import { CODEX_ENABLE_FLEET_ENV } from '../config/defaults.js';
import { getQuestionGuidance } from '../config/question-guidance.js';

const TRUTHY_VALUES = new Set(['1', 'true', 'yes', 'on']);

export const FLEET_DEVELOPER_INSTRUCTIONS_SUFFIX = [
  '',
  '[codex-worker-fleet]',
  'This thread is running under mcp-codex-worker fleet mode.',
].join('\n');

export function isFleetModeEnabled(value = process.env[CODEX_ENABLE_FLEET_ENV]): boolean {
  return value !== undefined && TRUTHY_VALUES.has(value.trim().toLowerCase());
}

export function appendFleetDeveloperInstructions(
  developerInstructions: string | null | undefined,
): string | undefined {
  if (!isFleetModeEnabled()) {
    return developerInstructions ?? undefined;
  }

  const base = developerInstructions?.trim();
  if (!base) {
    return FLEET_DEVELOPER_INSTRUCTIONS_SUFFIX.trim();
  }

  return `${base}\n${FLEET_DEVELOPER_INSTRUCTIONS_SUFFIX}`;
}

/**
 * Build the full developerInstructions string for a thread/start call.
 * Composes: user instructions → question guidance → fleet sentinel.
 */
export function buildDeveloperInstructions(
  userInstructions: string | undefined,
  provider: string,
): string | undefined {
  let base = userInstructions?.trim() ?? '';

  // Append provider-specific question guidance
  const questionGuidance = getQuestionGuidance(provider);
  base = base ? `${base}\n${questionGuidance}` : questionGuidance.trim();

  // Append fleet sentinel if enabled
  if (isFleetModeEnabled()) {
    base = `${base}\n${FLEET_DEVELOPER_INSTRUCTIONS_SUFFIX}`;
  }

  return base || undefined;
}