import type { HumanIdentity } from './protocol.js';

export function mentionToken(textBeforeCursor: string): string | null {
  const match = /(?:^|[\s(])@([A-Za-z0-9-]*)$/.exec(textBeforeCursor);
  return match ? match[1]! : null;
}

function fuzzyMatch(handle: string, query: string): boolean {
  let offset = 0;
  for (const character of query.toLowerCase()) {
    offset = handle.toLowerCase().indexOf(character, offset);
    if (offset < 0) return false;
    offset++;
  }
  return true;
}

export function completionItems(participants: readonly HumanIdentity[], query: string) {
  return participants
    .filter((participant) => fuzzyMatch(participant.handle, query))
    .slice(0, 20)
    .map((participant) => ({ value: `@${participant.handle}`, label: `@${participant.handle}`, description: 'Authenticated Chi participant' }));
}