/**
 * Separator characters that turn a single paste into multiple tag tokens:
 * commas, newlines, carriage returns, and tabs (so columns copied from a
 * spreadsheet split correctly).
 */
const BULK_TAG_SEPARATOR = /[,\n\r\t]+/;

/** Result of merging a raw paste/draft string into an existing tag list. */
export interface IBulkAddResult {
  /** Items appended to the existing list (after trim, dedupe, and cap). */
  added: string[];
  /** Total non-empty tokens parsed from the input. */
  total: number;
  /** Final list = `existing` + `added`. */
  next: string[];
}

/**
 * True when the text contains at least one bulk separator. Use this to
 * decide whether a paste should be intercepted (multi-value) or allowed
 * to land in the input as plain text (single-value, user is mid-typing).
 */
export const containsBulkSeparator = (text: string): boolean =>
  BULK_TAG_SEPARATOR.test(text);

/**
 * Parses a raw string into a list of trimmed, non-empty tag tokens.
 */
export const parseBulkTags = (raw: string): string[] =>
  raw
    .split(BULK_TAG_SEPARATOR)
    .map(token => token.trim())
    .filter(Boolean);

/**
 * Merges parsed tokens into an existing list with case-insensitive
 * dedupe and a hard cap. Overflow and duplicates are silently dropped;
 * the caller can compare ``added.length`` to ``total`` to surface a
 * "X of Y added" hint when something was skipped.
 */
export const addBulkTags = (
  raw: string,
  existing: string[],
  cap: number
): IBulkAddResult => {
  const tokens = parseBulkTags(raw);
  const seen = new Set(existing.map(tag => tag.toLowerCase()));
  const next = [...existing];
  const added: string[] = [];

  for (const token of tokens) {
    if (next.length >= cap) break;
    const key = token.toLowerCase();
    if (seen.has(key)) continue;
    seen.add(key);
    next.push(token);
    added.push(token);
  }

  return { added, total: tokens.length, next };
};