/**
 * Mention Protocol — Bot-to-Bot communication in mention-only groups
 *
 * Pure function module — no side effects, no shared state.
 *
 * When a group has gm_req_mention=1, bots need to:
 * 1. Know the group's "social rule" (must @-mention to trigger others)
 * 2. Know who's in the group (member list)
 * 3. Have their text-level @mentions translated to TIM protocol-level atUserList
 *
 * See: docs/audit/012-mention-mode-bot-to-bot-v3.4.4.md
 */

// ── Types ──

export interface MentionMember {
  id: string;
  nick: string;
}

// ── Regex utility ──

function escapeRegex(s: string): string {
  return s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
}

// ── Prompt injection ──

/**
 * Build the mention protocol prompt to inject into GroupSystemPrompt.
 * Tells the AI: this group is mention-only, here are the members,
 * you must @mention them to communicate.
 *
 * Returns empty string if no other members exist.
 */
export function buildMentionPrompt(
  members: MentionMember[],
  selfId: string,
): string {
  const others = members.filter(m => m.id !== selfId);
  if (others.length === 0) return '';

  const memberList = others
    .map(m => `- ${m.nick} (mention as: @${m.nick})`)
    .join('\n');

  return [
    '[GROUP COMMUNICATION PROTOCOL]',
    'This group uses mention-only mode.',
    'Your messages will ONLY be seen by members you @-mention.',
    'To mention someone, write @their_name in your message.',
    '',
    'Group members:',
    memberList,
    '',
    `Example: "@${others[0].nick} what do you think?"`,
    '[/GROUP COMMUNICATION PROTOCOL]',
  ].join('\n');
}

// ── Text → atUserList extraction ──

/**
 * Extract @-mention targets from AI output text.
 *
 * Strategy: iterate the known member list and search for each nick
 * in the text. This is more robust than parsing @-tokens from text,
 * because it handles:
 *   - Space after @:  "@ 投资人Bot"
 *   - Case mismatch:  "@投资人bot"
 *   - Trailing punct:  "@投资人Bot，你好"
 *   - Multiple @:     "@BotA @BotB hi"
 *
 * Only matches when @ prefix is present — mentioning a name without @
 * (e.g. "投资人Bot说得对") does NOT trigger a match.
 *
 * Returns an array of userIDs suitable for TIM createTextAtMessage.
 * Returns empty array if no matches found.
 */
export function extractAtTargets(
  text: string,
  members: MentionMember[],
  selfId: string,
): string[] {
  const results: string[] = [];
  for (const member of members) {
    if (member.id === selfId) continue;
    const pattern = new RegExp(`@\\s*${escapeRegex(member.nick)}`, 'i');
    if (pattern.test(text)) {
      results.push(member.id);
    }
  }
  return results;
}