHandle(
  raw: string | null | undefined,
): string | null {
  if (!raw || typeof raw !== "string") return null;

  let handle = raw.trim();
  if (!handle) return null;

  // If it contains "instagram.com", extract the first path segment
  if (handle.includes("instagram.com")) {
    try {
      // Add protocol if missing so URL constructor works
      const urlStr = handle.startsWith("http")
        ? handle
        : `https://${handle}`;
      const url = new URL(urlStr);
      // pathname is like "/banobagi_ps/" or "/banobagi_ps"
      const segments = url.pathname.split("/").filter(Boolean);
      handle = segments[0] || "";
    } catch {
      // URL parsing failed — try regex fallback
      const match = handle.match(/instagram\.com\/([^/?#]+)/);
      handle = match?.[1] || "";
    }
  }

  // Strip leading @
  if (handle.startsWith("@")) {
    handle = handle.slice(1);
  }

  // Strip trailing slash
  handle = handle.replace(/\/+$/, "");

  return handle || null;
}