// Turn whatever people pasted into a spreadsheet into clean Instagram usernames.

const HANDLE_COLUMNS = ['instagram', 'handle', 'username', 'ig', 'instagram_url', 'url', 'profile'];
const VALID_USERNAME = /^[a-z0-9._]{1,30}$/;
const RESERVED_PATHS = new Set(['p', 'reel', 'reels', 'stories', 'explore', 'tv', 'accounts']);

export type Rejected = { row: number; raw: string; reason: string };
export type Handle = { row: number; raw: string; username: string };

export function pickHandleColumn(headers: string[]): string {
  const normalized = headers.map((h) => h.trim().toLowerCase());
  for (const candidate of HANDLE_COLUMNS) {
    const index = normalized.indexOf(candidate);
    if (index !== -1) return headers[index];
  }
  throw new Error(
    `No handle column found. Name one of your columns: ${HANDLE_COLUMNS.join(', ')}`,
  );
}

export function normalizeHandle(raw: string): string | { reason: string } {
  let value = raw.trim();
  if (!value) return { reason: 'empty' };

  // Profile URLs: instagram.com/name, instagram.com/name/?igsh=..., m.instagram.com/name
  const url = value.match(/instagram\.com\/([^/?#\s]+)/i);
  if (url) {
    if (RESERVED_PATHS.has(url[1].toLowerCase())) {
      return { reason: 'post or reel link, not a profile' };
    }
    value = url[1];
  } else if (/^https?:\/\//i.test(value)) {
    return { reason: 'not an Instagram link' };
  }

  value = value.replace(/^@+/, '').toLowerCase();
  if (!VALID_USERNAME.test(value)) return { reason: 'not a valid Instagram username' };
  return value;
}

export function extractHandles(rows: Record<string, string>[], column: string) {
  const handles: Handle[] = [];
  const rejected: Rejected[] = [];
  const seen = new Set<string>();

  rows.forEach((record, index) => {
    const row = index + 2; // header is row 1 in the spreadsheet
    const raw = record[column] ?? '';
    const result = normalizeHandle(raw);
    if (typeof result !== 'string') {
      rejected.push({ row, raw, reason: result.reason });
    } else if (seen.has(result)) {
      rejected.push({ row, raw, reason: `duplicate of @${result}` });
    } else {
      seen.add(result);
      handles.push({ row, raw, username: result });
    }
  });

  return { handles, rejected };
}