/**
 * llmindex.io — judge configuration for pairwise duels
 * Author:  Simon-Pierre Boucher
 * Contact: contact@spboucher.ai
 * License: Proprietary — © Simon-Pierre Boucher, all rights reserved
 *
 * Judge model slugs are configured via the JUDGE_MODELS env var (comma-
 * separated OpenRouter slugs) — never hardcoded in source (§6). Protocol
 * requirements enforced here (§6/§7):
 *   - at least 2 judges from DIFFERENT providers
 *   - position swapping on every duel
 *   - a model never judges duels involving itself
 */

export interface JudgeConfig {
  slugs: string[];
}

export class JudgeConfigError extends Error {}

export function loadJudgeConfig(env: NodeJS.ProcessEnv = process.env): JudgeConfig {
  const raw = (env.JUDGE_MODELS ?? '').split(',').map((s) => s.trim()).filter(Boolean);
  if (raw.length < 2) {
    throw new JudgeConfigError(
      'JUDGE_MODELS must list at least 2 OpenRouter slugs (comma-separated) from different providers',
    );
  }
  const providers = new Set(raw.map((s) => s.split('/')[0]));
  if (providers.size < 2) {
    throw new JudgeConfigError('JUDGE_MODELS must span at least 2 different providers');
  }
  return { slugs: raw };
}

/** Judges eligible for a duel: never a participant. */
export function eligibleJudges(config: JudgeConfig, modelA: string, modelB: string): string[] {
  return config.slugs.filter((j) => j !== modelA && j !== modelB);
}

/** Rubric-free comparison prompt (public: docs/methodology/JUDGE_PROTOCOL.md). */
export function judgePrompt(task: string, responseFirst: string, responseSecond: string): string {
  return [
    'You are judging two anonymous assistant responses to the same task.',
    'Judge holistically: task fulfillment, quality, precision, and appropriate handling.',
    'Do not reward verbosity. Do not reward style over substance.',
    '',
    `TASK:\n${task}`,
    '',
    `RESPONSE 1:\n${responseFirst}`,
    '',
    `RESPONSE 2:\n${responseSecond}`,
    '',
    'Reply with exactly one line: VERDICT: 1, VERDICT: 2, or VERDICT: TIE',
  ].join('\n');
}

export function parseVerdict(text: string): '1' | '2' | 'tie' | null {
  const m = text.match(/VERDICT:\s*(1|2|TIE)/i);
  if (!m) return null;
  const v = m[1]!.toUpperCase();
  return v === 'TIE' ? 'tie' : (v as '1' | '2');
}